The

Health

Benefit

Basket

in

France

The

French

Health

Benefit

Basket

is

defined

principally

by

positive

lists

of

reimbursed

goods

and

services

however

global

budget-financed

hospital-delivered

services

are

more

implicitly

defined

The

range

of

reimbursable

curative

care

services

is

defined

by

two

coexisting

positive

lists/fee

schedules

the

Classification

Commune

des

Actes

Médicaux

-LRB-

CCAM

-RRB-

and

the

Nomenclature

Générale

des

Actes

Professionnels

-LRB-

NGAP

-RRB-

The

National

Union

of

Health

Insurance

Funds

has

been

updating

these

positive

lists

since

August

with

the

main

criterion

for

inclusion

being

the

proposed

procedure

's

effectiveness

This

is

assessed

by

the

newly

created

High

Health

authority

-LRB-

replacing

the

former

ANAES

-RRB-

In

addition

complementary

health

insurers

are

consulted

in

the

inclusion

process

due

to

their

important

role

in

French

healthcare

financing

The

French

health

insurance

system

a

mix

of

explicit

and

implicit

regulations

offers

wide-ranging

reimbursement

in

the

fields

of

preventive

curative

rehabilitative

and

palliative

care

The

present

analysis

of

the

health

benefit

basket

in

France

is

being

carried

out

during

a

period

of

reforms

This

contribution

describes

the

structure

of

the

statutory

health

insurance

system

followed

by

a

description

of

the

entitlements

and

benefits

and

of

the

actors

involved

in

the

decision-making

process

with

its

criteria

for

services

of

curative

care

Finally

we

analyze

the

main

changes

which

may

affect

the

health

basket

in

France

The

structure

of

the

French

statutory

health

insurance

system

The

financial

management

of

health

care

in

France

is

undertaken

mainly

by

the

statutory

health

insurance

system

as

a

branch

of

the

wider

social

security

system

The

health

insurance

system

's

current

structure

is

based

on

its

founding

text

the

Ordinance

of

October

and

subsequent

legislative

measures

This

system

has

covered

the

entire

population

of

France

since

January

when

the

Couverture

Maladie

Universelle

-LRB-

CMU

Universal

Health

Coverage

Act

-RRB-

extended

basic

health

insurance

cover

to

all

legal

residents

of

France

The

French

statutory

health

insurance

system

is

a

compulsory

scheme

and

covers

all

households

regardless

of

health

status

income

number

of

persons

etc.

It

provides

a

somewhat

uniform

field

of

reimbursement

with

the

basket

of

goods

and

services

covered

by

the

insurance

funds

being

identical

for

all

the

statutory

schemes

with

the

reimbursement

rate

being

the

same

for

the

three

main

insurance

schemes

since

The

exceptions

are

the

Alsace-Moselle

region

's

local

scheme

and

certain

public

sector

schemes

-LSB-

-RSB-

Membership

in

one

of

the

health

insurance

funds

of

the

statutory

health

insurance

depends

on

the

profession

of

each

person

In

the

context

of

the

CMU

however

participation

depends

on

legal

residence

in

France

and

on

the

level

of

income

Any

dependants

of

the

insured

person

are

also

covered

by

his/her

health

insurance

The

three

main

health

insurance

schemes

are

as

follows

-LRB-

a

-RRB-

The

General

Scheme

-LRB-

Régime

général

-RRB-

covers

employees

in

commerce

and

industry

and

their

families

-LRB-

about

of

the

population

-RRB-

as

well

as

persons

receiving

CMU

estimated

in

late

at

about

person

-LRB-

of

the

population

-RRB-

-LSB-

-RSB-

-LRB-

b

-RRB-

The

Agricultural

Scheme

-LRB-

Mutualité

sociale

agricole

-RRB-

covers

farmers

and

agricultural

employees

and

their

families

-LRB-

about

of

the

population

-RRB-

-LRB-

c

-RRB-

The

Scheme

for

the

Non-agricultural

Self-Employed

-LRB-

CANAM

-RRB-

covers

craftsmen

and

self-employed

persons

including

self-employed

professionals

such

as

lawyers

-LRB-

about

of

the

population

-RRB-

Another

ten

work-related

schemes

cover

specific

sections

of

the

population

Statutory

health

insurance

funds

three-quarters

of

the

health

expenditure

and

therefore

leaves

considerable

scope

for

complementary

sources

of

funding

An

estimated

of

the

population

have

complementary

health

insurance

Taking

into

account

recipients

of

Couverture

Maladie

Universelle

Complémentaire

-LRB-

Complementary

Universal

Health

Coverage

of

the

population

-RRB-

about

of

the

French

population

are

covered

by

the

complementary

health

insurance

scheme

which

covers

the

same

health

basket

as

the

statutory

schemes

and

not

other

goods

and

services

-LSB-

-RSB-

The

most

important

benefit

catalogues

for

France

and

their

underlying

criteria

are

displayed

in

Tables

and

while

the

following

sections

are

confined

to

curative

health

care

services.Table

Catalogues

and

implicit

regulationGBRCCAMNGAPLSAC

ATUMed

dev.NABM

Sp.

reg.HC

Curative

care

services

Inpatient

curative

care

Day-patient

curative

care

Outpatient

curative

care

Basic

medical

and

diagnostic

services

Outpatient

dental

care

All

other

specialized

health

care

All

other

outpatient

curative

care

-LRB-

paramedical

-RRB-

Services

of

curative

home

care

HC

Services

of

rehabilitative

care

Inpatient

rehabilitative

care

Day

cases

of

rehabilitative

care

Outpatient

rehabilitative

care

Services

of

rehabilitative

home

care

HC

Services

of

long-term

nursing

care

Inpatient

long-term

nursing

care

Day

cases

of

long-term

nursing

care

Long-term

nursing

care

home

care

HC

Ancillary

health

care

services

Medical

analysis

laboratory

Diagnostic

imaging

Patient

transport

and

emergency

rescue

HC

Medical

goods

dispensed

to

outpatients

Prescribed

medicines

Other

medical

nondurables

Therapeutic

devices

and

other

medical

durables

HC

Prevention

and

public

health

services

GBR

General

Benefit

Regulation

CCAM

list

of

physicians

and

dentists

technical

procedures

NGAP

list

of

physicians

consultations

and

other

health

professionals

activity

LSAC

ATU

positive

lists

of

drugs

Med

dev

positive

lists

of

medical

devices

NABM

positive

lists

NABM

biology

procedure

Sp.

reg

specific

regulationTable

Benefit-defining

laws/decrees

catalogues

and

implicit

regulationGBRCCAM

NGAPLSAC

ATUMed

dev.NABM

Sp.

reg.Legal

status

law

decreeLawUNCAM

decisionMinisterial

orderMinisterial

orderUNCAM

decisionAdministrative

documentDecision

makerParliament

UNCAM

on

the

advice

of

HAS

and

UNOCMinisters

of

health

and

social

security

on

the

advice

of

the

Transparency

CommissionMinisters

of

health

and

social

security

on

the

advice

of

the

ad

hoc

CommissionUNCAM

on

the

advice

of

HAS

and

UNOCOriginal

purpose

entitlements

reimbursement

target

settingReimbursementPositive

listPositive

listPositive

listPositive

listPositive

listTariffsFee

schedulePrices

or

reference

pricesReference

pricesFee

schedulePositive-negative

definition

of

benefitsPositivePositivePositivePositivePositivePositiveDegree

of

-LRB-

except

inpatient

care

-RRB-

or

itemized

goods/procedures

only

linked

to

indicationsMainly

goods

and

procedures

linked

to

indicationsProcedures

sometimes

linked

to

indicationsPharmaceutical

products

linked

to

indicationsGoods

linked

to

indicationsProcedures

linked

to

indicationsMainly

indicationsUpdating

RegularlyRegularlyRegularlyRegularly

GBR

General

Benefit

Regulation

CCAM

list

of

physicians

and

dentists

technical

procedures

NGAP

list

of

physicians

consultations

and

other

health

professionals

activity

LSAC

ATU

positive

lists

of

drugs

Med

dev

positive

lists

of

medical

devices

NABM

positive

lists

NABM

biology

procedure

Sp.

reg

specific

regulationa

all

necessary

areas

of

care

items

Organizational

structure

and

actors

involved

in

the

definition

of

the

benefit

basket

for

curative

services

In

France

the

general

conditions

of

the

reimbursement

system

are

established

by

law

Health

benefit

catalogues

are

drawn

up

at

national

level

with

the

whole

range

of

goods

and

services

reimbursed

by

the

statutory

scheme

being

specified

in

Article

of

the

Social

Security

Code

-LRB-

SSC

-RRB-

-LSB-

-RSB-

The

reimbursement

of

goods

and

services

depends

on

their

inclusion

in

positive

lists

according

to

Articles

and

L.

of

the

SSC

Until

positive

lists

were

officially

enforced

by

ministerial

orders

detailing

the

inclusion

of

new

goods

and

services

Ministers

made

their

decisions

upon

the

advice

of

ad

hoc

scientific

commissions

and

agencies

for

example

the

National

Agency

for

Accreditation

and

Evaluation

in

Health

Care

-LRB-

ANAES

-RRB-

The

inclusion

of

all

the

listed

procedures

depends

on

ANAES

advice

which

considers

the

effectiveness

and/or

safety

of

these

procedures

and

the

conditions

under

which

they

need

to

be

performed

Reimbursement

is

legal

only

when

goods

or

services

are

provided

in

an

appropriate

medical

context

Reimbursement

for

all

goods

and

all

paramedical

procedures

depends

on

the

provision

of

a

prescription

which

serves

as

confirmation

of

the

necessity

of

such

goods

and

services

For

some

types

of

treatment

such

as

physiotherapy

and

spa

treatment

the

prescription

from

a

physician

does

not

provide

the

needed

status

for

reimbursement

Coverage

by

statutory

health

insurance

is

subject

to

the

prior

authorization

-LRB-

entente

préalable

-RRB-

of

the

physicians

advising

the

health

insurance

funds

after

examination

of

the

patient

's

case

history

and

a

possible

interviewing

of

the

patient

According

to

Article

of

the

SSC

the

insured

person

's

copayment

is

fixed

by

a

decision

of

Union

Nationale

des

Caisses

d'Assurance

Maladie

-LRB-

UNCAM

National

Union

of

Health

Insurance

Funds

-RRB-

within

rate

limits

defined

by

a

Council

of

State

decree

The

copayment

can

be

either

a

percentage

of

the

charges

or

a

lump

sum

The

patient

's

contribution

to

the

total

cost

of

treatment

varies

according

to

the

type

of

treatment

being

higher

for

outpatient

care

and

drugs

compared

to

hospital

treatment

The

copayment

must

be

paid

by

the

insured

person

or

where

applicable

by

their

complementary

health

insurance

fund

Council

of

State

decrees

also

define

copayment

exemption

conditions

-LRB-

Article

of

the

SSC

-RRB-

The

most

important

exemptions

are

linked

to

the

health

status

especially

in

the

case

of

one

person

suffering

from

one

of

specified

long-term

illnesses

for

example

diabetes

AIDS

cancer

and

psychiatric

illness

and

if

the

patient

is

suffering

from

one

or

several

incapacitating

diseases

Other

health

status-based

exemptions

concern

for

example

disabled

persons

under

the

age

of

years

and

pregnant

women

during

the

final

months

of

pregnancy

The

health

benefit

basket

is

explicitly

defined

by

positive

lists

of

goods

for

both

the

public

and

the

private

sectors

Positive

lists

only

apply

to

services

delivered

by

private

sector

professionals

in

their

own

practices

or

in

private

for-profit

hospitals

Conversely

services

dispensed

in

public

hospitals

or

private

not-for-profit

hospitals

were

mainly

the

subject

of

implicit

definition

since

they

were

paid

for

by

a

global

budget

which

means

in

practice

that

basically

every

dispensed

service

was

reimbursed

The

situation

is

currently

undergoing

an

important

reform

services

qualifying

for

reimbursement

by

the

health

insurance

system

include

-LRB-

a

-RRB-

inpatient

care

and

treatment

in

public

or

private

healthcare

institutions

-LRB-

b

-RRB-

outpatient

care

provided

by

general

practitioners

specialists

dentists

and

midwives

and

-LRB-

c

-RRB-

diagnostic

services

and

care

prescribed

by

physicians

and

performed

by

laboratories

and

paramedical

professionals

such

as

nurses

physiotherapists

and

speech

therapists

In

July

two

health

benefit

catalogues

for

curative

services

exist

-LRB-

a

-RRB-

The

Classification

Commune

des

Actes

Médicaux

-LRB-

CCAM

-RRB-

which

revises

the

previous

medical

services

catalogue

has

been

adopted

in

with

its

application

still

only

partial

-LSB-

-RSB-

-LRB-

b

-RRB-

The

general

fee

schedule

-LRB-

Nomenclature

Générale

des

Actes

Professionnels

NGAP

-RRB-

which

is

the

medical

procedures

positive

list

for

health

professionals

in

private

practice

in

their

own

surgeries

and

consulting

rooms

and

in

private-for-profit

hospitals

remains

in

force

until

the

CCAM

is

fully

implemented

Inpatient

curative

service

The

Social

Security

Act

of

December

-LRB-

Loi

de

financement

de

la

sécurité

sociale

LFSS

-RRB-

changed

the

inpatient

acute

care

funding

rules

but

implementation

is

still

in

progress

The

situation

will

continue

to

change

during

the

next

few

years

for

at

least

two

reasons

Firstly

the

positive

list

for

physicians

procedures

the

CCAM

applies

to

both

private

and

public

hospitals

-LRB-

Article

of

the

SSC

-RRB-

which

had

not

been

the

case

before

Secondly

the

implementation

of

the

per-case

payment

reform

that

will

lead

to

the

result

of

both

sectors

being

brought

into

line

These

situations

before

and

after

the

reforms

of

are

shown

in

Table

Table

Definition

of

benefit

catalogues

for

inpatient

care

Before

rules

depend

upon

hospital

status

PH

and

PNFPH

vs.

PFPHNew

funding

rules

making

the

basket

more

explicitRange

of

reimbursed

medical

procedures

defined

at

least

for

PFPH

but

not

for

other

services

e.g.

nursing

careSame

list

of

medical

procedures

for

both

private

and

public

hospitals

-LRB-

Article

of

the

SSC

-RRB-

No

positive

list

for

PH

an

implicit

coverage

for

all

services

in

PH

and

PNFPH

mainly

financed

by

the

global

budgetSame

prospective

per-case

payment

system

for

PH

and

PFPH

for

all

medical

surgery

and

obstetrics

services

based

on

DRG-type

classification

of

GHS

but

tariffs

still

differ

from

PH

to

PFPH.Basket

of

reimbursable

drugs

defined

for

PH

and

PFPHBasket

of

reimbursable

drugs

defined

for

PH

and

PFPHPH

public

hospital

PNFPH

private

non-for-profit

hospital

PFPH

private-for-profit

hospital

DRG

diagnosis-related

group

GHS

homogeneous

stay

group

As

seen

in

Table

there

has

been

no

positive

list

to

define

reimbursable

services

in

public

and

in

private

not-for-profit

hospitals

in

which

inpatient

services

were

regulated

by

implicit

coverage

However

the

implementation

of

the

per-case

payment

system

will

simplify

the

situation

as

all

medical

surgery

and

obstetrics

services

in

all

hospitals

will

be

included

in

it

The

reform

will

also

change

the

remuneration

schemes

of

inpatient

and

outpatient

care

Services

provided

in

inpatient

or

outpatient

acute

care

will

be

financed

through

a

payment-per-case

system

This

is

based

on

a

diagnosis-related

group

type

of

classification

of

Groupes

Homogènes

de

Malades

-LRB-

GHM

-RRB-

considering

comorbidities

A

nationally

fixed

tariff

-LRB-

Groupe

Homogène

de

Séjours

GHS

Homogeneous

Group

of

Stays

-RRB-

is

applied

to

each

GHM

-LSB-

-RSB-

Outpatient

procedures

will

be

paid

on

a

fee-for-service

basis

and

organ

retrieval

and

emergency

services

by

annual

lump

sum

payments

This

payment

system

also

includes

earmarked

funding

-LRB-

Missions

d'intérêt

général

et

Aide

à

la

contractualisation

MIGAC

-RRB-

to

finance

other

activities

such

as

research

and

education

but

also

certain

healthcare

activities

promoted

by

contracts

between

hospitals

and

regional

health

agencies

The

new

GHS

payment

system

has

been

in

operation

since

March

for

private-for-profit

hospitals

Procedures

carried

out

by

physicians

are

always

paid

separately

and

directly

to

the

physicians

concerned

on

a

fee-for-service

basis

while

in

public

hospitals

tariffs

include

specialists

salaries

Since

July

the

CCAM

is

used

as

the

general

fee

schedule

and

can

be

considered

as

the

positive

list

for

private

for

hospitals

Health

insurance

funds

will

not

finance

any

stay

if

one

of

these

procedures

does

not

apply

CCAM

is

currently

available

only

for

technical

procedures

such

as

surgery

medical

imaging

and

radiotherapy

performed

by

physicians

Paramedical

services

including

physiotherapy

which

are

linked

to

inpatient

medical

procedures

are

reimbursed

only

if

they

are

an

essential

part

of

the

medical

treatment

Regarding

the

definition

of

the

health

basket

the

rules

for

day-case

patient

care

are

the

same

as

those

applicable

to

inpatient

care

GHS

tariffs

refer

to

day

hospital

treatment

Outpatient

curative

care

Patients

who

need

health

care

have

until

now

been

free

to

choose

which

physician

to

consult

and

have

also

been

allowed

to

refer

themselves

to

specialists

Only

few

general

practitioners

have

begun

playing

the

role

of

gatekeepers

although

a

few

of

them

have

been

making

some

attempts

in

this

regard

since

Recent

health

insurance

reforms

are

about

to

change

this

situation

Since

July

all

those

benefiting

from

health

insurance

coverage

in

France

are

obliged

to

choose

their

main

physician

-LRB-

médecin

traitant

-RRB-

As

a

result

there

will

be

higher

user

charges

if

a

person

chooses

to

consult

a

specialist

directly

without

being

referred

by

her/his

gate-keeping

médecin

traitant

general

practitioner

-LSB-

-RSB-

The

basket

of

reimbursable

outpatient

curative

services

is

defined

by

a

positive

list

which

is

also

used

as

a

fee-schedule

for

health

professionals

in

private

practice

Until

March

the

NGAP

was

the

only

list

and

applied

to

all

services

This

will

be

replaced

by

the

new

CCAM

classification

In

a

rather

lengthy

process

CCAM

is

currently

being

developed

At

this

stage

CCAM

specifies

only

technical

procedures

such

as

diagnosis

surgery

and

radiology

performed

by

specialists

and

dentists

CCAM

is

also

being

used

in

public

hospitals

to

charge

for

outpatient

care

and

to

specify

the

reimbursement

rate

This

classification

is

not

yet

used

for

specialist

consultations

or

procedures

carried

out

by

other

healthcare

professionals

who

are

still

in

use

of

the

NGAP

The

CCAM

is

fully

comprehensive

in

content

as

it

contains

details

of

all

medical

procedures

even

those

that

are

not

reimbursable

Each

procedure

corresponds

to

only

one

label

and

one

code

eliminating

any

ambiguity

and

making

it

easy

to

use

The

classification

is

structured

according

to

the

anatomical

classification

and

specialities

There

are

chapters

which

are

based

on

the

organ

system

to

which

the

procedures

refer

The

CCAM

is

based

on

the

rule

of

procedural

totality

meaning

that

each

label

implicitly

contains

all

the

operations

necessary

for

the

performance

of

the

medical

procedure

It

was

drawn

up

as

a

resource-based

relative

value

scale

-LRB-

RBRVS

-RRB-

by

the

main

health

insurance

fund

-LRB-

CNAMTS

-RRB-

with

the

collaboration

of

health

professionals

and

the

ANAES

being

involved

in

the

selection

of

effective

procedures

Since

the

reform

of

August

the

UNCAM

which

includes

representatives

of

the

three

main

sickness

funds

is

in

charge

of

preparing

and

updating

the

positive

lists

UNCAM

will

be

assisted

in

its

decision

making

by

the

advice

of

the

two

newly

created

bodies

the

High

Health

Authority

-LRB-

Haute

Autorité

de

Santé

-RRB-

which

replaced

the

ANAES

and

the

National

Union

of

Complementary

Health

Insurance

Organizations

-LRB-

Union

Nationale

des

Organismes

d'Assurance

Maladie

Complémentaire

UNOC

-RRB-

The

same

criteria

used

for

the

NGAP

will

be

used

for

the

taxonomy

of

medical

procedures

leaving

room

for

improvements

in

medical

services

and

achieving

cost-containment

at

the

same

time

-LSB-

-RSB-

Nevertheless

the

ministries

of

health

and

social

security

retain

the

right

to

reject

UNCAM

's

decisions

and

to

include

or

exclude

goods

and

services

in

or

from

the

list

especially

if

public

health

issues

are

concerned

A

commission

comprising

healthcare

professionals

unions

and

representatives

of

UNCAM

has

been

created

to

determine

the

general

rules

for

drawing

up

the

RBRVS

and

then

for

validating

the

scale

proposed

by

the

health

insurance

fund

services

In

addition

UNCAM

is

responsible

for

negotiating

the

tariffs

of

medical

procedures

with

healthcare

professionals

unions

and

for

determining

the

levels

of

copayment

and

coinsurance

Other

outpatient

services

such

as

auxiliary

services

provided

by

nurses

physiotherapists

orthoptists

speech

therapists

and

chiropodists

must

be

provided

on

medical

prescription

in

order

to

be

reimbursed

In

the

area

of

complementary

and

alternative

medicine

-LRB-

CAM

-RRB-

special

recognition

is

given

to

acupuncture

and

homeopathy

These

two

therapies

are

thus

recognized

and

may

be

legally

practiced

but

only

by

physicians

or

licensed

physiotherapists

on

medical

prescriptions

for

acupuncture

A

few

osteopathy

and

chiropractic

procedures

have

recently

been

included

in

the

CCAM

in

addition

to

certain

vertebral

manipulations

which

were

already

listed

in

the

NGAP

The

range

of

services

covered

by

statutory

health

insurance

does

not

include

cosmetic

surgery

and

some

other

treatments

and

services

of

uncertain

effectiveness

such

as

spa

treatments

The

issue

of

the

allocation

of

scarce

resources

means

that

choices

must

be

made

which

may

result

in

the

nonreimbursement

of

certain

procedures

for

example

bone

density

measurement

when

performed

in

the

private

sector

as

a

preventive

measure

and

the

imposition

of

limits

on

the

frequency

for

which

they

can

be

reimbursed

such

as

mammography

for

cancer

screening

purposes

Home

care

services

The

entitlements

laid

down

in

the

SSC

include

services

provided

by

independent

physicians

-LRB-

home

visits

-RRB-

and

by

other

health

professionals

such

as

nurses

and

hospital-at-home

services

Regarding

palliative

care

at

home

according

to

Article

R

of

the

SSC

a

multidisciplinary

team

of

health

professionals

can

be

organized

at

the

special

request

of

a

person

whose

state

of

health

demands

it

to

provide

palliative

home

care

The

remuneration

can

be

paid

on

a

fee-for-service

basis

or

as

a

lump

sum

Discussion

This

study

faces

a

number

of

limitations

which

may

affect

the

analysis

of

the

French

health

benefit

basket

Firstly

the

study

was

carried

out

in

a

period

of

changes

related

to

the

redefinition

of

the

medical

procedures

for

both

inpatient

and

outpatient

care

This

will

make

some

statements

in

the

previous

catalogue

become

obsolete

Furthermore

the

introduction

of

the

new

CCAM

catalogue

has

been

postponed

several

times

due

to

conflicts

of

interest

between

health

professionals

especially

those

between

the

physicians

unions

and

the

health

insurance

funds

The

catalogue

deals

with

the

two

issues

of

the

remuneration

of

healthcare

professionals

and

the

state

regulation

Secondly

the

recent

health

insurance

reform

-LRB-

Health

Insurance

Act

August

-RRB-

affects

all

actors

involved

in

the

definition

of

the

benefit

catalogue

and

thus

the

decision

criteria

The

High

Health

Authority

for

instance

is

expected

to

have

considerable

powers

At

the

same

time

UNCAM

is

also

playing

an

important

role

in

the

drawing

up

of

the

positive

lists

of

procedures

However

the

ministers

of

health

and

social

security

still

retain

their

right

to

reject

the

UNCAM

's

decisions

It

could

be

asked

whether

the

change

regarding

the

delegation

of

the

task

of

drawing

up

benefit

catalogues

to

a

so-called

self-governing

body

is

fully

effective

as

this

is

the

case

in

Germany

It

is

too

early

to

assess

the

consequences

that

these

new

regulations

will

bring

about

but

it

can

be

anticipated

that

it

might

well

be

a

case

of

plus

ça

change

plus

c’est

la

même

chose

as

both

the

French

government

and

the

physicians

have

always

played

a

major

role

in

the

healthcare

decision-making

process

Thirdly

the

French

system

offers

a

mix

of

explicit

regulation

for

ambulatory

care

pharmaceuticals

and

medical

devices

dental

care

etc.

with

benefit

catalogues

and

positive

lists

and

of

implicit

regulation

for

a

large

part

of

inpatient

care

-LSB-

-RSB-

Altogether

the

package

of

health

care

services

covered

is

comprehensive

and

wide-ranging

although

that

the

additional

billing

is

rather

high

for

certain

types

of

goods

and

services

As

a

consequence

of

the

implicitness

of

the

coverage

with

particular

respect

to

inpatient

care

we

have

noted

some

differences

between

principles

and

practice

indicating

that

not

all

services

are

actually

covered

to

the

same

extent

The

interviews

carried

out

at

the

Ministry

of

Health

confirmed

this

finding

Finally

the

drawing-up

of

the

positive

lists

still

remains

hotly

contested

among

those

at

the

health

and

social

security

ministries

who

were

interviewed

for

this

study

Current

French

health

policy

combines

the

harmonization

of

regulation

with

the

reduction

in

health

inequalities

on

the

basis

of

improved

knowledge

of

public

health

needs

However

this

policy

is

being

implemented

in

a

context

of

increasing

health

expenditure

and

especially

of

increasing

user

charges

It

is

a

contradictory

situation

in

which

things

that

have

been

received

by

the

one

hand

have

again

been

taken

away

by

the

other

one

O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O 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Depth cues , rather than perceived depth , govern vergence We studied the influence of perceived surface orientation on vergence accompanying a saccade while viewing an ambiguous stimulus . We used the slant rivalry stimulus , in which perspective foreshortening and disparity specified opposite surface orientations . This rivalrous configuration induces alternations of perceived surface orientation , while the slant cues remain constant . Subjects were able to voluntarily control their perceptual state while viewing the ambiguous stimulus . They were asked to make a saccade across the perceived slanted surface . Our data show that vergence responses closely approximated the vergence response predicted by the disparity cue , irrespective of voluntarily controlled perceived orientation . However , comparing the data obtained while viewing the ambiguous stimulus with data from an unambiguous stimulus condition -LRB- when disparity and perspective specified similar surface orientations -RRB- revealed an effect of perspective cues on vergence . Collectively our results show that depth cues rather than perceived depth govern vergence . Introduction In vision , binocular fusion is facilitated by vergence . Various different types of horizontal vergence have been distinguished based on inputs used by the vergence system , e.g. binocular disparity and accommodation . One of those , fusional vergence , uses binocular disparity as input . And another , proximal vergence , is associated with `` knowledge of nearness '' -LRB- Howard , 2002 -RRB- . Recently , the influence of depth perception on vergence has regained interest , because of the possibility to probe perception through vergence . In several studies , various depth cues were used to induce depth and the influence of perception on vergence was studied both without and with binocular disparity present . In this study , we investigate whether depth perception per se contributes to vergence . Enright -LRB- 1987b -RRB- measured vergence movements corresponding to the depth relations implied by perspective foreshortening , under monocular viewing conditions . He concluded that the perceived depth suggested by perspective foreshortening could elicit vergence . Ringach et al. -LRB- 1996 -RRB- used the kinetic depth effect to induce perception of depth . They measured vergence , also under monocular viewing conditions , and found that vergence corresponded to depth perceived by the subject . This led them to conclude that perceived depth can elicit vergence . More recently , several studies investigated the influence of perceived depth on vergence in the presence of disparity , i.e. under binocular viewing conditions . Sheliga and Miles -LRB- 2003 -RRB- used Ogle 's induced effect in which vertical disparities give rise to depth . The authors reported that depending on the condition , a maximum of 41 % of the vergence could be attributed to perceived depth . Both et al. -LRB- 2003 -RRB- used Werner 's illusion to induce depth . They reported slight vergence responses corresponding to perceived depth . These results led to the conclusion that perceived depth contributed to the vergence responses .1 However , in all aforementioned studies , depth perception was correlated with stimulus properties , i.e. the depth cues giving rise to the perceived depth . Therefore , the distinction between an effect on vergence caused by perception and an effect due to depth cues could not be made . Thus , it may be possible that signals related to the depth cues contributed to vergence rather than perceived depth itself . To investigate whether perceived depth itself is sufficient to influence vergence , a condition is required in which depth perception is not correlated with both monocular and binocular cues that give rise to the perceived depth -LRB- Allison et al. 1998 ; Gillam 1968 ; Gillam and Ryan 1992 ; Gillam and Cook 2001 -RRB- . The slant rivalry stimulus offers the possibility to dissociate vergence effects due to depth cues from those caused by perceived depth -LRB- van Ee et al. 2002 -RRB- . To create a slant rivalry stimulus , perspective foreshortening and binocular disparity are used to define slanted surfaces . If the cues specify opposite slant orientations , subjects report alternations between perceiving a slanted rectangle and perceiving an oppositely slanted trapezoid -LRB- van Ee et al. 2002 -RRB- . Thus , perceived slant alternates , whereas the depth cues remain constant . Using these slant stimuli , the contribution to vergence predicted by perception is different from that predicted by the depth cues . If perceived depth is sufficient to influence vergence , a difference in vergence should be observed while alternations occur between the two possibly perceived surface slants . However , if perceived slant does not influence vergence , vergence should remain stable regardless of the perceived surface slant orientation . To study the effect of perceived surface slant on vergence , we analyzed saccades made under various stimulus and perceptual conditions . Binocular saccades usually contain a conjugate component -LRB- version -RRB- and a disjunctive component -LRB- vergence -RRB- -LRB- Erkelens et al. 1989 -RRB- . Both components are preprogrammed , thus if perceived depth influences vergence , the disjunctive component should be related to the depth direction specified by the perceived slant . Hence , measured vergence at saccade offset can give insight into the input that drives the vergence system . Methods Experimental setup Stimuli were displayed using a conventional Wheatstone stereoscope consisting of two TFT displays -LRB- 20 ″ LaCie Photon20Vision II , 1,600 × 1,200 , 75 Hz -RRB- and two small mirrors , see Fig. 1 . The mirrors were slanted about the vertical axis at an angle of 45 ° with respect to the display . The virtual intersection point of the orthogonal mirrors was aligned with the center of the displays . Subjects were seated close to the mirrors so that the left eye could not see the right mirror and vice versa . The straight-ahead viewing distance -LRB- eye-mirror-display -RRB- was 57 cm . Subjects ' heads were fixated using a bite-board . Fig. 1Wheatstone stereoscope . Subjects viewed one TFT display with the corresponding eye via one of the mirrors . The viewing distance -LRB- eye-mirror-display -RRB- was 57 cm . Note that the subjects were in reality much closer to the mirrors than depicted here and that there was no crossover , i.e. each eye could only see via one mirror Eye movements were measured using the head-mounted Eyelink I system at 250 Hz . The cameras were positioned beneath the mirrors . The whole setup and experimental room were painted black matte and the room was darkened . Stimuli A stimulus consisted of two images displayed , one on each of the displays . The displayed images were generated using custom Open GL based software . The images used were trapezoidal or rectangular shapes composed of lines and a sparse random dot texture , as shown in Fig. 2 . The images were surrounded by a fronto-parallel sparse random dot background -LRB- not shown -RRB- . Fig. 2An image as shown on one display . Perspective foreshortening indicates a slant of 70 ° . The disparity gradient was produced by horizontally scaling the two eyes ' half images . The red fixation cross is positioned in the center of the stimulus Perspective foreshortening of both images corresponded with a 2D projection -LRB- cyclopean viewpoint -RRB- of a rectangular surface slanted -LRB- ± -RRB- 70 ° about the vertical axis . A horizontal -LRB- binocular -RRB- disparity gradient defined a -LRB- ∓ -RRB- 50 ° slant about the vertical axis , which was produced by scaling the two eyes ' half images horizontally . After scaling , the horizontal angular width of the stimulus was 20 ° for all stimuli independent of the imposed slant angles , see Fig. 3a . The same figure also shows that a counter clockwise rotation -LRB- CCW -RRB- about the vertical axis was defined as a positive slant angle and a clockwise rotation -LRB- CW -RRB- as a negative slant angle . Fig. 3a The subtended angle from center to left or right side of the stimulus was 10 ° -LRB- γ -RRB- irrespective of the imposed surface slants defined by disparity -LRB- D -RRB- and perspective -LRB- P -RRB- . A counter clockwise rotation of the surface about the vertical axis is defined as a positive surface slant angle -LRB- + -RRB- . b Examples of different stimulus conditions . The surface slant angle as defined by disparity was ± 50 ° -LRB- α -RRB- and the perspective defined surface slant angle -LRB- β -RRB- was ± 70 ° . In the unambiguous stimulus , disparity and perspective defined the same surface orientation yielding a stable perception of surface slant -LRB- 1 -RRB- . Whereas in the ambiguous stimulus condition -LRB- 2 -RRB- , the orientations of the defined surfaces were opposite , giving a bistable perception of surface slant Stimulus parameters could define any of the following possibilities : -LRB- 1 -RRB- a pair of trapezoids in which the signs of slant defined by perspective foreshortening -LRB- P -RRB- and disparity -LRB- D -RRB- were equal -LSB- unambiguous stimulus , e.g. P = 70 ° and D = 50 ° , see Fig. 3b -LRB- 1 -RRB- -RSB- or -LRB- 2 -RRB- a pair of trapezoids in which the signs of slant defined by perspective foreshortening and disparity were opposite -LSB- ambiguous stimulus , e.g. P = 70 ° and D = − 50 ° , see Fig. 3b -LRB- 2 -RRB- -RSB- . These physical parameters led to the following perceived slanted surfaces : ad -LRB- 1 -RRB- a slanted rectangle -LRB- stable slant -RRB- or ad -LRB- 2 -RRB- alternations of a slanted rectangle and an oppositely slanted trapezoid -LRB- bistable slant -RRB- . Note that the slant angle defined by the monocular cues is larger than the angle defined by the binocular cues , to produce a sufficient degree of bistability for all subjects . The disparity gradient could not be diminished , as this would deteriorate the signal-to-noise ratio of vergence -LRB- see Sect. 2.5 as well -RRB- . Furthermore , a standing disparity was added to all stimuli , which made all surfaces appear to be positioned in front of the display . A fixation cross was presented in the center of the stimulus . Procedure and tasks Experimental trials consisted of a sequence of five different displayed items . Subjects were first presented with a fixation dot -LRB- used for offline drift correction -RRB- in the center of the display at display depth for 1.5 s -LRB- 1 -RRB- . This dot was replaced by a fixation cross at the location and depth corresponding to the center of the stimulus -LRB- 2 -RRB- . After 1.5 s , the stimulus images were added -LRB- 3 -RRB- . A beep was sounded 2.0 s after stimulus onset . A monocular arrow appeared 2 s thereafter in the left eye 's image -LRB- 4 -RRB- . The screen was blanked after 4 s -LRB- 5 -RRB- . During the trial , subjects were instructed to fixate the cross . When the monocular arrow had appeared , subjects were instructed to make one single saccade towards the side of the surface indicated by the arrow . The arrow always pointed towards the near side of the slanted surface defined by disparity . By doing this the vergence response -LRB- disjunctive part of saccade -RRB- was maximized , because some subjects showed considerably less vergence change when saccades were made towards the uncrossed disparity side of the stimulus . This is in agreement with the effect of version -- vergence ratio on the disjunctive part of the saccade as described by Enright -LRB- 1984 -RRB- . Subjects had to report their percept prior to saccade onset . They were asked to report the perceived nearest side of the stimulus after the beep using a numerical keypad . By reporting which stimulus side they perceived as nearest , subjects implicitly indicated whether they perceived a slanted rectangle or a slanted trapezoid . When viewing a slant rivalry stimulus , subjects report perceiving spontaneous alternations of their percept . In addition , they are able to voluntarily control their perception as well -LRB- van Ee et al. 2002 , 2005b -RRB- . To obtain equal sized data sets for each of both perceptual conditions , we used this ability to voluntarily control perception of the ambiguous stimulus . Thus , subjects were instructed to hold one of both possible perceived surfaces when viewing the bistable stimulus before the experiment started . One experimental block consisted of a total of 16 trials , of which 8 were ambiguous stimuli conditions and the other 8 were unambiguous stimuli conditions . Both conditions were counter balanced for saccade direction and trials were randomized for conditions and saccade directions . Each experimental session contained three to four experimental blocks run consecutively . A calibration was performed , at the start of each block , i.e. every 5 min . Data analysis Raw data provided by the Eyelink system was analyzed off line . We used a custom calibration procedure specifically designed to calibrate the raw data . This procedure consisted of a weighted least square error fit with a third order polynomial -LSB- 35 measurement points , BFGS minimization technique -LRB- Press 1993 -RRB- -RSB- -LRB- van Beers 2007 -RRB- . Offset correction was performed offline for each trial using the data obtained with the first fixation dot . On the calibrated data , saccade detection was performed based on version -LRB- mean gaze angle of left and right eye -RRB- velocity . A saccade was detected when the version velocity was higher than 120 ° / s . The end of the saccade was defined when version velocity dropped below 20 ° / s. Only saccades with an amplitude of at least 7 ° in the indicated direction were analyzed . After the saccade , a slower vergence movement was usually present , vergence calculated as right eye gaze data -- left eye gaze data . This was assumed to be part of the initial preprogrammed vergence . We defined the preprogrammed vergence offset when vergence velocity was minimum within a timeframe of 100 ms after saccade offset and 5 ° / s at the most . We used the data at the point of minimum vergence velocity for further analysis . As we were interested in the vergence difference between the onset and offset of the saccade , we present the data relative to the gaze direction before onset of the saccade . Vergence data were averaged -LSB- three nearest neighbor average -LRB- 24 ms interval -RRB- -RSB- to remove high-frequency noise . Subjects Subjects -LRB- 6 females and 9 males aged between 18 and 30 -RRB- had normal or corrected to normal vision . Before taking part in the experiment , it was checked whether a subject was able to comply with the instructions of the experiment . Not all potential subjects could perceive the trapezoidal interpretation of the stimulus within the timeframe of the experiment -LRB- 2 s -RRB- , when disparity and perspective foreshortening were in conflict . These subjects either had poor stereovision or needed more than 2 s to elicit a voluntary controlled flip . In total eight subjects were excluded from further participation , because it would have been impossible to measure the effect of depth perception on vergence . Results Saccades had normal main sequence characteristics -LRB- amplitudes of about 9 ° , durations of about 56 ms , maximum velocities of about 310 ° / s -RRB- -LRB- Collewijn et al. 1988 -RRB- . Most saccades reached an amplitude of 80 -- 100 % of the amplitude defined by the width of the stimulus . Sometimes a correction saccade was made after about 150 ms. Only a small fraction of saccades -LRB- less than 2 % -RRB- was in the opposite direction as indicated by the monocular arrow presented . Experiment 1 : Contribution of perception of depth to vergence To investigate whether perceived surface orientation contributes to vergence , we analyzed the data obtained during the presentation of the ambiguous stimulus . As mentioned in Sect. 2.3 , we asked subjects to hold one of both possible orientations . In 52 % of the 659 trials subjects reported perceiving a slanted rectangle and the slanted trapezoid was perceived in 48 % of the trials . In 88 % of all trials the percept was in agreement with the instruction given before the experiment started . The data of trials in which they failed -LRB- due to spontaneous or no -LRB- controlled -RRB- flips -RRB- are not included in the data presented here , but were not significantly different from the trials in which subjects were successful in obliging to the instruction . Predictions While the cues remained constant , perceived orientations alternated . Thus , we predict that if perception contributes to vergence , vergence should alternate accordingly . But , if not , the measured vergence changes should be independent of perceived slant orientation . Because we asked subjects to report only the sign of the orientation -LRB- and not the magnitude -RRB- of perceived slant , we can only predict the direction of the vergence changes , as illustrated in Fig. 4a . When subjects perceived the trapezoid -LRB- disparity-based percept -RRB- , the saccades were directed towards the near side of the perceived surface , whereas saccades were directed towards the far side when subjects perceived the rectangle -LRB- perspective-based percept -RRB- . Consequently , the vergence changes predicted by perception are in the converging direction -LRB- blue area -RRB- when subjects perceived a trapezoid and in the diverging direction -LRB- red area -RRB- when they perceived the rectangle . The upper and lower limits of the predicted vergence regions in Fig. 4a are defined by the vergence based on a zero depth change -LRB- grey line -RRB- and a vergence change based on the maximum slant defined by either depth cue : disparity -LRB- perception of trapezoid , blue line -RRB- or perspective -LRB- perception of rectangle , red line -RRB- . Fig. 4a Predicted vergence changes based on perceived surface slant orientation . The transitions between vergence at saccade onset -LRB- t = 0 ms -RRB- and at saccade offset are described using a sigmoid function . The upper and lower limits of the predicted vergence regions are based on the vergence step corresponding with the depth defined by a single cue . The box indicates the range of the detailed graphs in b. b Vergence changes based on perceived surface slant orientation of subject S6 -LRB- top -RRB- and subject S1 -LRB- bottom -RRB- . Mean traces for each condition with SE of every fourth data point are displayed . Saccade offset occurred at 55 ms for S6 and at 46 ms for S1 conform main sequence characteristics -LRB- saccade onset at t = 0 ms -RRB- . These data show that -LRB- 1 -RRB- saccade offset does not coincide with offset of preprogrammed vergence per se , -LRB- 2 -RRB- that the `` perception of rectangle '' condition is more converging than the `` perception of trapezoid '' condition from S6 , which is opposite to the traces of S1 Results Figure 4b shows representative vergence traces from the `` perception of trapezoid '' and `` perception of rectangle '' conditions . These vergence traces are means of 25 trials at the least , with standard error -LRB- SE -RRB- displayed at every fourth data point . Saccade onset -LRB- t = 0 ms -RRB- has been used to align the individual vergence traces for calculating the mean . Saccade offset occurred at t = 55 ms for S1 and at t = 46 ms for S6 , which is in accordance with main sequence characteristics . Figure 4b shows that at this point in time , the preprogrammed vergence movement has not ceased . Preprogrammed vergence offset was determined for individual traces -LRB- see Sect. 2.4 -RRB- and can not be pinpointed exactly in these graphs . Preprogrammed vergence offset typically occurred at t = 120 ms -LRB- ± 30 ms -RRB- , at which point the vergence velocity -LRB- mean of all subjects -RRB- was 0.2 ° / s -LRB- SD = 0.15 ° / s -RRB- . The diverging movement present in the onset of the saccades is commonly observed in most conjugate saccades and caused by temporal/nasal eye movement differences -LRB- Collewijn et al. 1988 -RRB- . As Fig. 4b shows , the vergence changed in the converging direction for both perceptual conditions . Moreover , all subjects showed converging responses . Thus , if subjects perceived a slanted trapezoid , vergence was in the same direction as the perceived orientation of the surface . And , if they perceived a slanted rectangle , the direction of vergence was opposite to the perceived orientation of the surface . This indicates that the contribution of perceived orientation to vergence , if any , is small . When comparing the data traces with the predictions in Fig. 4b , it is clear that the measured vergence changes are close to the value predicted by the disparity cue -LRB- blue dotted line -RRB- . This result suggests that the largest contribution to vergence is related to the disparity cue . To investigate the magnitude of the effect of perceived orientation on vergence , we further analyzed the data of all subjects , starting with selecting the end of the preprogrammed vergence movement as described in Sect. 2.4 . We then normalized the data , using the calculated prediction based on the disparity cue , thereby effectively removing the variability caused by the interocular distance .2 These normalized data are presented in Fig. 5a . Because these data show individual biases -LRB- e.g. S4 -RRB- , we used the difference between the two conditions tested for calculations on group data -LRB- see Fig. 5b -RRB- . The data of leftward -LRB- bottom -RRB- and rightward -LRB- top -RRB- saccades are shown separately , because individual biases varied across these conditions -LRB- e.g. for S4 -RRB- . ANOVA statistics on individual and group data showed that there was no significant difference between the two investigated conditions -LRB- except for S1 leftward saccade , see Fig. 5 caption -RRB- , thereby rejecting the hypothesis that perceived orientation influences vergence . Thus , vergence is independent of perceived orientation . Fig. 5a Vergence -LRB- mean and SE selected as described in Sect. 2.4 -RRB- relative to predicted vergence based on the disparity cue -LRB- 0 on vertical axis -RRB- from leftward saccade trials -LRB- bottom -RRB- and rightward saccade trials -LRB- top -RRB- . These data show that -LRB- 1 -RRB- there are individual biases -LRB- e.g. S4 -RRB- , -LRB- 2 -RRB- the `` perception of rectangle '' -LRB- red circle -RRB- is not less convergent than the `` perception of trapezoid '' -LRB- blue pentagon -RRB- condition for all subjects -LRB- e.g. S2 , S5 -RRB- and both directions -LRB- e.g. S4 , S6 -RRB- , rebutting the predictions based on perception . b Vergence -LRB- mean and SE selected as described in Sect. 2.4 -RRB- relative to `` perception of a trapezoid '' condition -LRB- 0 on vertical axis -RRB- . On the right side of these graphs the mean -LRB- and SE -RRB- of all subjects is shown . There is no systematic trend visible across subjects . All differences are nonsignificant except for S1 , leftward saccade -LRB- F = 6.36 , P < 0.05 -RRB- Experiment 2 : Contribution of depth cues other than disparity to vergence The results from experiment 1 show that perceived orientation does not influence vergence . Still , as stated in the introduction , cues other than disparity may contribute to vergence . We investigated this hypothesis by analyzing the data from the ambiguous stimulus and the unambiguous stimulus presentations . Predictions For both conditions the disparity defined slant was identical . In the unambiguous stimulus , the orientation of slant angle defined by perspective foreshortening was identical to the one defined by disparity , whereas it was opposite in the ambiguous stimulus . Thus , if perspective contributes to vergence , we predict that the vergence change of the ambiguous condition should be less convergent than that of the unambiguous condition . But , if not , vergence should be independent of the stimulus presented . Predictions of vergence changes based on slant cues are illustrated in Fig. 6a . For both conditions , the disparity cue signaled a slant of 50 ° in magnitude and as saccades were directed towards the crossed disparity side of the stimulus , the corresponding predicted vergence change converges -LRB- blue dotted line -RRB- . The perspective cue signaled a slant of 70 ° in magnitude in both conditions . In the unambiguous condition , the vergence change predicted by perspective converges -LRB- green dashed line -RRB- and consequently , the predicted vergence change in the ambiguous condition diverges -LRB- red line -RRB- . Fig. 6a Predicted vergence changes based on the slant cues of the stimulus . The predicted values are based on the depth defined by a single cue . Details similar as in Fig. 4 . b Vergence changes from ambiguous and unambiguous stimulus trials of subject S6 -LRB- top -RRB- and subject S1 -LRB- bottom -RRB- . Mean traces of each condition with SE of every fourth data point are displayed . Saccade offset occurred at 56 ms for S6 and 46 ms for S1 -LRB- saccade onset at t = 0 ms -RRB- . These data show that the vergence step of the ambiguous stimulus condition is less convergent than the vergence step of the unambiguous stimulus condition for both subjects Results Figure 6b shows representative traces of the unambiguous and ambiguous stimulus conditions . The vergence traces are means of 25 trials at the least with the SE displayed at every fourth data point . The characteristics of these vergence traces are similar to the traces in Fig. 4b . The vergence traces in Fig. 6b both converge towards the predicted value based on the disparity cue , see Fig. 6a -LRB- blue dotted line -RRB- . Thus , the contribution to vergence that can be related to disparity is relatively large , consistent with the results described before . We further analyzed the data to investigate whether there was a significant effect of the perspective cue on vergence , using the same method as described in the previous subsection . Figure 7a shows the normalized data , whereas Fig. 7b displays the data from the ambiguous condition relative to the data from the unambiguous condition including the group means . Leftward -LRB- bottom -RRB- and rightward -LRB- top -RRB- saccades are shown separately . ANOVA statistics on group and individual data show that there is a significant difference between the ambiguous and unambiguous condition . The statistics for group data are : leftward saccades -LRB- lw -RRB- -LRB- difference = 0.14 ° , F = 13.04 , P < 0.05 -RRB- and rightward saccades -LRB- rw -RRB- -LRB- difference = 0.16 ° , F = 62.89 , P < 0.001 -RRB- . And for individual subjects : S0 lw -LRB- F = 11.29 , P < 0.01 -RRB- , S1 lw -LRB- F = 14.50 , P < 0.001 -RRB- and rw -LRB- F = 4.04 , P < 0.05 -RRB- , S2 lw -LRB- F = 25.22 , P < 0.0001 -RRB- and rw -LRB- F = 24.14 , P < 0.0001 -RRB- , S4 lw -LRB- F = 24.84 , P < 0.0001 -RRB- , S6 lw -LRB- F = 5.22 , P < 0.05 -RRB- and rw -LRB- F = 11.02 , P < 0.01 -RRB- . Fig. 7a Vergence -LRB- mean and SE selected as described in Sect. 2.4 -RRB- relative to predicted vergence based on the disparity cue -LRB- 0 on vertical axis -RRB- from leftward saccade trials -LRB- bottom -RRB- and rightward saccade trials -LRB- top -RRB- . Note that -LRB- 1 -RRB- there are some large individual biases , -LRB- 2 -RRB- that the ambiguous condition -LRB- purple triangle -RRB- is consistently less convergent than the unambiguous condition -LRB- cyan square -RRB- , supporting the predictions based on slant cues . b Vergence -LRB- mean and SE -RRB- relative to unambiguous condition . On the right side of these graphs the mean of all subjects is shown . The systematic trend visible between and across subjects is significant for the whole group -LRB- leftward saccades : F = 13.04 , P < 0.05 and rightward : F = 62.89 , P < 0.001 -RRB- . All significant differences are denoted by a star -LRB- values are stated in text -RRB- Thus , perspective , or signals related to it , significantly contributed to vergence . Discussion Our findings show that depth cues rather than depth perception itself contribute to vergence accompanying saccadic movements . Perspective being congruent or incongruent with disparity caused a difference of about 14 % in vergence changes predicted by disparity alone . Although our results show that vergence remained constant in the ambiguous stimulus condition , subjects perceived alternations of surface orientation . Collectively , these results show that perspective and disparity are each weighted differently for perception and vergence . Binocular studies Our result on the influence of perception on vergence refines the conclusions of previous studies relating perception and vergence -LRB- Sheliga and Miles 2003 ; Both et al. 2003 -RRB- . These studies investigated the influence of perception on vergence under binocular viewing conditions , similar as in our study . However , contributions of perception of depth to vergence could not be dissociated from those of depth-inducing cues . This dissociation was possible in our study . We found that , perspective contributes to vergence , independent of its perceptual effect . This conclusion suggests that vertical disparities -LRB- Sheliga and Miles 2003 -RRB- , global horizontal disparities -LRB- Both et al. 2003 -RRB- and perspective -LRB- present study -RRB- contribute to vergence similarly as local horizontal disparities do , albeit to a lesser extent . Monocular studies The perspective studies of Enright -LRB- 1987a , b -RRB- show that vergence occurs corresponding to the depth implied by -LRB- linear -RRB- perspective under monocular viewing conditions . Enright concluded that the perceived depth contributed to vergence . However , in light of the present study , his results show that depth cues contribute to vergence under monocular viewing conditions as well . Moreover , without the dominantly contributing factor -LRB- disparity -RRB- being present , other depth cues become the main contributors to vergence . The Necker cube study of Enright -LRB- 1987a , b -RRB- and the ambiguous rotating sphere study of Ringach et al. -LRB- 1996 -RRB- seem to provide similar stimulus conditions as our experiment . The single depth cue used induced alternations in depth perception . In both studies corresponding alternations in vergence were measured and both authors conclude that depth perception induced vergence . However , each depth cue used in these studies was inherently ambiguous . Thus , in these studies , the contribution of perception of depth to vergence could again not be dissociated from the contribution of the depth cues themselves . Taking the present study into consideration , there is evidence that their results reflect the alternations of the depth cue related signals and not those related to perception . In view of this conclusion , the fact that the vergence changes measured by Enright in the Necker cube experiment were much smaller than those in the linear perspective experiment may be explained by a degradation of the signals related to the depth cues due to the ambiguity herein . Influence of perception on other visual phenomena Our results indicate that vergence is influenced by low-level -LRB- sensory -RRB- processes and not by high-level -LRB- voluntary control -RRB- processes . Studies on bistability -LRB- van Ee et al. 2005b , a ; Toppino 2003 -RRB- show that high-level mechanisms can influence perception , whereas , as shown in the present study , they do not influence vergence . A recent study by Knapen and van Ee -LRB- 2006 -RRB- shows that slant adaptation is not influenced by perception or by voluntary control of perception , but is solely based on depth cues in the -LRB- slant rivalry -RRB- stimulus . Thus , both adaptation and vergence are influenced by low-level mechanisms , but not by high-level mechanisms . Different weighting of cues for vergence and perception To explain the current results and those of Enright -LRB- 1987a , b -RRB- and Ringach et al. -LRB- 1996 -RRB- , a single 3D surface representation used for perception and binocular eye movements as suggested by Ringach et al. -LRB- 1996 -RRB- is inappropriate . The perceptual states and the alternations thereof are not reflected in the vergence responses , suggesting that two separate representations are used for perception and eye movements . Moreover , the present results suggest that the weights assigned to signals related to monocular and binocular depth cues are different for perception and vergence , resulting in either alternating or stable outcomes respectively , see Fig. 8 . These outcomes may construct two separate 3D space representations one used for perception and the other for vergence or , as an alternative , one 3D representation for perception whereas the signals for vergence are directly wired to the oculomotor system . However , in the latter situation the monocular signals must still be disambiguated before the motor command can be given to reorient the eyes . Fig. 8Perception and vergence are based on separate processing streams . Both monocular cues -LRB- such as relative motion , linear perspective , blur and looming -RRB- and binocular cues -LSB- such as horizontal disparity -LRB- global and local -RRB- and global vertical disparity -RSB- are used for perception as well as for vergence . The weights assigned to the individual cues might be different when used for perception than when used for vergence , resulting in different outcomes . In the present study , for example , the ambiguous stimulus yields a bistable perception of surface slant , whereas it yields a stable vergence angle . Cognitive factors , such as voluntary control , do not seem to exert influence on vergence , but they do influence perception Perception and action Our results constitute another example of a dissociation between perception and action systems as suggested by Goodale and Milner -LRB- 1992 -RRB- . Since then evidence supporting a dissociation has been accumulating , for a review see Goodale and Westwood -LRB- 2004 -RRB- , Carey -LRB- 2001 -RRB- and Bruno -LRB- 2001 -RRB- . Haffenden and Goodale -LRB- 2000 -RRB- and Haffenden et al. -LRB- 2001 -RRB- have shown that there are conditions in which perception has no influence on action , whereas other studies -LRB- Erkelens and Collewijn 1985 ; Masson et al. 1997 ; Schreiber et al. 2001 ; Banks et al. 2001 ; van Ee and van Dam 2003 -RRB- have shown that conditions exist in which eye movements have no influence on visual perception . On the other hand , some studies conclude that action is influenced by perception -LRB- Franz et al. 2000 , 2001 ; Franz 2001 ; Smeets et al. 2002 ; Lopez-Moliner et al. 2003 ; de Grave et al. 2006a , b ; Bernardis et al. 2005 ; Knox and Bruno 2007 -RRB- . As we have shown all depth cues are used by the vergence system . The use of pictorial depth cues by other motor systems could perhaps explain this incongruence . Conclusion Our findings show that depth cues rather than perceived depth govern vergence that accompanies saccades . Perspective being congruent or incongruent with disparity caused a 14 % difference in vergence change . These results combined with other studies show that in addition to local horizontal disparity , also global disparity , relative motion and perspective are used as input by the vergence system . Furthermore , our findings suggest that monocular and binocular cues are weighted differently for perception and vergence .

O O O O O O O O O B O O O O O O O O O B O O O O O O B O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O B O O O O B O O O O B O O O O O O O O O O O O O O O O O O B O O O O O O O O O O B O O O O O O O O O O O O O O B O O O O O O O O O O O O O B O O O O O O O O O O B O O O O O O B O O O O O O O O O B O O O O B O O O O O O O O B O O O B O O O O O O O B O O O O O O O O O O O O O O O O O O O O B I O B O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O B O O O O O O O B O O O O O O O O O B I O O O O B O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O B O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O B O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O B O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O B O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O B O O O O B O O O O O O O O O O O O O O O O O O O O O O B O B O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O 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O O B O O O O O O O O O O O O B O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O B O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O B O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O 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O O O O B O O O B O O O O O O O O O O O B O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O B O O O O O O O O B O O O O O B O O O B O O O O O O O O O O O O O O O O O B O O O O O O O O O O B O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O B O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O B O O O B O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O B O O O O O O O B O O O O O O O O O O O O O O O O O O O B O O O O B O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O B O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O B O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O B O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O B I O O O B O O O O O O O O O O B O O O O O O O O B O O O B O O O O O O O B O O O O B O O O O O O O O O O O O O O O O O O B O O O O O O O B O O O O O O O O O O O B O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O B O O O O O O O O O O O O B O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O B O O O O O O O B I O B O O O O O O O O O O O O B O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O B O O O O O O O O O B O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O B O O O O O O B O O O O O O O O O O O O O O O B O O O B O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O B O

depth perception
vergence
disparity
ambiguous