150- 150
taok STIMULUS: 4°/ SEC? for 24 SEC laoL STIMULUS: 3°/SEC? for 24 SEC
130 NeS 130b Ne6
120 120F
3 110F 110F
$ oof 1ooF
2 90h —A DARK TRIAL gof
2
= eof sof
8 ° LIGHT TRIAL
wo 7oF (12 SEC LIGHT) Toh
TM — 6oF O----O LIGHT TRIAL eof
« (18 SEC LIGHT)
— sor sor
a
o  4r 4ob
in] 30F 30F
iva
gS _ 20f zo
2 & of to}
5
5 ° °
= & !0Pciowrs on 10
a :
5 aol ; L
§ 8 20 a 0 aera
Si L i L /
5 30 A, 30 ' i y A ¢
a 40r 40h i a y iY
y sob sob \ !
2 1
E  eoy 60 \
al
8 70 TOP Wa
> 80F 80F ‘
2 1
90F 90h \
1ooF look ‘
110F at
aVeUu EWE TUE EWE WESEUENUEUNNESENTSUS FUTNTSUSOTES] eaW SOUS Fae FET SVSNUS EOE POO SNTENT]
9 18 27 36 45 54 63 72 81 90 99 [0B IIT 126 136 144 153 9 18 27 36 45 54 63 72 81 90 99 10BII7

TIME IN SECONDS

Fiaure 10, Average ssubjective displacement in degrees of experienced turning for “dark” and for “light” trial

decelerations of 3°/sec? and 4°/sec? for Group C. Markings are similar to those in Figure 1.

One subject

was not included in data averages for the 4°/sec? stimulus due to his failure to provide complete signals

during the “dark” trial,

tion can be centrally integrated and enhance this
ongoing, opposed reaction.

The above view may also account for those
cases (25% of the comparisons) in which less
secondary nystagmus was demonstrated (al-
though the responses were still strong) following
room illumination than during trials in total
darkness. Subjects in this category appeared to
share two characteristics: on the average, they
had (1) more primary nystagmus (slow-phase
displacement) and (2) more secondary output
during their “dark” trials as compared with sub-
jects whose secondary mystagmus was increased
following periods of room illumination. For

12

Compare with Figures 7, 8, and 9.

both of these subject-groupings, the introduc-
tion of visual stimulation reduced the primary
nystagmic output by approximately the same
proportions but, of course, the amount of the
reduction was greater for one group than for
the other. It is possible that a combination of
high primary and secondary output in total dark-
ness reflects a delay in the release of the secon-
dary reaction. Thus, the primary responses may
be relatively unopposed (and therefore high in
magnitude) while the secondary response, being
released relatively late (perhaps very near the
end of the primary nystagmus), may appear
particularly vigorous. In these cases, visual in-


“dark” trial always preceding the “light” trial
for a given magnitude of angular stimulus.
“Dark” trials were the same for Groups A and
B; the “light” trials differed with respect to
visual conditions during deceleration (see Figure
1). The “light” trial decelerations for Group A
began with a 6-sec period of total darkness

followed by 12-sec of full-room illumination
(during which the subject saw his direction and
slowing speed of angular motion) ; the remaining
6 sec of deceleration and a period of 3-6 min at
a standstill were in total darkness. For Group
B, the first 18 sec of deceleration occurred in full-
room illumination, followed by 6 sec of decelera-

‘Taste 1. Order of stimulus presentation for Groups A and B, Acceleration and deceleration stimuli were always
24 see in duration. “Dark” ‘trials were in total darkness; “light” trials were in darkness with the exception
of the middle 12 see of the deceleration period for Group A and the first 18 sec of deceleration for Group B,
during which time the room was illuminated. For a given stimulus rate, a dark trial always preceded a light

trial.
Trials
Subjects 1 2 3 4 5 6

Group A Group B Dark Light Dark Light | Dark Light
> BM z BR 1°/sec? 3°/sec? 5°/sec?
é AW é MH 3°/sec? 5°/sec? 1°/sec*
2 RM FS MK 5°/sec? 1°/sec® 8°/sec?
2 RR 4 LT 1°/sec? 5°/sec® 38°/sec®
4 LM Z LM 3°/sec? 1°/sec? 5°/sec®

TB JH 5°/sec? 3°/sec? 1°/sec?

Taste 2. Order of stimulus presentation for Group ©. Acceleration and deceleration stimuli was always 24 sec

in duration. “Dark” trials were in total darkness; oth
middle 12 sec of the deceleration period or the first 18

er trials were in darkness with the exception of the
sec of the same period, during which time the room was

illuminated. Subjects received three trials each at 3°/sec? and 4°/sec? with the deceleration conditions pre-

sented in the order listed.

Deceleration Conditions

Subject Trials en )
JB 1-3 3
4-6 4
DG 1-3 3
4-6 4
MD 1-8 4
4-6 3
MC 1-3 4
4-6 3
Js 1-8 3
4-6 4
PC 1-3 4
4-6 3

18-sec light; 12-sec light; dark
12-sec light; 18-sec light; dark
dark; 18-sec light; 12-sec light
18-see light; 12-sec light; dark
dark; 18-sec light; 12-sec light
12-sec light; 18-sec light; dark
18-sec light; dark; 12-sec light
12-sec light; dark; 18-sec light
dark; 12-sec light; 18-sec light
12-sec light; dark; 18-sec light
dark; 12-sec light; 18-see light
18-sec light; dark; 12-sec light



ondary nystagmus is related to duration of stim-
ulation or to duration of the primary response.*+*
However, a systematic exploration of stimulus
rate-duration combinations has not been under-
taken and it seems possible that acceleration rate
may also be a factor (compare the occurrences of
both nystagmic and subjective secondary reac-
tions obtained here following 3°/sec? stimuli for
20 sec with those following 10°/sec? stimuli for
12 sec). In any event, it seems clear that at least
certain kinds of visual stimulation can exert
strong influences on secondary responses of both
nystagmus and sensation. The kind of visual
input which has been demonstrated as effective
in this regard is that which makes available in-
formation about objects fixed with reference to
the earth.°*° That is, the curtailment of primary
nystagmus and primary sensations and most
often some enhancement of secondary reactions
occur as a result of either still-fixation on an-
chored objects or conflicting visual information
regarding those same objects (optokinetic nys-
tagmus or visual observations of the true direc-
tion of turn, both of which oppose the vestibular
signals). Visual stimulation, of itself, does not
appear sufficient. to produce these effects, e.g., a
target light which rotates with the subject does
not obviate the turning sensation (although it re-
duces at least’ the amplitude of nystagmus).
Further, Mowrer noted that reversing normal

16

vision and the normal direction of optokinetic
nystagmus (with a prismatic pseudoscope)
during rotation, so that the response was in the
same direction as the vestibular reaction, had no
effect on the duration or strength of the post-
rotational nystagmus (comparisons were made
with responses following the exclusion of vision
during rotation). He did not report secondary
effects but they were also unlikely to be observed
since he examined all post-rotational responses in
a lighted room. It appears that the element of
conflict between vestibular and visual signals
(and perhaps others of a sensory nature) is re-
quired to produce these alterations in the vestib-
ular reaction (see also‘).

Vv. Summary.

Visual information in conflict with vestibular
signals was presented to groups of subjects by
illuminating the test room for brief periods
during angular deceleration, or immediately
after termination of deceleration. Trials were
otherwise in total darkness. Both primary nys-
tagmus and primary subjective reactions were
markedly shortened during the periods of dark-
ness subsequent to the intervals of light. In ad-
dition, strong secondary reactions (nystagmic
and subjective) frequently followed the vision-
attenuated primary responses.


3 7, 70
s STIMULUS: 4*/ SEC? for 24 SEC STIMULUS: 3*/ SEC? for 24 SEC

z 6 65

60 Nr6 60 N-6

= 55) 55

8

B50) 50

45 45)

& 40 a—A DARK TRIAL 40

a 35 35)

o @--@ LIGHT TRIAL

G30 (12SEC LIGHT) 30)

= 2 O---0 LIGHT TRIAL 25)

g ® (18 SEC LIGHT)

a 20 20

Q's 15)

z BI 10]

fis 5

ot re

5° ° ———

wis st vow ow AY

2 810 10) “NV

z*\5 15]

_ WOTEUVEUUEVERUT ESTE YUTTNTSOTEVUSUSNVS EYE TTSTTN TE TENIVE] SUUNWENESETETEVEEVITOSOSU SOO TOV ETT OST ENT TOT ETT)
& 9 18 27 36 45 54 63 72 BI 90 99 108 119 126 135 144 153 162 171 180 9 18 27 36 45 54 63 72 BI 90 99 108 II7 126 135144
ba

e TIME IN SECONDS

Fieure 6. Average slow-phase nystagmus for “dark” and for “light” trial decelerations of 3°/sec? and 4°/sec? for
Group C. Markings are the same as in Figure 1.

STIMULUS: 1° /SEC? for 24 SEC
N*6

TOP

ao
o5

4—A DARK TRIAL

aes
o0

O-—O LIGHT TRIAL
20F (12 SEC LIGHT)

LEFT

STIMULUS: 1° /SEC? for 24 SEC

70r

so N*6

50F

aot a&—4 DARK TRIAL
30h

-D LIGHT TRIAL
20r (18 SEC LIGHT)

1OF

Bw
36
1

SUBJECTIVE DISPLACEMENT

Peediidististirtiitistiitiitiiiitis

———
TOLLIGHTS ON

q
20h VP i
Vio\
30 Vv vad

4ot

Lesdiitististiiiistiitisiiitiitiet

DEGREES PER 3-SEC INTERVAL
RIGHT
So 0
5
a
24.
es

1
9 18 27 36 45 54 63 72 81 90 99 108 II7
TIME

totis
9 18 27 36 45 54 63 72 81 90 99 108 II7 126 135
IN SECONDS

Ficure 7, Average subjective displacement in degrees of experienced turning for “dark” and for “light” trial
decelerations of 1°/sec* for Group A (12-sec light) and Group B (18-see light). Markings are similar to those
in Figure 1. The primary sensation to the CW decelerations in darkness would be rotation to the left; visual
information during the periods of light frequently produced reversals in the perceived direction of turning

during the subsequent periods of darkness,

tive in this regard than either the 1°/sec? or the
5°/sec? decelerations. At the 5°/sec? stimulus
level, there was more of a tendency for the pri-
mary raction (apparent rotation to the left) to
occur during the last 6 sec of the stimulus or

following stimulus termination, ie, at the
highest stimulus magnitude the vestibular signals
appeared more effective in reinstating the pri-
mary subjective reaction following the period of
room illumination. For Group C, the 3°/sec?


secured around the chair so that a seated sub-
ject was totally enclosed but could see the walls
of the room when lights were turned on. Each
of 12 subjects was exposed to 8 visual conditions
at 2 stimulus rates (3°/sec? for 20 sec and
10°/sec? for 12 sec) as indicated in Table 3. For
both rates, subjects were rotated (a) in total
darkness; (b) with room lights on during the
first 14 see (3°/sec®) or first 6 sec (10°/sec?) of
the decelerations (ie., similar to the 18-see light
trials depicted in Figure 1, the last 6 sec of the
deceleration and the subsequent periods of stand-
still were in total darkness); and (¢) in total
darkness with the exception of a 3-sec period of
room illumination beginning one sec after the
end of deceleration (i.e. during the period of
standstill, see Figure 2).

Subjects were instructed to signal the onset of
their turning sensation by depressing the micro-
switch in their right hand if they perceived
turning to the right, or by depressing the micro-
switch in their left hand if the perceived di-
rection of turn was to the left. They then sig-
nalled each experience of turn through 90° angles
and the termination of these sensations by de-
pressing the appropriate switch. For experi-
mental trials in which the room was illuminated
during deceleration, the subjects were instructed
simply to watch the room walls and when the
lights were again turned off, to resume signalling
any further experiences of angular motion while
calling out the direction of their turning sensa-
tion. Many subjects, however, made signals
during the period of light.

For trials in which the room lights were turned
on for 3 sec during the period of standstill fol-
lowing deceleration (Group D only), subjects
were told actively to fixate on wall markers
during the interval of light and to resume sig-
nalling their sensations when the lights went
out.

Since all experimental trials were rotations in
a CW direction, subjects experienced turning to
th left at an increasing rate during decelera-
tions in total darkness; during periods of room
illumination during deceleration, they could see
that the direction of rotation was to the right
and that the velocity of turning was decreasing.
The deceleration stimulus in darkness also pro-
duced nystagmus with fast-phase to the left;
with illumination of the room during decelera-

tion, an optokinetic nystagmus was produced
with fast-phase to the right.

Scoring. Only deceleration data were scored.
Tracings were marked off in 3-sec intervals
(backwards through the stimulus period and ”
forward through the post-rotatory period) from
the point at which the deceleration ended and
the chair reached a complete standstill. Slow-
phase eye deviation was measured by summing
the slow-phase displacements of each nystagmic
beat, from peak to base-line, in each 3-sec in-
terval. These values were converted to degrees
of eye movement with a calibration factor ob-
tained prior to each trial (subjects moved their
eyes through a known arc across a specially con-
structed device). Subjective responses were also
scored in 8~sec intervals. Since each. signal rep-
resented 90° of experienced angular movment,
degrees of apparent displacement were readily
calculated.

III. Results and Discussion.
Groups A, B, AND C

Nystagmus. Mean slow-phase measures for

- Groups A and B were plotted in Figures 3, 4,

and 5 for stimulus magnitudes of 1°/sec*, 3°/sec”,
and 5°/sec?, respectively. For each group a
“dark” and a “light” trial were plotted on the
same graph for comparison purposes.

Data for Groups A and B were similar.
During “dark” trials a rise in nystagmic output
generally occurred throughout the deceleration
stimulus followed by a response decay during
the period of standstill. Primary nystagmus
eventually gave way to generally weak secon-
dary nystagmus in 24 of the 36 “dark” trials.
During “light” trials, primary vestibular nys-
tagmus quickly replaced the optokinetic responses
generated by watching the walls of the room
during part of the deceleration, increased during
the remaining 6 sec of stimulus in total darkness,
and then decayed in the standstill period. The
primary response following the period of room
illumination was clearly of lower magnitude than
that which occurred during comparable time
periods in the “dark” trials, i.e, although primary
nystagmus recommenced in the dark following
the interval of light, it did not reach the output-
level of the “dark-trial” responses. Further, the
duration of the primary response was signif-
icantly shorter and the onset of the secondary re-



Taste 38. Order of stimulus presentation for Group D. Stimuli were 3°/sec? for 20 sec and 10°/sec? for 12 sec.

Dark trials were in total darkness.

Other trials were in darkness with the exception of (a) the first 14 sec

of the 3°/sec? deceleration, (b) the first 6 sec of the 10°/sec* deceleration, (c) 3-sec periods beginning one
sec after the termination of deceleration while the subject was at a standstill (stst); during these intervals
the room was illuminated. Subjects received three trials each at 8°/sec* and at 10°/sec* with the decelera-
tion conditions presented in the order listed. For half of the subjects, trials 1-8 were at 3°/sec? and trials
4-6 were at 10°/sec?; the order was reversed for the remaining six subjects,

Stimulus
Rate
Subject Trials Subject Trials (°/sec?) Deceleration Conditions
BD 1-3 JP 4-6 3 dark; 14-sec light; 3-sec light (stst)
4-6 1-3 10 dark; 6-sec light; 3-sec light (stst)
GL 13 ML 4-6 3 14-sec light; 3-sec light (stst) ; dark
4-6 13 10 6-sec light; 3-see light (stst) ; dark
PH 1-3 DV 4-6 8 3-sec light (stst); dark; 14-sec light
4-6 1-3 10 3-sec light (stst) ; dark; 6-sec light
RW 1-3 BI 46 3 dark; 3-sec light (stst) ; 14-sec light
46 1-3 10 dark; 3-sec light (stst); 6-sec light
CP 1-8 RK 4-6 3 14-sec light; dark; 3-sec light (stst)
4-6 13 10 6-sec light; dark; 3-sec light (stst)
RM 1-3 CH 4-6 3 3-sec light (stst) ; 14-sec light; dark
4-6 1-3 10 3-sec light (stst); 6-sec light; dark

tion and 3-6 min at a standstill in total darkness.
Groups A and B thus differed in two respects:
(1) Group B was exposed to a longer period of
room illumination during decelerations (18 sec
vs. 12 sec); (2) Group A could experience mo-
tion to the left during the first 6 sec of decelera-
tion (in darkness) and then have this perception
visually corrected during illumination of the
room, whereas Group B was exposed to illumina-
tion at the moment the deceleration began, and
thus could not have an initial sensation of turn-
ing to the left.

To clarify some results obtained from Groups
A and B, Group C was given trials (a) in total
darkness, (b) with the 12-sec light period, and
(c) with the 18-sec light period, at stimulus rates
of 8°/sec? and 4°/sec? for 24 sec durations. A
counterbalanced order of presentation was used
as indicated in Table 2.

Group D provided additional information re-
garding the influence of visual stimulation on
vestibular responses. For complete assurance
that the subjects were not influenced by breeze
cues, a small cabin with a wide window was

3-SEC LIGHT TRIALS

CW Accel

3°/sec® for 20 sec or
10°/sec for 12 sec

Constant Velocity (3-6 min)

CW Decel

3°/sec® for 20 sec or
10% sec? for 12 sec

Standstill (3-6 min)

LIGHT 3 sec

Figure 2, The still-fixation light condition used for Group D.

4


am

4.

e

~

. Brown, R. H. and Guspry, F. EL:

; Cortins, W. E.:

. Contins, W. E.:

3. GuEpRY, F, EL:

REFERENCES

. AscHan, G. and Berestepr, M.: The Genesis of

Secondary Nystagmus Induced by Vestibular Stimuli.
Acta Soc. Med. Upsal., 60:118, 1955.

Influence of
Visual Stimulation on Habituation to Rotation. J.

gen, Psychol., 45:151, 1951.

Task-Control of Arousal and the
Effects of Repeated Unidirectional Angular Accelera-
tion on Human Vestibular Responses. Acta Oto-
laryng., Suppl. 190, 1964.

Coins, W. E.: Vestibular Responses from Figure
Skaters. Aerospace Med., 37:1098, 1966.

Special Effects of Brief Periods
of Visual Fixation on Nystagmus and Sensations of
Turning. Aerospave Med., 39:257, 1968.

Coutins, W. E. and Guxpry, F. E.: Duration of
Angular Acceleration and Ocular Nystagmus from
Cat and Man. I. Responses from the Lateral and
the Vertical Canals to Two Stimulus Durations.
Acta Otolaryng., 64 :873, 1967.

Dover, R.: Adequacy of Reflex Compensatory Eye-
Movements Including the Effects of Neural Rivalry
and Competition, J. ewp. Psychol., 6:169, 1923.

The Effect of Visual Stimulation
on the Duration of Post-Rotational Apparent Motion
Effects. J. gen. Psychol., 48 :313, 1950.

Gurvry, F. BE, and Coutins, W. E.: Duration of
Angular Acceleration and Ocular Nystagmus from
Cat and Man. II. Responses from the Lateral

17

10.

1.

12,

13.

14,

15.

16.

17.

Canals to Varied Stimulus Durations. Acta Oto-
laryng., 65: 257, 1968.

Guepry, F, Conmins, W. E. and Snerrey, P. L.:
Perceptual and Oculomotor Reactions to Interacting
Visual and Vestibular Information. Percept. Mot.
Skills, 12:307, 1961.

Guepry, F. E, and Lauver, L, S.: The Oculomotor
and Subjective Aspects of the Vestibular Reaction
During Prolonged Constant Angular Acceleration.
J. appl. Physiol, 16 :215, 1961.

Marxaryan, 8, §.: Vestibular Reactions Under the
Effect of Various Angular Accelerations. In Parin,
YV. V. (Ed. in Chief) Aviatsionnaya i Kosmicheskays
Meditsina (Aviation and Space Medicine), Akade-
miya Meditsinskikh Nauk, SSSR, Moscow, 1963.
(NASA Technical Translation F-228, 1964, 305-308.)
Mowser, 0. H.: The Influence of Vision During
Bodily Rotation Upon the Duration of Post- Rota-
tional Vestibular Nystagmus. Acta Otolaryng.,
25 :351, 1987.

Noro, A.: Studies on the Second Phase of Nys-
tagmus. J. Oto-, Rhino-Laryngol. Soc. Japan, 63:40,
1960.

Ou, J.: Uber den Einfluss des Sehens auf den
vestibularen Drehnystagmus und Nachnystagmus.
Z. f. Hals-, Nasen-, u. Ohrenheilk., 16:521, 1926.

Preser, L.: Vegetative Reactions in Caloric and
Rotatory Tests. Acta Otolaryng., Suppl. 144, 1958.
Wenpt, G. R.: Vestibular Function, In Stevens,

S. S. (Hd.), Handbook of Experimental Psychology.
Wiley & Sons, Inc., New York, 1951, 1191-1223.



105;
100]
95
|
z 85
80
& 20
gr 75
8 70 1 70)
3 68 i\ 6)
© 60 i 60
Bet] i ss
a? H STIMULUS: 5*/ SEC? for 24 SEC 50 STIMULUS : 5*/ SEC? for 24 SEC
s 4 Nee al Nee
§* san ra. a a. as mat
8 -=-0 LIGHT TRIAL 0-=-0 LIGHT TRIAL
, (12 SEC LIGHT) 3s (18 SEC LIGHT)
3 x0 »
g 2s 2
& 20] 20
a 5
B Eo] 10
i
zis °
3 oft °
‘UGHTS }
Se af tos om sf ve Je
10 10
* 5 “ 5
SAB IS as Sa es 72 8190-98 108 IT 126 135 144 155 62 171 160

Sis zr 36 45 54 63 72 81 90 99 108 IIT 126 135 144 153 162 171 160

TIME IN SECONDS

Fieure 5. Average slow-phase nystagmus for “dark” and for “light” trial decelerations of 5°/sec? for Group A
sec light) and Group B (18-sec light. Markings are the same as in Figure 1.

no statistically significant differences between the
2 “light” trials for these measures.

Subjective Reactions. The signals indicating
experience of turning through 90° angles were
scored, like nystagums, in 3-sec intervals.* The
data for Groups A and B were plotted in Figures
7, 8, and 9 for stimulus magnitudes of 1°/sec’,
3°/sec?, and 5°/sec?, respectively. Data for
Group C appear in Figure 10.

“Dark” trials. For Groups A and C, the sub-
jective rate of turning (to the left) increased
throughout the deceleration stimuli and then
decayed. Secondary turning sensations were ex-
perienced only occasionally in all 3 groups with
no more than 2 subjects reporting these reactions
at any given stimulus magnitude (see Table 4).
For Group B, an increasing rate of turning in
total darkness was experienced for the first 18-21
sec of the 24-sec deceleration for all 3 stimulus
magnitudes; however, a response decline con-
sistently began during the last 3-6 sec of the
decelerations and continued during the period of
standstill. A decay in the subjective reaction
(adaptation) during a prolonged stimulus is not

an unusual finding and has been examined in
detail elsewhere."

“Light” trials. The intervals of room ilumina-
tion during “light” trial decelerations markedly
influenced the reported subjective reactions. On
an overall basis, 11 of 18, 14 of 18, and 23 of 24
“light” trials for Groups A, B, and C, respec-
tively, produced responses in the direction of
a secondary sensation (see Table 4). Most strik-
ing, however, was the fact that in 7 Group A
trials, in 12 Group B trials, and in 20 Group C
trials, the “secondary” sensation of turning to the
right began during the last 6 sec of deceleration
in darkness (following the period of light).
‘That is, although the semicircular canals were sig-
nalling a sensation of turning to the left during
deceleration (and a left-beating nystagmus had
recommenced), the visual information obtained
during the period of room illumination, which
indicated actual turning to the right at a de-
creasing rate, apparently corrected the direc-
tional component of the sensation during the sub-
sequent dark period. For Groups A and B the
3°/sec? stimulus appeared somewhat more effec-



AM 68-28

ADAPTATION TO VESTIBULAR DISORIENTATION. X.
MODIFICATION OF VESTIBULAR NYSTAGMUS AND
“VERTIGO” BY MEANS OF VISUAL STIMULATION

William E. Collins, Ph.D.

Approved by Released by
J. Roverr Ditre, M.D. P. V. Sieeen, M.D.
Cuter, Civ. AEROMEDICAL Feperat Ar Surceon
Institute
October 1968

Department of Transportation

FEDERAL AVIATION ADMINISTRAYION
Office of Aviation Medicine



5 STIMULUS: 3°/ SEC? for 24 SEC 130) STIMULUS: 3° / SEC? for 24 SEC
< 20 Ne6 120) Nes.
& 10] 10;
= &—4 DARK TRIAL 100) 4——& DARK TRIAL
= too O-=-0 LIGHT TRIAL 0-=-0 LIGHT TRIAL
8 90 (12. SEC LIGHT) 90 (18 SEC LIGHT)
i 80) 80
« 70) 70)
i 60 60)
Q 50] 50
= 40 40}
©
g 30} 30)
Se

20 20
bo
g7 19 10)
= o t ° t
a — PPr0e Py rooeTM

aa a
2 wh ge ott eseeo® Of TENTS on nant
2 2 2 a a eral 20 re
ge 1 rs é
a 30) \ A f 30) ° t
wy i Af

¥ 40) ° 40 ress
5 50) 50 ai
g ;
3 9 69 it
B 70) 70 a

80] 80) it

90) 90) ut

100} 100 \

NO] 10}

9 18 27 36 45 54 63 72 81 90 99 108 II7 126 135 144 153

9 18 27 36 45 54 63 72 BI 90 99 108 II7 126 135 144

TIME IN SECONDS

Ficure 8. Average subjective displacement in degrees of experienced turning for “dark” and for “light” trial de-

celerations of 3°/sec* for Group A (12-see light) and Group B (18-see light).
Results are comparable to findings in Figure 7. One subject from Group B was not included in

Figure 1.

Markings are similar to those in

data averages due to his failure to provide complete signals during the “dark” trial.

the period of standstill. Secondary reactions
were reported by 2 subjects for the 3°/sec? rate
and by 5 subjects for the 10°/sec? rate. Intro-
duction of the room lights during the first part
of the deceleration periods resulted in 9 reports
of secondary reactions following the 3°/sec?
stimulus and in 10 such reports following the
10°/sec? stimulus. Five of the former and 6 of
the latter began during the last 6 sec of the
deceleration (see Table 5). The 3 sec of room
illumination with the chair at a standstill re-
sulted in no subsequent: sensation for 5 subjects
following the 3°/sec? deceleration and in secon-
dary sensations for the remaining 7 subjects, At
10°/sec?, weak primary sensations which gave
way to strong secondary reactions followed the
period of still fixation in 5 subjects; 6 others had
only secondary sensations while the remaining
subject reported no experience of motion subse-

10

quent to the 3-sec light interval. These data
support the results from Groups A and B in that
at higher stimulus magnitudes the primary sensa-
tion is often reinstated (albeit weakly) following
periods of visual information, whereas at lower
rates the primary sensation is almost always sup-
pressed (Tables 4 and 5).

IV. General Discussion.

Nystagmus. The present data support previous
reports which demonstrated a reduction of post-
rotatory primary nystagmus as a result either
of visual still-fixation or of opposing optokinetic
stimulation during angular accelerations, As
Dodge’ and Wendt" noted, the primary reaction
is quickly reestablished during a period of dark-
ness subsequent to a period of visual stimulation,
but the present data indicate that it clearly does


and 4°/sec? stimuli were equally effective in elic-
iting “secondary” sensations during the 6 sec of
deceleration following the light interval.

Group D

Nystagmus. Mean slow-phase nystagmus was
plotted in Figure 11. During “dark” trials, nys-
tagmic output increased throughout the decelera-
tion stimuli, decayed during the periods of stand-
still, and gave way to secondary responses in 21 of
the 24 trials. The introduction of room illumina-
tion, whether it was during or immediately fol-
lowing deceleration, sharply reduced the magni-
tude of the primary response. In comparison
with “dark” trials, the primary response to
“light” trials was significantly shorter and the
onset of secondary nystagmus occurred signif-
icantly sooner (.001 levels by t tests). Secondary
nystagmus appeared in all “light” trials and was

of greater overall output (especially during the
initial 45 sec) than that of the “dark” trials in
32 of the 48 comparisons.

For the 10°/sec? stimulus, there were no sig-
nificant differences between the two types of
“light” trials with regard to duration of pri-
mary, onset of secondary, and magnitude of
secondary nystagmus. For the 3°/sec? stimulus,
primary nystagmus ended earlier and secondary
nystagmus began sooner (,001 levels) in the 14—
sec “light” trials as compared with the 3-sec
“light” trials; the magnitude of the secondary
reaction was also greater, but not significantly
So.

Subjective Reactions. Figure 12 depicts the
time-course of the subjective reactions for Group
D. “Dark” trials showed an increasing rate of
experienced turn throughout the stimulus fol-
lowed by a decay in the primary reaction during

Taste 4, Subjective data from Groups A, B, and ©. The number of subjects experiencing primary and secon-

dary sensations is indicated for “dark” and for “light” trials.

The heading “During Decel” refers to the

final 6 seconds of deceleration (always in darkness). During the standstill period following deceleration, pri-
mary responses sometimes were succeeded by secondary reactions.

During Decet

Following Deceb

Trials °/sec? N Primary Secondary Primary Secondary
Group A
Dark 1 6 6 0 6 2
3 6 6 0 6 1
5 5* 5 0 5 0
12-sec. 1 6 0 2 0 3
Light 3 6 0 4 1 4
5 6 2 1 3 4
Group B
Dark 1 6 6 0 6 1
3 el 5 0 5 0
5 6 6 0 6 2
18-sec 1 6 0 4 0 4
Light 3 6 0 5 0 5
5 6 2 3 3 5
Group ©
Dark 3 6 6 0 6 1
4 Bee 5 0 4 1
12-sec 3 6 0 5 0 6
Light 4 6 0 5 0 6
18-sec 3 6 0 5 0 5
Light 4 6 0 5 0 6

*One subject was excluded due to mechanical failure of a microswitch.
**One subject was excluded for failure to provide complete signals.



na (30 STIMULUS : 1°/ SEC? for 24 SEC 30 STIMULUS : 1°/ SEC? for 24 SEC
zs N=6 28 Ne6

Ss Fa 20 &—2 DARK TRIAL 20 &——4 DARK TRIAL

é 5 15 O--~O LIGHT TRIAL 5 O-—-O LIGHT TRIAL

= = (12 SEC LIGHT) ' (18 SEC LIGHT)

OYE Io

Pus

2°92 5

woe

n

a ~ ~ aS

z i & gf users ov Vr poon Pn Nred

ag” 5
Ww 1 1 n dirtsat n n diit L 1 4 tout ‘weer L n L owes n ‘awe 5
2 9 18 27 36 45 54 63 72 BI 90 99 108 9 I8 27 36 45 54 63 72 BI 90 99 108 II7 126

TIME IN SECONDS

Freure 8, Average slow-phase nystagmus for “dark” and for “light” trial decelerations of 1°/sec* for Group A (12-
sec light) and Group B (18-sec light). Primary nystagmus is plotted above the zero line, secondary nystagmus
below that line. Arrows indicate termination of the stimuli. Horizontal bars beneath the zero line demarcate
the periods of full-room illumination during deceleration. Nystagmus (optokinetic) was not scored during the

interval of light.

O-—-0 LIGHT TRIAL
(12 SEC LIGHT)

55 55

50 STIMULUS : 3*/SEC? for 24 SEC 50 STIMULUS: 3°/SEC? for 24 SEC
“8 N-6 45 Ne

40 —4 DARK TRIAL 40 4 DARK TRIAL

O-==0 LIGHT TRIAL
(18 SEC LIGHT)

F]
Sz
z wu
zz *
g 8 25
2g
a7 os
ge.
geqe
ages
se
ag, °
ga°
280 v4
O15
SES a ee
Ficure 4. Average slow-phase nystagmus for “dark” and

see light) and Group B (18-sec light).

sponse significantly earlier (.05-01 levels by t
tests) for “light” trials as compared with “dark”
trials for the 2 groups, with the exception of the
5°/sec® stimulus for Group A. Secondary nys-
tagmus occurred more frequently (in 33 of the
36 “light” trials) and also showed greater overall
output in 27 of the 36 comparisons with “dark”
trials (particularly in comparing ‘the first 30 sec
of the response).

Group C provided a direct comparison of the
effects on nystagmus of the 12-sec and 18-sec

9 18 27 36 45 54 63 72 BI 90 99 108 II7 126 135 144 153 162 171 180
TIME IN SECONDS

for “light” trial decelerations of 3°/sec* for Group A (12-
Markings are the same as in Figure 1.

light periods (see Figure 6). As in Groups
A and B, comparisons of “dark” with “light”
trials showed that, for “light” trials: (a) pri-
mary nystagmus was clearly of lower magnitude;
(b) the primary response was significantly
shorter and the onset of the secondary response
(which occurred in 23 of 24 “light” trials and
in 11 of 12 “dark” trials) was significantly ear-
lier (.05 levels by t tests); and (c) the overall
amount of secondary nystagmus was greater in
21 of the 24 comparisons. However, there were


Il. Method.

Subjects. Four groups were tested in the
Stille-Werner Rotation Device. Groups A, B,
and C each comprised six subjects; thirteen of
these were males, five were females. Group D
comprised twelve male subjects. All subjects
were paid volunteers between 21-27 years of age.

Recording. Surface electrodes were taped by
the outer canthi of each subject’s eyes to record
horizontal components of eye movements. A
ground electrode was clipped to the ear lobe.
Recording was accomplished by means of an
Offner Type T polygraph with RC time con-
stants of 3 sec used in amplification. Subjects

The experimental trials differed among the

to the recorder, by means of which they could
signal onset and direction of turning, each 90°
turn which they experienced, and the termina-
tion of their sensations,

Procedure. Subjects were seated in the rotation
device with their eyes open and their heads up-
right but anteverted so that the lateral semicir-
cular canals were approximately in the plane of
rotation. They were instructed in detail re-
garding the signalling of turning experiences and
were given two familiarization trials in total
darkness. These trials, alternately CW and
CCW, consisted “of accelerations and decelera-
tions of 5°/sec? for 12 see separated by a 2-min
period of constant velocity.

"DARK" TRIALS

CW Accel (24 sec) | Constant Velocity ( 3-6 min)

CW Decel (24 sec) | Standstill (3-6 min)

TOTAL DARKNESS

Primary Sensation :
Primary Nystagmus :

Turning Right
Fast Phase Right

CW Accel (24 sec) | Constant Velocity (3-6 min)

12-SEC LIGHT TRIALS

Primary Sensation :
Primary Nystagmus:

Turning Left
Fast Phase Left

CW Decel (24 sec) | Standstill (3-6 min)

4 Dar NESS

CW Accel (24 sec)

Constant Velocity (3-6 min)

I8-SEC LIGHT TRIALS

CW Decel (24 sec) Standstill (3-6 min)

— DARKNESS

| <—L/GHT >} DARKNESS =I

Figure 1,

groups. Subjects in Groups A and B each re-
ceived 6 trials; 3 trials were conducted in total
darkness and 8 trials involved the introduction
of a period of room illumination during the
deceleration (see Figure 1). For these groups
a “dark” and a “light” trial were run with
stimulus rates of 1°/sec?, 3°/sec*, and 5°/sec?. In
all cases rotation was CW and the stimulus dura-
tion was 24 sec. Accelerations and decelerations
were provided with two microswitches, connected

Test conditions used for Groups A, B, and ©.

were separated by periods of 3-6 min of con-
stant velocity, depending primarily on the pres-
ence of secondary nystagmus. Time at a stand-
still from the end of deceleration to the start
of the next acceleration ranged from 6-9 min,
again depending upon the presence of secondary
reactions. At least 3 min were spent in room
illumination prior to the start of each trial. A
modified counterbalancing of stimulus presenta-
tions was used, as indicated in Table 1, with a


formation during primary reactions actually may
enhance the vigor of the opposed process but
may also serve to trigger its release earlier
thereby exhausting some of this previously con-
tained energy, reducing the primary output, and
resulting in relatively less observable secondary
nystagmus. An early release of the opposed
process may characterize those cases (75% of the
comparisons) in which secondary nystagmus was
enhanced during “light” trials and generally
weak or absent during trials in total darkness.
Here the primary response in “dark” trials may
be relatively less vigorous due to the early re-
lease of the opposed process. The latter is then.
“ysed up” during most of the primary reaction
and yields weak observable secondary reactions.

In these cases, visual information may enhance
the opposed reaction, reduce the primary nys-
tagmus, and produce a stronger secondary nys-
tagmus. It is also possible that differences among
subjects in the release time of the opposed reac-
tions may be related to susceptibility to habitua-
tion or to motion sicknss. In this regard,
Preber* has reported that pilot trainees who be-
came severly airsick during flight training
showed, prior to training, longer durations of
nystagmus and turning sensations and greater
maximum eye speed of nystagmus resulting from
laboratory rotations than did pilot trainees who
did not get airsick. A follow-up of 6 subjects
who overcame airsickness and completed the
flight course showed that post-training measures

120 120
us} ns}
110] 110
105 1085]
Pa 100)
2 9
% 95 5]
90) 90
2 as) 85
° a
gs 0
o 75 75
"10 STIMULUS: 10YSEC* FOR 12 SEC 70) ‘STIMULUS: 3*/SEC? FOR 20 SEC
G6 Nei2 65) Nel2
ar) a—4 DARK TRIAL 60 DARK TRIAL
Boss oe nno LIGHT TRIAL 5 LIGHT TRIAL
wi (3 SEC LIGHT) (3 SEC LIGHT)
WwW 50) 50)
s LIGHT TRIAL fo LIGHT TRIAL
mw 4 (6 SEC LIGHT) “8 (14 SEC LIGHT)
2 40) 40}
83 35]
a» 0
= as 25)
2
2,* 20)
we '5 15]
Hz
Ze Io 10
ge
a 5 |
Som ty | —
S stuicts on | 68
a,
= 10 10)
2 15)
3 15
B20 20)
sy 25
SOBER aS EES IEE So SS be air SE Tad es TA 0 203s a7 “sees 74 3 92 TO! 10 119 128 137 146 155

TIME IN SECONDS

Figure 11.

Average slow-phase nystagmus for “dark” and for “light” trial deceierations of 3°/sec? and 10°/sec?

for Group D. Markings are the same as in Figure 1.

13



of both sensations and nystagmus had undergone
reductions from pre-training levels.

Subjective Reactions. In previous studies,
when subjects were permitted briefly to see that
they were stationary shortly after the termina-
tion of angular deceleration, further sensations
of turning during subsequent periods of darkness
were either markedly reduced or were term-
inated.®° Secondary sensations, however, were
not reported to occur probably due to a combina-
tion of the type of subjects used, the timing of
the period of permitted vision, and a failure
to seek such information from the subjects.
Whether visual information regarding stationary
objects is provided during a deceleration stimulus
or while at a period of standstill (in either event,
when it is in conflict with the vestibular signals),
it seems clear that secondary sensations occur
much more frequently and are usually more
vigorous than when vestibular stimulation occurs
entirely in darkness.

That strong secondary sensations occur fol-
lowing such visual stimulation is perhaps not so
surprising in view of the similar effects that the
same type of input frequently produces on the
nystagmic reaction. However, the occurrence of
reversals in sensation dwring the last few seconds
of deceleration in darkness following a period
of room illumination is particiilarly striking.
Many of the “secondary” sensations which began
during the deceleration (23 of 39 for Groups
A, B, and C; 2 of 11 for Group D) were rela-
tively short in duration but were followed by
another (much more intense) rise and decline of
a turning sensation in the same direction (again
to the right), i.e, a bimodal secondary effect was
evidenced (and is apparent in many of the
graphs). In these cases, the initial response ap-
peared to have a fairly sudden onset 2 or 3 sec
after the lights were turned off; velocity then
increased quickly and quickly decayed. The fol-
lowing response (in the same direction) fre-
quently began just a few sec later, showed a rise
and decline of velocity, and was of long duration.

These brief-duration reversals of sensation
during the deceleration could be the result of
“suggestion” resulting from a weak, perhaps in-
definite sensation of motion following the visual
information, but they do not appear so. Subjects
reported with conviction (calling out the direc-
tion as they signalled) and, in Groups A and B,
most frequently had these experiences at the

15

lower rates of stimulation. The latter fact also
argues against the influence of breeze cues which
possibly could have affected subjects in Groups
A, B, and © (but not in Group D) in spite of
careful instructions; the fastest rate of turn
(5°/sec?) produced both the fewest sensations of
turning to the right during CW deceleration and
the only vestibularly “correct” sensations of turn-
ing to the left immediately following the light
period. Further, any feedback from the nystag-
mic reaction should have reinforced the occur-
rence of a primary sensation (turning to the
left) since, upon darkening the room, the opto-
kinetic response was quickly replaced by a left-
beating nystagmus. Some observations made
subsequent to these studies support this position.
Subjects rotating at constant velocity in a totally
dark room (nystagmus and turning sensations
were no longer present) were exposed to a 1-3
sec period of room illumination. Several seconds
after the lights were turned off, a clear turning
sensation (in the true direction) was experienced.
If decelerations in darkness were begun too soon
after this period of room illumination, markedly
long latencies of the vestibular turning sensation
occurred.

There is considerable evidence which suggests
that the subjective aspects of vestibular stimula-
tion follow a different time-course than nystag-
mic reactions (eg.**"1), The present data seem
to support this view. Thus, following a period
of room illumination, vestibular nystagmus rec-
ommenced almost immediately (although at an
attenuated level), whereas the subjective response
most often showed a reversal or was absent.
However, the early onset and the markedly en-
hanced secondary subjective reactions following
the visual stimulation, although they occurred at
a different time, were similar to the effects pro-
duced on nystagmus and may have the same
origin. That is, centrally integrated visual in-
formation appears to enhance an opposed vestib-
ular process which probably arises as a result of
“prolonged” stimulation. The fact that the sub-
jective response frequently decays (sometimes
terminating) during a prolonged stimulus, and
shows only a brief post-stimulus reaction as com-
pared with post-stimulus responses following
stimuli of shorter durations seems to support this
view.©914

Some Additional Considerations. There is evi-
dence which indicates that. the occurrence of sec-



ADAPTATION TO VESTIBULAR DISORIENTATION. X.. MODIFICATION
OF VESTIBULAR NYSTAGMUS AND “VERTIGO”
BY MEANS OF VISUAL STIMULATION

I. Introduction.

That visual fixation on still objects can mark-
edly reduce an ocular nystagmus of vestibular
origin was recognized by such early workers as
Barany, Abels, Bartels, and Frenzel, all of whom
developed or recommended special glasses to pre-
vent fixation during clinical examinations. In ex-
perimental evaluations of the influence of vision
on vestibular responses, Dodge" reported that (a)
opportunities for still-fixation during angular ac-
celeration resulted in a reduction only in the
amplitude of nystagmus, and (b) viewing the
environment during rotation produced an opto-
kinetic nystagmus which immediately gave way
to the vestibular response upon darkening the
field. Mowrer'? examined post-rotational nys-
tagmus in a lighted room and compared the
effects both of permitting vision (which gen-
erated optokinetic responses) and of excluding
vision during the period of rotation. He re-
ported much briefer and less vigorous post-rota-
tional responses following the visual stimulation
and credited these effects to the “post-stimulus
persistence tendency” of the optokinetic nys-
tagmus (which opposed the post-rotational vesti-
bular response).

The assistance of Billy P. Updegraff, David J.
Schroeder, Ruth Ann Mertens, and Alice Ramsey is
gratefully acknowledged.

Ohm" demonstrated that: still-fixation follow-
ing a period of rotation inhibited the post-rota-
tion nystagmus, while Wendt*” reported that the
response could be quickly reestablished during a
subsequent period of darkness. Guedry* and
Brown and Guedry? found attenuation in the
duration of the oculogyral illusion as a result of
introducing room illumination for a short in-
terval following rotatory stimulation.

Guedry, Collins and Sheffey"® confirmed the in-
hibition both of nystagmus and of the sensation

of motion by means of a brief period of room
{Illumination following a brisk deceleration; they
also noted that the rotatory sensation showed
little or no recovery during a subsequent period
of darkness, whereas nystagmus was restored, al-
beit incompletely. More recently, it has been
demonstrated that both control of balance and
rapid suppression of nystagmus in figure skaters
are achieved by means of visual still-fixation
following on-ice spins. In a comparison of
figure skaters and ordinary subjects in the lab-
oratory, active fixation on wall markers was re-
quired for 3-sec periods of room illumination.
which followed various deceleration stimuli; the
trials were otherwise in total darkness. For
both groups of subjects visual fixation produced
a suppression of nystagmus and of the sensation
of motion; during the subsequent period of dark-
ness (a) the subjective reaction was reinstated
(although markedly reduced) in only 1 of 48
cases among the skaters and in only 17 of 48
cases among the other subjects, (b) nystagmus
recommenced but clearly was not restored to
the level of an uninterrupted response, (c) the
duration of the primary nystagmus was sig-
nificantly shorter than that of an uninterrupted
response, and (d) an enhanced secondary nys-
tagmus appeared. Although the report does not
clearly define his test procedure, Markaryan’*
also noted strong secondary nystagmic reactions
after angular stimulation during eye closure fol-
lowing a period of visual fixation.

The present study was undertaken to examine
further the influence of visual information on
vestibular responses. Particular attention was
directed toward the occurrence and characteris-
ties of secondary vestibular reactions resulting
from variations inthe type and timing of the
visual input.



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not return to the level of an uninterrupted re-
sponse (see also”), The “post-stimulus persist-
ence tendency” of optokinetic reactions by which
Mowrer*® explained his findings is not sufficient
to account for these results since still-fixation on
stationary objects also produced attenuation of
nystagmus.

Of particular interest is the fact that vig-
orous secondary (“post-post”) nystagmic reac-
tions so frequently followed the reduced primary
response during “light” trials. This enhanced
(as compared with “dark” trials) secondary nys-

tagmus apparently can be triggered not only by
still-fixation as reported earlier® but also by op-
posing optokinetic impulses during vestibular
stimulation.

Secondary nystagmus is considered to be of
central origin! and may occur as a result of “pro-
longed” neutral activity in the primary direc-
tion.» Whether the secondary response is the re-
sult of an induced central imbalance or is ini-
tiated to oppose the primary nystagmus, it ap-
pears that at least some types of visual informa-

220, 220
210 210
200} 200
190) 190
180) 180
170 170]
160 160
150 150
140 140]
130] 130
120. STIMULUS : 5*/SEC? for 24 SEC 120) STIMULUS: 5*/SEC® for 24 SEC
> NES Ne6
Zz to 10
$
= 100 a4 DARK TRIAL 100 a—a DARK TRIAL
5 90 90)
2 O-=0 LIGHT TRIAL D-=0 LIGHT TRIAL
g 8 (2 SEC LIGHT) 80 (18 SEC LIGHT)
2 70 70
"60 60
fa
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g 40 40
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20
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8 60 60 4
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a 80 80 aw]
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100 100
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L tostiat Dette L J, WaNvenewyeen . iver Liu
@ 16 27 36 45 54 63 72 BI 90 99 108 NI7 126135 144 9 18 27 36 45 54 63 72 81 90 99 108 II7 126 135 (44 153 162 171
TIME IN SECONDS

Freure 9, Average subjective displacement in degrees of experienced turning for “dark” and for “light”. trial de-

celerations of 5°/sec? for Group A (12-see light) and Group B (18-sec light).
Results are comparable to findings in Figures 7 and 8. One subject from Group A was not included

Figure 1.

Markings are similar to those in

in data averages due to a malfunction of his signalling device during a “dark” trial.

di



STIMULUS: 107SEC? FOR 12 SEC
Nal2 140-
DARK TRIAL 130
LIGHT TRIAL

(3 SEC LIGHT)
LIGHT TRIAL 110)
(6 SEC LIGHT)

STIMULUS : 3°/SEC? FOR 20 SEC
Nez

a&——A DARK TRIAL

O——~—0 LIGHT TRIAL

(3 SEC LIGHT)

LIGHT TRIAL

(14 SEC LIGHT)

(DEGREES PER 3-SEC INTERVAL)

}
fl
H
‘
i
i
1
1
L
1
1
'
'
1
1
i
I
1
1
1
1
Il
'
1
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t
1
1
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i
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t

SUBJECTIVE DISPLACEMENT

ti
cca
R,
52
=

8s

9 18 27 36 45 54 63 72 BI 90 99 108 IIT 126 135 144 153 2 i 20 2938 47 56 65 74 83 92 101 10 119 128 137
TIME IN SECONDS

Figure 12. Average subjective displacement in degrees of experienced turning for “dark” and for “light” trial de-
celerations of 3°/sec? and 10°/sec? for Group D, Markings are similar to those in Figure 1.

Taste 5. Subjective data from Group D, The number of subjects experiencing primary and secondary sensations
is indicated for “dark” and for “light” trials. The heading “During Decel” refers to the final 6 seconds of decel-
eration (always in darkness). Room illumination wasprovided during the deceleration periods for the 14-sec light
(stimulus duration: 20 seconds) and 6-sec light (stimulus duration: 12 seconds) trials, and one second after the
end of deceleration (while at a standstill) for the 3-see light trials.

Group D
During Decel Following Decel

Trials °/sec? N Primary Secondary Primary Secondary
Dark 3 12 12 0 12 2

10 12 12 0 12 5
3-sec light 8 12 12 0 0 7
(Standstill) 10 12 12 0 5 11
14-sec light 3 12 1 by 2 9
6-sec light 10 12 1 6 3 10

14