Cognitive Neuroscience Lecture 15: Attention 1

*L15: Attention 1*

What is Attention?

William James:

**Selection**:
Choosing 1 possibility out of many

**Withdrawal**:
ignoring the rest

Many definitions

Filtering, Selecting, Binding, Focusing,
Enhancing

Basic characteristics

**Limited**
capacity

o
Can only attend to a subset of visual input
(some of space, a few objs)

o
Multiple object tracking: we go bad after
approx. 4-5 objs

o
This requires selection: what/how to select,
what results?

**Selection**

o
Consequences of attentional selection

§
**Inattentional**
blindness: **Moonwalking bear**

§
**Selective**
reading: **if you’re told to read only a certain type of text, you will**
unless something pops out at you like your name, special words like sex,
physically different stim like caps/numbers, or stuff relating to the topic to
main focus of attention (bold green example)

**Modulation**

o
Once selected, attention can enhance visual
perception and neural responses

o
Attention alters the contrast sensitivity

§
If given a cue on a particular side, you notice
more contrast on that side

**Vigilance**

o
ability to sustain attention over time

o
person seeks to detect appearance of a
particular target stim of interest

o
Long lasting tasks: e.g. airport scanner,
where’s waldo

Our definition of attention:

**Process**
by which one or a few among many competing representations are selected for
prioritized representation

**Mechanism**
**that controls perception and information being perceived**

Alters neural activity, giving stronger
responses to attended info and weaker to unattended info

Occurs across many cortical regions (even
subcortical), across all domains (sensory/motor/higher cognition)

When does attentional selection (aka filtering) happen?

In both early and late selection:

o
Stimulusà

o
Sensory registrationà

o
Semantic processingà

o
Response

**Early**
selection: selection before semantic processing

o
we have a limited capacity to process
information and we only select a small subset of this information for extensive
processing

o
**Bottleneck**
is BEFORE SEMANTIC PROCESSING

o
You only process SOME inputs

o
Evidence:

§
Dichotic listening task; only reported stream
attended to

·
What breaks through? **Sensory information.**

o
Switch to pure tone

o
Switch gender

·
What doesn’t break through? **Semantic information**.

o
Switch languages

o
Played backwards

§
Differences in EEG brain waves based on
attention as early as 100ms

o
Problems with Early selection:

§
**“Cocktail**
Party Effect”**: even if you’re not attending to a convo, you’ll hear if they**
say your name (and understanding your name is semantic info)

§
Some info can break through: your name and
“fire”

§
**Stroop**
Effect**: can’t filter out meaning of words**

**Late**
selection: selection after semantic processing

o
 both
attended and ignored inputs are processed equivalently by the perceptual
system, reaching stages of semantic encoding and analysis

o
**Bottleneck**
is AFTER SEMANTIC PROCESSING

o
AFTER you process it, you only respond to some

Basically, there’s evidence for both.

**The**
determining factor may be “attentional load”: how demanding is the task

o
Low-load/easy: late selection

§
None of them is hard, so you have more resources
to spread and don’t need to filter any out

o
High-load/requiring lots of resources: early
selection

§
You have less to focus on then

Irony of Load and Selection

Sometimes, under low-load you can be more
distracted since information can ‘break through’

Easy task: bad performance, “easily distracted”

Hard task: good performance, “difficult to
distract”

William James on Attention: “depends on…**what** the things are.”

What are the units of attention? What do we select?

**Space**

o
**Spatial**
orienting: Posner cuing task

§
Valid: cue pointed in direction of target

§
Invalid: cue pointed away from target

§
Neutral: cue pointed in both directions

o
**Covert**
attention**: attention without eye movements**

o
**Overt**
attention**: attention through eye movements**

o
Results of Posner cuing task: RT is shorter when
you shift your attention first

o
2 ways to selectively orient attention:

§
**Endogenous**
attention **(goal directed)**

·
Voluntary

·
Top-down

§
**Exogenous**
attention **(stimulus driven)**

·
Reflexive

·
Bottom-up

o
Posner cuing ARROW is based on endogenous (look
for the thing the arrow is pointing to…goal directed)

o
Posner cuing BOLDING is based on exogenous (no
one tells you to focus on the bolded square, but you do it)

o
Deficit in attending to space: spatial neglect

§
Following damage to dorsal pathway (parietal, usually
right)

§
Loss of attention or awareness to contralesional
side (usually left side)

§
Neglect on the left visual space

§
**Inferior**
parietal lobule & TPJ are important for space-centered, exogenous attention

§

o
**Neural**
Mechanisms: Parietal neurons and attention

§
Monkey fixating passively

§
Monkey not attendingànot much firing in parietal
neurons

·
Monkey makes an eye movement, big response from
parietal neurons (even before eye-movement occurs)

·
Overt attention: he’s moving his eyes

§
Covert attention

·
Monkey makes a hand movementà big response even
though eyes never move

·
Covert attention: no saccades, just reaching

o
What are these parietal activations doing?

§
Modulating activity in other visual areas: TPJ
affecting other regions

§
**Attention**
alters the contrast sensitivity

o
**Attention**
modulates the activity of V4 neurons

§
What will happen to V4 neuron response when both
stimuli are presented within the receptive field of the cell?

§
Depends on which object the monkey is attending
to

§
Monkey ignoring display, just paying attention
to fixation

·
Cell responds strongly to blue-vertical alone
but not white alone

·
**Response**
of neuron “biased” towards attended stimulus (increased when effective
stimulus, decreased when ineffective stimulus)

·
**V4**
responds more to effective

o
**Cue**
period: endogenous attention

o
**Target**
period: exogenous attention

o
Attention & Parietal lobe,

§
Parietal dissociation: different parts for
exogenous vs endogenous

·
**Intraparietal sulcus/superior parietal**
lobule: **endogenous, cue-related orienting, goal-directed**

·
**Temporoparietal**
junction/inferior parietal lobule**: exogenous, target detection,**
stimulus-driven

o
**Dual**
Network Theory

§
Dorsal attention network helps orient attention
in a goal-directed manner

§
Ventral attention network detects salient
stimuli and triggers reorienting to them

o
**Dorsal**
attention network: domain general shifting **(shows that any goal-oriented**
uses dorsal): GOAL DIRECTED; DORSAL

§
Shift task between magnitude and parity

§
Shift location between left and right

§
Same IPS/SPL regions mediate shifting spatial
attention and task sets