Lecture 6: Attention

Question 1

Change blindness

Answer 1

attention can select only a subset of the sensory input for further processing.
we may be completely blind for unattended portions of the input

Question 2

arousal vs. selective attention

Answer 2

Arousal is the global physiological and psychological state of an organism. From deep sleep to hyperalertness. involves ascending reticular activating systems at the brain stem.

selective attention is not global, but can act at any level of global state (arousal). selective attention is the allocation of resources among relevent inputs, thoughts, actions, while ignoring irrelevant or distracting ones. involves widespread cortical and subcortical networks.

Question 3

Distinctions with selective attention:

overt vs. Covert attention

Answer 3

overt: attention is directed to the same location as the eyes.

Covert: attention is directed at another location than the eyes (example; boring lecture)

Question 4

Voluntay vs. reflexive attention

Answer 4

voluntary: goal driven, top-down or endogenous attention is intentionally

reflexive: stimulus driven, bottom up, exogenous attention.

Question 5

neuropsychology of attention
Neglect

Answer 5

attentional problems in the left visual field.
problems controlateral to (right hemispheric) lesion (after stroke) of parietal, frontal, temporal cortices. in particular regions centered around right temporoparietal junction.

normal vision and no blindness in left visual field.

but patients act as if left regions of space and left parts of objects do not exist. and they have limited awareness of their deficit

Question 6

extinction

Answer 6

patients can detect left visual field stimuli normally when presented in isolation but not when presented simultaneously with stimuli in the right visual field.
can be partially overcome by directing patients attention to neglected locations

Question 7

balint’s syndrome

Answer 7

inability to attend to more than one object at a time
severe problem after bilateral occipitoparietal leasions

Question 8

simultanagnosia

Answer 8

difficulty in perceiving more than one object at the same time

Question 9

optic ataxia

Answer 9

problems with visual guidance of reaching and grasping

Question 10

ocular apraxia

Answer 10

problems making voluntary eye movements

Question 11

The levels of attentional selection

Early selection (Broadbent)

Answer 11

Attention selects inputs before perceptual analysis is complete.
no higher-level semantics (meaning) processing of unattended inputs

Question 12

The levels of attentional selection

Late selection

Answer 12

attention selects inputs only after perceptual analysis is complete.
partial or full higher-level, semantic processing of unattended inputs.

Question 13

attenuation model (Treisman)

Answer 13

unattended inputs are not fully blocked from higher-level analysis but degraded.

Question 14

cocktail party effect (Cherry)

Answer 14

one can focus on a single conversation while filtering out irrelevent chatter/music
however, one typically catches ones name despite being engaged in an intense conversation

Question 15

dichotic listening tas (Cherry)

Answer 15

input to one ear need to be voiced and input to other ear is ignored.

hardly any memory for input from ignored ear.

not noticed in ignored ear: change in language, repeating the same word over and over

noticed in ignored ear: human voice or not, change in speakers gender

Question 16

Cueing tasks (Posner)

Answer 16

Responses to a (visual) target stimulus under different conditions of attention
Three conditions: cues can either correctly (validly), incorrectly (invalidly), or not (neutrally) predict target

Question 17

Cueing tasks (Posner)

Voluntary (endogenous) variant of the cueing task

Answer 17

Cue needs to be voluntarily processed (interpreted) by participant (they can choose to use it or not)

Question 18

Cueing tasks (Posner)

Reflexive (exogenous) variant of the cueing task

Answer 18

Cue reflexively (automatically) attracts attention (participants cannot choose to use it or not)

Question 19

Biased competition model
Competition in receptive fields (RFs)

Answer 19

-Multiple stimuli can fall into a neuron’s RF, and they “compete” to control the neuron’s firing
-RFs become larger when climbing up the visual cortical hierarchy
-There should be greater competition at later stages (more stimuli in RFs)
-Attention resolves competition in favor of the attended stimulus
-Effects of attention should be greater at later stages (more competition)

Question 20

Greater competition at later stages
FMRI study comparing SEQ (sequential) vs. SIM (simultaneous) presentation of stimuli

Answer 20

Greater competition in SIM, reflected in reduced V4 but not V1 activity

Question 21

Subcortical effects of voluntary visual spatial attention

Answer 21

Earliest effects in thalamus
- Focused spatial attention modulates activity in lateral geniculate nucleus (LGN) of the thalamus
- Reflects both initial attentional gating by LGN and later feedback from V1 to LGN

Question 22

Reflexive visual spatial attention
Sensory-evoked ERPs measured with EEG

Answer 22

• Event-related potentials (ERPs) recorded during exogenous cueing task
• With short cue-target interval (ISI below 200 ms): larger P1 in cued trials (like endogenous variant)
• However, with long cue-target interval (ISI longer than 200 ms, inhibition of return), effect reverses: larger P1 in non-cued trials
• P1 reflects behavior both in exogenous and endogenous cueing task → similar effects of voluntary and reflexive attention on early visual processing
• But different control mechanisms!

Question 23

Visual search
Pop-out vs. conjunction search

Answer 23

Pop-out search
- Target stimulus differs from distractors by a single feature only (e.g., color)
- Search is easy and search slopes are flat (independent of the number of distractors in display)

Conjunction search
- Target stimulus differs from distractors by more than a single feature (e.g., color and letter identity)
- Search is more difficult and search slopes are steep (dependent on the number of distractors in display)
- Why is conjunction search slow? According to feature integration theory (Treisman), because it requires spatial attention

Question 24

Attention in conjunction search
Feature integration theory (Treisman)

Answer 24

• Individual features can be analyzed without attention and in parallel (in separate feature maps)
• Efficient pop-out search because differences in one feature are detected automatically
• Slow conjunction search because differences in one feature are not enough
• Instead, different features need to be “bound” together by the “glue” of spatial attention (in map of locations)
• Spatial attention is a serial bottleneck, therefore conjunction search is inefficient

Question 25

Object attention
An object-based attention system
Behavioral evidence for object attention (Duncan)

Answer 25

• Box (small/large, left/right opening) with overlaid bar (dotted/dashed, left/right tilt)
• Task: judge one or two features
• Two judgments on the same object are as fast as one judgment
• Two judgments on two different objects are slower than one judgment
• Processing limitation in attending two objects (remember Bálint’s syndrome) → An object-based attention system in addition to a space-based system

Question 26

Behavioral evidence for object attention: Cueing

Answer 26

• Standard voluntary arrow-cueing task but with wrench-like objects figures
• Spatial attention: faster responses to validly cued than to invalidly cued targets
• Object attention: faster responses to invalidly cued targets on the cued than on the uncued object
• Object attention “spreads” within the object, inaddition to the spatial “spotlight” of attention

Question 27

FMRI evidence for object-spreading of attention

Answer 27

• Spatial attention: increased early visual cortex activity for cued vs. uncued targets
• Object attention: greater activity for uncued targets on the cued than on the uncued object

Question 28

Object attention independent of spatial attention
FMRI: Ruling out spatial attention

Answer 28

• Superimposed transparent faces and houses, either moving or static
• Selective attention to either face, house, or motion (constant physical stimulation)
• Activity in face-sensitive fusiform face area (FFA) highest with attention to faces
• Activity in house-sensitive parahippocampal place area (PPA) highest with attention to houses
• Activity in motion-sensitive area MT/MST highest with attention to motion
• Demonstrates object-driven attentional effects independent of spatial attention

Question 29

Consequences vs. sources of voluntary spatial attention
Target vs. cue processing

Answer 29

• So far, we have discussed the consequences of attention by looking at target processing
• To reveal the sources of attention, check what happens before the target appears, after the cue is shown
• Cues evoke anticipatory activity in specific visual cortex regions where the target is going to appear (“priming” of processing)
• Which areas control such preparatory attentional processes? (remember neglect!)

Question 30

Effect of frontal control areas on sensory areas
FEF effects on V4 responses

Answer 30

• Microstimulation in FEF: map saccade vector of FEF neuron
• Stimulate FEF neuron below saccade threshold: no eye movement, but shift of attention to saccade goal (red arrow →)
• Record from V4 neuron with RFs (black circle) overlapping or not with saccade goal of FEF neuron
• Increased spiking with overlap of V4 RF and FEF saccade goal

Question 31

Dorsal vs. ventral attentional control networks
Dorsal attention network: Voluntary attention

Answer 31

• Brain regions respond to cues when participants actively use the cues (rather than passively view them)
• Intraparietal sulcus (IPS), superior parietal lobule (SPL), frontal areas including frontal eye field (FEF)
• Similar control areas for feature and object attention

Question 32

Dorsal vs. ventral attentional control networks
Ventral attention network: Reflexive attention

Answer 32

• Brain regions respond to salient, unexpected, novel stimuli that reorient attention
• Right lateralized temporoparietal junction (TPJ), ventral frontal cortex (VFC) incl. inferior and middle frontal gyrus (IFG, MFG)
• Damage results in neglect