Exam 3 Cognitive Neuroscience

Attention

process by which mind chooses from among various stimuli that strike the senses at any given moment

Balint’s Syndrome

• lesion of occipitoparietal lobe

• patients can only perceive one object at a time (simultanagnosia)

  • also exhibits optic ataxia & oculomotor apraxia

Selective Attention

allocation of attention among relevant inputs, thoughts, and actions while simultaneosuly ignoring irrelevant/distracting inputs

(not global brain state)

Top-down processing (goal-driven)

voluntary & uses personal knowledge to drive attention

(EX: looking for your friend in a crowd)

Bottom-up processing (stimulus-driven)

reflexive & stimulus-driven attention (captured automatically by something noticeable)

(EX: turning towards a sudden loud noise)

Voluntary attention (endogenous)

ability to intentionally pay attention to something in particular

(top-down/goal-driven; guided by expectations & rewards)

(EX: choosing to study your notes)

Reflexive attention (exogenous)

sensory event captures attention

(bottom-up, stimulus-driven; unintentional)

(EX: noticing flash of light)

Overt attention

orientating head towards stimulus (obvious, observable)

(EX: looking directly at someone)

Covert attention

attending to something without moving eyes (stealthy)

(EX: watching someone in your peripheral vision)

Hemispatial neglect

• ignores stimuli on left side of space following stroke in right parietal lobe

  • reduced awareness of side opposite to lesion

  • (EX: patient may fail to eat food on left side/draw left side of image)

Helmholtz’s experiment (Figure 7.9)

1. participants maintained central eye fixation while briefly illuminated letters appeared at different locations

2. letters in attended region were perceived more accurately

Attention can shift independently of eye movement (demonstrates covert attention)

Cocktail party (dichotic listening task)

• different messages are presented to each ear

  • participants repeat/shadow message from one ear while ignoring the other

  • remember relatively little about unattended message

Attention limits how much incoming information receives further processing

Posner spatial cuing task

participants fixate on central cross while a cue predicts where target may appear

1. valid cue → faster response

2. invalid cue → slower response

3. neutral cue → intermediate response

Attention behaves like a mental spotlight as it’ll enhance processing at attended locations even without eye movements

Broadbent’s model (early selection)

unattended information is filtered before complete perceptual/semantic processing

Late selection

stimuli undergo substantial processing before selection for awareness/response

Treisman’s attenuation account

unattended information is weakened rather than completely blocked

Early-selection ERP Experiment

• participants covertly attend to one visual field

• EEG records ERPs over visual cortex

• attended stimuli produce larger early P1 component

Single neuron experiment early-selection

• researchers record neurons in visual area V4

  • neuronal firing changes depending on which stimulus receives attention

• Attention selectively enhances sensory representations at single-neuron level

What happens after 50-200 ms after a sudden peripheral cue?

attention facilitates processing at cued location

What happens after ~300 ms after a sudden peripheral cue?

An inhibitory effect develops → making responses at that location relatively slower

Inhibition of return (IOR)

helps prevent attention from repeatedly returning to previously inspected locations

Tresiman’s feature integration theory

attention binds separate visual features (EX: color & shape) into a single perceived object

Pop-out searches

a distinctive feature is detected quickly (reaction time is relatively independent of set size)

Conjunction search

target requires combining features (reaction time increases with more distractors)

Connection to Helmholtz

spatial attention acts like a spotlight (help binds features at the selected location)

Dorsal network

supports voluntary goal-directed selection

Ventral network

network that responds to novel/salient stimuli & helps redirect attention

Object attention

attention can act on higher-order stimulus representations