22 - attention

default mode network

brain regions more active at rest than during any task

functions of default mode network

sentinel & internal mentation hypothesis

sentinel hypothesis

when at rest must broadly monitor our environment

internal mentation hypothesis

at rest we engage in thinking & remembering, particularly autobiographical events

bottom-up processing

certain features draw attention automatically

for bottom-up you begin…and then….

notice small details & piece them together

top-down processing

direct attention to object/place to serve a behavioral goal

stroop effect

brain automatically recognizes the word before physical features of the word

pop out search

target identified by a certain feature - bottom-up processing

conjunction search

target is defined by conjunction of >2 features (top down)

saccades

rapid voluntary shifts in eye position between steady fixations

_______ elicits saccades so novel stimulus falls on ______

visual orienting, fovea

same discrimination task

small elements vary in color, shape, speed

(A) selective attention experiment

pay attention to just one feature & indicate whether it was the same/different

(B) divided attention experiment

monitor all features & indicate if changes in any feature

B - A

shows brain activity associated w/ attention to 1 feature

what areas light up for color & shape

IT, V4 in temporal lobe

what area for motion

MT

visual cortex

V1, MT, V4, IT initiate bottom-up attention & feed into top-down processing

frontal cortex

establish behavioral goals for top-down attention

pulvinar nucleus of thalamus

integrate visual information from different parts of visual cortex

frontal eye fields

move eyes to target & enhance perception of target

parietal cortex (LIP)

create priority map

pulvinar nucleus processes _____

visual salience

lesions in pulvinar nucleus cause…

abnormally slow response to stimuli on contralateral side

stimulation of frontal eye fields enhances…

V4 response to visual stimuli

stimulating neurons in FEF will cause…

saccade to particular region of visual field

lateral intraparietal cortex

evaluate bottom-up & top-down inputs to determine which stimuli is priority

LIP guides…

eye movement & attention

when area LIP is active attention shifts…

prior to eye movement

attention shift takes

50 msec

saccades take

200 msec

salience map

certain visual features grab attention (bottom-up)

maps of individual features locate…

areas of high contrast

area with …& attention….

area with highest contrast wins & attention is moved to that area

priority map

adds top-down cognitive input onto salience map to direct what we’re paying attention to

priority maps adjust…

salience maps

show location where attention should be directed based on…

stimulus salience & cognitive input

area LIP for stimulus salience

LIP activated when 7 objects always shown & star flashes

area LIP for priority map

if 8 objects are always shown but a cue indicates which is significant, area LIP active

lesions in parietal cortex is known as

hemispatial neglect syndrome

hemispatial neglect causes..

ignore object, people, and own body from one side (usually left)

lesions usually located on

right hemisphere

frontoparietal network

controls goal-directed attention

steps of bottom-up attention in frontoparietal (4)

occipital lobe → LIP (salience map) → FEF (also salience map) → pulvinar nucleus

steps of top-down attention (4)

FEF → LIP (priority map) → modulate areas of visual cortex to enhance perception → create saccades