NEUR305 - models of attention

overt attention

target fixation

covert attention

without fixation

dichotic listening task

demonstrates access to information later in processing

cocktail party effect

refers to the ability to focus one’s attention to a particular stimulus while filtering out a range of other stimuli (ie. noise)

mental spotlight

reaction time costs and benefits have been attributed to the influence of covert attention

covert attention therefore is likened to mental spotlight

used to describe how the brain may attend to a spatial location

during cued attention there are

pronounced EEG signals

attention modulates neuron activity in V4

• identify receptive fields of V4 neurons, found that some neurons respond strongly to a red, horizontal bar and others to a green vertical bar (recall V4 receptive fields combine orientation and color)

• simultaneously present preferred and non-preferred stimulus in same visual field, and monkeys trained to covertly attend to a particular spatial location

• neuron that prefers red, horizontal bars is being recorded from

  • compare activity when attending to the preferred stimulus vs attending to a non-preferred stimulus

biased competition model

• when different stimuli in a visual scene fall within the receptive field of a visual neuron, the bottom-up signals from two stimuli compete for control of the neuron’s firing

• attention can resolve this competition by favoring or biasing one of the stimuli

the biased competition model - receptive fields

• receptive field sizes increase in size along visual hierarchy

• as information travels along hierarchy, greater need for attention to resolve competition

T/F: attention resolves competition

true

thalamic reticular nucleus

• not part of the primary visual pathway

• has reciprocal connections to and from V1

• modulates information flow from thalamus to cortex

• receives excitatory input, but inhibits the rest of the thalamus

• inhibitory thalamic reticular nucleus (TRN) is a hub to regulate selective attention during wakefulness and control the thalamic and cortical oscillations during sleep

• modulates pulvinar activity

feature integration theory

• a target item can be identified more quickly amongst distractors if it can be identified by a single stimulus feature (ie. color or shape)

• if features are shared between target and distractors, then time it takes to locate target increases as a function of the number of distractors

• conjunction search affects P1 ERP wave similarly to cued spatial attention

• spotlight of spatial attention employed during visual search is based on early modulations of visual processing

pop out search

easy to find something because of its unique features

ie. red circle in a field of green circles and xs

quicker reaction time

conjunction search

harder to find somethign because of its shared features

ie. red circle in a field of green and red xs and circles

slower reaction time

distractor stimuli in a visual search experiment

always slow down visual search for target stimuli

object vs feature

object is the whole

feature is an aspect of the object

spatial attend

left or right

feature attend

red or blue

spatial attention (P1) is absent

T/F: features are processed before objects

true

feature attention

T/F: attention modulates object representation in different brain areas

true