quiz 2 - object recognition Flashcards
(26 cards)
what is visual agnosia generally?
an impairment in recognizing visually presented objects despite otherwise normal visual field
what are the three types of visual agnosia
apperceptive
integration
associative
what is apperceptive agnosia
failure to extract features (figure-ground separation)
(early visual processing intact)
what is integrative agnosia
impaired shape/form processing
(relatively normal visual processing of color, illumination, motion etc)
associative agnosia
failure to render meaning (normal visual function)
- can identify forms/shapes but not able to name describe their functions
caused by damage to the temporal cortical region (bilateral inferior occipitotempral cortex)
what is it anomia and how is it different from agnosia and optic ataxia
anomia = language difficulty characterized by impaired word retrieval (esp. objects and people)
agnosia = language vs recognition
optic ataxia = neurological disorder characterized by difficuty reaching for objects using visual guidance (part of Balint syndrome)
what is the function of the lateral occipital complex?
it plays a role in shape processing (not recognition)
- driven by familiar & novel objects compared to scramble/shapeless stimuli
what structures respond to facial stimuli & what is the neural
superior temporal sulcus (STS) - expressions and gaze
fusiform face area (FFA)/fusiform gyrus
what are the two visual cortical pathways
- dorsal occipitoparietal pathway
- ventral occipitotemporal pathway
what is the dorsal occipitoparietal pathway
- has parietal cortical neurons have diverse spatial receptive field
- some foveal, some peripheral, nonselective
- spot new things
what is the ventral occipitotemporal pathway
- temporal cortical neurons have spatial receptive fields that encompass fovea
- highly selective
- identify stimulus by bringing them into central vision
what is binocular rivalry and what is the purpose of it?
when different stimuli are presented to each eye simultaneously –> both eyes receive constant input but perception switches between images
- useful for understanding perceptual selection & awareness because it lonks neural activity directly to perceptial experience
what are the five visual areas
area IT (inferior temporal cortex)
area V4
area V1 (primary visual cortex)
area MT (V5)
area V2 (secondary visual cortex)
function of area IT
object recognition & visual memory
function of area V4
object recognition, visual attention
extracts properties for properties (surface level, shape, depth)
function of area V1
sorting/mapping of visual field
1st stop, processes incoming information and sorts it
function of V5 (MT)
motion processing
function of area V2
takes information coming from V1 and sends it to V3/4/5, provides feedback loop
- also detects complex patterns, depth perception, and background distinction to sort accordingly
what is the repetition suppresion effect and where does it occur
drop in neuronal activity (BOLD) to repeated presentation of the same stimulus
what is the feedforward hierarchical coding model (in ventral visual pathway) and why is it incorrect?
def = information flows unidirectional, there is not feedback
–> incorrect because PFC activity peaks earlier than high-order visual activity in recognizing familar objects (and PFC is later in processing usually)
what are four visual test types
- unusual views test
- matching by function
- shadows
- visual reaching
what is the unusual views test? fail =?
asseses object constancy (from different POVs)
if failed = apperceptive agnosia
what is the matching-by-functions test? fail=?
participants match items by shared function, not appearance
if fail, associative agnosia
what is the shadows test? fail =?
participants must identify objects that are partially distorted or obscured
fail = apperceptive agnosia
