Perception Flashcards
What is sensation?
detection of internal/external stimuli
raw info about environment is made available to brain through senses
What is perception?
awareness & interpretation of sensory information by the brain
What is the primary visual cortex (V1)?
first part of cortex to receive VISUAL info
visual information travels from retina through subcortical areas to V1
What happens if the primary visual cortex (v1) gets damaged?
blindsight = lose conscious vision but can still respond to visual stimuli
What is the secondary visual cortices (~24)?
process visual info (form, motion, shape) received from V1
What happens if bilateral damage to secondary cortex v5?
akinetopsia = unable to process motion smoothly, flashing
selective loss of visual motion perception
What are visual association cortices (~7)?
multisensory integration = receive input from visual cortex & from cortices of 1 or more other sensory systems (dorsal & ventral stream)
What is the dorsal stream (visual association cortex)?
flows from V1 to dorsal prestriate cortex -> posterior parietal association cortex
what is the ventral stream (visual association cortex)?
flows from V1 to ventral prestriate cortex -> inferotemporal cortex
what is theory 1 of the function of dorsal/ventral streams? give example!
“What vs Where”
Dorsal stream = where pathways (patients easily describe object, can’t reach accurately)
Ventral stream = what pathway (patients easily reach for object, can’t describe)
what is theory 2 of the function of dorsal/ventral streams? give example!
“Action vs Perception”
(patient DF)
Dorsal stream = direct behavioural interaction w/ object (accurately changed width of grasp when reach for object)
Ventral stream = mediate conscious perception of objects (could not verbally discriminate b/w 2 blocks)
What is apperceptive agnosia?
failure in object recognition linked to problems in perceptual processing
ie. can see it but difficult to recreate it
What is associative agnosia?
normal visual perception but unable to use visual information to recognise things
ie. can copy it but don’t know what it is
what are the brain regions associated w/ face perception?
- fusiform face area (FFA)
- occipital face area (OFA)
- anterior temporal cortex (AT)
What is Prosopagnosia?
failure face recognition BUT intact object recognition (injury/developmental
can recognize ppl w/ different things (ie. clothing, voice)
treatment: developing training programs & patients develop coping strategies (ie. other features, particular seating)
What is Prosometamorphosia?
only faces (not objects) perceived to be distorted
involve 1 or both sides of face, reflects abnormal activity in face processing network
effect can be induced on normal patient (receive stimulation through intracranial electrodes in right inferior temporal lobe
What is the primary visual pathway?
pathway for vision from retina - primary visual cortex VIA lateral geniculate nucleus of thalamus & optic radiations = geniculostriate pathway
What is the effect of Optic Nerve lesions?
total blindness in one eye
What is the effect of Optic Chiasm lesions?
loss of vision in the outer parts of both eyes (bitemporal hemianopia)
What is the effect of Primary Visual Cortex Lesion lesions?
loss of vision in the same side of both eyes (homonymous hemianopia), but if the lesion is small, there may be no loss of central vision (macular sparing)
What is the phenomenon of blindsight?
person unable to consciously see something BUT still respond/react to it (ie. knowing where it is or detecting its movement)
what are 2 possible explanations for blindsight?
- visual info processed through alternative pathways (ie. retina-geniculate-striate pathway)
- residual brain activity in damaged cortex = process some visual information, though at a reduced sensitivity.
what do the authors (Dankert) mean by “bootstrapping”
using something the patients consciously notice (like the color aftereffect) to learn about the parts of their brain that are still processing visual information without them being aware of it
reaction to the color change
as one small clue to figure out something bigger that’s happening without them knowing
What was done in Aglioti et al’s study?
tested patient SF, who had difficulty discriminating between letters, including “R” and “V.”
gave him a Stroop test where the letters were either printed in congruent colors (R in red, V in green) or incongruent colors (R in green, V in red)
