Perception Flashcards
What is a receptive field
Response in a visual neurons to a stimulus that is presented in a specific region of space
What is a retinotopic map
A visualisation that shows neural activity in response to visual cues
Do next door parts of the visual cortex respond to stimulus in next door bits of visual space
Yes
What is the optic nerve made up of
Axons of the ganglion cells
Where do medial axons intersect in the optic nerve
Optic ciasm
Do medial (nasal) neurons cross at the optic chiasm
Yes
Do temporal (lateral) neurons cross at the optic chiasm
No
What region of the visual cortex is sensitive to colour
V4
Do different regions of the visual cortex have different retinotopic maps
Yes
Do full retinotopic maps contain a representation of an entire contralateral hemifield
Yes
Where is V1 located
Calcarine sulcus
What stimulus is V4 sensistive to?
Colour
Is conscious perception linked to lower or higher areas of activity
Higher
Do early sensory regions “see through” illusions
Yes
In secondary areas, how can perception be elicited
- Visual stimulus
- Direct electrical stimulation of the cortex
What is achromatopsia
Inability to perceive colour
Do lesions to V4 lead to deficits in shape perception
Yes
What is akinetopsia
An impairment in the ability to perceive motion
Damage to what region leads to akinetopsia
V5
Does disruption at V1 cause problems sooner than disruption at V5
No! There is a direct connection between the optic nerve and V5
What damage is more significant to V5: unilateral or bilateral
Bilateral
What region is responsible for motion
V5(MT)
What region is responsible for vision
V1
What region is responsible for processing whole objects
V3
Does V4 process complex shapes as well as colour
Yes
What is object constancy
Ability to recognise objects in different context despite variation in physical stimulus
What is the “What” stream of visual perception
The ventral (occipitotemporal) stream
What is the “Where” stream of visual perception
The dorsal (occipitoparietal) stream
What pathway does the ventral stream take
From the occipital striate cortex to the temporal lobe
What pathway does the dorsal stream take
From the occipital striate crotex to the parietal lobe
What is another name for the ventral stream
The inferior longitudinal fasciculus
What is another name for the dorsal stream
The superior longitudinal fasciculus
What is the main difference between the ventral and dorsal streams
The dorsal focuses on things, while the ventral is peripheral
What area do dorsal neurons receptive fields focus encompass
The fovea (centre region)
What is the breakup of ventral neurons
40% fovea, 60% elsewhere
Does the ventral stream get more detailed the further along you go
Yes
What stream is more important for guiding interaction with objects
The dorsal stream
What problems might patients with lesions in the ventral stream face
They may be unable to identify objects but use the visual info to guide movement (telephone/clock case study)
What problems might patients with optic ataxia (lesions to the parietal cortex) face
They may be able to identify objects but cannot use visual info to guide action
What is a delayed matching to sample experiment
Monkeys must pick out one object out of two to get a reward thereby engaging the ventral “what” stream
What is a land mark discrimination problem
Monkeys must choose a location to get a reward thereby engaging the dorsal “where” stream
Do unilateral lesions produce apparent deficits in the dorsal or ventral streams
No.
Do bilateral lesions produce apparent deficits in the dorsal or ventral streams
Yes
Is there cross-talk across hemispheres via the corpus callosum in the dorsal and ventral streams
Yes
What is the primary area of the brain for processing objects
The Lateral occipital complex
How was the lateral occipital complex discovered
PET that controlled for scrambled objects and familiar objects
Do visual processing areas have connection to memory areas
Yes
What is the repetition suppression effect
Lower BOLD response in second presentation.
What does the repetition suppression effect represent
Perhaps increased neural efficiency
Is the lateral occipital complex sensitive to texture or shape changes in infants
Shape
What is a gnostic unit
A neuron that recognises a complex object (the grandmother cell)
What is the hierarchical coding hyptohesis
Perception of elementary features is combined to create an object that can be recognised by gnostic units
What is the ensemble coding hypotheseis
Objects are defined by simultaneous activation of a set of defining properties
What is top-down facilitation
Orbitofrontal cortex predicts an object from partial visual input then it goes to the ventral stream for object recognition
What is decoding
Looking at brain activity and predicting stimulus
What is specificity
Certain brain areas are responsible for facial recognition
What brain areas are responsible for movement information about the face such as direction of gaze and emotive expression
The right STS
What brain areas are responsible for invariant features such as eye spacing
Ventral face pathway
What brain areas are responsible for the face
Fusiform face area
What area is responsible for scenes
Parahippocampal place area
What areas are responsible for bodies
Extrastriate body area and fusiform body area
What is view invariance
The ability to differentiate beween ambiguous cirucmstances - see things from any angle
What is recognition by components?
The ability to infer from features (geons) basic 3D objects
What is apperceptive visual agnosia
Cant put the whole together but can do basic components
Lesions to what area lead to apperceptive visual agnosia
Ventral right posterior
What is integrative visual agnosia
Can perceive parts but not the whole. Difficulty with overlap
What is associative visual agnosia
Can perceive objects with visual system but can’t give them meaning. There is no coneptual knowledge
Lesions to what area lead to associative visual agnosia
Left posterior
What is the sensory/functional hypothesis
Conceptual knowledge comes from the sensory input and motor input (for objects)
- these dependent on the relevant neural regions
What is the domain sepcific hypothesis
Conceptual knowledge organisaed by evolutionary categories
What is prosopagnosia
The inability to recognise faces
How does prosopagnosia usually occur
Bilateral lesions in the ventral pathway especially the occipital and FFA
