PPVK Vision 3 Flashcards
Extrastriate cortex
the region of the cortex bordering the primary visual cortex and containing multiple areas involved in visual processing
At higher levels of the visual pathway, neurons have ________________
larger receptive fields
This progressive increase in receptive field size is accompanied by an increase in____________
neuronal tuning complexity
složenost neuronskog ugađanja
V2 neurons prefer combinations of __________
orientation elements (curved spirals, sharp angles, gratings…)
V4 neurons show highly ________ responses to _______ and ______ frequency; they respond less to simple lines or gratings
heterogenous, orientation, spatial frequency
achromatopsia
area V4 has also been implicated in color perception and color constancy
complete or partial absence of color vision. People with this condition typically see the world in shades of gray
What is “border ownership” in V2 neurons, and what does it demonstrate?
Border ownership refers to V2 neurons’ ability to determine which side of a border “owns” the edge.
These neurons respond differently depending on figure-ground context.
Example: They distinguish between the edge of a black square on gray vs. a gray square on black.
This shows that V2 encodes not just edges, but also which object a contour belongs to — a key step in object perception.
Two main pathways from the extrastriate regions of the occipital lobe?
Dorsal (where) - parietal lobe
Ventral (what) pathways - temporal lobe
DORSAL (Where) pathway:
important for representing objects in space (location); actions; deployment of attention
VENTRAL (What) pathway:
important for object recognition, form, color
Starts from V1 → V2 → V4 → IT cortex
Basic information is presented in ______ pathways of extrastriate cortex
both (dorsal and ventral)
Inferotemporal (IT) cortex
Is a high-level region
receptive fields are very large
Specialized for recognizing complex objects like faces, hands, and shapes
Damage to IT can cause ________ (e.g., prosopagnosia = face blindness)
visual agnosias
Who represented a hierarchical model of visual perception?
Horace Barlow
Feed-forward process
carries out a computation (e.g. object recognition) in successive steps
Inferotemporal cortex cells learn their receptive field properties ->
plasticity
Reverse - hierarchy theory
Teorija obrnute hijerarhije kaže da mozak prvo brzo prepozna opće vrste objekata, a zatim povratnim signalima iz viših u niže dijelove dodaje detalje, koristeći greške u predviđanju da poboljša percepciju i usmjeri pažnju
is when you first vaguely recognize a shape as a “bird” (feed-forward process), then feedback from higher brain areas refines details like its beak and feathers (stored in lower visual areas), correcting initial errors to confirm it’s a “sparrow.”
Mid-level vision
- Occurs after basic feature extraction (low-level vision) and before object recognition/scene understanding (high-level vision).
- Involves perception of edges and surfaces.
- Groups image regions into objects.
An example of mid-level vision is perceiving the edges and surfaces of a cup on a table, grouping those visual features to distinguish it as a distinct object before recognizing it as a “cup.”
feature extraction = odvajanje značajki
Gestalt grouping rules
a set of organizing principles, describe the visual system perception of the raw retinal image
Good continuation
Gestalt grouping rule stating that two elements will tend to group together if they lie on the same contour
Closure
Gestalt principle that holds that a closed contour is preferred to an open contour
vizualni sustav teži tome da zatvori oblike
Texture grouping, related to?
proximity and similarity (closer objects are grouped together)
Parallelism
parallel contours likely belong to the same group
Symmetry
symmetrical groups, more likely to be seen as a group
