Chapter 3: Visual perception Flashcards
What is akinetopsia?
Unable to perceive motions( a for “without”, kine for “to move” and opsia for “seeing”)
What is the route from the eye to the brain?
eye > optic nerve > LGN in thalamus > V1 in visual cortex
What is/does the Lateral geniculate nucleus (LGN)
relay from optic nerve to V1
What is the blind spot?
Without any rods or cones, optic nerve is there
What is the blind spot?
Without any rods or cones, optic nerve is there
What is lateral inhibition?
The way in which cells are stimulated inhibits neighbouring cells; enchanges edges
What are Mach Bands?
Optical illusion illustrating edge enchantment, demonstrates that intrepretation and analysis begins in the eyeball
Where does visual processing/analysis start?
In the eye (lateral inhibition)
What is single-cell recording?
investigating moment-by-moment the pattern of electrical charges in a single neuron. Used to define receptive field
What is single-cell recording?
investigating moment-by-moment the pattern of electrical charges in a single neuron. Used to define receptive field
What is the receptive field?
The size and the shape of the area in the visual world to which a cell responds.
What are center-surround cells?
In the visual system, center-surround cells fire more when they centre is stimulated.
What are orientation-specific visual fields?
In the visual system, orientation-specific visual fields fire more when they detect a line in a specific orientation, less if that is not the case.
What are edge-detectors?
In the visual system edge-detectors fire more when they detect notches or corners.
What are motion detectors?
In the visual system movement detectors fire more when a stimulus moves from left to rights etc.
What is parallel processing in the brain?
Different neurons in V1 are specialised, resulting in parallel processing which is quick because it is split up. Afterwards they are integrated.
Where does the area V1 lies and what gives it its input?
Between the two hemispheres and in the occipital lobe. Gets it input from the thalamus.
What are the two big upsides to parallel processing?
Speed and mutual influence among systems which is useful in some cases
Is there a priority in systems in parallel processing?
No, systems negotiate a solution that satisfies both systems.
What are P-cells: give it’s function, location and what they are specialised to do?
In the optic nerve P-cells provide main input for LGN parvocellular cells, which seem to be specialised for spatial analysis and detailed analysis of form.
What are M-cells give it’s function, location and what they are specialised to do?
In the optic nerve M-cells provide main input for LGN magnocellular cells which are specialised for the detection of motion and the perception of depth.
Define the what system; pathway and function
Some activation from occipital lobe passed to cortex of temporal lobe. Major role in object identification.
Define the where system; pathway and function
Some activation from occipital lobe passed to cortex of parietal lobe. Major role in object in spacial recognition.
What does a lesion in the what or where system mean?
They can for example not grab an object but can correctly identify it.
What is the binding problem?
The question how parallel processed elements are combined. We see the world not as disjointed, it is combined somehow
Give the three elements that contribute to the solution of the binding problem:
- Spatial position
- Rhythms/neural synchrony
- Synchronised neural firing
What is spatial position (in the binding problem)?
Each brain part which does parallel processing keeps track of where the target/stimuli is, therefore the information can be resembled using the reference to the position.
What is rhythms/neural synchrony (in the binding problem)?
if neurons for example a vertical line are firing in synchrony with movement detectors, these features are bound together.
What is synchronised neural firing (in the binding problem)?
Synchronised firing occurs only when attending to a specific stimulus but does not occur in neutrons activated by unattended stimuli.
What are conjunction error and when do they happen?
When a person’s attention is overloaded (for example coloured colour words), they can bound/conjoin features wrongly.
Where does binding happens?
Visual system
What is a Necker Cube
A ambiguous figure; you can see either A or B but not at the same time.
What is figure/ground
We split the figure (foreground) from ground (what is in back)
What is spatial arrangement?
neurons that are sensitive to information in a region are close to neurons that are sensitive to information in adjacent regions.
Why do we only see one form?
Brain goes for the simplest interpretation of a object
What are the Gestalt Principles?
your perception is guided by similarity, proximity, good continuation, closure and simplicity
What causes a illusion (example table)
Shape constancy > Cues to depth, which are not suppressible, cause wrong interpretation.
What is cue to depth?
Perceiving 2D figures as 3D figures adjusting for viewing angles
What is perceptual, size, shape and brightness constancy?
We perceive constant properties of objects in the world even when sensory information changes
What happens in unconscious inference?
In perceptual constancy, taking one aspect of the input (e.g., the distance to the target) into account in interpreting another aspect (e.g., the target’s size). This process is usually quite accurate, but it can produce illusions.
What can cause a contrast effect in a illusion?
Lateral inhibition.
What are distance cues?
features of a stimulus that indicate a object’s position.
What the difference between two eye’s views in perception called?
Binocular disparity, help to see depth without distance cues.
What are monocular cues?
depth cues that depend on what one eye sees, for example pictorial cues(depth on a flat surface) and interposition (something blocks view of object means it is closer)
What is linear perspective?
A cue for distance based on the fact that parallel lines seem to converge as they get farther away from the viewer.
How can you perceive depth trough motion?
motion parallax or optic flow
Why is our visual system influenced by so many (distance) cues?
Because different distance cues become important in different circumstances
How do we achieve constancy?
Trough unconscious inference we take one aspect of the input and take it into account interpreting other aspects
