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28 Cards in this Set
- Front
- Back
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What is a receptive field |
(of an individual sensory neuron) is the particular region of the sensory space (e.g., the body surface, or the visual field) in which a stimulus will trigger the firing of that neuron |
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What is a receptive field
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(of an individual sensory neuron) is the particular region of the sensory space (e.g., the body surface, or the visual field) in which a stimulus will trigger the firing of that neuron
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Where is contrast processed? |
Retina, LGN, Cortex |
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How do you calculate contrast? |
Michelson Contrast = (max lum - min lum)/ (max lum + min lum) |
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What does simultaneous contrast tell us? |
We take context into account |
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What are computational models useful for? |
To predict neural responses |
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What are the four main levels of representations of sensory info in the brain? |
1. Pathways eg LGN - V1 2. Attributes eg motor cortex processes motor info 3. Maps eg retina topic map - representation on retina - coded by 2 cells next to each other -retain representation of real world space 4. Cells eg individual level |
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What is contrast? |
Difference in luminence levels (measured in candelas per square metre) |
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Contrast sensitivity varies as a function of ...? |
Spatial frequency (size between bars. high sp freq is narrow bars/lots of them). As sp freq increases our sensitivity gets worse. |
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What is lateral inhibition? |
The result of an ON centre - OFF surround receptive field.
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What are linear receptive fields? |
As stimulus intensity increases, the activity of the neuron increases at a comparable rate. Retinal ganglion cells (coding contrast) are the sum of overall inhibition and excitation, which is a linear equation |
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What type of receptive field models is thought to be the better fit for contrast? |
Nonlinear because we can see high and low luminence. |
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What are some monocular cues for depth (using one eye) |
Occlusion Size constancy Pictorial Cues (ames room - do not need disparity info to determine these) Motion Parallax (riding in the car, close and far objects moving slow vs fast) |
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What do illusions like the Ames room tell us about perception |
Context is important and what we expect in the environment can influence perception |
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What is the horopter? |
Where you're fixating |
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When are your eyes crossed? |
Before the horopter, disparity |
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When are your eyes uncrossed? |
Beyond the horopter, disparity |
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What is accommodation? |
When the lens is stretched or relaxed to bring a target into focus, cillary muscles push/pull the lens |
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What is (con)vergence? |
Angle of gaze of 2 eyes, eyes can be turned in to focus on small objects (larger angle) and outward to focus on further objects |
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What are thresholds for disparity comparable to? |
Width judgements, humans are slightly better at determining disparity than width, meaning we must use inference as well. |
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What is accommodation used for? |
Strain on the lens is sensed by the visual system to calculate the distance of an object. |
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What happens to accommodation when we age? |
Lens becomes less flexible, might result in hyperopic eye (long sighted - image falls beyond retina) or myopic (sort sighted - falls too short) |
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What is strabismus? |
Exotrope - eye points outwards Esotrope- eye points inward |
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List monocular depth cues
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Size constancy Occlusion
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What does the Ames Room do?
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Exploits pictorial cues when using our monocular vision
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What is motion parallax?
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Depth cue, close things move fast and further things move slow (ie taking off on a plane) (relative motion to you).
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What is binocular vision?
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Difference in position to left and right eye to see depth (binocular disparity).
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How do you measure disparity threshold?
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Westheimer & McKee - 2 lines when can you discriminate the difference between 2 lines, method of constant stimuli.
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