Chapter 4,5,6 Vocab Flashcards Preview

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Flashcards in Chapter 4,5,6 Vocab Deck (294)
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126

Saccades

Small jerky movements or flicks of the eye

127

Transduction

Conversion of one form of energy to the other visual transduction is the conversion of light to neural signals by the visual receptors



128

Pigment

Any substance that absorbs light

129

Rhodopsin


The photopigment of rods; Absorbs light and bleaches when exposed to intense light; G-Protein that responds to light

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Bleaching

Lose its color

131

Absorption Spectrum

A graph of the ability of a substance to absorb light of different wavelengths

132

Retina

Geniculate-Striate Pathways - Conduct signals from each retina to the primary visual cortex via the lateral geniculate nuclei

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Primary Visual Cortex



Striate cortex

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Lateral Geniculate Nuclei

The six-layered thalamic structures that receive input from the retinas and transmit their output to the primary visual cortex


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Retintopic

Each level of the retina-geniculate-striate system is organized like a map of the retina

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Parvocellular Layers

Layers composed of neurons with small cell bodies- run through the top four layers through each lateral geniculate nucleus

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Magnocellular Layers

Composed of neurons with large cell bodies—bottom two layers of lateral geniculate nucleus

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Mach Bands

Nonexistent stripes of brightness and darkness running adjacent to the edges –they enhance the contrast at each edge and make it easier to see

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Contrast Enhancement

Every edge we look at is highlighted for us by contrast-enhancing mechanisms of our nervous system; Intensification of the perception of edges

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Lateral Inhibition

When a receptor fires, it inhibits its neighbors via the lateral neural network it spreads laterally across the array of receptors

141

Receptive Field

The area of the visual field within which it is possible for a visual stimulus to influence the firing of that neuron


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Monocular

Each neuron had a receptive filed in one eye, but not the other

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On-Center Cells

Respond to lights shone in the central region of their receptive fields with “on” firing and to lights shone in the periphery of their receptive fields with inhibition, followed by “off” firing when the light is turned off

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Off-Center Cells

They respond with inhibition and “off” firing in response to lights in the center of their receptive fields and with “on” firing to lights in the periphery of their receptive fields

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Simple Cells

Receptive fields (on and off regions) unresponsive to diffuse light; monocular; are straight lines rather than circles
Respond best to bars of light in a dark field, dark bars in a light field, or single straight edges between dark and light areas; Each simple cell preferred straight-edge stimulus is in a particular position and in a particular orientation


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Complex Cells

More numerous than simple cells; Rectangular receptive fields and respond best to straight-line stimuli; Larger receptive fields; Not possible to divide the fields of complex cells into static on or off regions


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Binocular

Responds to stimulation of either eye


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Ocular Dominance

Respond more robustly to stimulation of one eye than they do to the same stimulation of the other (monkeys)

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Retinal Disparity

Some binocular cells fire best when the preferred stimulus is presented to both eyes at the same time, but in slightly different positions on the two retinas; Depth perception

150

Component Theory (trichromatic)

There are three different kinds of color receptors, each with a different spectral sensitivity; Mixing together three different wavelengths of light in different proportions (for visual color); The color of any one of them cannot be matched by a mixing of the other two


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Opponent Process Theory

Ewald Hering in 1878; Two different classes of cells in the visual system for encoding color and another class for encoding brightness; Each of the three classes of cells encoded two complementary colors of perception

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Complementary Colors

Pairs of colors that produce white or gray when combined in equal measure (green light and red light)



153

Catecholamines

The three neurotransmitter that are synthesized from the amino acid tryrosine dopamine, epinerphrine, and norepinephrine

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Trichromats

Possessing three color vision photo pigments
Color Constancy - the fact that the perceived color of an object is not a simple function of the wavelengths reflected by it ; wavelengths by colored shirt changed, color of shirt did not

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Retinex Theory

the color of an object is determined by its reflectance (proportion of light of different wavelength that a surface reflects)