6.2 The Neural Basis of Visual Perception Flashcards
Receptive field
The part of the visual field to which any one neuron responds to
Lateral inhibition
The reduction of activity in one neuron by activity in neighboring neurons; The main function is to heighten the contrast at borders
Parvocellular neurons
Small cell bodies and small receptive fields; located mostly in or near the fovea; Well-suited to detect visual details; highly sensitive to color
Magnocellular neurons
Large cell bodies and receptive fields; distributed fairly evenly throughout the retina; Not color sensitive; respond strongly to moving stimuli and large overall patterns
Koniocellular neurons
The least numerous; the least responsive; and the least understood
Primary visual cortex
Area V1; striate cortex, because it’s striped appearance; responsible for the first stage of visual processing; receives visual information from the lateral geniculate area; Responds to any kind of visual stimulus; active when people close their eyes and imagine visual stimuli
Secondary visual cortex
Area V2; conducts a second stage of visual processing; transmits the information to additional areas; can return information to V1
Ventral stream
Visual paths in the temporal cortex; “what” pathway; Specialized for identifying and recognizing objects
Dorsal stream
The visual path in the parietal cortex; “where” or “how” path; helps the motor system find objects and determine how to move toward them, grasp them, and so forth; sensitive to shape
Simple cells
Found exclusively in the primary visual cortex; the receptive field has fixed excitatory and inhibitory zones
Complex cells
Located in either area V1 or V2; have receptive fields that cannot be mapped into fixed excitatory and inhibitory zones; respond to a pattern of light in a particular orientation anywhere within its a large receptive field, regardless of the exact location of stimulus; Responds most strongly to a stimulus moving perpendicular to its axis
End-stopped or hypercomplex cells
Resemble complex cells with one additional feature: has a strong inhibitory area at one end of its bar-shaped receptive field; the cell responds to the bar-shaped pattern of light anywhere in its broad receptive field provided that the bar does not extend beyond a certain point
Feature detectors
Neurons whose responses indicate the presence of a particular feature
Inferior temporal cortex
Because cells in this area have huge receptive fields, always including the foveal field of vision, their responses provide almost no information about stimulus location; however, many of the cells do provide detailed information about stimulus shape
Shape constancy
The ability to recognize an object’s shape even as it approaches or retreats or rotates
Visual agnosia
An inability to recognize objects despite otherwise satisfactory vision
Prosopagnosia
Ability to recognize other objects but not faces
Fusiform gyrus
Involved in the recognition of faces and complex visual stimuli
Blobs
A path of cells highly sensitive to color emerges in parts of area V1
Stereoscopic depth perception
The ability to detect depth by differences in what the two eyes see
MST
Medial superior temporal cortex; responds best to the expansion, contraction, or rotation of a large visual scene; Where cells respond whenever an object moves in a certain direction relative to its background
Motion blind
People are able to see objects but unable to determine whether they are moving or, if so, in which direction or how fast
Blindsight
The ability to localize visual objects within and apparently blind visual field
Lateral geniculate nucleus
A nucleus of the thalamus specialized for visual perception
