Organic Brain Biopsychology Chapter 6

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Action potential: rapid depolarization and slight reversal of the usual polarization caused by stimulation beyond the threshold.
Amblyopia (lazy eye): reduced vision resulting from disuse of one eye, usually associated with failure of the two eyes to point in the same direction.
Astigmatism: blurring of vision for lines in one direction because of the nonspherical shape of the eye.
Binding problem: question of how the visual, auditory, and other areas of the brain influence one another to produce a combined perception of a single object.
Binocular vision: based on the simultaneous stimulation of two eyes.
Bipolar cells: type of neuron in the retina that receives input directly from the receptors.
Blind spot: point in the retina that lacks receptors because the optic nerve exits at this point.
Blindsight: ability to localize objects within an apparently blind visual field.
Color constancy: ability to recognize the color of an object despite changes in lighting.
Color vision deficiency: inability to perceive color differences as most other people do.
Column: collection of cells having similar properties, arranged perpendicular to the laminae.
Complex cell: a cell type of the visual cortex that responds best to a light stimulus of a particular shape anywhere in its receptive field; its receptive field cannot be mapped into fixed excitatory and inhibitory zones.
Cone: a type of retinal receptor that contribute to color perception.
Critical (sensitive) period: stage of development when experiences have a particularly strong and long-lasting influence.
Dorsal stream: visual path in the parietal cortex, sometimes known as the where or how pathway.
End-stopped (hypercomplex) cell: a cell of the visual cortex that responds best to stimuli of a precisely limited type, anywhere in a large receptive field, with a strong inhibitory field at one end of its field.
Feature detector: neuron whose responses indicate the presence of a particular feature.
Fovea: area in the center of the human retina specialized for acute, detailed vision.
Functional magnetic resonance imaging (fMRI): a modified version of MRI that measures energies released by hemoglobin molecules in an MRI scan, and then determines the brain areas receiving the greatest supply of blood and oxygen.
GABA (gamma amino butyric acid): the most abundant inhibitory neurotransmitter.
Ganglion cell: type of neuron in the retina that receives input from the bipolar cells.
Graded potential: membrane potential that varies in magnitude and does not follow the all-or-none law.
Horizontal cell: type of cell that receives input from receptors and delivers inhibitory input to bipolar cells.
Hypercomplex (end-stopped) cell: a cell of the visual cortex that responds best to stimuli of a precisely limited type, anywhere in a large receptive field, with a strong inhibitory field at one end of its field.
Hypothalamus: forebrain structure near the base of the brain just ventral to the thalamus.
Inferior temporal cortex: portion of the cortex where neurons are highly sensitive to complex aspects of the shape of visual stimuli within very large receptive fields.
Koniocellular neurons: ganglion cells located throughout the retina.
Lateral geniculate nucleus: thalamic nucleus that receives incoming visual information.
Lateral inhibition: restraint of activity in one neuron by activity in a neighboring neuron.
Law of specific nerve energies: the statement that each nerve always conveys the same kind of information to the brain.
Lazy eye (amblyopia): reduced vision resulting from disuse of one eye, usually associated with failure of the two eyes to point in the same direction.
Magnetic resonance imaging (MRI): method of imaging a living brain by using a magnetic field and a radio frequency field to make atoms with odd atomic weights all rotate in the same direction and then removing those fields and measuring the energy that the atoms release.
Magnocellular neuron: large-celled neuron of the visual system that is sensitive to changing or moving stimuli in a relatively large visual field.
Midget ganglion cells: ganglion cells in the fovea of humans and other primates.
Motion blindness: impaired ability to perceive the direction or speed of movement, despite otherwise satisfactory vision.
MST: medial superior temporal cortex, an area in which neurons are sensitive to expansion, contraction, or rotation of the visual field or to the movement of an object relative to its background.
MT (area V5): a portion of the middle temporal cortex, where neurons are highly sensitive to the speed and direction of movement of visual stimuli.
Negative color afterimage: the result of prolonged staring at a colored display and then looking at a white surface, in which one sees green where the display had been red, red where it had been green, yellow where it had been blue, blue where it had been yellow, black where it had been white, and white where it had been black.
Nerve growth factor (NGF): protein that promotes the survival and growth of axons in the sympathetic nervous system and certain axons in the brain.
Neurons: cells that receive information and transmit it to other cells by conducting electrochemical impulses. See also Synapses.
Opponent-process theory: the theory that we perceive color in terms of paired opposites: white versus black, red versus green, and blue versus yellow.
Optic nerve (or optic tract): the bundle of axons that travel from the ganglion cells of the retina to the brain.
Parvocellular neuron: small-celled neuron of the visual system that is sensitive to color differences and visual details in its small visual field.
Photopigment: a chemical that releases energy when struck by light.
Postsynaptic neuron: a neuron on the receiving end of a synapse.
Primary visual cortex (V1): the area of the cortex responsible for the first stage of visual processing.
Prosopagnosia: an impaired ability to recognize or identify faces.
Psychophysical observations: reports by observers concerning their perceptions of various stimuli.
Pupil: the opening in the center of the iris through which light enters.
Receptive field: the part of the visual field to which any one neuron responds.
Receptor potential: the local depolarization or hyperpolarization of a receptor membrane.
Retina: the rear surface of the eye, lined with visual receptors.
Retinal disparity: discrepancy between what the left eye sees and what the right eye sees.
Retinex theory: the concept that when information from various parts of the retina reaches the cortex, the cortex compares each of the inputs to determine the color perception in each area.
Rod: a type of retinal receptor that does not contribute to color perception.
Secondary visual cortex (V2): the area of the visual cortex responsible for the second stage of visual processing.
Sensitive (critical) period: the time early in development during which some event (such as an experience or the presence of a hormone) has a strong and long-lasting effect.
Shape constancy: the ability to perceive the shape of an object despite the movement or rotation of the object.
Simple cell: a type of visual cortex cell that has fixed excitatory and inhibitory zones in its receptive field.
Stereoscopic depth perception: the sensation of depth by comparing the slightly different inputs from the two eyes.
Strabismus: a condition in which the two eyes point in different directions.
Superior colliculus: the swelling on each side of the tectum in the midbrain.
Thalamus: a structure in the center of the forebrain.
Trichromatic (Young-Helmholtz) theory: the theory that we perceive color through the relative rates of response by three kinds of cones, with each kind maximally sensitive to a different set of wavelengths.
Ventral stream: visual paths in the temporal cortex, sometimes known as the what pathway.
Visual agnosia: the impaired ability to identify visual objects despite otherwise satisfactory vision.
Visual field: the area of the world that an individual can see at any time.
Young-Helmholtz (trichomatic) theory: the theory that we perceive color through the relative rates of response by three kinds of cones, with each kind maximally sensitive to a different set of wavelengths.

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