Topic 4: The Visual Brain Flashcards
Optic Chiasm
an x-shaped bundle of fibers on the underside of the brain, where nerve fibers activated by stimulation of one side of the visual field cross over to the opposite side of the brain
Contralateral
side of the body opposite to the side on which a particular condition occurs
Lateral Geniculate Nucleus (LGN)
the nucleus in the thalamus that receives inputs from the optic nerve and, in turn, communicates with the cortical receiving area for vision
Superior Colliculus
an area in the brain that is involved in controlling eye movements and other visual behaviors
this area receives about 10% of all ganglion cell fibers that leave the eye in the optic nerve
Visual Receiving Area
the area of the occipital lobe where signals from the retina and LGN first reach the cortex
Striate Cortex
the visual receiving area of the cortex, located in the occipital lobe
Area V1
the visual receiving area of the brain
called area V1 to indicate that it is the first visual area in the cortex
also called the striate cortex
Simple Cortical Cells
a neuron is the visual cortex that responds best to bars of a particular orientation
Orientation Turning Curve
a function relating the firing rate of a neuron to the orientation of the stimulus
Complex Cells
a neuron in the visual cortex that responds best to moving bars with a particular orientation
End-Stopped Cells
a cortical neuron that responds best to lines of a specific length that are moving in a particular direction
Feature Detectors
a neuron that responds selectively to a specific feature of the stimulus such as orientation or direction of motion
Selective Adaptation
a procedure in which a person or animal is selectively exposed to one stimulus, and then the effect of this exposure is assessed by testing with a wide range of stimuli
typically, sensitivity to the exposed stimulus is decreased
Contrast Threshold
the intensity difference between two areas that can just barely be seen
this is often measured using grating with alternating light and dark bars
Selective Rearing
a procedure in which animals are reared in special environments
an example us the experiment in which kittens were reared in an environment of vertical striped to determine the effect on orientation selectivity of cortical neurons
Neural Plasticity
the capacity of the nervous system to change in response to experience
examples are how early visual experience can change the orientation selectivity of neurons in the visual cortex and how tactile experience can change the sizes of areas in the cortex that represent different parts of the body
Experience-Dependent Plasticity
a process by which neurons adapt to the specific environment within which a person or animal lives
this is achieved when neurons change their response properties so they become tuned to respond best to stimuli that have been repeatedly experienced in the environment
Retinotopic Map
a map on a structure in the visual system, such as the lateral geniculate nucleus or the cortex, that indicates locations on the structure that correspond to locations on the retina
in retinotopic maps, locations adjacent to each other on the retina are usually represented by locations that are adjacent to each other on the structure
Cortical Magnification
occurs when a disproportionally large area on the cortex is activated by stimulation of a small area on the receptor surface
one example of cortical magnification is the relatively large area of visual cortex that is activated by stimulation of the fovea
an example in the somatosensory system is the large area of somatosensory cortex activated by stimulation of the lips and fingers
Cortical Magnification Factor
the size of the cortical magnification effect
Location Columns
a column in the visual cortex that contains neurons with the same receptive field locations on the retina
Orientation Columns
a column in the visual cortex that contains neurons with the same orientation preference
Hypercolumn
in the striate cortex, unit proposed by Hubel and Wiessel that combines location, orientation, and ocular dominance that serve a specific area on the retina
Tiling
the adjacent (and often overlapping) location columns working together to cover the entire visual field (similar to covering a floor with tiles)
Extrastriate Cortex
collective term for visual areas in the occipital lobe and beyond known as V2, V3, V4, and V5
Ablation
removal of an area of the brain
this is usually done in experiments on animals to determine the function of a particular area
also called lesioning
Object Discrimination Problem
the behavioral task used in Ungerleider and Mishkin’s experiment in which they provided evidence for the ventral, or what, visual processing stream
monkeys were required to respond to an object with a particular
Landmark Discrimination Problem
the behavioral task used in Ungerleider and Mishkin’s experiment in which they provided evidence for the dorsal, or where, visual processing stream
monkeys were required to respond to a previously indicated location
Ventral Pathway
pathway that conducts signals from the striate cortex to the temporal lobe
also called the what pathway because it is involved in recognizing objects
Dorsal Pathway
pathway that conducts signals from the striate cortex to the parietal lobe
the dorsal pathway has also been called the where, or how, or the action pathway by different investigators
