Cortical Areas

IT

Participates mainly in the acts of noticing and remembering an object's qualities. Cells do not have a retinotopic organization. Very large receptive fields. Virtually every cell's receptive field includes the foveal region. Receives input from V4. Some cells show a preferential response to such stimuli as hands or faces.

MST (Medial Superior Temporal Area), V5a

Seems to be involved in visually tracking moving target. Projects along with MT to the dorsolateral pontine nuclei in the brain stem.

MT (Middle Temporal Area), V5

Characterized by strong motion-directionally sensitive neurons with large receptive fields organized into columns. Some neurons respond to the whole rather than the component motion of moving plaid patterns. Implicated in the analysis of movement, and stereoscopic depth. Receives input from layer 4B in V1 and thick stripes in V2. Projects to MST.

Posterior Parietal Cortex

Concerned with the perception of the spatial relations among objects.

STP (Superior Temporal Polysensory Area)

Area of monkey cortex. Virtually all cells respond to visual stimuli but some also activated by somatosensory and auditory input. Large receptive fields covering most of the visual field with no visuotopic order. Show radial or opponent direction selectivity. Some cells have fields responding to motion either towards the area centralis or away from it. Others show selective responses for object moving in depth, producing either looming or contracting pattern of motion in the field. Seem to be sensitive to information about peripheral optic flow.

Striate Cortex

(See V1).

V1

Principle projection site of the LGN. Characterized by ocular dominance columns. Sends projections to and receives reciprocal projections from V2, V3, MT, V4 & PD. Theoretically composed of three functional subdivisions, blobs, interblobs and layer 4B. (See also Calcarine Sulcus).

(Livingstone & Hubel 1988)

Blobs

Pillar like cortical sections, round or oval in sections cut parallel to the surface. Stain darkly when using cytochrome oxidase (Wong-Riley). Receive most input from parvocellular layers in the LGN via V1 layer 4C. Color selective cells, with no orientation preferences. Projects to thin stripes of V2.

Interblobs

Areas in V1 between blobs. Receive input from parvocellular layers in the LGN via V1 layer 4C Cells respond best to lines of a particular orientation, but are insensitive to direction of movement. Most lack color selectivity, but may response to color-contrast borders. Some cells are end-stopped responding to short but not long lies or edge stimuli. Projects to pale stripes of V2.

Layer 4B

Receives input from magnocellular layers in the LGN via V1 layer 4C. Cells show orientation selectivity. Most are also selective for direction of movement. Projects to thick stripes of V2.

V2

When stained with cytochrome oxidase shows alternative thick, thin and pale stripes which receive different input information suggesting three functional subdivisions.

Thin Stripes

Receives input from blobs in V1. Cells show no orientation selectivity, many are doubly opponent color-cells. Other are broadband. Theorized pathway (LGN Parvo + Magno -> V1 layer 4C -> Blobs -> Thin Stripes).

Thick Stripes

Receives input from interblobs in V1. Cells show orientation selectivity, but are not selective for direction or motion. About half the cells are end-stopped. Cells are no color coded. Theorized pathway (LGN Parvo -> V1 layer 4C -> Interblobs -> Thick Stripes).

Pale Stripes

Receive input from layer 4B in V1. Cells show orientation selectivity, and stereoscopic selectivity. Few cells are end-stopped and none show color selectivity. Cells show retinal disparity selectivity, responding poorly to stimulation or either eye alone, but vigorously when both eyes are stimulated together. Theorized pathway (LGN Magno -> V1 layer 4B -> Pale Stripes).

V3

Contains a representation for only the lower part of the visual field.

VP (Ventral Posterior Area)

Contains a representation for only the upper part of the visual field.

V4

Characterized by a large number of chromatically sensitive neurons with orientation selectivity. Evidence for importance in visual learning, selection of non-salient objects, and recognition of transformed visual objects. After damage deficits seen in the ability to recognize objects that have been transformed in size, in the degree of occlusion, and the amount of contour information provided. Provides major input to IT.

Area TE

Area TEO

Area PO

Corpus Callosum

Cell Types

Type I, II, III and IV

Hubel and Wiesel's scheme for different color opponent cells Modified Type II cells (Ts'o and Gilbert, 1988).

Disparity Selective Cells

TN, TF, FA, NE, T0, TI