PSY 4180 Chapter Notes - Chapter 6: Motor Action F.C., Euglena, Visual Cortex
5 Jun 2018
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p. 350-360
The Occipital Lobes
No clear landmarks separate the occipital cortex from the temporal or parietal cortex on the lateral hemisphere surface. The
lack clear landmarks makes precisely defining the extent of the occipital areas. Important areas are as follows:
• the calcimine sulcus which contains the much of the primary visual cortex (V1)
• the calcarine sulcus divides the upper and lower halves of the visual world
• on the ventral surface of each hemisphere are two gyri (lingual and fusiform)
• the lingual gyrus includes part of the visual cortical lesions V2 and VP
• V4 is in the fusiform gyrus
V1 has complex laminar organization.
• typically the neocortex has six layers
• the V1 has more
• cortical layer after IV has four distinct layers in an apparent thick stripe
• the thick stripe gives the occipital cortex the nickname striate cortex
V1 is heterogenous as seen when staining with cytochrome oxidase. Cytochrome rich areas (called blobs) are separated by
inter blob regions.
V2 is also heterogenous.
The thin stripes takes part in colour perception. The thick stripes and pale stripes have roles in form and motion perception.
V1 — colour, form, and motion.
V2 — perserved information.
V4 — colour processing.
Thick stripes — motion
Thin stripes — colour
Colour enriches our capacity to detect motion, depth, and position. The absence of significant colour analysis results in
reduced survival behaviours.
Connections of the Visual Cortex
Distributions of hierarchal processes with multiple parallel interconnecting pathways at each level.
V1 (Striate Cortex) is the first processing level in the hierarchy receiving the largest input from the lateral geniculate nucleus
of the thalamus and projecting to all other occipital regions.
V2 is the second processing level, projects to all other occipital regions.
After V2, three distinct parallel pathways emerge en route to the parietal cortex, the multimodal superior temporal sulcus
(STS) and inferior temporal cortex for further processing.
The dorsal stream (parietal pathway) participates in the visual guidance of movement, and the ventral stream, including
both the inferior temporal pathway and the STS pathway, is concerned with object perception (including colour and faces).
The Theory of Occipital-Lobe Function
Areas V1 and V2 are functionally heterogenous: both segregate processing for form, colour, and motion. In a sense areas V1,
V2 appear to serve as in-boxes into which different types of information area assembled before being sent on to more
specialized visual neurons.
From areas V1 and V2 flow three parallel pathways that convey different attributes of vision. The information derived from
the blob areas of V1 goes to area V4; considered the colour area. Cells in the area V4 are not solely responsible to colour,
however, some cells respond to both form and colour.
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Document Summary
No clear landmarks separate the occipital cortex from the temporal or parietal cortex on the lateral hemisphere surface. The lack clear landmarks makes precisely defining the extent of the occipital areas. V1 has complex laminar organization. typically the neocortex has six layers the v1 has more cortical layer after iv has four distinct layers in an apparent thick stripe the thick stripe gives the occipital cortex the nickname striate cortex. V1 is heterogenous as seen when staining with cytochrome oxidase. Cytochrome rich areas (called blobs) are separated by inter blob regions. The thin stripes takes part in colour perception. The thick stripes and pale stripes have roles in form and motion perception. Colour enriches our capacity to detect motion, depth, and position. The absence of significant colour analysis results in reduced survival behaviours. Distributions of hierarchal processes with multiple parallel interconnecting pathways at each level.
