Brain visual cortex

Altmann L,Gutowski M, Wiegand H. 1994. Effects of maternal lead exposure on functional plasticity in the visual cortex and hippocampus of immature rats. Develop Brain Res 81 50-56. 

Hilbig, H. Punkt, K. (1997). 24-hour rhythmicity of NADPH-diaphorase activity in the neuropil of rat visual cortex. Brain Res. Bull. 43, 337-40. 

Bonnet people also sometimes see serene landscapes or vortices. Many see entire new worlds, replete with landscapes or groups of people, which are either life size or tiny. Perhaps when vision deteriorates, the brain s visual cortex is starved for information, and the brain is free to access parallel realities or create new ones. 

A possible link between the movement of the eyes (which is real) and the hallucinated dream movements (which are fictive) is provided by the PGO system. This is because the neuronal firing patterns associated with each PGO wave encode (at least) the direction of the eye movements and provide that encoded information to (at least) the visual thalamus and visual cortex. This means that in the absence of real sensory input from the eyes, feed forward information about the direction of the (also fictive) gaze is provided to the upper brain, which could (and we think almost certainly must) use it in the elaboration of the convincing visuomotor illusion that is dreaming. 

Lauriat T. L., Dracheva S., Chin B., Schmeidler J., Mclnnes L. A., and Haioutunian V. (2006). Quantitative analysis of glutamate transporter mRNA expression in prefrontal and primary visual cortex in normal and schizophrenic brain. Neuroscience 137 843-851. 

Figure 2.9 Path from the retina to the visual cortex. On its way to the lateral geniculate nucleus, some axons cross at the optic chiasm. Information from the right half of the visual field is processed inside the left hemisphere of the brain. Information from the left half of the visual field is processed inside the right hemisphere. (Reproduced from Semir Zeki. A Vision of the Brain. Blackwell Science, Oxford, 1993, by permission of Blackwell Science, UK.)...

A normal observer is able to exchange information between the left and the right hemisphere of the brain through the corpus callosum. A normal observer is therefore able to report on the correct color of the test region if the neutral-density filters are not used. In contrast, the subject with a cut corpus callosum can only report on the visual information processed by the left hemisphere of the brain. His color perception depends on whether a mirror setup is used. Therefore, the visual cortex is also involved in the process of color constancy. 

This isomerization converts the energy of a photon into an atomic motion which in turn is converted into an electrical signal. The electrical signal generated in the retina of the eye is transmitted through the optic nerve into the brain s visual cortex. 

The function of the eye is to produce a clear image of the external world and to transmit this to the visual cortex of the brain. In order to do this the eye must have constant dimensions, an unclouded optical pathway and the ability to focus light on the retina. These requirements and the need for protection of the globe determine the special structure of the eye and its associated apparatus. 

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