Cortical column

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A cortical column is a group of neurons in the brain cortex which can be successively penetrated by a probe inserted perpendicularly to the cortical surface, and which have nearly identical receptive fields. The human cortical column is composed of 6 layers. Each layer receives and sends signals to different parts of the brain. The human cerebral cortex is a roughly 2 mm thick sheet of neuronal cell bodies that forms the external surface of the telencephalon. The columnar functional organization, as originally framed by Vernon Mountcastle, states that neurons that are horizontally more than a half mm from each other do not have overlapping sensory receptive fields. An important distinction is that this rule is functional in origin, and reflects the local connectivity of the cerebral cortex. Connections "up" and "down" within the thickness of the cortex are dramatically denser than connections that spread from side to side.

The dolphin cortical column is composed of only 5 layers. Although the dolphin brain is larger than the human brain, the dolphin has a need to sleep and still surface to breathe. It accomplishes this by having one-half of its brain sleep at a time. The reptilian cortex has only three layers.

Hubel and Wiesel followed up on Mountcastle's discoveries in the somatic sensory cortex with their own studies in vision. A part of the discoveries that resulted in them winning the 1981 Nobel Prize[1] was that there were cortical columns in vision as well, and that the neighboring columns were also related in function in terms of the orientation of lines that evoked the maximal discharge. Hubel and Wiesel followed up on their own studies with work demonstrating the impact of environmental changes on cortical organization, and the sum total of these works resulted in their Nobel Prize.

[edit] See Also

• Ocular dominance column
• Cortical minicolumn

[edit] External links and references

• Mission to build a simulated brain begins "the initial phase of Blue Brain will model the electrical structure of neocortical columns - neural circuits that are repeated throughout the brain. These are the network units of the brain, says Markram. Measuring just 0.5 millimetres by 2 mm, these units contain between 10 and 70,000 neurons, depending upon the species. Once this is complete, the behaviour of columns can be mapped and modelled"
• Blue Brain Project Aims to simulate a cortical column
• BrainMaps at UCDavis Cortical column
• On Intelligence -- a popsci book about column function by Jeff Hawkins