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I have read about cortical circuits in the context of connectomics (e.g. any example here) and computational neuroscience (e.g. any example here), but a simple Google/Wikipedia does search not show an exact definition.

What exactly is a cortical circuit?

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  • $\begingroup$ Could you maybe give an example of one or two places where you read about them? $\endgroup$ – Amory Jul 30 '13 at 14:00
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I may be simplifying this, but I think it's just a fancy schmancy way of referring to the electrical "circuits" found in the brain, in this case the cortex (overall, or more specifically motor, visual, etc., as the case may be). Connectomics tries to map the connections between neurons, mainly in the brain, building what is, in some sense, a circuit. For some sentences in context:

http://www.jneurosci.org/content/32/31/10562.short

These results indicate a tight correlation between the effects of sensory drive and maturation on cortical neurons and provide a new set of cellular mechanisms engaged in the postnatal refinement of cortical circuits.

http://www.jneurosci.org/content/32/32/10982.short

...spontaneous cortical activity provides a recurring template of functional cortical circuits within the developing cortex and could contribute to the maturation of integrative connections between sensory and motor cortices.

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  • $\begingroup$ +1 as it is correct, although I don't really see how it is fancy... a series of cortical neurons connected between each other forms a cortical circuit. Doesn't seem too fancy to me :P $\endgroup$ – nico Jul 30 '13 at 16:48
  • $\begingroup$ Thanks Amory and @Nico. So does the term "cortical circuits" refer to circuits found anywhere in the brain, or in a specific place? $\endgroup$ – Amelio Vazquez-Reina Jul 30 '13 at 18:09
  • $\begingroup$ "the cortex (overall, or more specifically motor, visual, etc., as the case may be" I meant to imply that "cortical circuit" appears to broadly refer to the cortex, but there are instances of more specific uses. Visual cortex circuits, motor circuits, etc. $\endgroup$ – Amory Jul 30 '13 at 18:21
  • $\begingroup$ @user815423426: In general you can speak of a "circuit of neurons" anywhere in the brain. For instance you can talk about hypothalamic feeding circuits, in reference to the circuit of neurons controlling feeding in the hypothalamus (a region at the base of the brain). $\endgroup$ – nico Jul 30 '13 at 18:25
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    $\begingroup$ @user815423426: I don't think a distinction between white and gray matter is really necessary in this case. The fibers that compose the white matter come from neurons, so they can still be part of a circuit. "Cortex" refers to the outer layer of the brain, which is connected to many other parts of the brain (for instance connections between neurons in the cortex and neurons in the thalamus will form cortico-thalamic circuits, and so on). Of course you can also have purely cortical circuits (i.e. connection of neurons in the cortex between each other) $\endgroup$ – nico Jul 31 '13 at 10:44
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The term "cortical circuit" refers to the generalization that the neocortex is a uniform structure. For the most part, the outer sheet of the brain (the neocortex) is the same structure of neurons all the way around the brain. It consists of the canonical six layers and it generally looks something like this. Different research will emphasize different aspects of the circuit.

Anyway, it's quite an interesting evolutionary step for mammals. The neocortex.. or "associative cortex" as it's sometimes called... is a very dexterous structure. Someone born without sight will still make use of their occipital lobe to process nonvisual sensations.

Of course, as a I qualified above, it's not strictly true that the neocortex is uniform all the way around; there are exceptions.

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