According to Wikipedia...

Interneurons are neurons that connect to brain regions, i.e. not direct motor neurons or sensory neurons.


Approximately 20–30% of the neurons in the neocortex are interneurons, while the remaining neurons are pyramidal neurons.

Is it saying that (A) an interneuron is ANY neuron that is not a motor or a sensory neuron? Or is it just saying that (B) interneurons CONNECT TO neurons that are not motor or sensory neurons(hence saying there are neurons in between that are not inter, motor, or sensory)?

If (A) is correct, the second quote implies that (C) 70-80% of neurons in the neocortex are motor neurons since pyramidal neurons are multipolar and sensory neurons are not multipolar.

So is (C) correct? And are all motor neurons pyramidal?

Also, are there pyramidal neurons that are not motor neurons(perhaps there are pyramidal neurons in other parts of the brain like the hippocampus that are not motor neurons)? Or is (B) correct and are there pyramidal neurons in the neocortex that are not motor neurons?


1 Answer 1


Ah... nevermind. It seems that the two paragraphs from Wikipedia are using "interneurons" in two different ways. First meaning all neurons that are not motor or sensory. The second meaning inhibitory interneurons. So (A) would be correct, and pyramidal neurons are either motor neurons or interneurons in the first sense, while inhibitory neurons are not pyramidal.

  • 2
    $\begingroup$ Yeah, you've got it figured out. That first definition is really only ever used in the spinal cord and perhaps in non-vertebrates. There's also a third similar meaning for interneuron used within the brain where an interneuron is only locally projecting within a given brain region, even if the target region isn't a muscle but rather a different brain area. $\endgroup$
    – Bryan Krause
    Commented Jan 20 at 20:59

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