Editing Cerebral cortex (section)

====Layer VI====
Layer VI, the '''polymorphic layer''' or '''multiform layer''', contains few large pyramidal neurons and many small spindle-like pyramidal and multiform neurons; layer VI sends [[Efferent nerve fiber|efferent fibers]] to the thalamus, establishing a very precise reciprocal interconnection between the cortex and the thalamus.<ref>Creutzfeldt, O. 1995. ''Cortex Cerebri''. Springer-Verlag.</ref> That is, layer VI neurons from one cortical column connect with thalamus neurons that provide input to the same cortical column. These connections are both excitatory and inhibitory. Neurons send [[Excitatory postsynaptic potential|excitatory]] fibers to neurons in the thalamus and also send collaterals to the [[thalamic reticular nucleus]] that [[Inhibitory postsynaptic potential|inhibit]] these same thalamus neurons or ones adjacent to them.<ref name="Lam">{{cite journal | vauthors = Lam YW, Sherman SM | title = Functional organization of the somatosensory cortical layer 6 feedback to the thalamus | journal = Cerebral Cortex | volume = 20 | issue = 1 | pages = 13–24 | date = January 2010 | pmid = 19447861 | pmc = 2792186 | doi = 10.1093/cercor/bhp077 }}</ref> One theory is that because the inhibitory output is reduced by [[cholinergic]] input to the cerebral cortex, this provides the [[brainstem]] with adjustable "gain control for the relay of [[Posterior column-medial lemniscus pathway|lemniscal]] inputs".<ref name="Lam"/>