The origin of the acetylcholinesterase-rich afferents to layer IV of infant somatosensory cortex. A histochemical analysis following lesions.

In this histochemical study, possible origins of the acetylcholinesterase-rich inputs to the barrel field of somatosensory cortex (SmI) were examined. Rats were studied between 6 and 16 days of age when acetylcholinesterase (AChE) positivity is readily detectable in the barrel centers. The experiments involved making lesions in either the ventrobasal thalamus or midbrain and noting the effects on AChE staining in SmI. Also, the results of destroying the large mystacial vibrissae at birth and 6 days of age were histochemically evaluated. Thalamic lesions eliminated most of the AChE positivity in layer IV but midbrain hemisection had no detectable effect. Destruction of the contralateral vibrissae, at birth, altered the pattern of AChE staining of the barrel field. Vibrissal damage at 6 days of age did not result in a noticeable alteration in staining of the barrel centers for AChE. We conclude that the AChE-positive barrel afferents are likely to originate from the ventrobasal complex.