Quantitative analysis of glutamic acid decarboxylase-immunoreactive neurons in the anterior thalamus of the human brain

Local circuit neurons in the human anterior thalamus (AT) were identified on the basis of glutamic acid decarboxylase immunoreactivity (GAD-IR). GAD-IR neurons of the AT displayed small diameter somas with thin, sparsely-branching dendrites, consistent with the morphological characteristics of local circuit neurons found in the thalami of other mammals. Sampling techniques revealed an average of 42% of all neurons within the AT were GAD-IR. one of the highest reported percentages of local circuit neurons in the mammalian thalamus. The presence of high proportion of local circuit neurons in the AT may indicate the extent to which the Papez circuit has evolved within the human brain in comparison to other mammals. Crown copyright (C) 2001 Published by Elsevier Science B.V. All rights reserved.