Specific circular organization of the neurons of human interthalamic adhesion and of periventricular thalamic region.

Interthalamic adhesion between the medial surfaces of the left and right thalamus is a variable structure and contains the midline thalamic nuclei, which are not much developed in humans. The research has been done on 6 human brains obtained during routine autopsy (age 45 to 65; 4 male and 2 female). Every tenth 10 microm thick frontal section was stained according to Klüver-Barrera method. In all cases the authors found a specific organization of certain groups of neurons within the interthalamic adhesion (IA) in form of circles on frontal sections. These circular groups were present on all sections but only 1-2 in each. The larger mean diameter of these circular arrangements was R = 229.4 microm, and smaller was r = 203.1 microm. These circular groups within the human IA were formed in average by 7.29 neurons. In periventricular region (PVR) of thalamus similar circular groups of neurons also were present in all cases as in IA. These neuronal groups in PVR were of smaller size than in the IA, with larger mean diameter R = 201.4, smaller mean diameter r = 181.2 microm and they contained fewer neurons, 6.69 on average. All three values (both diameters of circular arrangements, and number of neurons forming them) were significantly smaller in PVR (p < .01). Morphological types and sizes of neurons in both investigated structures (IA and PV) were not different. The circular neuronal groups in IA were formed in 61% of fusiform neurons and in PVR in 48% of fusiform neurons. According to their subependymal localization, size and form, these circular groups can represent in vivo correlates of neurospheres.