Quantitative analysis of spiny neurons in the adult human caudate nucleus: can it confirm the current qualitative cell classification?

The caudate nucleus, as a part of the striatum (neostriatum or dorsal striatum), is involved in the control of cognitive, motor and limbic functions. The majority of the caudate nucleus cells are projection spiny neurons, whose activity is determined by excitatory inputs from the cortex, thalamus, globus pallidus and brainstem. A qualitative analysis of human caudate nucleus neurons involves the description of the structure and features of cells, and accordingly, their classification into an appropriate type. The aim of this study is to determine the justification of the current qualitative classification of spiny neurons in the precommissural head of the human caudate nucleus by quantifying morphological properties of neurons. After the qualitative analysis of microscopic images of the Golgi-impregnated caudate nucleus neurons, five morphological properties of cells were measured/quantified. In terms of the dendritic field area, caudate nucleus neurons were divided into two subgroups: small and large neurons. In our sample of 251 projection nerve cells, 58.17 % (146) were small and 41.83 % (105) were large neurons. These data show that suggested groups of spiny neurons in the human caudate nucleus differ in their morphology. Since the structure and function of cells are closely correlated, it is possible that these morphologically different types of neurons may represent different functional groups.