Morphological characteristics of different types of neurons in the ventrooralis anterior, ventrooralis internus, and ventrooralis posterior nuclei in the human thalamus

Abstract

1. Golgi-Kopsch preparations of the oral ventral nuclei of human thalamus were analyzed in an attempt to classify the neuronal types. 2. Three types of neurons are described for the first time in humans. Type I neurons are large or medium in size and bear dendrites with protrusions, spines, and short hair-like appendages. Some have a radiate dendritic arbor and others have dendrites grouped in tufts. The dendritic trees of these neurons are dense. 3. Type II neurons are medium or small in size with less dense dendritic trees. These cells have somatic as well as dendritic appendages of different forms. 4. Relatively rare is a type of very small neurons, type III, with few and sparsely branching dendrites.

Neuronal Types in the Human Anterior Ventral Thalamic Nucleus: A Golgi Study

“…However, both tufted and radiating dendritic branching patterns were found in almost every type I neuron in this study and therefore it was not possible to subclassify these neurons into tufted and radiating subtypes as reported in some studies of some thalamic nuclei such as the AV nucleus, the motor thalamic nuclei and the sensory thalamic nuclei (Somogyi et al 1979;Kiss and Tombol 1972;Pearson and Hairen 1980;Spreafico et al 1983;Winer 1984;Yen et al 1985). The results of this study came in agreement with similar results reported in the motor thalamic nuclei in both human (Al-Hussain 1995) and cat (Al-Hussain 1987) where both radiating and tufted dendritic branching patterns were found in almost every type I neuron. It has been suggested that the Fig.…”

“…The type II neurons in the human AV nucleus were found to have grape-like dendritic appendages not only at the dendritic shafts but also at dendritic tips. In the sensory thalamic nuclei, large number of spines and grape-like appendages were described for the dendrites of Golgi-type II neurons including their branching points and dendritic tips (Guillery 1966;Morest 1975;Pearson and Hairen 1980;Friedlander et al 1981) while in the motor thalamic nuclei few spines and grapelike appendages were found along the shafts of Golgi-type II dendrites but never at their dendritic tips (Al-Hussain 1987;Al-Hussain 1992). Whether the location of these appendages along the dendritic trees of the type II neurons make a significant difference was not clear.…”

“…Whether the location of these appendages along the dendritic trees of the type II neurons make a significant difference was not clear. The grape-like appendages were found to be part of complex synaptic structures called glomeruli where they act as postsynaptic to afferent fibres and presynaptic to dendrites of Golgi-type I neurons (Morest 1975;Al-Hussain 1987). These appendages were connected to the main stem of the type II dendrites via a thin stalk.…”

“…The dendrites of the first type (tufted) give rise to three or more branches while the dendrites of the second type (radiating) divide into two branches. Results in another study in the motor thalamic nuclei (Al-Hussain 1987), however, showed that these two dendritic branching patterns (tufted and radiating) were in fact present in almost every Golgi-type I neuron.…”

“…Some quantitative features such as diameter of dendrites of different orders, number of branching points and analysis of dendritic branching patterns of both Golgi-type I and Golgi-type II neurons were reported only in the motor thalamic nuclei (Al-Hussain 1987).…”