Cytometric analysis of the thalamic ventralis intermedius nucleus in humans

Abstract

1. The cytoarchitecture and the exact borders of the thalamic ventralis intermedius (Vim) nucleus of humans as originally delineated by Hassler (17) have been studied on the basis of stereotaxic coordinates correlated with Nissl- and Golgi-impregnated sections, using a microscopic image analyzer. 2. The Vim nucleus forms part of a relatively "cell-sparse zone" which includes the other ventrolateral thalamic subnuclei. It is distinguished by the presence of darkly stained, large and medium sized, angular cells with areas of approximately 500-1,000 microns 2 and 300-400 microns 2, respectively, and a cell density of approximately 50-90 (mean 65)/mm2 in 50-microns-thick sections. 3. Both sets of neurons have the characteristics of thalamocortical relay neurons in Golgi preparations. Large neurons have rectangular or square somata 30-50 microns diam and are concentrated mainly in the lateral and ventral two-thirds of the nucleus. The medium neurons have square to round somata, 15-25 microns diam, and are distributed homogeneously through the nucleus. The total dendritic arborization of both types is usually symmetrical in all directions and at least 500-600 microns diam. 4. The borders between the Vim nucleus and the Nucleus ventrooralis (Vo) and between the Vim nucleus and the Nucleus ventrocaudalis internus (Vci) are clearly identified by clearcut differences in cell size and cell density. The borders between the Vim nucleus and the Nucleus ventrooralis internus (Voi) and between the Vim nucleus and the Nucleus zentrolateralis intermedius (Zim) are quite obscure, and these nuclei, with Vim, seem to be parts of the large cell sparse zone comparable to that described in monkeys as VLp or VL. The border between the Vim nucleus and the Nucleus ventrocaudalis externus anterior (Vcea) is also unclear but the increased cell density and intermingling of small and medium-to-small neurons with large neurons are the major features that distinguish the Vcea nucleus from the Vim nucleus cytometrically. 5. The position and anatomic organization of the human Vim nucleus make it likely that it is the region in which kinesthetic response were recorded in the accompanying paper but extension of the recording sites into the Vcea nucleus cannot be ruled out.

Measurement of Evoked Potentials During Thalamic Deep Brain Stimulation

“…The resulting scale factors were used to calculate potentials at the recording contacts as a function of the transmembrane current amplitude. The magnitude of the model-generated ECAP signal was scaled by 364 to account for the cell density of 1,300 cells/mm 3 derived from (31). This signal was then filtered with two cascaded first-order 10 Hz – 10 kHz bandpass filters to replicate typical experimental filtering, the stimulus artifact generated by passive charging of neural elements was removed using a template subtraction method in which the artifact was calculated using a sub-threshold stimulus (32), and averaging 8 individual responses using stimulus-triggering.…”

Neural origin of evoked potentials during thalamic deep brain stimulation

“…The voltages generated by these currents at each recording contact were summed across every compartment of all neural elements and the time-dependent ECAP calculated as the differential voltage between the two recording contacts. We accounted for the true cell density [65 cells/mm 2 in 50-m sections (Hirai et al 1989)] by scaling the ECAP magnitude by a factor of 102. As well, we filtered the model-generated signals with two cascaded first-order 10-Hz to 10-kHz band-pass filters to replicate the filtering performed experimentally.…”

Comparative Anatomical Study of Ventrolateral Thalamic Mass in Humans and Monkeys

“…According to the data obtained from cytometric analysis [13], the histogram patterns of cell dimensions and cell density in each ventro lateral thalamic nucleus in both humans and monkeys were very simi lar. Moreover, acetylcholinesterase-stained sections revealed a parcellation of the ventrolateral thalamic nuclei that could be correlated with that used in the monkey thalamus [14][15][16].…”