Shozo Matano

The cells of origin of cat trigeminothalamic projections: especially in the caudal medulla.

Thalamic projections from the caudal medulla of the cat were examined using the method of retrograde axonal transport of horseradish peroxidase (HRP). Injections were made unilaterally in various thalamic regions. Large injections labeled cells in the subnuclei: zonalis (Vcz), gelatinosus (Vcg), magnocellularis (Vcm), reticularis dorsalis (Vcrd) and ventralis (Vcv) medullae oblongatae. The largest number of labeled cells were in Vcz, Vcrd and Vcrv. Most of the labeled cells in Vcz and Vcrd were contralateral to the injection site, although the labeled cells in the Vcrv were bilateral. Small injections were made into the medial, lateral and dorsal regions of the nucleus ventralis posteromedialis (VPM), rostral regions of the posterior nuclei (POm and PO1), caudal POm, the nucleus centralis lateralis (CL) and the center median-parafascicular nuclear complex (CM-Pf). Most of the neurons in Vcz were found to project to the medial VPM and some to the caudal POm. A small number of cells in the Vcrd project to the medial VPM, but a large number project to the caudal POm and CM-Pf complex. The largest number of neurons projecting to the CM-Pf complex was present in Vcrv, where the labeled cells were bilateral. The types of trigeminothalamic projecting cells and the sizes of their somata were observed for different subnuclei and a considerable difference was found to exist among the subnuclei. This anatomical differentiation of the trigeminothalamic projections probably reflects a functional specialization of neuronal location since the functional properties of neurons vary according to their locations.

Brief communication: Proportions of the ventral half of the cerebellar dentate nucleus in humans and great apes

In a previous study about volume comparisons of the cerebellar complex in some hominoid species (1997), progressive development of only the lateral zone group of nuclei was found in the human cerebellar complex. This development was considered to be related not to bipedalism, but to versatile and coordinated finger movement, evolving after bipedalism was established. It was also considered a prerequisite for the evolution of human language. The lateral zone groups of nuclei are represented by the dentate nucleus. Therefore, the present study reports the development of the dentate nucleus in humans in comparison with that in some great apes. One finding is that the average value of ratios for nucleus size of the ventral half (v) to the dorsal half (d) (v/d) was found to be 2.11 in humans, while it was 1.64 in great apes. This finding shows that the greater part of progressive development of the dentate nucleus in humans is due to the development of its ventral half. Therefore, the fiber connection to the frontal association area from the cerebellar cortex, which is involved in the performance of higher cerebellar functions such as cognitive and language functions, would be mediated by the ventral half of the dentate nucleus.

Analysis of head and body movements of elderly people during locomotion

In order to elucidate the effect of aging on head and limb motions, 10 young and 8 elderly normal subjects were studied kinesiologically during i) walking, ii) stepping, and iii) hopping, with their eyes open or closed. For this study, a 16-mm high-speed cinecamera and accelerometers were used. Analysis of head movements showed that pitch rotation seemed to counteract the translational movement in the sagittal plane. Although this phenomenon was observed in both the young and elderly groups, the mean pitch position of the head, as measured by the cantho-meatal line relative to the horizontal line, was larger for the elderly group, while head acceleration of elderly people showed a higher frequency in the power spectrum. With eyes closed, the head tended to be tilted downward.

Volume comparisons in the cerebellar complex of primates. II: Cerebellar nuclei

Volumes of medial, interposed, and lateral cerebellar nuclei (MCN, ICN, and LCN) were measured in Insectivora, Scandentia, and Primates, including man. The relative size of the nuclei was expressed in size indices. Insectivora had by far the smallest cerebellar nuclei. The simians, in general, had larger cerebellar nuclei than the prosimians, but there was considerable overlap. From Insectivora to man, the MCN was the least progressive and the LCN the most progressive. The indices are expected to reflect the relative size of the three longitudinal zones of the cerebellum (vermis/MCN, pars intermedius/ICN, hemisphere/LCN). They, together with those of the ventral pons and cerebellum (part I), are discussed in relation to the predominant locomotor pattern of a species, and with reference to evolutionary trends in primate phylogeny.

Volumetric comparisons in the cerebellar complex of anthropoids, with special reference to locomotor types

Seven measurements in the cerebellar complex were completed on 45 individuals, including 26 species of anthropoids from Stephans collection. These included 12 species of New World monkeys, 10 species of Old World monkeys, and Hylobates, Gorilla, Pan, and humans. The measurements were the volume of medial (fastigial) (CM), interpositus (globose and emboliform) (CI), and lateral (dentate) (CL) cerebellar nuclei, ventral pons (VPo), inferior olivary principal (OLIPr), and accessory (OLIAc) nuclei and vestibular nuclear complex (VES). The relative size of each nucleus was expressed in size indices based upon the allometric line obtained by the reduced major axis analysis. The indices of three cerebellar nuclei reflect the relative size of three longitudinal zones of the cerebellum. The cerebellar hemisphere-lateralis zone is represented by the CL indices, the vermis-medialis zone by the CM indices, and the pars intermedius-interpositus zone by the CI indices. The results show that the VPo and OLIPr indices are closely related to the CL indices. This lateral zone group of nuclei is the most progressively developed in humans, whereas the CM, CI, OLIAc, and VES are independent of the developmental trend manifest by the lateral zone group of nuclei. The indices are discussed in relation to the predominant locomotor pattern exhibited by a species. The size indices of arboreal quadrupeds show a development of all nuclei in the cerebellar complex. This is interpreted as indicating that arboreal monkeys live in complicated, discontinuous, three-dimensional space and need exceptional cerebellar capacity for each pattern of locomotion and positional behavior. Progressive development of the lateral zone group of nuclei only compared to other nuclei was recognizable in humans. This development is considered to be related not to bipedalism, but to versatile and coordinated finger movement, resulting after bipedalism was established. This cerebellar reorganization is also a prerequisite (Leiner et al. [1993] TINS 16: 444-447) for the evolution of human language. The differences between size indices of the nuclei of Macaca (= pronograde primate) and Ateles (= antipronograde one) are compared in relation to their vertical climbing kinesiological data.

The Central Projections of the Monkey Tooth Pulp Afferent Neurons

Transganglionic transport of horseradish peroxidase conjugated to wheatgerm agglutinin (HRP:WGA) entrapped in hypoallergenic polyacrylamide gel was used to study the patterns of termination of primary afferents that innervate the upper and lower tooth pulps within the trigeminal sensory nuclear complex (TSNC) of the monkey. HRP:WGA injections were also made into the lower incisors and molars, in order to examine the topographic arrangement of pulpal afferent projections. HRP-labeled pulpal afferents innervating lower and upper teeth projected ipsilaterally to the rostral subnucleus dorsalis (Vpd) and caudal subnucleus ventralis (Vpv) of the nucleus principalis (Vp); the rostrodorsomedial (Vo.r) and dorsomedial (Vo.dm) subdivisions of the nucleus oralis (Vo); the dorsomedial subdivision of the nucleus interpolaris (Vi); and laminae I-II and/or V of the nucleus caudalis (Vc) at its rostralmost level. The HRP-labeled terminals from upper and lower pulpal afferents formed a rostrocaudal column from the midlevel of Vp to the rostral tip of Vc. The label in Vp and Vo was considerably dense, but the column of terminals was interrupted at the Vpd-Vpv transition. The label in Vi and Vc was much less dense compared to that in the rostral nuclei, and the column of terminals was interrupted frequently. The representation of the upper and lower teeth in TSNC was organized in a somatotopic fashion that varied from one subdivision to the next, though their terminal zones overlapped within Vpd. The upper and lower teeth were represented in Vpv, Vo.r, Vo.dm, Vi, and Vc in a ventrodorsal, dorsoventral, lateromedial, lateromedial, and lateromedial sequence, respectively. Topographic arrangement was also noticed for the projections of pulpal afferents from the lower incisors and molars: The representations of the lower incisors and molars in Vpv, Vo.r, Vo.dm, Vi, and Vc were organized in a lateromedial, dorsoventral, ventrodorsal, ventrodorsal, and lateromedial sequence, respectively. The present results indicating sparse projections from pulpal afferents in the monkeys Vc are in good correspondence with a clinical report that trigeminal tractotomy just rostral to the obex has no significant effect on dental pain perception in patients. Furthermore, the present study indicates that projection patterns of pulpal afferents--which include the termination sites, the density of terminations between nuclei, and topographic arrangement--differ among animal species.

Convergence of Ampullar and Macular Inputs on Vestbular Nuclei Unit of the Rat

181 vestibular nucleus neurons were examined for their responsiveness to rotation about the vertical axis and static tilts in roll and pitch planes in the rat. 68 of these units were sensitive to rotation and tilts (canal-otolith cells). In other words, 41.0% of the neurons responded to rotation (68/166). There was no significant difference in percentage of canal-otolith cells in type I and II neurons, which were 48.6% and 37.0% respectively. Vertical axis rotation when the head was tilted produced a simultaneous stimulation of the canal and otoliths. Using this stimulus method, the bias effect was observed in 72.5% of the canal-otolith cells (29/40). Furthermore, since vertical axis rotation with the head tilted elicited vertical canal responses, the rate of ampullary convergence was estimated by analysing response profiles obtained such rotations. The results obtained in the rat were compared with those in other species.

A volumetric comparison of the vestibular nuclei in primates

The volumes of each of the four vestibular nuclei, superior, lateral, medial and descending, were measured in 80 brains from 2 species of Scandentia, 18 species of prosimians, and 26 species of anthropoids. Size indices were calculated by comparing species-specific points to the nucleus volume-body weight allometry in prosimians, where the average prosimian was set at 1.00. The indices range from 1.78 in Saimiri to 0.48 in Gorilla, and the distributions by families overlap partially or completely. The observed trend in size indices is independent of changes in the neocortex and the ventral pons; average indices are 1.35 in New World monkeys, 1.20 in Old World monkeys, 0.74 in apes, 0.82 in man. Among prosimians, Galago, Galagoides and Tarsius (leaping locomotion) show significantly higher indices than Nycticebus, Loris and Perodicticus (slow movement without leaping). The lateral vestibular nuclear indices in Pongidae and man are extremely low, about half of those of the average prosimians. Correlation coefficients of size indices between the vestibular nuclei and other motor nuclei, such as the cerebellar nuclei, ventral pons and striatum, are analysed. The ratio of the vestibular nuclear volumes to the total brain volumes and the distribution of percentages of each vestibular nuclear volume to the total complex are also obtained.

Specific cholinergic destruction in the basal magnocellular necleus and impaired passive avoidance behavior of rodents

A nerve growth factor (NGF)-diphtheria toxin conjugate (NGDT) was found to selectively abolish or depress the activity of NGF receptor-bearing cholinergic neurons of the basal magnocellular nucleus (BMN). Bilateral cortical injections of NGDT impaired the retention of passive avoidance behavior in mice. A memory deficit was also revealed when cortical injections of NGDT were administered after the acquisition of a passive avoidance response. Thus, retrograde destruction of BMN cholinergic neurons by the cortical injection of NGDT interfered with both learning and memory processes. The animal model outlined here should be useful in analyzing the pathogenesis of Alzheimers disease and the functions of the cholinergic system in the BMN.

Learning Set Formation in Ring-Tailed Lemurs (Lemur catta)

Following the study on nocturnal slow lorises ( Nycticebus coucang ), the visual discrimination learning set was tested on diurnal ring-tailed lemurs ( Lemur catta )