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Biomedical subjects

R S Babb

Publications and source records attributed to R S Babb.

6 recordsLinked to original sources
PubMed1985

Motor effects produced by stimulation of secondary somatosensory (SII) cortex in the monkey.

Threshold for evoking movements by microstimulation of the second somatosensory area of the cynomolgus monkey's cortex to intracortical microstimulation was examined. Motor effects were obtained contralateral to the side of stimulation, in a region histologically verified to be in grey matter deep in the sylvian cortex, and which corresponds to the second somatosensory cortex. The thresholds were low but higher than for movements evoked by stimulation of the motor cortex. The results are explained in terms of increased specialization of the motor cortex for movements in the monkey compared with the cat.

Animals↗
PubMed1984

Corticocortical connections to the motor cortex from the posterior parietal lobe (areas 5a, 5b, 7) in the cat demonstrated by the retrograde axonal transport of horseradish peroxidase.

Neurons in the parietal region of the cerebral cortex, projecting to the ipsilateral distal forelimb area of the motor cortex (area 4 gamma) were identified in the cat brain using the horseradish peroxidase (HRP) retrograde tracing method. After making microinjections of HRP into the distal forelimb area of the motor cortex, clusters of HRP-labeled cell bodies were observed in different regions of the ipsilateral parietal cortex. In particular these clusters of labeled cells were found in areas 5a, 5b and 7. The area 5a cluster is formed from closely packed irregularly-shaped cells, the area 5b cluster is made up of dispersed medium-sized pyramidal cells, while area 7 contains a cluster of widely dispersed small pyramidal cells. Typically, labeled cell bodies were found in lamina III of cortex. Labeled cell bodies were neither observed in the contralateral cortex nor in the visual cortex (areas 17, 18 and 19). Since parietal cortex receives projections from primary somatosensory and visual cortex, the projections from parietal to motor cortex may well form the neural substrate for the processing of convergent sensory information used in voluntary movements.

Afferent Pathways↗
PubMed1980

The pregeniculate nucleus of the monkey (Macaca mulatta). I. A study at the light microscopy level.

A study of the pregeniculate nucleus of the monkey (Macaca mulatta), in Klüver-Barrera-stained, and Golgi-impregnated material confirmed, with reservations, that the nucleus is bilaminar. The inner lamina extends anterior to posterior as a compact band of neuropil within the optic tract, passing from a dorsomedial position to occupy a more dorsolateral position with respect to the lateral geniculate nucleus. The neuropil of this lamina is formed from a plexus of very fine fibers, many having varicosities, which appear to make contact with dendrites. The outer lamina appears to be formed from that part of the thalamic reticular nucleus that is apposed to the lateral geniculate nucleus. Three types of neurons were observed in the nucleus: Type I are found only in the inner lamina; they have small (12--14 micrometers) spheroid somata with thin dendrites having terminal arborizations formed by long protrusions and axons exhibiting varicosities. Type II neurons in contrast are found only in the outer lamina; their cell bodies are large (21 by 33 micrometers to 26 by 37 micrometers) and polygonal, contain much Nissl substance, and exhibit thick, relatively spine-free dendrites. Type III neurons, which are the most common, are found in both laminae; they have medium-sized (13 by 27 micrometers to 19 by 40 micrometers ellipsoid somata containing moderate amounts of Nissl substance and exhibiting well-developed spine-bearing dendrites. Since the axon of the type I neuron impregnates and is found only within the nucleus, this cell is considered to be an intrinsic neuron; on the other hand, types II and III are judged to the principal neurons, as their axons do not impregnate.

Animals↗
PubMed1980

The pregeniculate nucleus of the monkey (Macaca multatta). II. A study at the electron microscopic level.

An electron microscope study of the ultrastructure of the pregeniculate nucleus of the monkey (Macaca mulatta) shows it to contain three neuronal types and four varieties of presynaptic terminals. Type I neurons are found only in the inner lamina, have small rounded profiles with few axosomatic synapses; the cytoplasm is poor in organelles and the nucleus is deeplly infolded. Type II neurons were observed infrequently and only in the outer lamina; they have large oblong profiles, exhibiting many axosomatic contacts, and containing abundant cytoplasm rich in organelles, particularly arrays of granular and agranular endoplasmic reticulum. Type III neurons were the most frequently seen and are found in both laminae; their profiles are elliptical and exhibit only a few axosomatic synapses. The cytoplasm surrounding the infolded nucleus is moderately rich in organelles with agranular endoplasmic reticulum predominating. These three neuronal types were found to correlate well with types of neurons found in material stained with cresylecht violet or impregnated by the Golgi method. Four presynaptic terminal types were discerned: a small cup-shaped profile containing spheroid vesicles and found predominantly in the outer lamina, a larger elliptical profile containing flattened spheroid vesicles, a large ramifying profile also containing round vesicles and largely restricted to the inner lamina, and a rounded profile containing larger flattened vesicles. Three days after eye enucleation, darkened degenerating profiles containing vesicles and forming asymmetric synapses were observed in the inner lamina, while the third terminal type described above could no longer be seen. The first three types are usually associated with asymmetric synaptic densities, whereas in the case of the last type, the postsynaptic synapse is symmetrical. The profile of this last terminal type was also sometimes observed to be both postsynaptic as well as presynaptic to other profiles; however, it was never observed to contain ribosomes. Such a pre- and postsynaptic terminal always forms part of the in series or triadic configuration of terminals occasionally observed in the pregeniculate nucleus.U

Animals↗