Search PubMed⌕ Search

Biomedical subjects

R B Masterton

Publications and source records attributed to R B Masterton.

44 records · Page 3Linked to original sources
PubMed1976

An anatomical study of some somesthetic afferents to the intercollicular terminal zone of the midbrain of the opossum.

Following lesions of the dorsal column nuclei, spinal cord and sensorimotor cortex, anterograde degeneration was traced to a common target in the central midbrain; the intercollicular terminal zone. Although not all the midbrain projections of the three pathways are contained within this zone, it receives overlapping projections from each of the three body-related somesthetic pathways studied. The intercollicular terminal zone covers the entirety of the external nucleus of the inferior colliculus and the intercollicular nucleus of Mehler, spilling over into adjacent parts of the central gray and deep layers of the superior colliculus. Little evidence of somatotopy in the somesthetic projections was disclosed, and bilateral input was found in each experimental case, regardless of the type of lesion. Golgi-stained material was examined to explore the basis of the extensiveness of the terminal zone. These materials showed that the dendritic spread of neurons in the external nucleus of the inferior colliculus and the intercollicular nucleus, taken together, covers the entirety of the intercollicular terminal zone. That is, the dendrites invade the same portions of the central gray and deep layers of the superior colliculus which are covered by the terminal field. We conclude that a tripartite division of the sensory midbrain may be justified: with the somesthetic modality being represented anatomically in a fashion at least roughly analogous to that of vision and audition.

Afferent Pathways↗
PubMed1976

Origins of anthropoid intelligence. III. Role of prefrontal system in delayed-alternation and spatial-reversal learning in a prosimian (Galago senegalensis).

A species of prosimian (bush baby, Galago senegalensis) was tested on delayed-alternation and spatial-reversal learning before and after ablation of prefrontal cortex. The results show that normal performance on the two behavioral tasks depend on different subdivisions of the MD-prefrontal system. Delayed alternation is disrupted by prefrontal lesions which cause degeneration in the lateral division of MD while spatial-reversal learning is disrupted by lesions causing degeneration of the medial division of MD. Therefore, the bush baby prefrontal system can be subdivided either on behavioral or anatomical grounds into at least two chief parts. Because of several similarities in the MD-prefrontal system of bush baby and monkey despite their remote common ancestry, it can be concluded that the differentiation of the MD-prefrontal system into distinct divisions and the involvement of this system in delayed alternation and spatial reversal are features probably as old as the order Primates itself. It can be further concluded that the further evolution of the anthropoid variety of prefrontal system beyond this common primate stage probably depended on selective pressure on abilities other than those measured here.

Animals↗
PubMedDate not supplied

Central auditory system.

A biological view of the central auditory system seems to be replacing the older Galilean or physics-based view as the guide for research in the late 20th century. This emerging view is primarily Darwinian in origin and recognizes that the entire auditory system is an adaptation for extracting information from natural sounds and their sources, usually for the guidance of immediate behavioral action. The fact that natural sounds themselves are almost always transients, too brief in duration to have tonal quality, suggests that the ear is far more of a Fast Fourier Transformer (and less of a Fourier analyzer) than is usually explicitly stated. Since the brief sounds constituting most of the acoustical environment contain critical information for guiding behavioral activity, several further hypotheses regarding the cell-level and tissue-level contributions of the central auditory system also follow. For example, the new view suggests that the central auditory system's role is likely to include the extraction of the behaviorally most important features, aspects, or dimensions of the sources of sounds in addition to, or possibly instead of, the physical dimensions of the sounds themselves. Because this new view has already enjoyed some measure of success and has also suggested a number of new and unusual directions for future research, it may become the dominant theory for research in the 21st century.

Animals↗