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Biomedical subjects

N Geschwind

Publications and source records attributed to N Geschwind.

At least 55 records · Page 3Linked to original sources
PubMed1980

Small-diameter nonmyelinated axons in the primate corpus callosum.

The splenium of the corpus callosum of a primate (Macaca mulatta), examined with the electron microscope, was found to contain both myelinated and nonmyelinated axons. The majority of nonmyelinated axons had diameters of less tha 0.25 micron. On the basis of this diameter distribution, it is expected that many callosal axons conduct impulses at velocities of less than 1 m/s and that interhemispheric conduction times for some callosal axons are at least 30 ms and possibly much longer.

Animals↗
PubMed1978

Right-left asymmetrics in the brain.

Structural asymmetries between the hemispheres are found in the human brain. Asymmetries in the auditory regions and in the Sylvian fissures are present even in the fetus. The Sylvian asymmetries may have existed in Neanderthal man and are found consistently in some apes. They may relate to right-left differences infunction. Thus, the striking auditory asymmetries could underlie language lateralization. The asymmetries in the frontal and occipital lobes and the lateral ventricles are correlated with hand preference. Anatomical asymmetries may help to explain the range of human talents, recovery from acquired disorders of language function, certain childhood learning disabilities, some dementing illnesses of middle life, and the evidence for behavioral lateralization in nonhuman primates.

Animals↗
PubMed1978

Human brain. Cytoarchitectonic left-right asymmetries in the temporal speech region.

The auditory regions in four normal brains were mapped and the full extent of the cytoarchitectonic subdivisions was measured for the presence of right-left asymmetries. It was found that asymmetries similar to those found in the planum temporale (left commonly larger than right) are also seen in auditory cytoarchitectonic area Tpt, and area of probable importance for language function. There is a strong positive correlation between the planum asymmetry and the asymmetry of Tpt. It is concluded that the previously described planum asymmetries probably reflect asymmetries in an auditory cytoarchitectonic area and therefore may represent, at least in part, the anatomic substrate for language lateralization.

Anthropometry↗
PubMed1978

Anatomical asymmetry as the basis for cerebral dominance.

Despite repeated assertions by some critics of the impossibility of linking behaviour to study of the brain, there have been major, although not always continuous advances in this field over the past 100 years, some of them based on simple techniques. One example is the study of cerebral dominance, for which it was believed until quite recently that no anatomical basis had been specified. The paper summarizes the findings of striking anatomical asymmetry of the upper surface of the temporal lobe, in an area known to be involved in speech functions. Asymmetries observed in autopsy brains of adults and fetuses, both by gross and by cytoarchitectonic techniques, are reported. By use of radiological methods asymmetries have been shown in the brains and skills of living persons. Asymmetries also appear to be present in the endocasts of skulls of ancient humans, and in nonhuman primates. The distribution of asymmetries is different in left and right handers. The implications of these findings are discussed.

Behavior↗
PubMed1977

Limbic and sensory connections of the inferior parietal lobule (area PG) in the rhesus monkey: a study with a new method for horseradish peroxidase histochemistry.

The caudal part of the inferior parietal lobule (area PG) was injected with horseradish peroxidase (HRP) in 6 hemispheres of 5 rhesus monkeys. The retrograde transport of HRP resulted in the labeling of neurons in diverse cortical and subcortical areas. In cortex, labeled neurons were noted in prefrontal cortex (areas 8, 45, 46), in the banks of the intraparietal and superior temporal sulci, in medial parietal cortex, in cingulate cortex, in the retrosplenial area, in area TF and the caudal portions of the parahippocampal region. Subcortical sites with labeled neurons included the necleus basalis of the substantia innominata, the claustrum, the pulvinar and intralaminar thalamic nuclei, the pretectal area, the nucleus locus coeruleus and the raphe nuclei. Although many of the labeled neurons were seen in layers IIIc and V, each cortical area had an individual laminar pattern of labeled neurons. In these experiments, a benzidine dihydrochloride (BDHC) method was used which yields a blue reaction-product at sites containing HRP. BDHC affords superior visibility of labeled neurons, and a significant improvement in sensitivity when compared to a diaminobenzidine procedure in matching series of sections. Additional sections were also stained with a method which allows the simultaneous demonstration of HRP (blue) and acetylcholinesterase (reddish-brown). These revealed that virtually all substantia innominata (nucleus basalis) neurons which project to area PG are also rich in the enzyme acetycholinesterase. These afferents of PG may be classified into 'sensory association', 'limbic' and 'reticular' categories. It is argued that this arrangement of afferent imput may afford a convergence of limbic and sensory information in area PG and that this may subserve a significant function in the process of sensory attention.

Acetylcholinesterase↗