Changes in cortical dendritic branching subsequent to partial social isolation in stumptailed monkeys

Maternal influences on body temperature in the infant primate

The following study investigated the diurnal variation in body temperature of the young monkey infant and assessed the role that the mother plays in the development of the temperature rhythm. Using an implantable biotelemetry system, core body temperature and motoric activity were evaluated in maternally-reared and hand-reared rhesus monkey infants across the first several months of life. Our results indicated that the nocturnal temperatures of hand-reared infants are lower than those of mother-reared infants at one month of age, and that there are persistent differences in the orientation and shape of the diurnal temperature rhythm. The initial thermal challenge and the prolonged rhythm shift may have implications for the normal development of several physiological systems in the hand-reared infant monkey.

Deprived somatosensory-motor experience in stumptailed monkey neocortex: dendritic spine density and dendritic branching of layer IIIB pyramidal cells

Infant macaque monkeys (Macaca arctoides) were individually raised to age 6 months in large clear cubes built into one wall of a control colony that allowed them visual access to it but not tactile contact. The two deprivation conditions (Cond 2 and Cond 3) were equal both in physical size and with respect to partial social isolation. They differed in the degree of somatosensory-motor opportunity available during development in that the Cond 2 chamber was empty, whereas Cond 3 contained ladders, a trapeze, and play objects. Four monkeys from each of these conditions were compared with four colony-reared (Cond CR) monkeys. Neuroanatomical changes were evaluated by using light microscopy in Golgi-Cox-stained neocortex. Dendritic spines on the apical shafts of layer IIIB pyramidal cells were counted in primary motor (MI), somatosensory (SI), and visual (area 17, V1) cortical regions. Layer IIIB pyramidal neurons with somas of medium size were selected from each cortical region and the density of apical dendritic spines determined. The basilar dendritic branches of these same neurons were traced, and the dendritic branching complexity was assessed in order to compare the sensitivity of the dendritic spine and branching measures consequent to deprived rearing. The number of apical dendritic spines was significantly reduced in Cond 2 when compared with either Cond 3 or Cond CR (which did not differ from each other). This occurred in both MI and SI cortex, but not in the visual cortex, the region used as a control for a global brain effect. Branching complexity measured on the same pyramidal neurons was reduced only in MI cortex of Cond 2. These results show spine density, a more direct measure of neuronal connectivity, to be the more sensitive measure of early environmental deprivation. Also, the enriched environment provided by Cond 3 relative to Cond 2 offset the effect of partial social isolation such that both morphometric measures had values comparable to Cond CR monkeys.

Dysesthesias and self-mutilation in humans and subhumans: a review of clinical and experimental studies

The chronic deafferentation syndrome includes a complex pattern of abnormal self-directed behavior and a stress response. Subhuman self-mutilation is a secondary consequence of the chronic deafferentation syndrome. The evidence indicates that the chronic deafferentation syndrome in subhumans is a valid model for the induced and the spontaneous dysesthesias in humans. Objective criteria for the definition of subhuman dysesthesias have been derived from independent sources of evidence, in neurally intact subjects; those criteria are then found to match the subhuman syndrome of deafferentation. Support for the validity of the inference of subhuman dysesthesias derives from the parallels with the various facts of the human dysesthesias. The credibility of this argument is significantly strengthened by reports of morphological and excitatory physiological abnormalities, in central somatosensory structures, in response to deafferentation. There is no independent subhuman evidence in support of alternate interpretations of the deafferentation syndrome, and those interpretations seem to be inadequate in several aspects. Doubts concerning the validity of this animal model have been allayed by reports of dysesthesias in humans with spinal posterior rhizotomies or ganglionectomies, and also those with congenital analgesia. Moreover, the occurrence of this syndrome in hypoalgesic areas as a consequence of anterolateral cordotomy in monkeys, can best be interpreted as a reflection of dysesthesias. This syndrome is released by neuropathological or neurosurgical lesions in the peripheral or central nervous system; lesions which involve small caliber peripheral afferents or the spinothalamic tract. Variability in the release of this syndrome has been associated with several different factors. So far, the chronic syndrome is intractable. Evidence relates the abnormalities of this syndrome to pathophysiological foci in central relays of the somatosensory system, and suggests that the chronic abnormalities of this syndrome can be sustained at brain levels.

A neural plasticity hypothesis of schizophrenia

An extensive research effort has failed, thus far, to conclusively identify a specific disease process (or processes) underlying the behavioral symptoms of schizophrenia. The present paper will entertain the hypothesis that the structural and functional plasticity of the brain can constitute a "nonspecific" biological etiology of schizophrenia. This plasticity need not be accompanied by infectious processes or gross alterations in neurotransmitter levels, enzyme activities, etc. that are specific to schizophrenia. The monkey isolation syndrome provides a precedent for a causal relationship between brain plasticity and pathological behavior. In a speculative manner, it will be demonstrated that neural plasticity concepts can be invoked to potentially explain several aspects of schizophrenia: the various types of behavioral symptoms exhibited by schizophrenics, the regional alterations in brain structure and function seen in chronic schizophrenics, the involvement of genetic and environmental etiological factors, the pharmacological support for the dopamine hypothesis, and the delayed onset of neuroleptic antipsychotic action. Considering the explanatory potential of neural plasticity concepts, a research program which focuses on these concepts seems warranted.

Cerebellar plasticity: modification of Purkinje cell structure by differential rearing in monkeys

Dendritic branching in Purkinje and granule cells and the diameters of Purkinje cell somas were compared in several cerebellar areas of monkeys reared in isolation, with social experience, or in a large colony. In the colony-reared monkeys, spiny branchlets of Purkinje cells were more extensive in the paraflocculus and the nodulus than they were in the other two groups. Granule cell dendritic branching in the paraflocculus and nodulus did not differ across groups. In addition, Purkinje cell somas were larger in the uvula and the nodulus of the colony animals than in the other groups. These data indicate that the social and physical environment during development influences the morphology of cerebellar Purkinje cells.