Phenotypic and genetic associations between gray matter covariation and tool use skill in chimpanzees (Pan troglodytes): Repeatability in two genetically isolated populations.

Humans and chimpanzees both exhibit a diverse set of tool use skills which suggests selection for tool manufacture and use occurred in the common ancestors of the two species. Our group has previously reported phenotypic and genetic associations between tool use skill and gray matter covariation, as quantified by source-based morphometry (SBM), in chimpanzees. As a follow up study, here we evaluated repeatability in heritability in SBM components and their phenotypic association with tool use skill in two genetically independent chimpanzee cohorts. Within the two independent cohorts of chimpanzees, we identified 8 and 16 SBM components, respectively. Significant heritability was evident for multiple SBM components within both cohorts. Further, phenotypic associations between tool use performance and the SBM components were largely consistent between the two cohorts; the most consistent finding being an association between tool use performance and an SBM component including the posterior superior temporal sulcus (STS) and superior temporal gyrus (STG), and the interior and superior parietal regions (p < 0.05). These findings indicate that the STS, STG, and parietal cortices are phenotypically and genetically implicated in chimpanzee tool use abilities.

Comparative analysis of encephalization in mammals reveals relaxed constraints on anthropoid primate and cetacean brain scaling.

There is a well-established allometric relationship between brain and body mass in mammals. Deviation of relatively increased brain size from this pattern appears to coincide with enhanced cognitive abilities. To examine whether there is a phylogenetic structure to such episodes of changes in encephalization across mammals, we used phylogenetic techniques to analyse brain mass, body mass and encephalization quotient (EQ) among 630 extant mammalian species. Among all mammals, anthropoid primates and odontocete cetaceans have significantly greater variance in EQ, suggesting that evolutionary constraints that result in a strict correlation between brain and body mass have independently become relaxed. Moreover, ancestral state reconstructions of absolute brain mass, body mass and EQ revealed patterns of increase and decrease in EQ within anthropoid primates and cetaceans. We propose both neutral drift and selective factors may have played a role in the evolution of brain-body allometry.

Age-related differences in corpus callosum area of capuchin monkeys.

Capuchin monkeys (Cebus apella) are New World primates with relatively large brains for their body size. The developmental trajectories of several brain regions-including cortical white matter, frontal lobe white matter, and basal ganglia nuclei-are similar to humans. Additionally, capuchins have independently evolved several behavioral and anatomical characteristics in common with humans and chimpanzees-including complex manipulative abilities, use of tools, and the use of precision grips-making them interesting species for studies of comparative brain morphology and organization. Here, we report the first investigation into the development of the corpus callosum (CC) and its regional subdivisions in capuchins. CC development was quantified using high-resolution structural magnetic resonance imaging (MRI) images from 39 socially reared subjects (male n=22; female n=18) ranging in age from 4 days (infancy) to 20 years (middle adulthood). The total area of the CC and the subdivisions of the genu, rostral midbody, medial midbody, caudal midbody, and splenium were traced from the midsagittal section. Total CC area displayed significant differences across this time span and was best explained by quadratic growth. Sustained linear growth was observed in the subdivisions of the genu, rostral midbody, and splenium; sustained quadratic growth was seen in the subdivision of the medial midbody. Differences in growth were not detected in the subdivision of the caudal midbody. Females had a larger raw area of the total CC and of the medial midbody and caudal midbody throughout the lifespan. Our results indicate that capuchins show continued white matter development beyond adolescence in regions related to cognitive and motor development.

Comparative analysis of the nucleus basalis of Meynert among primates.

Long projection axons from the Ch4 cell group of the nucleus basalis of Meynert (nbM) provide cholinergic innervation to the neurons of the cerebral cortex. This cortical cholinergic innervation has been implicated in behavioral and cognitive functions, including learning and memory. Recent evidence revealed differences among primate species in the pattern of cholinergic innervation specific to the prefrontal cortex. While macaques displayed denser cholinergic innervation in layers I and II relative to layers V and VI, in chimpanzees and humans, layers V and VI were as heavily innervated as the supragranular layers. Furthermore, clusters of cholinergic axons were observed within the prefrontal cortex of both humans and chimpanzees to the exclusion of macaque monkeys, and were most commonly seen in humans. The aim of the present study was to determine whether the Ch4 cell group was modified during evolution of anthropoid primates as a possible correlate of these changes in cortical cholinergic innervation. We used stereologic methods to estimate the total number of choline acetyltransferase-immunoreactive magnocellular neurons within the nbM of New World monkeys, Old World monkeys, apes, and humans. Linear regression analyses were used to examine the relationship of the Ch4 cell group with neocortical volume and brain mass. Results showed that total nbM neuron numbers hyposcale relative to both neocortical volume and brain mass. Notably, the total number of nbM neurons in humans were included within the 95% confidence intervals for the prediction generated from nonhuman data. In conclusion, while differences in the cholinergic system exist among primate species, such changes appear to involve mostly axon collateral terminations within the neocortex and, with the exception of the relatively small group of cholinergic cells of the subputaminal subdivision of the nbM at the anterointermediate and rostrolateral levels, are not accompanied by a significant extra-allometric increase in the overall number of subcortical neurons that provide that innervation.

Species-specific distributions of tyrosine hydroxylase-immunoreactive neurons in the prefrontal cortex of anthropoid primates.

In this study, we assessed the distribution of cortical neurons immunoreactive for tyrosine hydroxylase (TH) in prefrontal cortical regions of humans and nonhuman primate species. Immunohistochemical methods were used to visualize TH-immunoreactive (TH-ir) neurons in areas 9 (dorsolateral prefrontal cortex) and 32 (anterior paracingulate cortex). The study sample included humans, great apes (chimpanzee, bonobo, gorilla, orangutan), one lesser ape (siamang), and Old World monkeys (golden guenon, patas monkey, olive baboon, moor macaque, black and white colobus, and François' langur). The percentage of neurons within the cortex expressing TH was quantified using computer-assisted stereology. TH-ir neurons were present in layers V and VI and the subjacent white matter in each of the Old World monkey species, the siamang, and in humans. TH-ir cells were also occasionally observed in layer III of human, siamang, baboon, colobus, and François' langur cortex. Cortical cells expressing TH were notably absent in each of the great ape species. Quantitative analyses did not reveal a phylogenetic trend for percentage of TH-ir neurons in these cortical areas among species. Interestingly, humans and monkey species exhibited a bilaminar pattern of TH-ir axon distributions within prefrontal regions, with layers I-II and layers V-VI having the densest contingent of axons. In contrast, the great apes had a different pattern of laminar innervation, with a remarkably denser distribution of TH-ir axons within layer III. It is possible that the catecholaminergic afferent input to layer III in chimpanzees and other great apes covaries with loss of TH-ir cells within the cortical mantle.

Cortical dopaminergic innervation among humans, chimpanzees, and macaque monkeys: a comparative study.

In this study, we assessed the possibility that humans differ from other primate species in the supply of dopamine to the frontal cortex. To this end, quantitative comparative analyses were performed among humans, chimpanzees, and macaques using immunohistochemical methods to visualize tyrosine hydroxylase-immunoreactive axons within the cerebral cortex. Axon densities and neuron densities were quantified using computer-assisted stereology. Prefrontal areas 9 and 32 were chosen for evaluation due to their roles in higher-order executive functions and theory of mind, respectively. Primary motor cortex (area 4) was also evaluated because it is not directly associated with cognition. We did not find an overt quantitative increase in cortical dopaminergic innervation in humans relative to the other primates examined. However, several differences in cortical dopaminergic innervation were observed among species which may have functional implications. Specifically, humans exhibited a sublaminar pattern of innervation in layer I of areas 9 and 32 that differed from that of macaques and chimpanzees. Analysis of axon length density to neuron density among species revealed that humans and chimpanzees together deviated from macaques in having increased dopaminergic afferents in layers III and V/VI of areas 9 and 32, but there were no phylogenetic differences in area 4. Finally, morphological specializations of axon coils that may be indicative of cortical plasticity events were observed in humans and chimpanzees, but not macaques. Our findings suggest significant modifications of dopamine's role in cortical organization occurred in the evolution of the apes, with further changes in the descent of humans.

Inspection of care: findings from an innovative demonstration.

In this article, information is presented concerning the efficacy of a sample-based approach to completing inspection of care reviews of Medicaid-supported nursing home residents. Massachusetts nursing homes were randomly assigned to full (the control group) or sample (the experimental group) review conditions. The primary research focus was to determine whether the proportion of facilities found to be deficient (based on quality of care and level of care criteria) in the experimental sample was comparable to the proportion in the control sample. The findings supported such a hypothesis: Deficient facilities appear to be equally identifiable using the random or full-sampling protocols, and the process can be completed with a considerable savings of surveyor time.

Discharged rehabilitation patients: impact of follow-up surveillance by a friendly visitor.

The period after hospital discharge is the most critical for rehabilitation patients returning to a community setting. A friendly visitor surveillance program using nonprofessional volunteers was designed to monitor treatment regimen compliance by alerting medical professionals of impending crises among discharged rehabilitation patients. A randomized experimental design was used to evaluate the impact of 1 year of program exposure on rehospitalization, service use, and psychosocial outcomes experienced by 142 patients. Patients were randomized into 3 groups: friendly visitors (FV) and biannual nursing visits; biannual nursing (RN) visits only; and controls (CON). Over 1/3 of the sample was rehospitalized at least once during the 1-year impact period, yet no differences were found across experimental groups nor patients' diagnostic category. No meaningful pattern of significant differences between the groups was observed at the p less than 0.1 probability level in any of the other outcome areas. The need to alert the medical system of impending patient problems occurred rarely, suggesting that existing informal support systems and regular use of medical services may be sufficient to monitor rehabilitation patients' progress.

Comparison of community adjustment of older vs. younger mentally retarded adults.

The relationship between age and community adjustment was studied in a sample of 153 deinstitutionalized mentally retarded adults. Those aged 18 to 54 were compared with those aged 55 and older with respect to IQ, rate of recidivism, community adjustment, and residential environment. Results showed that although the two groups were comparable in IQ and recidivism rate, the older subjects lived in less autonomous residences in the community and functioned at a lower level. Alternative explanations for these results were offered, and policy implications were presented.

Stroke rehabilitation: analysis of repeated Barthel index measures.

Functional abilities of stroke patients in a rehabilitation hospital are recorded every 2 weeks using the Barthel index. For purposes of this study, data were collected retrospectively and prospectively from consecutive records according to predetermined criteria on forms coded for computer analysis. Total scores of 110 patients were correlated with length of stay, placement at discharge and scores in individual functional abilities. Analysis of the data reveals that an initial score over 40 on the Barthel index defines a population with a greater proportion of discharges to home and that patients with initial scores over 60 have a shorter length of stay. Further analysis indicates a predictable progression in the development of functional skills in this population so that with a Barthel score below 40, no one was independent in the mobility skills and fewer than 50% were independent in the very basic skills, such as feeding, grooming and sphincter control. A score of 60 appears to be a pivotal score where patients move from dependency to assisted independence.