Brain size

About: Brain size is a research topic. Over the lifetime, 2537 publications have been published within this topic receiving 197556 citations. The topic is also known as: brain size.

Regional Brain Changes in Aging Healthy Adults: General Trends, Individual Differences and Modifiers

Abstract: Brain aging research relies mostly on cross-sectional studies, which infer true changes from age differences. We present longitudinal measures of five-year change in the regional brain volumes in healthy adults. Average and individual differences in volume changes and the effects of age, sex and hypertension were assessed with latent difference score modeling. The caudate, the cerebellum, the hippocampus and the association cortices shrunk substantially. There was minimal change in the entorhinal and none in the primary visual cortex. Longitudinal measures of shrinkage exceeded cross-sectional estimates. All regions except the inferior parietal lobule showed individual differences in change. Shrinkage of the cerebellum decreased from young to middle adulthood, and increased from middle adulthood to old age. Shrinkage of the hippocampus, the entorhinal cortices, the inferior temporal cortex and the prefrontal white matter increased with age. Moreover, shrinkage in the hippocampus and the cerebellum accelerated with age. In the hippocampus, both linear and quadratic trends in incremental age-related shrinkage were limited to the hypertensive participants. Individual differences in shrinkage correlated across some regions, suggesting common causes. No sex differences in age trends except for the caudate were observed. We found no evidence of neuroprotective effects of larger brain size or educational attainment.

Equal numbers of neuronal and nonneuronal cells make the human brain an isometrically scaled‐up primate brain

Abstract: The human brain is often considered to be the most cognitively capable among mammalian brains and to be much larger than expected for a mammal of our body size. Although the number of neurons is generally assumed to be a determinant of computational power, and despite the widespread quotes that the human brain contains 100 billion neurons and ten times more glial cells, the absolute number of neurons and glial cells in the human brain remains unknown. Here we determine these numbers by using the isotropic fractionator and compare them with the expected values for a human-sized primate. We find that the adult male human brain contains on average 86.1 +/- 8.1 billion NeuN-positive cells ("neurons") and 84.6 +/- 9.8 billion NeuN-negative ("nonneuronal") cells. With only 19% of all neurons located in the cerebral cortex, greater cortical size (representing 82% of total brain mass) in humans compared with other primates does not reflect an increased relative number of cortical neurons. The ratios between glial cells and neurons in the human brain structures are similar to those found in other primates, and their numbers of cells match those expected for a primate of human proportions. These findings challenge the common view that humans stand out from other primates in their brain composition and indicate that, with regard to numbers of neuronal and nonneuronal cells, the human brain is an isometrically scaled-up primate brain.

Hippocampal volume reduction in major depression.

Abstract: OBJECTIVE: Elevated levels of glucocorticoids in depression have been hypothesized to be associated with damage to the hippocampus, a brain area involved in learning and memory. The purpose of this study was to measure hippocampal volume in patients with depression. METHOD: Magnetic resonance imaging was used to measure the volume of the hippocampus in 16 patients with major depression in remission and 16 case-matched nondepressed comparison subjects. RESULTS: Patients with depression had a statistically significant 19% smaller left hippocampal volume than comparison subjects, without smaller volumes of comparison regions (amygdala, caudate, frontal lobe, and temporal lobe) or whole brain volume. The findings were significant after brain size, alcohol exposure, age, and education were controlled for. CONCLUSIONS: These findings are consistent with smaller left hippocampal volume in depression.

Smaller hippocampal volume predicts pathologic vulnerability to psychological trauma

Abstract: In animals, exposure to severe stress can damage the hippocampus. Recent human studies show smaller hippocampal volume in individuals with the stress-related psychiatric condition posttraumatic stress disorder (PTSD). Does this represent the neurotoxic effect of trauma, or is smaller hippocampal volume a pre-existing condition that renders the brain more vulnerable to the development of pathological stress responses? In monozygotic twins discordant for trauma exposure, we found evidence that smaller hippocampi indeed constitute a risk factor for the development of stress-related psychopathology. Disorder severity in PTSD patients who were exposed to trauma was negatively correlated with the hippocampal volume of both the patients and the patients’ trauma-unexposed identical co-twin. Furthermore, severe PTSD twin pairs—both the trauma-exposed and unexposed members—had significantly smaller hippocampi than non-PTSD pairs.

Longitudinal Mapping of Cortical Thickness and Brain Growth in Normal Children

Abstract: Recent advances in magnetic resonance imaging (MRI) technology now allow the tracing of developmental changes in the brains of children. We applied computer-matching algorithms and new techniques for measuring cortical thickness (in millimeters) to the structural MRI images of 45 children scanned twice (2 yr apart) between the ages 5 and 11. Changes in brain size were also assessed, showing local brain growth progressing at a rate of ∼0.4-1.5 mm per year, most prominently in frontal and occipital regions. Estimated cortical thickness ranged from 1.5 mm in occipital regions to 5.5 mm in dorsomedial frontal cortex. Gray matter thinning coupled with cortical expansion was highly significant in right frontal and bilateral parieto-occipital regions. Significant thickening was restricted to left inferior frontal (Broca's area) and bilateral posterior perisylvian (Wernicke's area on the left) regions. In the left hemisphere, gray matter thickness was correlated with changing cognitive abilities. For the first time, developmental changes in gray matter thickness, brain size, and structure-function relationships have been traced within the same individuals studied longitudinally during a time of rapid cognitive development.