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PubMedDate not supplied

The aging brain: the cognitive reserve hypothesis and hominid evolution.

Compared to other primates, humans live a long time and have large brains. Recent theories of the evolution of human life history stages (grandmother hypothesis, intergenerational transfer of information) lend credence to the notion that selection for increased life span and menopause has occurred in hominid evolution, despite the reduction in the force of natural selection operating on older, especially post-reproductive, individuals. Theories that posit the importance (in an inclusive fitness sense) of the survival of older individuals require them to maintain a reasonably high level of cognitive function (e.g., memory, communication). Patterns of brain aging and factors associated with healthy brain aging should be relevant to this issue. Recent neuroimaging research suggests that, in healthy aging, human brain volume (gray and white matter) is well-maintained until at least 60 years of age; cognitive function also shows only nonsignificant declines at this age. The maintenance of brain volume and cognitive performance is consistent with the idea of a significant post- or late-reproductive life history stage. A clinical model, "the cognitive reserve hypothesis," proposes that both increased brain volume and enhanced cognitive ability may contribute to healthy brain aging, reducing the likelihood of developing dementia. Selection for increased brain size and increased cognitive ability in hominid evolution may therefore have been important in selection for increased lifespan in the context of intergenerational social support networks.

Aging↗
PubMed2001

Magnetic resonance imaging predicts neuropathology from soman-mediated seizures in the rodent.

Intoxication by the organophosphate compound soman causes prolonged seizures that lead to neuropathology in the brain. This MRI-based study describes the temporal and spatial evolution of brain pathology that follows soman-induced convulsions. We observed significant decreases in apparent diffusion coefficients (ADC; 23% below control) of the hippocampus and thalamus by 12 h after soman treatment. The ADC then returned to near normal values in all regions at 24 h but declined again during the next 7 days. These data suggest that the initial cellular degradation may be resolved but is ultimately followed by regional cellular remodeling. T2 relaxation values declined significantly at 12 h (37% decrease) returning to near normal values by 24 h. These data lend detail to the model suggesting that injured tissues experience an edematous influx that is resolved by 24 h. The imaging data was fully supported by histopathological comparisons where moderate cell loss and swelling within the hippocampus and piriform cortex was observed. This is the first report providing excellenttemporal and spatial resolution of emerging soman-mediated, seizure-induced neuropathology using MRI with histological correlation.

Amygdala↗
PubMed2003

Survival of the fattest: fat babies were the key to evolution of the large human brain.

In the past 2 million years, the hominid lineage leading to modern humans evolved significantly larger and more sophisticated brains than other primates. We propose that the modern human brain was a product of having first evolved fat babies. Hence, the fattest (infants) became, mentally, the fittest adults. Human babies have brains and body fat each contributing to 11-14% of body weight, a situation which appears to be unique amongst terrestrial animals. Body fat in human babies provides three forms of insurance for brain development that are not available to other land-based species: (1) a large fuel store in the form of fatty acids in triglycerides; (2) the fatty acid precursors to ketone bodies which are key substrates for brain lipid synthesis; and (3) a store of long chain polyunsaturated fatty acids, particularly docosahexaenoic acid, needed for normal brain development. The triple combination of high fuel demands, inability to import cholesterol or saturated fatty acids, and dependence on docosahexaenoic acid puts the mammalian brain in a uniquely difficult situation compared with other organs and makes its expansion in early humans all the more remarkable. We believe that fresh- and salt-water shorelines provided a uniquely rich, abundant and accessible food supply, and the only viable environment for evolving both body fat and larger brains in human infants.

Adipose Tissue↗
PubMed2006

[Mirror brain systems, concepts and language: the price for anthropogenesis].

The paper discusses the problem of cognitive evolution and the basis for the origin of language and mind, genetic history of Homo sapiens and whether the basic concepts are inborn or effected by experience, sensory or cognitive per se. The problem of localization of higher functions and Theory of Mind in norm and pathology is analyzed.

Biological Evolution↗
PubMedDate not supplied

Conditional visuo-motor learning in primates: a key role for the basal ganglia.

Sensory guidance of behavior often involves standard visuo-motor mapping of body movements onto objects and spatial locations. For example, looking at and reaching to grasp a glass of wine requires the mapping of the eyes and hand to the location of the glass in space, as well as the formation of a hand configuration appropriate to the shape of the glass. But our brain is far more than just a standard sensorimotor mapping machine. Through evolution, the brain of advanced mammals, in particular human and non-human primates, has acquired a formidable capacity to construct non-standard, arbitrary mapping using associations between external events and behavioral responses that bear no direct relationship. For example, we have all learned to stop at a red traffic light and to go at a green one, or to wait for a specific tone before dialing a phone number and to hang up when hearing a busy signal. These arbitrary associations are acquired through experience, thereby providing primates with a rich and flexible sensorimotor repertoire. Understanding how they are learned, and how they are recalled and used when the context requires them, has been one of the challenging issues for cognitive neuroscience. Valuable insights have been gained over the last two decades through the convergence of multiple complementary approaches. Human neuropsychology and experimental lesions in monkeys have identified a network of brain structures important for conditional sensorimotor associations, whereas imaging studies in healthy human subjects and electrophysiological recordings in awake monkeys have sought to identify the different functional processes underlying the overall function. The present review focuses on the contribution of a network linking the prefrontal cortex, basal ganglia, and dorsal premotor cortex, with special emphasis on results from recording experiments in monkeys. We will first review data pointing to a specific contribution of each component of the network to the performance of well-learned arbitrary visuo-motor associations, as well as data suggesting how novel associations are formed. Then we will propose a model positing that each component of the fronto-striatal network makes a specific contribution to the formation and/or execution of sensorimotor associations. In this model, the basal ganglia are thought to play a key role in linking the sensory, motor, and reward information necessary for arbitrary mapping.

Animals↗