Aging affects the neural representation of speed in Macaque area MT.

Human perception of speed declines with age. Much of the decline is probably mediated by changes in the middle temporal (MT) area, an extrastriate area whose neural activity is linked to the perception of speed. In the present study, we used random-dot patterns to study the effects of aging on speed-tuning curves in cortical area MT of macaque visual cortex.

Aging affects the direction selectivity of MT cells in rhesus monkeys.

The ability to accurately perceive the direction and speed of moving objects declines during normal aging. This is likely due to functional degradation of cortical neurons. Most neurons in the primate middle temporal area (MT) are direction-selective and their activity is closely linked to the perception of coherent motion.

Spatial and temporal sensitivity degradation of primary visual cortical cells in senescent rhesus monkeys.

Human visual function declines with age. Much of this decline is mediated by changes in the central visual pathways. In this study we compared the spatial and temporal sensitivities of striate cortical cells in young and old paralysed macaque monkeys.

Functional degradation of visual cortical cells in old cats.

Visual function declines with age. Using extracellular single-unit in vivo recordings, we compared the function of primary visual cortical (area 17) cells in young and old paralyzed, anesthetized cats. The results reveal that cortical neurons in old cats exhibit higher visually evoked responses, higher spontaneous activities, lower signal-to-noise ratios, and weaker orientation and direction selectivity than do cells in young adult cats.

Degradation of signal timing in cortical areas V1 and V2 of senescent monkeys.

Senescence in monkeys results in a degradation of the functional properties of cortical cells as well as prolonged hyperactivity. We have now compared the spontaneous and visually evoked activity levels, as well as the visual response latencies of cells in cortical areas V1 and V2 of young and very old monkeys. We found that V1 cells within layer 4 exhibit normal latencies.

GABA and its agonists improved visual cortical function in senescent monkeys.

Human cerebral cortical function degrades during old age. Much of this change may result from a degradation of intracortical inhibition during senescence. We used multibarreled microelectrodes to study the effects of electrophoretic application of gamma-aminobutyric acid (GABA), the GABA type a (GABAa) receptor agonist muscimol, and the GABAa receptor antagonist bicuculline, respectively, on the properties of individual V1 cells in old monkeys.