Relations between brain and cognitive development.

Goldman-Rakic reports important new data on cortical development in rhesus monkeys. Some of her findings, especially concurrent cortical synaptogenesis, may be related to cognitive capacities that develop in infancy. The developmental pattern of concurrent synaptogenesis in rhesus is consistent with a straightforward model of relations between brain and cognitive development: Concurrent synaptogenesis is hypothesized to lay the primary cortical foundation for a series of developmental levels in middle infancy that have been empirically documented in both human and rhesus infants. Other general brain changes, especially in the electroencephalogram, also seem to correlate with these levels, as well as with other levels that develop at other periods. In the simplest form of the model, these several factors all show synchronous developmental discontinuities at the time of emergence of a level. Specific research methods are available for specifying when discontinuities occur in development of both brain and behavior.