Recording and manipulating the in vivo correlational structure of neuronalactivity during visual cortical development

Many aspects of visual cortical functional architecture, such as orientatio n and ocular dominance columns, are present before animals have had any vis ual experience, indicating that the initial formation of cortical circuitry takes place without the influence of environmental cues. For this reason, it has been proposed that spontaneous activity within the developing visual pathway carries instructive information to guide the early establishment o f cortical circuits. Recently developed recording and stimulation technique s are revealing new information about the in vivo organization of this spon taneous activity and its contribution to cortical development. Multielectro de recordings in the developing lateral geniculate nucleus (LGN) of ferrets demonstrate that retinal spontaneous activity is not simply relayed to the visual cortex, but is reshaped and transformed by a variety of mechanisms including cortical feedback and endogenous oscillatory activity. The result ing patterns are consistent with many of the predictions of correlation-bas ed models of cortical development. In addition, the introduction of artific ially correlated activity into the visual pathway disrupts some but not all aspects of orientation tuning development. Thus, while these results suppo rt an instructive role of spontaneous activity in shaping cortical developm ent, there still appears to be a number of aspects of this process that can not be accounted for by activity alone. (C) 1999 John Wiley & Sons, Inc.