Development of Neuronal Activity in Neocortex of the Kitten

Abstract

MAMMALIAN cerebral cortex undergoes rapid structural changes during the postnatal period. Dendritic connexions increase in number and complexity, the volume of neurone somata increases, and myelination occurs in subcortical and cortical fibres¹. Little is known about the functioning state of cerebral neurones during this period of rapid development. In kittens, spontaneous and evoked activity has been recorded from the cortical surface during the ‘new-born’ period, but such records have been difficult to interpret^2,3. For example, it is not possible to be certain whether the activity recorded from surface originates in cortex itself, or is transmitted from sub-cortical structures. In the present investigations, recordings were obtained from single cortical neurones and from subcortical fibres in unanaesthetized, unrestrained kittens. The results indicate that large parts of neocortex in the kitten are electrically silent at birth, but that neuronal activity rapidly develops in the postnatal period. The early patterns of neuronal discharge show striking differences from those seen in adult animals.