Age-dependent emergence of a parieto-insular corticocortical signal flow in developing rats

Abstract

By using the procedure that we developed for inducing population oscillation, it was previously demonstrated that insular cortex stimulation can evoke insulo-parietal field potential propagation and synchronized population oscillation in the parietal cortex in slices obtained from mature rats (27–35 days old). By using the same procedure, we have now studied the reciprocal parieto-insular projection. Parietal cortex stimulation elicited synchronized population oscillation in the parietal—but not insular—cortex in mature tissues. In the insular cortex, the initial wavelet of the oscillation generated by parietal cortex stimulation propagated, but the entire oscillation did not. A prior induction—but not simultaneous occurrence—of oscillation in the parietal cortex sufficed to have this initial wavelet propagate. In immature tissue (9–10 days old), both the parietal cortex oscillation and the parieto-insular propagation were induced only with low [Mg 2+] o. This age dependence is exactly the same as we previously observed for the reciprocal insulo-parietal propagation. Given that the parietal cortex receives somatosensory inputs from the oral cavity and the insular cortex receives primarily chemosensory inputs from the same source, the age-dependent changes in the availability of bidirectional signal traffic between these cortices might contribute to the development of multimodal responsiveness of taste neurons.