Excitatory and inhibitory connections show selectivity in the neocortex

The cerebral cortex is pivotal in information processing and higher brain function and its laminar structure of six distinct layers, each in receipt of a different constellation of inputs, makes it important to identify connectivity patterns and distinctions between excitatory and inhibitory pathways. The 'feedforward' projections from layer 4-3 and from 3-5 target pyramidal cells and to lesser degrees interneurones. 'Feedback' projections from layer 5-3 and from 3-4, on the other hand, mainly target interneurones. Understanding the microcircuitry may give some insight into the computation and information processing performed in this brain region.