L6 modulates cortical activity in the neonatal rat pups
The barrel cortex in rodents is responsible for the contact of the animal with the external world using vibrissa on the whisker pad of the animal. It contains a topographic map of the facial whiskers formed by the functionally united groups of neurons of layer 4 that forms visually detected structures - barrels, where each barrel is tuned to a corresponding whisker. Recently it was shown that among thalamic excitatory inputs barrel’s layer 4 (L4) has also inhibitory inputs from infragranular layer 6 (L6). Recently group of Scanziani demonstrated that L6 modulates cortical activity through an inhibition and identifies the neurons that are able to regulate the strength of cortical responses throughout cortical depth. However, the question remains what is the role of this modulation and when this modulation of the L4 activity by L6 emerges. In our research we have found that inhibitory effect of L6 on L4 is established starting from the first postnatal week. Activation of the L6 neurons following early gamma oscillation (EGO) in layer 4 strongly modified it that resulted in disappearance of the EGO cycles. Emergence of the L6 evoked inhibition during critical period of the barrel cortex development suggests that L6 possibly is involved in the formation of cortical maps.