IFISC, Universitat de les Illes Balears, Spain
On the role of inhibitory neurons in the information processing capacity of the dentate gyrus of the hippocampus
Excitation and inhibition in the brain are tightly regulated, but periods of imbalance have been associated with learning episodes both in the cortex and hippocampus. However, the mechanism breaking this tight equilibrium are poorly understood. We performed electrophysiological recordings in vivo and in vitro, and computational models to show that synaptic potentiation of excitatory granule cells (GC) of the dentate gyrus (DG) of the hippocampus not only strengthens excitatory inputs but, unexpectedly, also transiently depresses feed-forward inhibition onto GCs. This depressed inhibition is found to occur into the soma of the GCs, leaving intact their dendritic inhibitory input. Computational models validate this finding and suggest a reorganization of the dentate gyrus network as the responsible of breaking the excitation/inhibition balance. Models also predict that this change favours burst firing in GCs, improves the consistency of input/output transformations in the dentate gyrus and facilitates the transmission of distinct temporal and spatial patterns.