Final Report Summary - HIPPOCHRONOCIRCUITRY (The chronocircuitry of the hippocampus during cognitive behaviour)
In this project we have established a novel technique that allows the recording and labelling of identified neurons during free behaviour and without the influence of drugs or anaesthesia. Using this technique we have been able to show how distinct types of GABAergic interneuron make differential contributions to the hippocampal representations during behaviour. We found that parvalbumin-expressing basket cells, making synapses onto the cell bodies and dendrites of pyramidal cells, dynamically change their firing according to the ongoing behavioural state including running, sleep and quiet wakefulness. In contrast, ivy cells, which provide also extrasynaptic modulation of pyramidal cells, fire with similar activity throughout different behaviours to provide homeostasis to the hippocampal network. In addition, bistratified and O-LM cells, targeting different sections of the dendritic tree of pyramidal cells, provide well-timed inhibition for the generation of network synchrony and operations. Also, using a novel optogenetic technique, we demonstrated that pyramidal cells in the ventral hippocampus route different types of information selectively to distinct target areas: Pyramidal cells which project to the prefrontal cortex convey preferentially information about anxiety and other pyramidal cells projecting to the nucleus accumbens carry enriched information about goal locations. Our data demonstrate how distinct types of neuron differentially organise information-processing in the working brain.