Even within a small cortical area a rich diversity of distinct neurons contributes differentially to information processing. Cortical neurons can be divided into excitatory pyramidal cells, which use glutamate as a neurotransmitter and give both local and long-range axonal projections, and inhibitory interneurons, which are GABAergic and control the activity and timing of pyramidal cells mainly through local axons.
Both types of neuron can be further subdivided on the basis of their distinct axo-dendritic arborisations, subcellular post-synaptic targets, in vitro firing patterns and by their differential expression of signalling molecules.
In this research programme we aim to determine how identified neurons of the hippocampus and prefrontal cortex contribute to the generation of network oscillations. For this we record the activity of single neurons during network oscillations in the hippocampus and/or medial prefrontal cortex. After the recording of the cell during spontaneously occurring network oscillations, the recorded cell is selectively filled with neurobiotin using the juxtacellular labelling method. This allows the unequivocal identification of the recorded neuron using several histological techniques. The soma, dendrites and axons are visualised with light microscopy and digitally reconstructed with neurolucida. The post-synaptic targets of the cell are identified with electron microscopy. Furthermore we use immunofluorescence microscopy to test the expression of different molecules by the recorded cells.