Synchronous oscillations of neuronal populations are observed in many cortical regions and have been hypothesized to participate in perception and attention. Networks of inhibitory interneurons seem to be crucial for the synchronization of groups of pyramidal cells to produce these gamma range (30-70 Hz) oscillations. But how is this achieved?
Tamás et al. recorded from pairs of coupled interneurons in cortical layer 2/3. One group of interneurons was connected by g-aminobutyric acid(GABA)ergic synapses; another group made electrical connections via gap junctions. In both cases no gamma range coupling was found. If, however, the connection between the interneurons comprised both electrical and chemical synapses, then phasing at gamma frequency could be observed. This combination of inputs generates a biphasic postsynaptic compound potential that determines precisely the timing of the postsynaptic action potential. Morphological analysis revealed that the gap junctions and the GABAergic synapses in these cells are close to each other in a perisomatic position, enforcing local integration of the postsynaptic potentials and minimizing the effect of dendritic filtering. -- PRS
Nature Neurosci. 3, 366 (2000).
