Distance-dependent synaptic inhibition in hippocampal neuronal networks
Final Report Abstract
Synaptic interactions between GABAergic inhibitory interneurons and glutamatergic excitatory principal cells (PCs) play a key role in the processing of information in neuronal networks of the brain. Interneuron axons, in particular the ones of parvalbumine (PV)-expressing perisomatic inhibitory interneurons (PVIs), distribute densely over large distances and thereby control the activity and spike timing of several target PCs by their inhibitory output synapses. Here we examined whether interneuron output signalling in the mature hippocampus is homogeneous and independent on the distance between the presynaptic interneuron and its postsynaptic PC. Indeed, by applying sequential multiple paired recordings between a presynaptic PVI and its target PCs we show that in the dentate gyrus (DG) PVI output signalling is not uniformly strong and rapid as previously described, but highly heterogeneous. We show that the functional properties of perisomatic inhibition depend on the axonal distance between connected partners, with strong and fast inhibition to close neighbours and weaker and slower inhibition to distant cells. We term this synaptic property distance-dependent inhibitory signalling. Moreover, by using in vivo local field potential (LFP) recordings we found that fast rhythmic network activity patterns at gamma (30-150 Hz) emerge in the DG in two flavors: as focal high frequency gamma (70-150 Hz) bursts and global low frequency gamma oscillations (30-70 Hz). Network modeling based on our experimental data further demonstrate that distance-dependent inhibition supports the generation of multiple highly synchronous focal gamma bursts and thereby allow the network to process complex inputs in parallel in flexibly organized neuronal centers.
Publications
- (2017) Distance-dependent inhibition facilitates focality of gamma oscillations in the dentate gyrus. Nat Commun 8:758-773
Strüber M, Sauer JF, Jonas P, Bartos M
(See online at https://doi.org/10.1038/s41467-017-00936-3) - (2018) Recording Spatially Restricted Oscillations in the Hippocampus of Behaving Mice. J Vis Exp 137
Sauer JF, Strüber M, Bartos M
(See online at https://doi.org/10.3791/57714)
