Mirasso, C. | Search bioRxiv

bioRxiv2023

Somatic disinhibition of granule cells improves information transmission and pattern separation in the dentate gyrus

Cortical circuits operate in a tight excitation/inhibition balance. This balance is relaxed during learning processes, but neither the mechanism nor its impact on network operations are well understood. In the present study, we combined in-vivo and in-vitro neuronal recordings with computational modelling and demonstrated that synaptic plasticity in the afferents from the entorhinal cortex (EC) to the dentate gyrus (DG), in addition to strengthening the glutamatergic inputs into granule cells (GCs), depressed perisomatic inhibition. Computational modelling revealed a functional reorganization in the inhibitory network that explained several experimental findings, including depression of the feed-forward inhibition. In vitro results confirmed a perisomatic dominance of the inhibitory regulation with important functional consequences. It favoured GCs burst firing, improved reliability of input/output transformations and enhanced separation and transmission of temporal and spatial patterns in the EC-DG-CA3 network.

neuroscience↗

bioRxiv2019

Frequency-dependent organization of the brain’s functional network through delayed-interactions

The structure of the brain network shows modularity at multiple spatial scales. The effect of the modular structure on the brain dynamics has been the focus of several studies in recent years but many aspects remain to be explored. For example, it is not well-known how the delays in the transmission of signals between the neurons and the brain regions, interact with the modular structure to determine the brain dynamics. In this paper, we show an important impact of the delays on the collective dynamics of the brain network with modular structure; that is, the degree of the synchrony between different brain regions is dependent on the frequency. In particular, we show that increasing the frequency the network transits from a global synchrony state to an asynchronous state, through a transition region over which the local synchrony inside the modules is stronger than the global synchrony. When the delays are dependent on the distance between the nodes, the modular structure of different spatial scales appears in the correlation matrix over different specific frequency bands, so that, finer spatial modular structure reveal in higher frequency bands. The results are justified by a simple theoretical argument and elaborated by simulations on several simplified modular networks and the connectome with different spatial resolutions.

neuroscience↗