Blue Brain Virtual Talk - Similarities and differences of human and rodent neocortical synapses, neurons and networks

The EPFL Blue Brain Project is delighted to welcome Gabor Tamas for a virtual talk.

Biography

Gabor Tamas is Professor of Neuroscience at the University of Szeged, Hungary.

He started his neuroscience studies in the laboratory of Profs. Peter Somogyi and Eberhard Buhl at the University of Oxford and defined the effect, number and location of synapses between neocortical neurons. This work also revealed that certain types of cortical neurons could control themselves by establishing autapses between their axons and the parent soma/dendrites. When establishing a laboratory in Szeged, he developed a combined electrophysiological and neuroanatomical approach to study the interactions between neurons of the cerebral cortex and identified an intercellular mechanism capable of synchronizing neurons at gamma frequency.

He received training from Prof. Rafael Yuste at Columbia University in two photon and high-speed confocal imaging and the collaboration revealed that dendrites of interneurons consist of Ca²⁺ microdomains separating individual synapses. He applied standardized procedures in his laboratory in order to develop a library of specimens currently containing >15000 functionally connected pairs of neocortical neurons recorded and archived for correlated light and electron microscopy.

This dataset allows the analysis of rare cell types or connections in the cortex and was essential in discovering the first type of interneuron, the so-called neurogliaform cell, capable of eliciting slow, GABAB receptor mediated inhibition in the cerebral cortex. Moreover, his group demonstrated that axo-axonic cells, which were considered as the most specific inhibitory neurons, are not only inhibitory but also function as the most powerful excitatory neurons of the cerebral cortex. This was the first study for which the group successfully performed multiple patch clamp recordings in slices taken from the human cerebral cortex in collaboration with Prof. Pál Barzó (University of Szeged). The dataset concerning synaptic interactions of human neurons also showed that single neurons are capable of activating Hebbian networks in the human cerebral cortex.

His group went on explaining the function of neurogliaform cells and revealed that this cell type uses GABA for a single cell driven form of nonsynaptic or volume transmission for the modulation of the surrounding microcircuit. The group also found that insulin is expressed and released by neocortical neurogliaform cells and discovered novel cell types in the human cerebral cortex in collaboration with the Allen Institute. His current experiments focus on identified microcircuits in behaving humans.
Gabor Tamas is a member of the Academia Europaea and the Hungarian Academy of Sciences.

Abstract
Experiments on animal models showed that the efficacy of chemical transmission between neurons depends on several factors including the number, spatial distribution and size of synapses, presynaptic release mechanisms, postsynaptic membrane properties and synaptic plasticity. Recordings from human synaptic connections indicated species related differences in synaptic properties leading to altered signal propagation in human cortical microcircuits compared to animal models.

The presentation will elucidate quantal and structural differences of human and rat neocortical synapses mechanistically explaining why single neurons of the human neocortex can trigger high and low frequency rhythmic activity in local networks. In turn, experiments will be presented from freely behaving animals detecting rhythmic network episodes at various frequencies and the corresponding firing of identified interneurons and pyramidal cells during defined epochs of slow wave sleep. The suggestion that evolutionally conserved network episodes could be differentially recruited in mammalian species will be discussed.


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