Inserm, Institute of Mediterranean Neurobiology (INMED), Aix-Marseille University, France
The inhibitory GABAergic synapse in hippocampal circuits
Recurrent connectivity in the CA1 region of the adult hippocampus is mainly supported by inhibitory GABAergic transmission originating from local interneurons. Most network dynamics in that region are coordinated locally with minimal influence of extrinsic sources. Therefore, the diverse population of CA1 interneurons should carry an important functional influence on local dynamics. While many studies have elucidated the physiology and connectivity of single interneurons, the spatiotemporal relationship of the activity of groups of interneurons and its relation to population dynamics remain unclear. Here we use an all-optical approach to simultaneously record the activity of CA1 interneurons and pyramidal cells and activate single or multiple interneurons using holographic light stimulation. We show that interneurons single-handedly exert a positive modulation on the activity of their functional partners. This amplification of functional links by single interneurons often leads to an increase in the rate of synchronous events associated with sharp-wave ripples. This network impact contrasts with other cortical regions where interneurons contribute to feature-specific suppression.
Rosa Cossart is the Director of the Institute of Mediterranean Neurobiology (INMED), affiliated to INSERM and Aix-Marseille University, a pioneering Institute in the field of Systems Developmental Neuroscience. After graduating in Mathematics and Physics from the Ecole Centrale Paris, she studied the functional rewiring of GABAergic circuits in epilepsy during her PhD with Drs. Bernard and Ben-Ari. As a postdoctoral fellow with Pr. Yuste at Columbia University, she pioneered the use of calcium imaging to study cortical circuit function. Her lab made seminal contributions to the understanding of how development scaffolds hippocampal circuits. They discovered “hub cells” and more recently “assemblies” forming the functional building blocks of hippocampal function.