Connectivity and plasticity of neocortical basket cells, by Alberto Bacci

Abstract Connectivity and plasticity of neocortical basket cells

In the neocortex, perisomatic inhibition onto principal pyramidal neurons (PNs) determines the dynamic range of pyramidal neuron responses during sensory processing and drive several forms of network oscillations, believed to be the network correlate of several cognitive functions. The inhibitory control of the perisomatic region of PNs originates from two GABAergic basket cell (BC) subtypes: parvalbumin (PV)-expressing interneurons and PV-negative BCs, expressing the cannabinoid receptor type 1 (CB1). Whereas the role and function of PV cells within cortical networks has been studied in detail, the properties and function of CB1 BCs are poorly understood.
This presentation will revolve around the specific connectivity and plasticity properties of PV and CB1 BCs. In particular, I will describe a PV cell-specific microcircuit: autaptic self-inhibition, which represents an exceptionally large and fast disinhibitory mechanism, favoring synchronization of PV-cell firing during cognitive-relevant cortical network activity. I will also discuss how activity-dependent plasticity of perisomatic inhibition effectively influences the participation of single PNs to γ-oscillations. Finally, I will show how the morpho-functional properties of CB1 BCs and thus their control of PNs, is cortical area- and layer-specific. This work will highlight specific strategies operated by distinct BCs in controlling the output spikes of PNs during cortical activity.

Alberto Bacci’s short biography

I obtained my Masters’ degree at the Dept. of Physiology, University of Milano (Italy) where I worked with Dr. Enzo Wanke on ion channels and excitability of cortical neurons. I then did my Ph.D. thesis (Ph.D. obtained in 2000) at the Dept. of Pharmacology of the University of Milano, under the direction of Dr. Michela Matteoli. During my Ph.D., I was interested in the cellular and molecular mechanisms underlying formation of synapses and how astrocytes modulates synaptogenesis and synaptic function. In 1999, I moved to the Dept. of Neurology at Stanford University in the lab led by Drs. John R. Huguenard and David A. Prince to study the physiology of cortical circuits using electrophysiological approaches. I started working on fast synaptic inhibition and diversity of cortical interneurons. I worked at Stanford as a postdoctoral fellow (1999 – 2003) and as a staff scientist (2003 – 2005). In December 2005, I was awarded an Armenise – Harvard Career Development Award to start my laboratory at the newly established European Brain Research Institute in Rome, Italy. There, I setup my own laboratory and kept working on the inhibitory control of cortical microcircuits. In 2011, following competitive recruitment, I moved my laboratory at the Institut du Cerveau (ICM) in Paris as a senior group leader. In 2012 I obtained a DR position at the CNRS. From 2016 to 2018 I served as the scientific director of the ICM.

Research in my lab focuses on cortical neuron diversity, which is expressed at different levels: cortical areas, cortical networks, cortical neurons and synapses. We are especially interested in fast synaptic inhibition originating from a rich diversity of cortical interneurons, and how the division of labor of different interneuron subtypes, their synaptic properties and plasticity are responsible for the emergence of different forms of cognitive-relevant network activity. The lab uses a combination of neurophysiological approaches, including multiple patch-clamp recordings in acute brain slices, optogenetics, in vivo patch-clamp and multi-electrode recordings and 2-photon calcium imaging in awake mice. We also use quantitative neuroanatomy and cellular and molecular approaches.

My research has been and is being funded by the Armenise – Harvard Career Development Award, European Research Council (ERC), EU Marie-Curie Actions, Agence Nationale de la Recherce (ANR), Fondation pour la Recherche Medicale (FRM), DIM -Ile de France and NARSAD