Organisation et spécificité des schémas de connectivité des interneurones du striatum dorsal
Juliette Contadini
Equipe “Circuits cortico-basalet comportement

Abstract
The striatum, the main input structure of the basal ganglia, plays a key role in integrating cortical and subcortical information to select appropriate actions. Input integration at the level of striatal projection neurons (SPN), the principal output of the striatum, has been extensively studied. In contrast, much less is known about local interneurons, which potently regulate SPN activity and plasticity. Among these, interneurons expressing parvalbumin (PV) or somatostatin (SOM) exhibit distinct morphological, electrophysiological, and functional differences that influence their intrastriatal connectivity and role in integrative processes. PV interneurons are strongly and locally connected to SPN, with dense arborization and fast activity, whereas SOM interneurons form more diffuse and longer-range connections. Importantly, these differences also vary across striatal regions, including the dorsolateral (DLS), and dorsomedial (DMS), suggesting complementary roles in the modulation of subcortical and corticostriatal networks.
This thesis aims at characterizing the connectivity patterns of PV and SOM striatal interneurons using anatomical and functional approaches. From an anatomical perspective, tracing with modified rabies virus combined with a semi-automated analysis of presynaptic cells allows to map and compare the brain-wide connectivity of both striatal interneurons and compare these patterns between the DMS and the DLS. This project deepens our understanding of how region-specific characteristics of interneuron connectivity could mediate cell-specific functions within striatal networks. In parallel, the functional organization of connectivity from sensory cortical areas to each striatal interneuron was tested, using patch-clamp electrophysiological recordings coupled with laser-scanning photostimulation (glutamate uncaging). The cortical distribution and weight of the presynaptic cells from the primary and secondary somatosensory cortex (S1 and S2) to PV and SOM interneurons in the DLS were characterized and paralleled with SPN features. This work reveals cell-specific differences in density and spatial organization of connectivity patterns across cortical areas.
Together our findings suggest that DLS PV interneurons integrate focused sensorimotor information with strong feedback from neurons in basal ganglia. Locally in the striatum, they integrate broad band first order somatosensory inputs that match those of large populations of SPN. In contrast, DLS SOM interneurons integrate heterogeneous, widespread inputs from sensorimotor, associative and frontal territories. Locally in the striatum, inputs to SOM interneurons are complementary to those targeting SPN. These distinctive wiring properties suggest parallel functions in striatal integration of brain information and in controlling SPN activity, the main striatal output.

Jury
Isabelle Férézou, Rapporteur – NeuroPSI, Paris Saclay
Jérôme Baufreton, Rapporteur – IMN, Université de Bordeaux
Nicolas Mallet, Examinateur – IMN, Université de Bordeaux
Corinne Beurrier, Examinateur – INT, Aix-Marseille Université
Mario Carta, Examinateur – IINS, Université de Bordeaux
Valéry Matarazzo, Président du jury –  INMED, Aix-Marseille Université
Ingrid Bureau, Directrice de thèse –  INMED, Aix-Marseille Université

Thursday, 2 April 2026 at 2 p.m. – INMED conference room