How does the striatum control our movements?
Proper control of movement relies primarily on the correct functioning of the striatum, a subcortical brain region adjacent to the basal ganglia. Alterations in its functioning are at the heart of various neuropsychiatric disorders such as Parkinson's disease, autism spectrum disorders and schizophrenia.
The striatum is mainly composed of two populations of so-called projection neurons (SPNs): one population forming the direct pathway (dSPN) and the other population forming the indirect pathway (iSPN). The exact organization of SPN neuronal activity in the striatum and how it controls behavioral expression remained the subject of conflicting interpretations. Indeed:
- In vivo loss- or gain-of-function experiments in transgenic mouse models revealed antagonistic functions of SNPs: dSPNs, pro-kinetic and facilitating locomotion, and iSPNs, anti-kinetic and inhibiting locomotion.
- Recent results, however, contradicted this antagonistic role. Recordings based on imaging techniques in mice, enabling the specific activity of SNPs to be assessed, showed that the dSPN and iSPN populations were jointly activated, with similar properties during the initiation and execution of specific movements.
Work in Alban de Kerchove d'Exaerde's laboratory resolved this paradox by combining artificial intelligence to analyse spontaneous locomotor behavior patterns in mouse models, with recordings of SNP activity using calcium imaging (which measures a neuron's activity through its calcium release dynamics). The laboratory demonstrated that concerted and cooperative activity of dSPNs and iSPNs is necessary for the correct initiation and execution of action, concomitant with complementary profiles of neuronal activation and inactivation enabling the selection of movements to be executed.
This study sheds crucial light on the functioning of the striatum and paves the way for future research aimed at deepening our understanding of movement control and associated diseases.
Reference : Varin et al, The respective activation and silencing of striatal direct and indirect pathway neurons support behavior encoding, Nat Commun (2023) 14, 4982
Source: Press release ULB
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