Martel, A.-C. | Search bioRxiv

bioRxiv2024

MICROENDOSCOPIC CALCIUM IMAGING IN SUPPLEMENTARY MOTOR AREA AND PRIMARY MOTOR CORTEX OF RHESUS MACAQUES AT REST AND DURING ARM MOVEMENT

The study of motor cortices in non-human primates is relevant to our understanding of human motor control, both in healthy conditions and in movement disorders. Calcium imaging and miniature microscopes allow the study of multiple genetically identified neurons with excellent spatial resolution. We used this method to examine activity patterns of projection neurons in deep layers of the supplementary motor (SMA) and primary motor areas (M1) in four rhesus macaques. We implanted gradient index lenses and expressed GCaMP6f to image calcium transients while the animals were at rest or engaged in an arm reaching task. We tracked the activity of SMA and M1 neurons across conditions, examined cell pairs for synchronous activity, and assessed whether SMA and M1 neuronal activation followed specific sequential activation patterns. We demonstrate the value of in vivo calcium imaging for studying patterns of activity in groups of corticofugal neurons in SMA and M1. HIGHLIGHTSO_LIUse of one-photon miniature microscopes and microendoscopic calcium imaging to study the activity of cortical projection neurons in the supplementary motor area (SMA) and primary motor cortex (M1) of rhesus macaques at rest or performing simple arm reaches. C_LIO_LICalcium transients were related to arm reaches and showed directional sensitivity in a proportion of cells in SMA and M1. C_LIO_LISubsets of cell pairs showed coactivation in SMA and M1 during rest and reaching tasks. The strength of coactivity was not related to the distance between cells. C_LIO_LISMA and M1 neurons displayed sequential activation patterns. C_LIO_LIWe demonstrated that microendoscopic calcium imaging can be used to assess dynamic activity within genetically identified cell populations in deep layers of SMA and M1. C_LI

neuroscience↗

bioRxiv2022

Activity of tonically active neurons in the primate striatum reflects interaction between time processing and reward prediction

The striatum and its dopaminergic input participate in temporal processing and numerous studies provide evidence that interactions between dopamine and acetylcholine are critical for striatal functioning. However, the role of local cholinergic innervation of the striatum in behaviors requiring precise timing has not been specifically investigated. Here, we recorded from presumed striatal cholinergic interneurons, identified as tonically active neurons (TANs), in two male rhesus monkeys performing self-initiated movements after specified learned time intervals have elapsed since a visual cue. We found that 38% of all recorded TANs responded to the cue with a pause in firing and the strength of these responses could be modulated according to the duration of the interval being timed and the accuracy of time estimates. By examining the TAN response to the reward itself and by recording from TANs during a Pavlovian procedure in which no action was required, we found evidence that TAN activity modulation may potentially reflect differences in the animals prediction of reward. Thus, besides their well-known role in predicting and detecting rewarding events, TANs may generate signals related to the processing of time. Our findings suggest a role of the local cholinergic circuitry in the representation of time within the striatum.

neuroscience↗