Biology subjects

Pi, J. S.

Publications and source records attributed to Pi, J. S..

3 recordsLinked to original sources

bioRxiv2024

Control of tongue movements by the Purkinje cells of the cerebellum

We use our tongue much like our hands: to interact with objects and transport them. For example, we use our hands to sense properties of objects and transport them in the nearby space, and we use our tongue to sense properties of food morsels and transport them through the oral cavity. But what does the cerebellum contribute to control of tongue movements? Here, we trained head-fixed marmosets to make skillful tongue movements to harvest food from small tubes that were placed at sharp angles to their mouth. We identified the lingual regions of the cerebellar vermis and then measured the contribution of each Purkinje cell (P-cell) to control of the tongue by relying on the brief but complete suppression that they experienced following an input from the inferior olive. When a P-cell was suppressed during protraction, the tongues trajectory became hypermetric, and when the suppression took place during retraction, the tongues return to the mouth was slowed. Both effects were amplified when two P-cells were simultaneously suppressed. Therefore, suppression of P-cells in the lingual vermis disrupted the forces that would normally decelerate the tongue as it approached the target. Notably, the population simple spike activity peaked near deceleration onset when the movement required precision (aiming for a tube), but not when the movement was for the purpose of grooming. Thus, the P-cells appeared to signal when to stop protrusion as the tongue approached its target.

neuroscience↗

bioRxiv2023

Complex spikes perturb movements, revealing the sensorimotor map of Purkinje cells

The cerebellar cortex performs computations that are critical for control of our actions, and then transmits that information via simple spikes of Purkinje cells (P-cells) to downstream structures. However, because P-cells are many synapses away from muscles, we do not know how their output affects behavior. Furthermore, we do not know the level of abstraction, i.e., the coordinate system of the P-cells output. Here, we recorded spiking activities of hundreds of P-cells in the oculomotor vermis of marmosets during saccadic eye movements and found that following the presentation of a visual stimulus, the olivary input to a P-cell encoded a probabilistic signal that coarsely described both the direction and the amplitude of that stimulus. When this input was present, the resulting complex spike briefly suppressed the P-cells simple spikes, disrupting the P-cells output during that saccade. Remarkably, this brief suppression altered the saccades trajectory by pulling the eyes toward the part of the visual space that was preferentially encoded by the olivary input to that P-cell. Thus, analysis of behavior in the milliseconds following a complex spike unmasked how the P-cells output influenced behavior: the preferred location in the coordinates of the visual system as conveyed probabilistically from the inferior olive to a P-cell defined the action in the coordinates of the motor system for which that P-cells simple spikes directed behavior. SignificanceWe are lacking general principles that can describe how changes in a P-cells simple spikes might alter behavior. Here, we show that a brief suppression of a P-cells simple spikes in the oculomotor vermis consistently pulls the eyes in a direction that corresponds to the preferred location of the sensory space as conveyed probabilistically to that P-cell from the inferior olive. Thus, the inferior olive defines the coordinate system regarding the information that a P-cell is providing to the rest of the brain.

neuroscience↗

bioRxiv2022

Signaling the agency of an erroneous outcome via synchronization of spikes in the cerebellum

Neurons in the inferior olive are thought to anatomically organize the Purkinje cells (P-cells) of the cerebellum into computational modules. To better understand what is computed by these modules, we designed a saccade task in marmosets that dissociated sensory and motor events and then recorded the complex and simple spikes of hundreds of P-cells. We found that when a visual target was presented at a random location, the olive reported the direction of that sensory event to one group of P-cells, but not to a second group. However, just before movement onset it reported the direction of the planned movement to both groups, even if that movement was not toward the target. At the end of the movement if there was an error but the subject chose to withhold the corrective movement, only the first group received information about the sensory prediction error. We organized the P-cells based on the information content of their olivary input and found that in the group that received sensory information, the simple spikes were suppressed during fixation, then produced a burst before saccade onset in a direction consistent with assisting the movement. In the second group the simple spikes were not suppressed during fixation but burst near saccade deceleration in a direction consistent with stopping the movement. Thus, the olive differentiated the P-cells based on whether they would receive sensory or motor information, and this defined their contributions to control of movements as well as holding still. Significance statementWe found that in the oculomotor region of the vermis, the olive informed a subset of P-cells about sensory events that were prediction errors, but all P-cells about the forthcoming movement. Using the information content of the olivary input we labeled the P-cells and produced a population code, revealing two groups with simple spikes that were antagonistic to each other, one contributing to movement initiation, the other signaling movement end.

neuroscience↗