Gating of cutaneous input to cerebellar climbing fibres during a reaching task in the cat

Abstract

Task‐dependent modulation of cutaneous input to climbing fibres projecting to the C1, C2 and C3 zones in the cerebellar paravermal lobule V was investigated in awake cats during performance of a reaching task. Climbing fibre responses resulting from low intensity (non‐noxious) electrical stimulation of the ipsilateral superficial radial nerve were recorded as extracellular field potentials in the cerebellar cortex using chronically implanted microwires. Response size, measured as the time–voltage integral of the evoked field potential, was assessed during three phases of the reaching movement, reaction, reach and grasp, and compared with the response size at rest. At C1 and C3 zone recording sites response size was usually reduced during the task (7/10 sites). The reduction was most pronounced in the grasp phase, occasionally accompanied by a smaller reduction in the reach and reaction phases. In one case an enhancement was found in the reach phase. Response size was also modulated during the task at four of six C2 zone recording sites. However, the results were mixed. In three cases the modulation resembled the pattern at C1/C3 sites with the responses being reduced in the grasp phase accompanied on occasion by a lesser reduction in the reach phase. In the remaining case there was an enhancement during grasp. In this case and one other there was also an enhancement during the reaction phase. The findings indicate significant gating of cutaneous input to climbing fibres projecting to the C1, C2 and C3 zones during reaching movements, while the variability between recording sites suggests functional differences, both between and within zones.

Role of the Olivo-Cerebellar System in Timing

“…Because the synchronization task required both perception and motor performance of temporal sequences, the "suppression" of the inferior olive response to the perception component of the task can conceivably be attributed to the concurrent motor activity. This interpretation would be most consistent with electrophysiological studies showing that the responsiveness of the olivary neurons to sensory input is mostly decreased during expected self-produced movement (Gellman et al, 1985;Horn et al, 1996;Apps et al, 1997;Gibson et al, 2002). This may further explain the failure to demonstrate inferior olive activation during timing tasks in previous functional imaging studies that mostly used paradigms requiring motor preparation or motor response (Rao et al, 1997;Schubotz et al, 2000;Ramnani and Passingham, 2001;Dhamala et al, 2003).…”

Changes in Excitability of Ascending and Descending Inputs to Cerebellar Climbing Fibers during Locomotion

“…Each measurement was obtained by manually placing cursors at the start and end of individual responses (as determined by a clear positive or negative deflection from baseline and a return to baseline) and the computer calculating the area of the intervening waveform. In two cases in animal ME1, large mossy fiber-related potentials preceded the climbing fiber potentials, and peak-to-peak amplitude was measured (Apps et al, , 1997.…”

“…For the Montreal experiment (ME1), all signals were captured through a custom-built interface system (sampling rate, 2 kHz). In all experiments, the amplitude of individual nerve compound action potentials was measured peak to peak, and the size of individual cerebellar field potentials was measured as the area (millivolts ϫ milliseconds) under each response from onset to offset of the initial waveform (Apps et al, 1997). Each measurement was obtained by manually placing cursors at the start and end of individual responses (as determined by a clear positive or negative deflection from baseline and a return to baseline) and the computer calculating the area of the intervening waveform.…”

Feedback Control in the Olivo-Cerebellar Loop

“…Maybe most importantly, it should be noticed in this context that transmission in the inferior olive is deeply suppressed during the execution of limb movements (Apps et al 1997;Gibson et al 2002;Horn et al 2004). …”