Contribution of somatosensory cortex to responses in the rat cerebellar granule cell layer following peripheral tactile stimulation

Abstract

The spatial coincidence of somatosensory cerebral cortex (SI) and trigeminal projections to the cerebellar hemisphere has been previously demonstrated. In this paper we describe the temporal relationship between tactilely-evoked responses in SI and in the granule cell layer of the cerebellar hemisphere, in anesthetized rats. We simultaneously recorded field potentials in areas of common receptive fields of SI and of the cerebellar folium crus IIa after peripheral tactile stimulation of the corresponding facial area. Response of the cerebellar granule cell layer to a brief tactile stimulation consisted of two components at different latencies. We found a strong correlation between the latency of the SI response and that of the second (long-latency) cerebellar component following facial stimulation. No such relationship was found between the latency of the SI response and that of the first (short-latency) cerebellar component, originating from a direct trigeminocerebellar pathway. In addition, lidocaine pressure injection in SI, cortical ablation, and decerebration all significantly affected the second cerebellar peak but not the first. Further, when tactile stimuli were presented 75 ms apart, the response in SI failed, as did the second cerebellar peak, while the short-latency cerebellar response still occurred. We found a wide spatial distribution of the upper lip response beyond the upper lip area in crus IIa for the long-latency component of the cerebellar response. Our results demonstrate that SI is the primary contributor to the cerebellar long-latency response to peripheral tactile stimulation. These results are discussed in the context of Purkinje cell responses to tactile input.

Pontine Maps Linking Somatosensory and Cerebellar Cortices Are in Register with Climbing Fiber Somatotopy

“…For example, tactile information arising from the face is forwarded to the cerebellar A2 zone by the climbing fiber system with an onset latency of ϳ17 ms (Atkins and Apps, 1997), whereas the indirect path via the somatosensory cortex and the pontocerebellar mossy fiber projection is likely to reach the same region of cerebellar cortex around the same time (Morissette and Bower, 1996). The direct (climbing fibermediated) and indirect (mossy fiber-mediated) signals arriving in register are likely to have a profound influence on ongoing cerebellar cortical activity.…”

“…Tactile responses mediated by mossy fibers are thought to be generated by a combination of direct (trigeminocerebellar and spinocerebellar) and indirect (cerebrocerebellar) pathways (cf. Morissette and Bower, 1996). The latter involves the SI cortex and a relay within the pontine nuclei.…”

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

“…(5) The duration of the responses was always considerably shorter than those attributable to activity in longerlatency mossy fiber pathways (cf. Kennedy et al, 1966;Morissette and Bower, 1996). For SR and CP stimulation, responses ranged in duration from 2.6 to 5.9 msec and 2.7 to 7.1 msec, respectively (SR mean, 4.5 Ϯ 1.2 SD; CP mean, 3.6 Ϯ 1.3 SD).…”

Peripheral stimuli excite coronal beams of Golgi cells in rat cerebellar cortex

“…Indeed, the late response component has been observed to decline during inactivation of the somatosensory cortex (Morissette and Bower, 1996). It must also be noted that the stimulus probe, which was in contact with the rat's face during 10 ms in the punctate experiments, may have evoked a response when retracted (OFF response; Kyriazi et al, 1994).…”