Summary
This paper gives an account of single mossy fiber responses when three types of mechanical stimulation are applied to the forefoot and hindfoot of the cat which is either decerebrate and unanesthetized or lightly anesthetized by pentothal or chloralose. The mechanical stimuli were applied either to footpads (brief pulses, taps, or longer square pulses or ramps) or to the hairy skin by air jets.
Recording of single mossy fibers was extracellular by glass microelectrodes that were inserted into the granular layer of the cerebellar cortex or the subjacent white matter. As described in previous papers computer averaging techniques usually of 64 responses have been employed to enhance reliability.
Taps evoked pure excitatory responses from many mossy fibers, which were usually brief high frequency bursts resembling those evoked by nerve volleys. Usually the threshold displacement was less than 0.2 mm and thresholds as low as 0.01 mm were observed. There were often considerable differences in the intensities of responses from different pads of the same foot. Successive pulses of mechanical stimulation evoked mossy fiber responses of diminished intensity. Longer mechanical stimuli with square or ramp onsets evoked various admixtures of phasic and tonic responses. Hair stimulation was often a very effective excitant, the receptive field for a single mossy fiber usually covering a considerable area of foot and leg.
Taps and pressure to the pads were also effective in inhibiting the background discharge of some mossy fibers, and admixtures of excitatory and inhibitory actions were observed.
The results are discussed in relationship to the discharges evoked in primary afferent fibers by cutaneous mechanoreceptor stimulation. They provide an intermediate stage of information between mechanoreceptor stimulation and the response of Purkyně cells as described in the next paper.
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Eccles, J.C., Sabah, N.H., Schmidt, R.F. et al. Cutaneous mechanoreceptors influencing impulse discharges in cerebellar cortex. I. In mossy fibers. Exp Brain Res 15, 245–260 (1972). https://doi.org/10.1007/BF00235910
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DOI: https://doi.org/10.1007/BF00235910