PMC

Single Purkinje cells can acquire pause responses to two different CSs. (A) Raster plots showing the responses of four Purkinje cells to 20 trials of CS_A (superior colliculus, n = 3, or whisker air puff, n = 1, red) and CS_B (forelimb, n = 4, green). (B) Composite raster diagram with spikes from 10 Purkinje cells showing pause responses to CS_A (superior colliculus, n = 6, or whisker air puff, n = 4) and CS_B (forelimb, n = 10). (C) Line diagram showing average response profiles to each of the two CSs in the 10 cells.

The probability that a periorbital US elicits a complex spike is reduced if it is preceded by a CS-induced suppression of Purkinje cell activity. (A) The probability that a periorbital stimulus elicits a complex spike depends on whether it is preceded by a CS. (B) Simple spike activity during the presentation of different CS combinations or without a CS, relative to the background-firing rate in the same cell. (C) Correlation between the suppression of Purkinje cell activity induced by a CS and the probability that a subsequent periorbital stimulus elicits a complex spike in the same Purkinje cell. Each point in the scatterplot corresponds to the average value for each CS type, for each cell (1 cell = 4 points).

Experimental setup and field potential recordings. (A) Illustration of the experimental setup including relevant afferent and efferent cerebellar pathways. As CS, we used stimulation of the forelimb, superior colliculus (SC) pontine nuclei, or whiskers. As US, we used stimulation of climbing fibers (CF) or the periorbital skin (eye). CN, cerebellar nuclei; GC, granule cells; NO, nucleo-olivary pathway; PC, Purkinje cell. (B) Examples of field potentials elicited on the cerebellar cortex following stimulation of cerebellar afferents. (C) A Purkinje cell recording showing simple spikes, complex spikes, and a learned pause response or Purkinje cell CR.

Presentation of two CSs simultaneously results in a stronger pause response than any of the two CSs elicits individually. (A) Sample recordings from one cell showing five trials for each CS (red and green) as well as five trials in which both CSs were presented as a compound (blue). (B) Raster plots showing how two cells respond to two different CSs (red and green), and to both CSs combined (blue). (C) Boxplot showing the distribution of Purkinje cell activity during CS_A (red), CS_B (green), and CS_A ± CS_B (blue). (D) Line diagram illustrating the average profile of the Purkinje cell pause response (mean ± SEM), for CS_A (red), CS_B (green), and CS_A ± CS_B (blue).