The climbing fiber input to Purkinje cells acts as a teaching signal by triggering a massive influx of dendritic calcium that marks the occurrence of instructive stimuli during cerebellar learning. synchrony beyond that expected solely from the calcium-event probability of two independent dendrites. Figure 5D shows that there was a gradual boost in the amount of extra synchrony as the airpuff duration or pressure was increased (Duration data: two-way ANOVA: F[4361] = 113.49, p 0.0001; Tukey’s HSD: p 0.0001, except for d3Cd4 comparison. Pressure data: two-way ANOVA: F[2136] = 10.27, p 0.0001; Tukey’s HSD: p 0.05, except for p1Cp2 comparison). In other words, the degree to which CFs are dependent on each other scales up smoothly with their overall response probability. These results suggest that CF co-activation may be controlled upstream, perhaps in the inferior olive, in a way that provides information about stimulus strength at the level of the PC population. Size of CF-triggered calcium events We have recently shown that the amplitude of CF-triggered calcium events is enhanced during sensory stimulation (Najafi et al., 2014). Here, we examined if the magnitude of this sensory-driven enhancement is graded according to periocular airpuff strength. Compared to the average fluorescence traces for spontaneous calcium events (Figure 6A, sp), the average fluorescence traces for sensory-driven calcium events revealed a Dabrafenib distributor gradual enhancement as the duration or the pressure of the airpuff was increased (Figure 6A top; only duration data is displayed). Note that the fluorescence trace of each individual dendrite was normalized to the peak value of its mean spontaneous calcium event (Materials and methods). However, calcium events occurred with variable latency after the periocular airpuff, and for this reason the peaks of the average fluorescence traces in Figure 6A are substantially lower than 1 (for comparison purposes, the sp trace is plotted with the same temporal jitter as the d1Cd4 traces). Open in a separate window Figure 6. Stimulus strength is represented in the size of calcium events and size of non-CF signals.(A) Top: mean F/F trace of calcium events across all dendrites for the spontaneous (sp, green) and airpuff-evoked conditions (d1Cd4: different airpuff Rabbit Polyclonal to FA12 (H chain, Cleaved-Ile20) durations; shades: SEM). Bottom: mean size of calcium events (F/F-integral) shown for each dendrite (black dots). Left: duration data: Right: pressure data. F/F-integral values are normalized to the mean size of spontaneous events (dashed line). Red: mean SEM. (B) Same as (A), but for the non-CF signal. (C) Each panel corresponds to a duration of airpuff, and compares F/F traces of calcium-event enhancement (i.e., evoked minus spontaneous event; black) and non-CF signal (green) in response Dabrafenib distributor to that particular airpuff duration (lines: mean across dendrites; shades: SEM). (D) Mean size of calcium-event enhancement is compared with mean size of non-CF signal for different airpuff durations (d1Cd4; circles: average across dendrites; bars: SEM; dashed: unity line; F/F-integral values are normalized to the mean size of spontaneous events. Arrowhead marks the longest duration airpuff, for which supralinearity is evident). DOI: http://dx.doi.org/10.7554/eLife.03663.008 To quantify the gradual enhancement in Dabrafenib distributor Figure 6A (top), we measured the size of each individual calcium event by computing the integral of its fluorescence trace over a 100 ms time window after the peak (F/F-integral), and normalizing this value to the average F/F-integral of all the spontaneous calcium events of the corresponding PC dendrite. Note that we only examined the fluorescence traces of individual calcium events and excluded trials in which the periocular stimulation resulted in two.