These data are consistent with an important and rapid recruitment of inhibition during active touch, which is likely to impose the hyperpolarized reversal potentials for the touch-evoked PSPs found in excitatory layer 2/3 neurons. Internal cortical dynamics and precontact membrane potential therefore play a major role Talazoparib concentration in governing the trial-by-trial touch-evoked PSP, but one would also expect important contributions to the response variability mediated by differences in kinetics during different whisker-object

contacts. However, in agreement with previous local field potential measurements (Hentschke et al., 2006), in most neurons we found that the amplitude of the touch-evoked PSP was modulated neither by precontact velocity nor contact duration (Table S2). However, we did find a strong influence of the intercontact interval (ICI) upon the touch response. The first whisker-object contact in a touch sequence generally evoked the largest membrane potential depolarization (Figures 6A and 6E).

Subsequent touches on average evoked smaller depolarizations, indicating a dependence upon the recent history of C2 whisker-related touches (Figure 6I). Averaging active touch responses for different intercontact interval ranges revealed a decrease in response Nutlin-3 research buy amplitude as the ICI becomes smaller (Figures 6B and 6F). In order to evaluate further the impact of ICI, we plotted the amplitude of the touch response as Thiamine-diphosphate kinase a function of the preceding intercontact interval (Figures 6C and 6G). Spearman’s rank test revealed a significant modulation of response amplitude by ICI in 13/17 neurons. For those neurons, the time course of the recovery of the touch response was quantified by an exponential fit, yielding the intercontact interval time-constant for the half-maximal response, which we denote as ICI50. The time course of suppression

of the touch response varied strongly across the population of recorded neurons with a mean ICI50 of 87 ± 61 ms (median 63 ms; range 14 to 194 ms). Across our population of recorded C2 column layer 2/3 neurons, the mean amplitude of the touch response for long preceding ICI (>500 ms) was 8.3 ± 4.1 mV and decreased significantly to 3.1 ± 2.2 mV for short ICI (10–40 ms) (Figure 6J). The major impact of ICI on response variability could be seen by the linear relationship between the coefficient of variation of the response and the ICI50 (r = 0.94) (Figure 6K). Since the duration of the touch response was often longer than the ICI, consecutive touch responses also in many cases began from a more depolarized baseline Vm. Indeed, plotting the precontact Vm against the preceding ICI indicates a near parallel increase in precontact Vm and decrease in response amplitude at shorter ICI (Figures 6C and 6G).