Fig. 3: Hyperpolarizing MCS increases multi-unit (MU) spike rates, amplitude, and variabilities in PD rats.
a Illustration of MU and SU analysis methods in Figs. 3 to 5. The effects of MCS on MU activities in PD rats are shown in (b–e), and those in normal rats in (f–i) in this figure. b Sample sweeps of MU activities in MC of PD rat in quiescent or active moving states upon sham stimulation or MCS. c, d There is an evident increase in MU spike rates (c) and amplitude (d) during MCS if compared to sham in PD rats. However, there is no definite change of spike rates (c) or just a small increase of spike amplitude (d) from quiescence to active moving in spike rate both during sham (n = 273 MU segments from 13 rats) and MCS (n = 238 MU segments from 14 rats). e Box plots including the lower and upper quartiles and the median show the data distribution from part (d). The whiskers mark the 10th and 90th values of the dataset to display the range of outliers. The MU spike amplitude is skewed upward, suggesting a wider distribution of spike amplitude with an increase of larger spikes with MCS in PD. In contrast, the MU spike amplitude shows a much narrower distribution (or much higher homogeneity) at baseline in all recording site. f–i Similar experiments and analyses are done in normal rats. There is just a small increase in MU spike rate and spike amplitude with MCS. There is also a small increase of spike amplitude from quiescence to active moving with both sham stimulation (n = 301 MU segments from 14 rats) and MCS (371 MU segments from 19 rats). The distribution of MU spike amplitude, however, do not show an obvious change with MCS in normal subjects. *p < 0.05, **p < 0.01, ***p < 0.001, Student’s t tests or simple main effects from 2*2 independent-model ANOVA (see Methods).
