Article Figures & Data
Figures
- Figure 1.
Experimental setup and task schematics. A, Arrays of microelectrodes were implanted in S1 and M1. Stimulating electrodes for monkey M (inset) are highlighted in red (AT) and yellow (noise). B, Monkeys manipulated a joystick to move a virtual arm and reach toward objects on a computer screen. C, Experimental task sequence. In the illustrated case, the selection of the right-hand object resulted in reward. The activity of both AT and noise ICMS channels are shown below each box.
- Figure 2.
Detection of signal in noise and M1 modulations. Example traces of horizontal movement of the virtual hand for three trials with different noise levels: low (A), optimal (B), and high (C). The colored horizontal bars represent the position of the targets (green, RAT; brown, NAT). In the trials shown in A and C, the monkey incorrectly selected the NAT, whereas in B it correctly picked the RAT and received a reward (indicated by a black arrow). The pulses delivered through both stimulating channels are shown. The RAT is subthreshold. The corresponding neuronal ensemble activity (monkey M, 120 units from M1) is shown in the bottom plots. Note that neuronal modulations reflect the speed and direction of arm movements. The color scale shows normalized firing rate (in Hz).
- Figure 3.
Stochastic facilitation via ICMS. A, B, Fraction of trials correct per session in terms of the noise amplitude level for monkey M (blue diamonds) and N (red squares) for suprathreshold (A) and subthreshold (B) RAT. *Significantly different from average performance (p < 0.05 in all cases, randomization test). C, Psychometric curves (in terms of ICMS amplitude) for monkeys M (blue) and N (red). Lines, Best sigmoidal fits; open circles, performance at chance level (p > 0.05, Wilcoxon rank sum test).
- Figure 4.
Movement predictions from M1 activity. A, Position of the avatar and off-line predictions from M1 activity for six consecutive trials with different noise amplitudes. B, C, Performance of the decoding algorithm measured as the correlation coefficient in terms of noise level for monkey M (B) and monkey N (C). n.s., No significant difference (one-way ANOVA test, n = 1724, p > 0.57 for monkey M; n = 3421, p > 0.07 for monkey N).
