Figure 7. Effect of pontine nuclei (PN) stimulation on neural activity in motor cortex during reaching.

(A) Lower inset: experimental schematic. Animals performed the reaching task as neural activity in motor cortex was recorded. On some trials, PN neurons were activated with a 40 Hz, 2 s laser stimulus. Top panels: lift-aligned spike times and average firing rates on control and laser trials for three motor cortex neurons. Black dots indicate the laser onset. (B) Heatmap displaying lift-aligned average firing rate z-scores on control trials for all motor cortex neurons (n = 1157 neurons, n = 10 mice). (C) Heatmap displaying lift-aligned average firing rate z-scores for laser trials. Upper inset: the black line shows the rank correlation (Spearman’s ρ) between firing rates of the 1157 neurons on control and laser trials at each time point. The magenta inset shows the q-value against the null hypothesis that the correlation is zero. Right inset: black circles show the rank correlation (Spearman’s ρ) between the control and laser firing rates over time for each neuron. Magenta crosses show the q-value against the null hypothesis that the correlation of control and laser values over time is zero. (D) Difference between lift-aligned z-scores for control and laser trials. Orange regions indicate neurons and time points in which the firing rate is higher on control trials, and blue regions indicate points in which the firing rate is higher on laser trials.

Figure 7—figure supplement 1. Relationship between laser-aligned and lift-aligned activity in motor cortex.

(A) Upper: experimental schematic (see also Figure 7). Lower: peri-laser firing rate z-scores for cortical neurons (n = 839). Only trials in which a laser stimulus but no cue was delivered were included. Data are sorted by the average z-scored firing rate within the first 100 ms of laser onset. (B) Peri-lift firing rates on control trials for the same neurons as in (A). (C) Peri-lift firing rates on laser + cue trials. (D) Effect of pontine nuclei (PN) stimulation on neural activity in the motor cortex during behavior. The heatmap shows the difference in z-scored peri-lift firing rates on laser and control trials; it was obtained by subtracting the map in (A) from the map in (B). Blue indicates higher peri-lift activity on laser trials, and orange indicates higher firing rates on control trials. (E) Predicted effect of PN stimulation on neural activity during behavior based on laser-only response. For each neuron, the neural activity aligned to laser stimulation in the absence of a cue was offset at the lift-to-laser offsets in the corresponding session and averaged over trials. The resulting heatmap in the lower panel shows the lift-aligned firing rate changes expected based on the laser-only responses. The upper panel shows the correlation (Spearman’s ρ) between the expected and observed effect of the laser on the neural population at each time point (black), along with the q-value for the test against the null hypothesis that this correlation is zero.

Figure 7—figure supplement 2. Difference in lift-aligned cortical activity on pontine nuclei (PN) stimulation and control trials for PN-tagged and non-tagged neurons.

(A) Left: firing rate z-scores aligned to movement onset for neurons tagged by PN stimulation (n = 107) on control trials. Center: lift-aligned firing rate z-scores for the same neurons on laser trials. Right: firing rate z-score differences for cortical neurons in which a response was evoked by PN stimulation. In all three panels, neurons are sorted by the average difference between control and laser conditions. (B) Firing rate z-scores aligned to movement onset on control trials (left), laser trials (center), and the difference between control and laser trials (right) for non-tagged cortical neurons (n = 741). Neurons are sorted by the average laser – control difference, as in (A). (C) Mean lift-aligned firing rate z-score differences for PN-tagged neurons (blue) and non-tagged neurons (gray).