Figure 8. Thalamic electrical stimulation in central thalamus arouses monkeys.

(A) Behavioral wake-up score as a function of thalamic current for monkey 1 (left subplot) and monkey 2 (right subplot). Mean ±+ 1 SEM. A high-current and low-current condition was individually titrated per monkey for producing scores on average above or below a wake-up score of 2. (B) A histological image from monkey 1 showing the thalamic leads in the central thalamus. (C) Change in EMG from the pre-stimulation Unconscious baseline for high-current (red) vs. low-current (blue) conditions. Change in the physiological signal was tested for difference from Unconscious during the stimulation period (0–28.5 s with respect to electrical stimulation onset), post-1 (0–30 s with respect to electrical stimulation offset), post-2 (30–60 s with respect to electrical stimulation offset), and post-3 (60–90 s with respect to electrical stimulation offset). Significant differences from zero are indicated with red (for high current) or blue (for low current) stars. Significant differences between high vs. low current are indicated with black stars. Mean ± 1 SEM. (D) Same as C, but for eyeblink response to air puffs. (E) Same as C, but for blood oxygenation. (F) Same as C but for the heart rate response.

Figure 8—figure supplement 1. Effects of thalamic electrical stimulation on wake-up sub-scores.

Behavioral wake-up score as a function of thalamic current defined separately for eye opening (blue), puff-evoked eye blinks (red), and arm/body movements (black). For eye opening, 0 = eyes closed, 1 = one or both eyes slightly open, 2 = one or both eyes fully open. For puff-evoked eyeblinks, 0 = no response, 1 = occasional blinking not necessarily in response to puffs, 2 = clear response to airpuffs. For arm/body movements, 0 = none, 1 = some mouth/jaw movement, 2 = arm/full-body movement. Plots are mean ±/- 2 SEM.

Figure 8—figure supplement 2. Effects of thalamic electrical stimulation on arousal relative to the Awake state.

(A) EMG relative to the Awake state during high-current thalamic stimulation. Unconscious denotes the period from 0 to 30 s prior to stimulation onset. Stim denotes the stimulation period (0–28.5 s with respect to electrical stimulation onset, not shown for EMG due to artifacts), post-1 (0–30 s with respect to electrical stimulation offset), post-2 (30–60 s with respect to electrical stimulation offset), and post-3 (60–90 s with respect to electrical stimulation offset). (B) Same as A, but for eyeblink response to air puffs. (C) Same as A, but for heart rate. (D) Same as A but blood oxygenation. Stars indicate significant differences from the pre-stimulation Unconscious state (p<0.01, non-parametric randomization test). Mean and the 99 percent bootstrap confidence interval of the mean.