Sleep as a Model to Understand and Manipulate Cortical Activity in Order to Promote Functional Recovery After Stroke

The investigators recently showed that the repeated application of the so-called continuous theta burst protocol (cTBS) over the contralesional hemisphere resulted in a long-standing improvement of visual hemineglect (Cazzoli et al., 2012). The cTBS protocol was developed by Huang et al. (Huang et al., 2005) and modified by the investigators' group (Nyffeler et al., 2006). TBS protocol consists of a burst of 3 pulses at a frequency of 30 Hz, repeated at 6 Hz. One continuous train includes 801 pulses, the duration of one cTBS train is 44 seconds.

TACS stimulation involves two electrodes placed on either side of the desired site of cortical stimulation. The mode of stimulation used in this experiment is identical to previous studies using tACS in sleep ( Marshall et al., 2006; Prehn-Kristensen et al., 2014 ). Stimulation follows a sinusoidal pattern from 0 to 260 μA. This pattern is delivered at 0.75 Hz and is repeated for 225 cycles; a total of 5 minutes of stimulation. This 5 minute pattern is again repeated 5 times, with a minute of no stimulation between each; thus for a total of 30 minutes.

Sham coil will be used to exclude possible nonspecific effects of the TMS. The sham coil is shielded i.e., the magnetic field output is weakened and therefore insufficiently powerful to stimulate the cortex.

Sham stimulation will be used to exclude possible nonspecific effects of the tACS. Sham tACS stimulation will involve actual stimulation for the first 30 seconds of the ramp-up period (stimulation power is gradually increased until its final level), and then immediately gradually decreased until zero (without the intermediate 4 minutes of actual stimulation). This procedure will be repeated 5 times every 6 minutes and shall induce similar cutaneous sensations as real stimulation.