In a sample of 28 subacute anterior circulation ischemic stroke patients with severe arm paresis, reduced motor cortex excitability (increased motor thresholds, reduced MEP amplitudes, reduced number of active points) and a reduced conduction velocity in the corticospinal system were found in the affected hemisphere. At the same time motor cortex topology for the abductor pollicis brevis (APB) representation was comparable for the affected and non-affected hemisphere. Considerable arm motor recovery (Fugl-Meyer test) was observed when assessed four weeks later after a period of rehabilitation intervention. Motor cortex excitability and conduction velocity in the corticospinal system improved in the affected hemisphere. In addition, APB representation showed a medial shift in patients with such a representation at pre test (n=14). Multiple stepwise regression indicated that of all transcranial magnetic stimulation (TMS) parameters only the medial shift of the motor cortex map predicted motor recovery. Assessing the effect of training time (non-intensified vs. intensified therapy) and type of arm training (Bobath approach vs. Arm BASIS training) with a randomised controlled design revealed that the impairment-oriented Arm BASIS training improved motor control more than the control conditions. In addition, patients of the group receiving the Arm BASIS training with an APB representation at pre test showed a medial shift of the motor cortex map and improved conduction times. In conclusion, changes in motor cortex topology were likely to be relevant for motor recovery and might have been induced by the impairment-oriented training.

Studies using transcranial direct current stimulation (tDCS) typically compare an active protocol relative to a shorter sham (placebo) protocol. Both protocols are presumed to be perceptually identical on the scalp, and thus represent an effective method of delivering double‐blinded experimental designs. However, participants often show above‐chance accuracy when asked which condition involved active/sham retrospectively. We assessed the time course of sham‐blinding during active and sham tDCS. We predicted that participants would be aware that the current is switched on for longer in the active versus sham protocol. Thirty‐two adults were tested in a preregistered, double‐blinded, within‐subjects design. A forced‐choice reaction time task was undertaken before, during and after active (10 min 1 mA) and sham (20 s 1 mA) tDCS. The anode was placed over the left primary motor cortex (C3) to target the right hand, and the cathode on the right forehead. Two probe questions were asked every 30 s: “Is the stimulation on?” and “How sure are you?”. Distinct periods of non‐overlapping confidence intervals were identified between conditions, totalling 5 min (57.1% of the total difference in stimulation time). These began immediately after sham ramp‐down and lasted until the active protocol had ended. We therefore show a failure of placebo control during 1 mA tDCS. These results highlight the need to develop more effective methods of sham‐blinding during transcranial electrical stimulation protocols, even when delivered at low‐intensity current strengths.

No abstract

Background: Studies using transcranial direct current stimulation (tDCS) typically compare the effects of an active (10-30min) relative to a shorter sham (placebo) protocol. Both active and sham tDCS are presumed to be perceptually identical on the scalp, and thus represent an effective method of delivering double-blinded experimental designs. However, participants often show above-chance accuracy when asked which condition involved active/sham retrospectively.Objective/Hypothesis: We aimed to assess the time course of sham-blinding during active and sham tDCS. We predicted that 1) Participants will be aware that the current is switched on for a longer duration in the active versus the sham protocol, 2) Active anodal tDCS will reduce reaction times more effectively than sham.Methods: 32 adults were tested in a pre-registered, double-blinded, within-subjects design. A forced-choice reaction time task was undertaken before, during and after active (10min 1mA) andsham (20s 1mA) tDCS. The anode was placed over the left primary motor cortex (C3) to target the right hand, and the cathode on the right forehead. Two probe questions were asked every 30s: "Is the stimulation on? "and "How sure are you?".Results: Distinct periods of non-overlapping confidence intervals were identified between the active and sham conditions, totalling 5min (57.1% of the total difference in stimulation time). These began immediately after sham ramp-down and lasted until the active protocol had ended. Active tDCS had no effect on reaction times compared to sham (ΔRT active vs sham p>0.38 in all blocks). Conclusions:We show a failure of placebo control during low-intensity tDCS.