No effects of cerebellar transcranial direct current stimulation on force field and visuomotor reach adaptation in young and healthy subjects

Abstract

Previous studies have shown that cerebellar transcranial direct current stimulation (tDCS) leads to faster adaptation of arm reaching movements to visuomotor rotation and force field perturbations in healthy subjects. The first aim of the present study was to confirm a stimulation-dependent effect on motor adaptation. Second, we investigated whether tDCS effects differ depending on onset, that is, before or at the beginning of the adaptation phase. A total of 120 healthy and right-handed subjects (60 women, mean age 23.2 ± SD 2.7 yr, range 18–31 yr) were tested. Subjects moved a cursor with a manipulandum to one of eight targets presented on a vertically orientated screen. Three baseline blocks were followed by one adaptation block and three washout blocks. Sixty subjects did a force field adaptation task (FF), and 60 subjects did a visuomotor adaptation task (VM). Equal numbers of subjects received anodal, cathodal, or sham cerebellar tDCS beginning either in the third baseline block or at the start of the adaptation block. In FF and VM, tDCS and the onset of tDCS did not show a significant effect on motor adaptation (all P values >0.05). We were unable to support previous findings of modulatory cerebellar tDCS effects in reaching adaptation tasks in healthy subjects. Prior to possible application in patients with cerebellar disease, future experiments are needed to determine which tDCS and task parameters lead to robust tDCS effects. NEW & NOTEWORTHY Transcranial direct current stimulation (tDCS) is a promising tool to improve motor learning. We investigated whether cerebellar tDCS improves motor learning in force field and visuomotor tasks in healthy subjects and what influence the onset of stimulation has. We did not find stimulation effects of tDCS or an effect of onset of stimulation. A reevaluation of cerebellar tDCS in healthy subjects and at the end of the clinical potential in cerebellar patients is demanded.

Cerebellar transcranial direct current stimulation for learning a novel split-belt treadmill task: a randomised controlled trial

“…We individualised the calculation of early adaptation and rate of adaptation whereas Jayaram et al used a fixed number of strides to estimate early adaptation (150 strides) and calculated rate by fitting an exponential function to the group data rather than analysing individual data 20 . Inconsistent findings have been reported in previous studies of ctDCS, particularly when a single session of ctDCS is applied during the adaptation tasks 54 – 56 . The merits of this findings need to be considered in the context of the methodological rigour of the research 18 .…”

“…The merits of this findings need to be considered in the context of the methodological rigour of the research 18 . However, these findings may highlight the need to understand how the cerebellar structure, within- and between-individual variability, task characteristics or parameters 18 , 56 – 58 may influence the ctDCS effects.…”

Lack of cerebellar tDCS effects on learning of a complex whole body dynamic balance task in middle-aged (50–65 years) adults

“…Positive effects in one experiment could not be replicated in a second experiment using the same experimental set-up, paradigm and stimulation parameters. Likewise, two studies of our group [ 17 , 25 ] found no effect of cerebellar tDCS in a visuomotor reach adaptation task. Kaminski et al [ 19 ] investigated the effect of tDCS in the same whole body dynamic balance task as in the present study but with different electrode positioning: the supplementary motor area was chosen as the stimulation target, as it is an area assumed to control multi-joint whole body movements.…”

Beyond the classic extinction network: a wider, comparative view

“…Our attempts, however, to use cerebellar transcranial direct current stimulation (tDCS) to modulate extinction and contextrelated extinction effects of conditioned eyeblink responses in healthy participants were largely unsuccessful (Beyer et al, 2017;Lipp et al, 2019). Lack of robustness and reproducibility of cerebellar tDCS effects are increasingly recognized (Mamlins et al, 2019) and call for further methodological refinement before more firm conclusions can be drawn in the application to patient-oriented studies.…”