Cerebellar tDCS Does Not Improve Learning in a Complex Whole Body Dynamic Balance Task in Young Healthy Subjects

Abstract

Transcranial direct current stimulation (tDCS) of the cerebellum is of increasing interest as a non-invasive technique to modulate motor performance and learning in health and disease. Previous studies have shown that cerebellar tDCS facilitates reach adaptation and associative motor learning in healthy subjects. In the present study it was tested whether cerebellar tDCS improves learning of a complex whole body motor skill. Because this task involves learning of posture and balance likely including learning of a new motor sequence and cognitive strategies, cerebellar tDCS was applied over midline cerebellar structures and the posterolateral cerebellar hemispheres. 30 young and healthy subjects performed two days of balance training on a Lafayette Instrument 16030 stability platform®. Participants received either anodal, cathodal or sham cerebellar tDCS during training on day 1. The cerebellar electrode (7 cm width by 5 cm height) was centered 2 cm below the inion. Mean platform angle deviation and mean balance time were assessed. All subjects showed significant effects of learning. Learning rate was not different between the three modes of stimulation neither on day 1 nor on day 2. Cerebellar tDCS did not facilitate learning of a complex whole body dynamic balance task in young and healthy subjects. tDCS effects, however, may have been missed because of the small group size. Furthermore, it cannot be excluded that young and healthy subjects learned and performed already at a near optimal level with little room for further improvement. Future work has to evaluate potential benefits of cerebellar tDCS in elderly subjects and subjects with cerebellar deficits, whose motor control and motor learning network is not optimally tuned.

Comparison of Transcranial Direct Current Stimulation of the Primary Motor Cortex and Cerebellum on Static Balance in Older Adults

“…2020; 22(3):e96259. a-tDCS of the cerebellum had no significant effects on balance (25)(26)(27). These controversial findings show that age is a factor, which may affect the outcomes of brain stimulation techniques (7,28,29).…”

Cerebellar transcranial direct current stimulation improves adaptive postural control

“…The faster and more efficient postural adaptation induced by active stimulation, warrants exploration of this type of intervention in combination with behavioral training in elderly individuals or patient populations with impaired postural balance (e.g., Parkinson's disease or stroke). It needs to be noted that several recent studies failed to find positive effects of ctDCS on postural control (e.g., Steiner et al 2016) or reported positive effects of inhibitory cathodal ctDCS (e.g., Inukai et al 2016). However, the protocol used in the latter study substantially deviated from our study (e.g., regarding stimulation parameters, outcome measures, visual cues) and only assessed ctDCS effects on quiet standing performance (i.e., no disturbance requiring adaptive postural control was investigated).…”

“…However, the protocol used in the latter study substantially deviated from our study (e.g., regarding stimulation parameters, outcome measures, visual cues) and only assessed ctDCS effects on quiet standing performance (i.e., no disturbance requiring adaptive postural control was investigated). Likewise, while the study by Steiner et al (2016) involved learning of a complex motor skill, the authors speculated that their healthy young subjects may have performed at "maximum possible learning level", which may have prevented further improvement by ctDCS. Nonetheless, these studies highlight that multiple factors that are currently not well understood mediate ctDCS response (van Dun et al, 2016).…”

Cerebellar Transcranial Direct Current Stimulation Improves Maximum Isometric Force Production during Isometric Barbell Squats

“…Additionally, it was demonstrated that CB-tDCS elicits improvements in postural control, both in healthy participants [31] as well as chronic stroke patients [32]. Nevertheless, some studies show no effects of CB-tDCS on balance control in healthy participants [32,33]. To date, no study has tested the effects of CB-tDCS on core features of muscle strength, such as MIVC.…”