The effect of anodal cerebellar transcranial direct current stimulation on learning a novel walking task in healthy adults.

Participants will attend a total of four data collection sessions: the first three sessions held on consecutive days (without any gap between the sessions) and the last follow up session conducted after a gap of one week.The intervention constitutes three consecutive sessions of active anodal cerebellar transcranial direct current stimulation (ctDCS) in conjunction with split-belt treadmill (SBT) walking.The first session will involve completion of screening, consent and the recording of fastest comfortable walking speed on the treadmill which will determine the speed of the two belts of the SBT, such that the belts move at a ratio of 2:1. During SBT walking, kinematic data will be measured through computerized gait analysis that will record 3-dimensional position data from reflective markers placed on legs. The participant’s walking will be assessed during three phases: 1) baseline phase, where both the belts will move at the same speed for 2 minutes; 2) adaptation phase, where both the belts will move at different speeds for 15 minutes; and 3) de-adaptation phase, where the belts will move at same speed again for 10 minutes. During the adaptation phase, active anodal ctDCS intervention will be delivered by a direct current stimulator (Magstim Co, UK) adminstered by a doctoral research student. The active elecrode will be placed on the back of the head (lateral cerebellum) and the reference electrode will be on the cheek (buccinator muscle). The current will be slowly ramped up to 2 mA over 30 seconds, held constant at 2 mA for 15 minutes and then decreased over 30 seconds at the end of the stimulation. Motor performance and strides to steady-state performance will be evaluated before (baseline), during (adaptation) and after (de-adaptation) the intervention. The outcomes will be measured one week later to assess absolute learning and during the three intervention sessions to evaluate cumulative, between and within-session effects. Each session will take approximately 80 minutes (50 minutes- assessment and setting up, 27 minutes SBT walking).