To explore the trends of locomotor skill learning in three groups: stroke survivors after five sessions of anodal tDCS (a-tDCS, real brain stimulation), stroke survivors after five sessions of sham tDCS (s-tDCS), and stroke survivors with no brain stimulation (control; CON).

measure changes in cortical neuronal activation before and after five sessions of locomotor skill training in healthy adults and stroke participants.

Compare stimulation-induced improvements in learning capacity between three groups: stroke group, healthy young group, and healthy older group.

Compare functional improvements (gait performance, balance, motor and cognitive function) between healthy adults and stroke participants after five sessions of brain stimulation.

Stroke participants will be randomly assigned into one of three groups: anodal transcranial direct current stimulation (a-tDCS), sham tDCS (s-tDCS), or control groups (i.e. no brain stimulation). Stroke participants in the first two groups will receive five sessions of the assigned brain stimulation combined with visuomotor stepping training over five consecutive days. Healthy adults will be randomly assignments into a-tDCS or s-tDCS groups.

Stepping motor control will be quantified by the time (seconds) that each participant takes to initiate a forward step onto a visual target displayed on the wall screen.

The neuronal activations will be quantified by peak-to-peak electrical signals detected by surface electromyographic (EMG) electrodes on leg muscles after transcranial magnetic stimulations

LE motor function will be quantified by Fugl-Meyer LE motor test, Short Physical Performance Battery (SPPB), and gait speed (meters/second) during ground walking tests.