Attention modulates adaptive motor learning in the ‘broken escalator’ paradigm

The physical stumble caused by stepping onto a stationary (broken) escalator
represents a locomotor after‐effect (LAE) that attests to a process of adaptive motor
learning. Whether such learning is primarily explicit (requiring attention resources) or
implicit (independent of attention) is unknown. To address this question, we diverted
attention in the adaptation (MOVING) and aftereffect (AFTER) phases of the LAE by
loading these phases with a secondary cognitive task (sequential naming of a vegetable,
fruit, and a colour). Thirty‐six healthy adults were randomly assigned to 3 equally sized
groups. They performed 5 trials stepping onto a stationary sled (BEFORE), 5 with the
sled moving (MOVING) and 5 with the sled stationary again (AFTER). A ‘Dual‐Task‐
MOVING (DTM)’ group performed the dual‐task in the MOVING phase and the ‘Dual‐
Task‐AFTEREFFECT (DTAE)’ group in the AFTER phase. The ‘control’ group performed
no dual‐task. We recorded trunk displacement, gait velocity and gastrocnemius muscle
EMG of the left (leading) leg. The DTM, but not the DTAE group, had larger trunk
displacement during the MOVING phase, and a smaller trunk displacement aftereffect,
compared to controls. Gait velocity was unaffected by the secondary cognitive task in
either group. Thus, adaptive locomotor learning involves explicit learning, whereas, the
expression of the aftereffect is automatic (implicit). During rehabilitation, patients
should be actively encouraged to maintain maximal attention when learning new or
challenging locomotor tasks.