The ipsilateral motor cortex contributes to cross‐limb transfer of performance gains after ballistic motor practice

Abstract

Although it has long been known that practicing a motor task with one limb can improve performance with the limb opposite, the mechanisms remain poorly understood. Here we tested the hypothesis that improved performance with the untrained limb on a fastest possible (i.e. ballistic) movement task depends partly on cortical circuits located ipsilateral to the trained limb. The idea that crossed effects, which are important for the learning process, might occur in the 'untrained' hemisphere following ballistic training is based on the observation that tasks requiring strong descending drive generate extensive bilateral cortical activity. Twenty-one volunteers practiced a ballistic index finger abduction task with their right hand, and corticospinal excitability was assessed in two hand muscles (first dorsal interosseus, FDI; adductor digiti minimi, ADM). Eight control subjects did not train. After training, repetitive transcranial magnetic stimulation (rTMS; 15 min at 1 Hz) was applied to the left (trained) or right (untrained) motor cortex to induce a 'virtual lesion'. A third training group received sham rTMS, and control subjects received rTMS to the right motor cortex. Performance and corticospinal excitability (for FDI) increased in both hands for training but not control subjects. rTMS of the left, trained motor cortex specifically reduced training-induced gains in motor performance for the right, trained hand, and rTMS of the right, untrained motor cortex specifically reduced performance gains for the left, untrained hand. Thus, cortical processes within the untrained hemisphere, ipsilateral to the trained hand, contribute to early retention of ballistic performance gains for the untrained limb.

Preconditioning tDCS facilitates subsequent tDCS effect on skill acquisition in older adults

“…The left palm faced down with the elbows slightly bent (100-120°). Vertical wooden pegs designed to restrict movements to the second metacarpophalangeal joint (Carroll et al 2008, Lee et al 2010, inserted into the board helped participants to maintain a consistent posture with hand and forearm muscle relaxed throughout the experiment (Hinder et al 2012, Hinder et al 2011). …”

Functional role of left PMd and left M1 during preparation and execution of left hand movements in older adults

“…Both palms faced down, with the elbows slightly bent (100 -120°). Vertical wooden pegs designed to restrict movements to the second metacarpophalangeal joint (Carroll et al 2008;Lee et al 2010) inserted into the board helped participants to maintain a consistent posture with hand and forearm muscle relaxed throughout the experiment . About 80 cm in front of participants at eye level, two light-emitting diodes (LEDs) were vertically arranged on a black panel 3 cm apart.…”

The effects of a single bout of exercise on motor memory interference in the trained and untrained hemisphere

“…Thus, we would have expected to observe similar results in the trained and untrained hand. The cross-activation hypothesis actually states that unilateral motor learning causes adaptations in the trained as well as in the untrained hemisphere and is supported by a number of studies showing that ballistic types of movements result in increased levels of cortical and/or corticospinal excitability in both hemispheres Lee et al, 2011). It was additionally shown that changes in ballistic performance as well as after learning a visuomotor tracking task correlate with changes in corticospinal excitability (Lauber et al, 2013).…”

“…It was previously shown that this task can cause very rapid performance enhancements Lee et al, 2011;Lauber et al, 2013;Lundbye-Jensen et al, 2010). Before the recording started, all subjects were instructed to produce maximal lateral force as fast as possible by solely flexing the index finger.…”