Learning from the other limb's experience: sharing the ‘trained’ M1 representation of the motor sequence knowledge

Abstract

Key points Participants were scanned during the untrained‐hand performance of a motor sequence, intensively trained a day earlier, and also a similarly constructed but novel, untrained sequence.The superior performance levels for the trained, compared to the untrained sequence, were associated with a greater magnitude of activity within the primary motor cortex (M1), bilaterally, for the trained sequence.The differential responses in the ‘trained’ M1, ipsilateral to the untrained hand, were positively correlated with experience‐related differences in the functional connectivity between the ‘trained’ M1 and (1) its homologue and (2) the dorsal premotor cortex (PMd) within the contralateral hemisphere.No significant correlation was evident between experience‐related differences in M1 – M1 and M1 – PMd connectivity measures.These results suggest that the transfer of sequence‐specific information between the two primary motor cortices is predominantly mediated by excitatory mechanisms driven by the ‘trained’ M1 via two independent neural pathways. AbstractFollowing unimanual training on a novel sequence of movements, sequence‐specific performance may improve overnight not only in the trained hand, but also in the hand afforded no actual physical experience. It is not clear, however, how transfer to the untrained hand is achieved. In the present study, we examined whether and how interaction between the two primary motor cortices contributes to the performance of a sequence of movements, extensively trained the day before, by the untrained hand. Acordingly, we studied participants during the untrained‐hand performance of a finger‐to‐thumb opposition sequence (FOS), intensively trained a day earlier (T‐FOS), and a similarly constructed, but novel, untrained FOS (U‐FOS). Changes in neural signals driven by task performance were assessed using functional magnetic resonance imaging. To minimize potential differences as a result of the rate of sequence execution per se, participants performed both sequences at an identical paced rate. The analyses showed that the superior fluency in executing the T‐FOS compared to the U‐FOS was associated with higher activity within the primary motor cortex (M1), bilaterally, for the T‐FOS. The differential responses in the ‘trained’ M1 were positively correlated with experience‐related differences in the functional connectivity between the ‘trained’ M1 and (1) its left homologue and (2) the left dorsal premotor cortex. However, no significant correlation was evident between the changes in connectivity in these two routes. These results suggest that the transfer of sequence‐specific information between the two primary motor cortices is predominantly mediated by excitatory mechanisms driven by the ‘trained’ M1 via at least two independent neural pathways.

Use-Dependent Plasticity in Human Primary Motor Hand Area: Synergistic Interplay Between Training and Immobilization

“…Our finding raises the possibility that learning transfer can occur at the executive level in the M1 HAND through shared cortical motor representations. This hypothesis is in line with a recent study showing that the “trained” motor representation may contribute to intermanual transfer by “educating” the untrained motor representation or supporting the exchange of information between them (Gabitov et al 2015). However, the exact neural mechanisms that underpin the observed skill transfer from one finger of the hand to another remain to be clarified.…”

“…Muret and colleagues (2014) reported perceptual improvements cross the hand–face border after an increase in somatosensory input. Transfer of skill also occurs interhemispherically, between homologous body parts (Gabitov et al 2015). Coactivation of the trained body part representation during movements of the nontrained body part may contribute to intermanual transfer by “educating” the untrained motor representation (Gabitov et al 2015).…”

Explaining Individual Differences in Motor Behavior by Intrinsic Functional Connectivity and Corticospinal Excitability

“…Could behavior be predicted from an integration of neural measurements acquired prior to task performance? Execution of a motor task requires multiple levels of precise neural processes involving motor planning, motor control and skill acquisition at the central nervous system (Allen et al, 1997;Braitenberg et al, 1997;Muellbacher et al, 2002;Hanakawa et al, 2008;Cohen et al, 2009;Narayana et al, 2014;Gabitov et al, 2016), transformation of the motor command along the corticospinal tract to the peripheral nervous system (Rossini et al, 1994;Di Lazzaro et al, 1998;Groppa et al, 2012), and a correct execution of the movement by the corresponding peripheral muscle.…”

Weaker Inter-hemispheric and Local Functional Connectivity of the Somatomotor Cortex During a Motor Skill Acquisition Is Associated With Better Learning

“…The segregation of the somatomotor network from other functional networks not only underlies actual motor sequence production, but is also associated with higher performance levels and better learning (23, 31, 41, 45). This suggests that specialized regions within this low-level network may contain dedicated neural populations that encode and represent motor sequences (46–48). Second, the stimulus-free mode of performance and the continuous nature of the task minimize attentional and cognitive load, thereby allowing greater isolation of the endogenous processes within the somatomotor network.…”