Early consolidation in human primary motor cortex

Abstract

Behavioural studies indicate that a newly acquired motor skill is rapidly consolidated from an initially unstable state to a more stable state, whereas neuroimaging studies demonstrate that the brain engages new regions for performance of the task as a result of this consolidation. However, it is not known where a new skill is retained and processed before it is firmly consolidated. Some early aspects of motor skill acquisition involve the primary motor cortex (M1), but the nature of that involvement is unclear. We tested the possibility that the human M1 is essential to early motor consolidation. We monitored changes in elementary motor behaviour while subjects practised fast finger movements that rapidly improved in movement acceleration and muscle force generation. Here we show that low-frequency, repetitive transcranial magnetic stimulation of M1 but not other brain areas specifically disrupted the retention of the behavioural improvement, but did not affect basal motor behaviour, task performance, motor learning by subsequent practice, or recall of the newly acquired motor skill. These findings indicate that the human M1 is specifically engaged during the early stage of motor consolidation.

Neurofeedback fMRI‐mediated learning and consolidation of regional brain activation during motor imagery

“…Meanwhile, both the ROI analysis (Fig.3) and the subjective evaluation score (Fig.5) showed the two-week practice period did not result in any further increase in either the level of BOLD signal or the perception of task performance. The seemingly plateaued level of activation that we have seen in this study is in accordance with other behavioral/neuroimaging studies whereby newly acquired motor skill, once rapidly consolidated ('fast learning'), tapers off in terms of both performance and functional representation in the long term [Karni et al, 1998;Muellbacher et al, 2002;Krakauer and Shadmehr 2006]. However the current study does not provide enough data to examine this 'learning curve' effect and calls for the examination of the longitudinal studies extending to longer terms beyond the tested two-week practice period.…”

Motor sequence consolidation: constrained by critical time windows or competing components

“…Previous studies have shown that similar improvements develop provided sleep occurs within a critical time after initial practice (Fischer et al 2002;Walker et al 2003). Some procedural memories also remain susceptible to interference for a critical time following acquisition (Brashers-Krug et al 1996;Muellbacher et al 2002;Walker et al 2003). Thus, a critical time window may be a general feature of offline processing.…”

Chronic low-frequency rTMS of primary motor cortex diminishes exercise training-induced gains in maximal voluntary force in humans

“…Finally, we did not administer rTMS to a cortical area other than M1 of the FDI area to determine the motor cortical specificity of rTMS's effects on strength gains and also used only one frequency and one intensity. Considering that rTMS of occipital and dorsolateral prefrontal cortex did not affect motor consolidation in a previous study (41), we excluded such control experiments.…”

“…In addition, voluntary activation tested with TMS was deficient in an intrinsic hand muscle, suggesting that there is some supraspinal capacity rTMS can act upon (28). We thus examined the possibility that, akin to homeostatic-like effects, voluntary muscle contractions, which raise corticospinal excitability, would potentiate the inhibitory effects of subsequently administered 1-Hz rTMS (41,45,56). This enhanced inhibitory effect would in turn reduce corticospinal excitability and interfere with the processes involved in generating voluntary force.…”