Differential Modulation of Motor Cortical Plasticity and Excitability in Early and Late Phases of Human Motor Learning

Motor learning is associated with plasticity in both motor and somatosensory cortex. It is known from animal studies that tetanic stimulation to each of these areas individually induces long-term potentiation in its counterpart. In this context it is possible that changes in motor cortex contribute to somatosensory change and that changes in somatosensory cortex are involved in changes in motor areas of the brain. It is also possible that learning-related plasticity occurs in these areas independently. To better understand the relative contribution to human motor learning of motor cortical and somatosensory plasticity, we assessed the time course of changes in primary somatosensory and motor cortex excitability during motor skill learning. Learning was assessed using a force production task in which a target force profile varied from one trial to the next. The excitability of primary somatosensory cortex was measured using somatosensory evoked potentials in response to median nerve stimulation. The excitability of primary motor cortex was measured using motor evoked potentials elicited by single-pulse transcranial magnetic stimulation. These two measures were interleaved with blocks of motor learning trials. We found that the earliest changes in cortical excitability during learning occurred in somatosensory cortical responses, and these changes preceded changes in motor cortical excitability. Changes in somatosensory evoked potentials were correlated with behavioral measures of learning. Changes in motor evoked potentials were not. These findings indicate that plasticity in somatosensory cortex occurs as a part of the earliest stages of motor learning, before changes in motor cortex are observed. NEW & NOTEWORTHY We tracked somatosensory and motor cortical excitability during motor skill acquisition. Changes in both motor cortical and somatosensory excitability were observed during learning; however, the earliest changes were in somatosensory cortex, not motor cortex. Moreover, the earliest changes in somatosensory cortical excitability predict the extent of subsequent learning; those in motor cortex do not. This is consistent with the idea that plasticity in somatosensory cortex coincides with the earliest stages of human motor learning.

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The Role of Interneuron Networks in Driving Human Motor Cortical Plasticity

Cerebral Cortex ◽

10.1093/cercor/bhs147 ◽

2012 ◽

Vol 23 (7) ◽

pp. 1593-1605 ◽

Cited By ~ 407

Author(s):

M. Hamada ◽

N. Murase ◽

A. Hasan ◽

M. Balaratnam ◽

J. C. Rothwell

Keyword(s):

Cortical Plasticity ◽

Human Motor ◽

Motor Cortical

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Effects of aging on the human motor cortical plasticity studied by paired associative stimulation

Clinical Neurophysiology ◽

10.1016/j.clinph.2009.07.048 ◽

2010 ◽

Vol 121 (1) ◽

pp. 90-93 ◽

Cited By ~ 89

Author(s):

Dina Fathi ◽

Yoshino Ueki ◽

Tatsuya Mima ◽

Satoko Koganemaru ◽

Takashi Nagamine ◽

...

Keyword(s):

Cortical Plasticity ◽

Paired Associative Stimulation ◽

Human Motor ◽

Motor Cortical ◽

Effects Of Aging

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P006 Effects of Zonisamide on human motor cortical plasticity: A TMS study

Clinical Neurophysiology ◽

10.1016/j.clinph.2016.10.136 ◽

2017 ◽

Vol 128 (3) ◽

pp. e13-e14

Author(s):

T. Shimizu ◽

R. Hanajima ◽

N. Tanaka ◽

R. Tsutsumi ◽

Y. Shirota ◽

...

Keyword(s):

Cortical Plasticity ◽

Human Motor ◽

Motor Cortical

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Dose-response curve of associative plasticity in human motor cortex and interactions with motor practice

Journal of Neurophysiology ◽

10.1152/jn.00920.2012 ◽

2014 ◽

Vol 111 (3) ◽

pp. 594-601 ◽

Cited By ~ 10

Author(s):

Behzad Elahi ◽

William D. Hutchison ◽

Z. Jeff Daskalakis ◽

Carolyn Gunraj ◽

Robert Chen

Keyword(s):

Motor Learning ◽

Time Course ◽

Cortical Plasticity ◽

Motor Evoked Potential ◽

Long Term Potentiation ◽

Human Motor Cortex ◽

Motor Practice ◽

Term Potentiation ◽

Human Motor

Associative plasticity is hypothesized to be an important neurophysiological correlate of memory formation and learning with potentials for applications in neurorehabilitation and for the development of new electrophysiological measures to study disorders of cortical plasticity. We hypothesized that the magnitude of the paired associative stimulation (PAS)-induced long-term potentiation (LTP)-like effect depends on the number of pairs in the PAS protocol. We also hypothesized that homeostatic interaction of PAS with subsequent motor learning is related to the magnitude of the PAS-induced LTP-like effect. We studied 10 healthy subjects. In experiment 1a, subjects received 90 (PAS90), 180 (PAS180), or 270 (PAS270) pairs of stimuli, followed by a dynamic motor practice (DMP) 1 h after the end of the PAS protocols. In experiment 1b, the DMP preceded the PAS protocol. In experiment 2, the time course of PAS270 was studied. We found that PAS270 resulted in greater increase in motor evoked potential (MEP) amplitude compared with protocols with fewer pairs of stimuli. Moreover, the interaction between PAS protocols with motor learning differed depending on the number of stimulus pairs used to induce PAS. While DMP alone increased MEP amplitudes, DMP during the LTP-like effects induced by PAS270 led to a long-term depression (LTD)-like effect (homeostatic interaction). This homeostatic interaction did not occur after PAS90 and PAS180. In conclusion, we found a dose-dependent effect of the number of stimulus pairs used in the PAS protocol on cortical plasticity. Homeostatic interaction between PAS and DMP was observed only after PAS270.

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