Cerebellar Control of Motor Activation and Cancellation in Humans: An Electrophysiological Study

Abstract

Execution of rapid ballistic movement is characterized by triphasic, alternating electromyographic bursts in agonist (AG) and antagonist (ANT) muscles. The ability to rapidly initiate movement and cancel ongoing action is a basic requirement for efficient control of motor function. Normal functioning of the cerebellum is necessary for the generation of AG and ANT muscle activity that should be both of appropriate magnitude and timing to control the dynamic phase of arm movements. We studied AG, ANT reaction time (RT), and RT differences in both motor activation (MA) and motor cancellation (MC) tasks, in response to an auditory stimulus. The results showed that right cerebellar transcranial magnetic stimulation (TMS) with a horizontally applied focal coil resulted in decreased AG RT and increased latency difference between AG RT and ANT RT (DIFF) in the ipsilateral upper limb during MC. No effect was apparent during sham stimulation, MA tasks, left upper limb recording, and other coil orientations. While the high correlation between AG and ANT RT suggests a close relationship in both MA and MC, significant DIFF changes point to an alteration of this relationship by TMS during MC. Although TMS resulted in significantly increased DIFF during MC tasks, this was not due to delayed ANT RT. This suggests that the short ANT burst observed invariably during MC may not be a cerebellum-generated response, but is derived from the cortical or subcortical level. The focal nature of our TMS coil and the horizontally effective orientation supports the hypothesis of interference with the parallel fiber system. Our findings contribute to the understanding of cerebellar neural networks involvement in movements, in particular, those pertaining to cessation of an ongoing action not previously addressed.

Is the Cerebellum a Potential Target for Stimulation in Parkinson's Disease? Results of 1-Hz rTMS on Upper Limb Motor Tasks

“…To our knowledge, a test of gross motor function of the upper limb, such as our ball test, has not been similarly used with rTMS. The improvement of gross motor functions in the ball test may be correlated with the study conducted by Lo et al [16], in which subjects were able to more quickly cancel activation of the biceps brachii muscle after TMS over the right cerebellum (our test also involved the use of the biceps brachii muscle). A test similar to the nine-hole peg test (ten-hole pegboard task) for a partially comparable TMS protocol was applied in a study with healthy volunteers [13], in which the authors demonstrated an extension of time in the ten-hole pegboard task after rTMS-this result correlates with our findings.…”

“…Lo et al studied upper limb agonist and antagonist reaction time. Subjects were able to more rapidly cancel activation of the biceps brachii muscle after TMS over the right cerebellum [16]. Thus, consistent evidence has been provided about the effect of cerebellar TMS (or rTMS) on the motor cortex and motor function.…”

“…The clinical impact has to be confirmed in long-term extended studies. Our study is among the recently emerging studies that contribute to understanding the involvement of cerebellar neural networks in movements not previously addressed [16].…”

Transcranial Magnetic Stimulation of the Cerebellum

“…Sakihara et al 35 (10 healthy subjects) used sTMS over the left lateral cerebellum side to elicit a new late electromyographic responses at the bilateral soleus muscles with a mean latency of approximately 100 ms. Lo et al 36 (6 healthy subjects) studied the reaction time of agonists and antagonists, and the differences between their activations in a task with cancellation of motor activity of upper limb. The subjects were able to cancel activation of the biceps brachii muscle in a shorter time after sTMS over the right cerebellum.…”

“…The authors suggested that there is a reduced cerebellar modulation of motor cortex excitability in patients with focal dystonia. Lo et al 47 utilized a previously used protocol with agonist and antagonist reaction times, and the differences between their activations in a task with cancellation of motor activity of the upper limb (see above: Lo et al 36 ) with 3 patients with MillerFisher syndrome. The agonist (biceps) reaction time was not significantly reduced during the initial sTMS study, but significant reduction was observed during the repeat sTMS study in tandem with clinical recovery in the case of this disease (the authors previously observed this reduction in healthy subjects).…”