Motor activation is modulated by visual experience during cyclic gait observation: A transcranial magnetic stimulation study

Abstract

Transcranial magnetic stimulation (TMS) has been widely utilized to noninvasively explore the motor system during the observation of human movement. However, few studies have characterized motor cortex activity during periodic gait observation. Thus, this study examined the effects of an observer's visual experience and/or intention to imitate on corticospinal excitability during the observation of another's gait. Twenty-six healthy volunteers were included in this study and allocated to two different groups. Participants in the visual experience group had formal experience with gait observation (physical therapist training), while those in the control group did not. Motor-evoked potentials induced by TMS in the tibialis anterior and soleus muscles were measured as surrogates of corticospinal excitability. Participants were seated and, while resting, they observed a demonstrator's gait or observed it with the intention to subsequently reproduce it. Compared with the resting state, cyclic gait observation led to significant corticospinal facilitation in the tibialis anterior and soleus muscles. However, this pattern of corticospinal facilitation in the measured muscles was not coupled to the pattern of crural muscle activity during actual gait and was independent of the step cycle. This motor cortex facilitation effect during gait observation was enhanced by the observer's visual experience in a manner that was not step cycle-dependent, while the observer's intent to imitate did not affect corticospinal excitatory input to either muscle. In addition, visual experience did not modulate corticospinal excitability in gait-related crural muscles. Our findings indicate that motor cortex activity during gait observation is not in line with the timing of muscle activity during gait execution and is modulated by an individual's gait observation experience. These results suggest that visual experience acquired from repetitive gait observation may facilitate the motor system's control on bipedal walking, but may not promote the learning of muscle activity patterns.

Mirror neuron activity depending on the content and stage of the observed action: a TMS study

“…Our first finding of MEP amplitude increasing while participants watched another person’s action including an object and goal is consistent with previous TMS studies [ 23 – 25 ]. One study showed that corticospinal excitability increased in recordings from the tibialis anterior and soleus muscles during gait observation [ 26 ]. Another study found MEP facilitation during observations of direct movement [ 27 ].…”

Visual Attention and Motion Visibility Modulate Motor Resonance during Observation of Human Walking in Different Manners

“…Fourteen healthy volunteers (sex, seven men and seven women) aged 20–22 years (mean age, 20.6 ± 0.6 years) without history of neurological or psychiatric disorders participated in the study. As our previous research had explored the effect of visual experience on motor cortical activity during gait observation [ 26 ], the participants who had formal experience with gait observation in clinical education were excluded from this study. Prior to conducting the experiments, we confirmed that all participants were right-handed using the Edinburgh Handedness Inventory [ 32 ].…”

“…Motor-evoked potentials (MEPs) induced by TMS during action observation are reported to be closely coupled to the muscles involved in the action execution [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ] and the temporal pattern of the observed action [ 14 , 15 , 22 , 23 , 24 ], which are remarkable and meaningful findings elucidated by TMS studies. Regarding the motor system activity during mere cyclic gait observation, prior TMS studies have demonstrated that the motor resonance to the observed whole-body gait movement was enhanced in the crural flexor and extensor muscles throughout the step cycle [ 25 , 26 ], which is incompatible with the kinematic feature of actual walking in terms of the time course of muscle activity. Although AOT is often used to improve walking ability in clinical settings [ 4 , 7 , 9 ], the motor cortical activity while observing human bipedal walking is not well-known; for example, it is unknown whether this curious motor resonance during gait observation replicates the original time course of the motor cortical activity during gait execution, or whether it is interfered with by factors affecting the inner automatic motor response process of the observed gait in a top-down modulation manner [ 27 ].…”

Motor Imagery and Action Observation as Appropriate Strategies for Home-Based Rehabilitation: A Mini-Review Focusing on Improving Physical Function in Orthopedic Patients

“…These results suggest that different imagery perspectives are mediated through separate neural systems, which contribute differently during processes of motor learning and neurological rehabilitation ( Mulder, 2007 ). Besides, previous experience or gaining experience by observing repetitive movements may facilitate motor learning of the specific task ( Ito et al, 2020 ). However, the discrepancies between the different types and perspectives of cognitive practice, as well as the control of the subjects’ actual involvement in the practice, could be overcome by modifying and adapting old strategies such as PME with MVF to the rehabilitation practice of patients with orthopedic lower limb disorders, or by using a new tool such as the VR practice.…”