Functional connectivity between cortical hand motor and language areas during recovery from aphasia

Previous data indicate that in healthy subjects, there is a connectivity between cortical areas for hand movement and language on the left hemisphere. This link is possibly mediated by the so-called mirror neuron system. The present study investigated the functional relationship between linguistic and hand movement processing in patients who were recovering from post-stroke aphasia. The excitability of the right- and left-hand motor cortex during language production in patients who were recovering from post-stroke aphasia and age-matched controls was investigated. As control, phonation was investigated. Hand motor cortex excitability was assessed with Motor Evoked Potentials which were elicited by Transcranial Magnetic Stimulation (TMS). In patients, reading aloud enhanced the excitability of the right hemispheric hand motor cortex, whereas phonation had no effect on hand motor cortex excitability. In the control group, an increased excitability of the left hemispheric hand motor system was found during reading aloud in accordance with previous data. The present data suggest a functional connectivity between regions mediating hand movements and reading. This may indicate that the right hemisphere participates in language processing as far as involved in single word reading in patients recovering from aphasia. The coactivation between cerebral representations of hand movements and language may be used therapeutically for aphasia rehabilitation.     

Altered speech-related cortical network in frontotemporal dementia

BackgroundIn healthy subjects (HS), transcranial magnetic stimulation (TMS) demonstrated an increase in motor-evoked potential (MEP) amplitudes during specific linguistic tasks. This finding indicates functional connections between speech-related cortical areas and the dominant primary motor cortex (M1).ObjectiveTo investigate M1 function with TMS and the speech-related cortical network with neuroimaging measures in frontotemporal dementia (FTD), including the non-fluent variant of primary progressive aphasia (nfv-PPA) and the behavioral variant of FTD (bv-FTD).MethodsM1 excitability changes during specific linguistc tasks were examined using TMS in 24 patients (15 with nfv-PPA and 9 with bv-FTD) and in 18 age-matched HS. In the same patients neuroimaging was used to assess changes in specific white matter (WM) bundles and grey matter (GM) regions involved in language processing, with diffusion tensor imaging (DTI) and voxel-based morphometry (VBM).ResultsDuring the linguistic task, M1 excitability increased in HS, whereas in FTD patients it did not. M1 excitability changes were comparable in nfv-PPA and bv-FTD. DTI revealed decreased fractional anisotropy in the superior and inferior longitudinal and uncinate fasciculi. Moreover, VBM disclosed GM volume loss in the left frontal operculum though not in the parietal operculum or precentral gyrus. Furthermore, WM and GM changes were comparable in nfv-PPA and bv-FTD. There was no correlation between neurophysiological and neuroimaging changes in FTD. Atrophy in the left frontal operculum correlated with linguistic dysfunction, assessed by semantic and phonemic fluency tests.ConclusionWe provide converging neurophysiological and neuroimaging evidence of abnormal speech-related cortical network activation in FTD.     

Motor cortex hand area and speech: implications for the development of language

Recently a growing body of evidence has suggested that a functional link exists between the hand motor area of the language dominant hemisphere and the regions subserving language processing. We examined the excitability of the hand motor area and the leg motor area during reading aloud and during non-verbal oral movements using transcranial magnetic stimulation (TMS). During reading aloud, but not before or afterwards, excitability was increased in the hand motor area of the dominant hemisphere. This reading effect was found to be independent of the duration of speech. No such effect could be found in the contralateral hemisphere. The excitability of the leg area of the motor cortex remained unchanged during reading aloud. The excitability during non-verbal oral movements was slightly increased in both hemispheres. Our results are consistent with previous findings and may indicate a specific functional connection between the hand motor area and the cortical language network.     

Early non‐specific modulation of corticospinal excitability during action observation

Activity of the primary motor cortex (M1) during action observation is thought to reflect motor resonance. Here, we conducted three studies using transcranial magnetic stimulation (TMS)‐induced motor‐evoked potentials (MEPs) of the first dorsal interosseus muscle (FDI) during action observation to determine: (i) the time course of M1 corticospinal excitability during the observation of a simple finger movement; (ii) the specificity of M1 modulation in terms of type of movement and muscle; and (iii) the relationship between M1 activity and measures of empathy and autistic traits. In a first study, we administered single‐pulse TMS at 30‐ms intervals during the observation of simple finger movements. Results showed enhanced corticospinal excitability occurring between 60 and 90 ms after movement onset. In a second experiment, TMS‐induced MEPs were recorded from the FDI and abductor digiti minimi muscles while pulses were delivered 90 ms after movement onset during observation of simple finger movement and dot movement. Increased corticospinal excitability was restricted to finger movement and was present in both muscles. Finally, in an exploratory experiment, single‐pulse TMS was administered at 30, 90 and 150 ms after movement onset, and participants were asked to complete the Empathy Quotient (EQ) and the Autism Spectrum Quotient (AQ). Correlational analysis revealed a significant link between motor facilitation at 90 ms and the EQ and AQ scores. These results suggest that corticospinal excitability modulation seen at M1 during action observation is the result of a rapid and crude automatic process, which may be related to social functioning.     

Primary motor cortex long‐term plasticity in multiple system atrophy

In humans, intermittent and continuous theta‐burst stimulation (iTBS and cTBS) elicit long‐term changes in motor‐evoked potentials (MEPs) reflecting long‐term potentiation (LTP)‐ and depression (LTD)‐like plasticity in the primary motor cortex (M1). In this study, we used TBS to investigate M1 plasticity in patients with MSA. We also assessed whether responses to TBS reflect M1 excitability as tested by short‐interval intracortical inhibition (SICI), intracortical facilitation (ICF), short‐interval intracortical facilitation (SICF), and the input/output curves. We studied 20 patients with MSA and 20 healthy subjects (HS). Patients were clinically evaluated with the Unified Multiple System Atrophy Rating Scale. The left M1 was conditioned with TBS. Twenty MEPs were recorded from the right first dorsal interosseous muscle before TBS and 5, 15, and 30 minutes thereafter. In a subgroup of 10 patients, we also tested MEPs elicited by SICI, ICF, SICF, and input/output curves, before TBS. Between‐group analysis of variance showed that at all time points after iTBS MEPs increased, whereas after cTBS they decreased only in HS. In both subgroups tested, patients with predominant parkinsonian and cerebellar features, iTBS and cTBS left MEPs unchanged. MSA patients had reduced SICI, but normal ICF, SICF, and input/output curves. No correlation was found between patients' clinical features and responses to TBS and M1 excitability variables. These findings suggest impaired M1 plasticity in MSA. © 2013 International Parkinson and Movement Disorder Society     

Early semantic and phonological effects on temporal- and muscle-specific motor resonance

Previous studies using functional magnetic resonance imaging and transcranial magnetic stimulation (TMS) explored the relationships between linguistic processing and motor resonance, i.e. the activation of the motor system while perceiving others performing an action. These studies have mainly investigated a specific linguistic domain, i.e. semantics, whereas phonology has been largely neglected. Here we used single‐pulse TMS to compare the effects of semantic and phonological processing with motor resonance effects. We applied TMS to the primary motor hand area while subjects observed object‐oriented actions and performed semantic and phonological tasks related to the observed action. Motor evoked potentials were recorded in two hand muscles, one of them more involved in the execution of the observed actions than the other one, at three different timepoints (0, 200 and 400 ms after stimulus onset). The results demonstrated increased corticospinal excitability that was muscle‐specific (i.e. restricted to the hand muscle involved in the observed action), hemisphere‐specific (left), and time‐specific (400 ms after stimulus onset). The results suggest an additive effect of independent semantic and phonological processing on motor resonance. The novel phonological effect reported here expands the links between language and the motor system and is consistent with a theory of shared control for hand and mouth. Furthermore, the timing of the semantic effect suggests that motor activation during semantic processing is not an ‘epiphenomenon’ but rather is essential to the construction of meaning.     

Hands on the future: facilitation of cortico‐spinal hand‐representation when reading the future tense of hand‐related action verbs

Reading action‐related verbs brings about sensorimotor neural activity, suggesting that the linguistic representation of actions impinges upon neural structures largely overlapping with those involved in actual action execution. While studies of direct action observation indicate that motor mirroring is inherently anticipatory, no information is currently available on whether deriving action‐related knowledge from language also takes into account the temporal deployment of actions. Using transcranial magnetic stimulation, here we sought to determine whether reading action verbs conjugated in the future induced higher cortico‐spinal activity with respect to when the same verbs were conjugated in the past tense. We recorded motor‐evoked potentials (MEPs) from relaxed hand and leg muscles of healthy subjects who were reading silently hand‐ or leg‐related action, sensorial (non‐somatic) and abstract verbs conjugated either in future or past tense. The amplitude of MEPs recorded from the hand was higher during reading hand‐related action verbs conjugated in the future than in the past. No future‐related modulation of leg muscles activity was found during reading leg‐related action verbs. In a similar vein, no future‐related change of hand or leg muscles reactivity was found for abstract or sensorial verbs. These results indicate that the anticipatory mirroring of hand actions may be triggered by linguistic representations and not only by direct action observation.     

Postexercise facilitation of motor evoked potentials elicited by ipsilateral voluntary contraction

Motor evoked potentials (MEPs) to transcranial magnetic stimulation (TMS) increase in amplitude when obtained immediately after a period of exercise of the target muscle (postexercise facilitation). We studied postexercise facilitation of MEPs to TMS after periods of voluntary activation of either the ipsilateral or contralateral primary motor cortex (simple finger movements) or supplementary motor area (complex finger movements). Postexercise facilitation of the first dorsal interosseous MEPs occurred ipsilaterally even after simple, unilateral finger movements of the dominant hand. The findings are taken to suggest transcallosal transfer of excitability from the dominant to nondominant cerebral hemisphere, perhaps related to mechanisms involved in bimanual motor coordination.     

Transcranial magnetic stimulation of motor pathways directed to muscles supplied by cranial nerves in amyotrophic lateral sclerosis.

OBJECTIVES: In amyotrophic lateral sclerosis (ALS), transcranial magnetic stimulation (TMS) detects remarkable abnormalities of central motor circuits: cortical excitability threshold, silent period (SP) duration and intra-cortical inhibition. TMS directed to cranio-facial musculature was performed in ALS patients in order: (1) to document the neurophysiological involvement of motor central and peripheral cranial pathways by evaluating changes of threshold and SP; (2) to discover a possible correlation between the clinical picture and abnormal excitability properties. METHODS: Motor evoked potentials (MEPs) were recorded from masseter, genioglossus and orbicularis oris muscles of both sides in 25 ALS patients and 25 controls, in response to TMS delivered over the face M1 area and the vertex. RESULTS: TMS gave rise to two orders of responses: bilateral MEPs during contraction represented the central responses, and motor action potentials (MAPs) during rest represented the peripheral responses. MEPs were followed by SPs, which increased linearly with increasing TMS intensity (r=0.8). At least one of the analyzed parameters was abnormal in all patients: central abnormalities (increased active threshold, delayed MEPs, reduced SP) were found in 96% of patients, alone or combined with abnormalities of the MAPs (reduced area and/or prolonged latency). The reduction of SP was linearly related to the Norris score (r=0.95). CONCLUSIONS: Our study shows that TMS is able to detect the involvement of multiple cranial muscles in ALS. This finding offers often pre-clinical information about the disease picture. Therefore, it can be employed as a valuable means for early diagnosis.     

Parietal transcranial direct current stimulation modulates primary motor cortex excitability

The posterior parietal cortex is part of the cortical network involved in motor learning and is structurally and functionally connected with the primary motor cortex (M1). Neuroplastic alterations of neuronal connectivity might be an important basis for learning processes. These have however not been explored for parieto‐motor connections in humans by transcranial direct current stimulation (tDCS). Exploring tDCS effects on parieto‐motor cortical connectivity might be functionally relevant, because tDCS has been shown to improve motor learning. We aimed to explore plastic alterations of parieto‐motor cortical connections by tDCS in healthy humans. We measured neuroplastic changes of corticospinal excitability via motor evoked potentials (MEP) elicited by single‐pulse transcranial magnetic stimulation (TMS) before and after tDCS over the left posterior parietal cortex (P3), and 3 cm posterior or lateral to P3, to explore the spatial specificity of the effects. Furthermore, short‐interval intracortical inhibition/intracortical facilitation (SICI/ICF) over M1, and parieto‐motor cortical connectivity were obtained before and after P3 tDCS. The results show polarity‐dependent M1 excitability alterations primarily after P3 tDCS. Single‐pulse TMS‐elicited MEPs, M1 SICI/ICF at 5 and 7 ms and 10 and 15 ms interstimulus intervals (ISIs), and parieto‐motor connectivity at 10 and 15 ms ISIs were all enhanced by anodal stimulation. Single pulse‐TMS‐elicited MEPs, and parieto‐motor connectivity at 10 and 15 ms ISIs were reduced by cathodal tDCS. The respective corticospinal excitability alterations lasted for at least 120 min after stimulation. These results show an effect of remote stimulation of parietal areas on M1 excitability. The spatial specificity of the effects and the impact on parietal cortex–motor cortex connections suggest a relevant connectivity‐driven effect.     

Effects of musical training on speech-induced modulation in corticospinal excitability

We investigated the effect of previous musical training on lateralization of language as indexed by the effects of reading aloud on the modulation of motor evoked potentials (MEPs) induced in the first dorsal interosseus muscles (FDI) by transcranial magnetic stimulation (TMS) of the primary motor cortex. We studied 13 right-handed subjects, seven musicians who had been playing a musical instrument for >10 years and six controls who had never studied a musical instrument. In all subjects, the amplitude of MEPs in the right FDI was facilitated by reading aloud. However, the musicians also showed significant facilitation in the left FDI, while controls did not. These results illustrate striking effects of musical training on lateralization of motor and language functions.     

Anticipation and execution of a simple reading task enhance corticospinal excitability.

OBJECTIVE: Electromyographic responses (EMG) evoked in the right hand by transcranial magnetic stimulation (TMS) of the left motor cortex are enhanced during continuous reading. This enhancement is the result of increased excitability of the motor cortex. We proposed that anticipation and reading of single words would also enhance corticospinal excitability. We studied the temporal course of corticospinal excitability changes following left and right hemisphere TMS. METHODS: Ten normal volunteers were studied. A warning stimulus (S1) was followed by an imperative stimulus (S2) whereupon a word was presented. Subjects responded by reading the word aloud or reading it silently. In other conditions, no word was displayed and the subjects responded to S2 by saying the word 'Cat', pursing their lips, or doing nothing. EMG was recorded over the contralateral hand following a TMS pulse over the motor cortex during and after the S1-S2 period. RESULTS: Enhancement of EMG amplitudes was significantly greater following left hemisphere TMS. The enhancement in the S1-S2 period and that following S2 had a time course similar to several event-related brain potentials. CONCLUSIONS: There may be a common mechanism underlying both corticospinal excitability and the contingent negative variation, readiness potential and N400.     

Force requirements of observed object lifting are encoded by the observer’s motor system: a TMS study

Several transcranial magnetic stimulation (TMS) studies have reported facilitation of the primary motor cortex (M1) during the mere observation of actions. This facilitation was shown to be highly congruent, in terms of somatotopy, with the observed action, even at the level of single muscles. With the present study, we investigated whether this muscle‐specific facilitation of the observer’s motor system reflects the degree of muscular force that is exerted in an observed action. Two separate TMS experiments are reported in which corticospinal excitability was measured in the hand area of M1 while subjects observed the lifting of objects of different weights. The type of action ‘grasping‐and‐lifting‐the‐object’ was always identical, but the grip force varied according to the object’s weight. In accordance to previous findings, excitability of M1 was shown to modulate in a muscle‐specific way, such that only the cortical representation areas in M1 that control the specific muscles used in the observed lifting action became increasingly facilitated. Moreover, muscle‐specific M1 facilitation was shown to modulate to the force requirements of the observed actions, such that M1 excitability was considerably higher when observing heavy object lifting compared with light object lifting. Overall, these results indicate that different levels of observed grip force are mirrored onto the observer’s motor system in a highly muscle‐specific manner. The measured force‐dependent modulations of corticospinal excitability in M1 are hypothesized to be functionally relevant for scaling the observed grip force in the observer’s own motor system. In turn, this mechanism may contribute, at least partly, to the observer’s ability to infer the weight of the lifted object.     

Task-dependent differences in corticobulbar excitability of the submental motor projections: Implications for neural control of swallowing

It has been suggested that the primary motor cortex plays a substantial role in the neural circuitry that controls swallowing. Although its role in the voluntary oral phase of swallowing is undisputed, its precise role in motor control of the more reflexive, pharyngeal phase of swallowing is unclear. The contribution of the primary motor cortex to the pharyngeal phase of swallowing was examined using transcranial magnetic stimulation (TMS) to evoke motor evoked potentials (MEPs) in the anterior hyomandibular muscle group during either volitional submental muscle contraction or contraction during the pharyngeal phase of both volitionally, and reflexively, initiated swallowing. For each subject, in all three conditions, TMS was triggered when submental surface EMG (sEMG) reached 75% of the mean maximal submental sEMG amplitude measured during 10 volitional swallows. MEPs recorded during volitional submental muscle contraction were elicited in 22 of the 35 healthy subjects examined (63%). Only 16 of these 22 subjects (45.7%) also displayed MEPs recorded during volitional swallowing, but their MEP amplitudes were larger when triggered by submental muscle contraction than when triggered by volitional swallowing. Additionally, only 7 subjects (of 19 tested) showed MEPs triggered by submental muscle contraction during a reflexively triggered pharyngeal swallow. These differences indicate differing levels of net M1 excitability during execution of the investigated tasks, possibly brought about by task-dependent changes in the balance of excitatory and inhibitory neural activity.     

The involvement of primary motor cortex in mental rotation revealed by transcranial magnetic stimulation

We used single‐pulse transcranial magnetic stimulation of the left primary hand motor cortex and motor evoked potentials of the contralateral right abductor pollicis brevis to probe motor cortex excitability during a standard mental rotation task. Based on previous findings we tested the following hypotheses. (i) Is the hand motor cortex activated more strongly during mental rotation than during reading aloud or reading silently? The latter tasks have been shown to increase motor cortex excitability substantially in recent studies. (ii) Is the recruitment of the motor cortex for mental rotation specific for the judgement of rotated but not for nonrotated Shepard & Metzler figures? Surprisingly, motor cortex activation was higher during mental rotation than during verbal tasks. Moreover, we found strong motor cortex excitability during the mental rotation task but significantly weaker excitability during judgements of nonrotated figures. Hence, this study shows that the primary hand motor area is generally involved in mental rotation processes. These findings are discussed in the context of current theories of mental rotation, and a likely mechanism for the global excitability increase in the primary motor cortex during mental rotation is proposed.     

Lee Silverman Voice Treatment for dysarthria in patients with Parkinson’s disease: a systematic review and meta‐analysis

Approximately 89% of patients with Parkinson’s disease (PD) suffer from dysarthria. Lee Silverman Voice Treatment (LSVT), a behavioral therapy, aims to improve speech and voice functions. The objective was to assess the effectiveness of LSVT compared with other/no speech interventions for dysarthria in patients with PD. Electronic databases, including PubMed, Embase and the Cochrane Library, were searched. The publication date of all included studies was before 6 March 2020. Only randomized controlled trials (RCTs) that evaluated the LSVT intervention compared with other/no speech intervention were considered. The data obtained from the included studies were described and the mean differences were calculated. Eight RCTs were included in this meta‐analysis comparing LSVT with other/no speech interventions. In the comparison of LSVT versus no intervention, vocal intensity for sustained ‘Ah’ phonation, reading the ‘Rainbow passage’, monologue and describing a picture increased by 8.87, 4.34, 3.25 and 3.31 dB, respectively, after 1 month of therapy. Compared with the respiratory therapy group, the LSVT group also showed significant improvement in vocal intensity for sustained ‘Ah’ phonation, reading the ‘Rainbow passage’ and monologue immediately after treatment (13.39, 6.66 and 3.19 dB). Positive improvement still existed after 24 months. There was no difference in the therapeutic effect between face‐to‐face and online LSVT. The effectiveness of LSVT for dysarthria in patients with PD was verified in these trials. However, future RCTs with sufficient participants are essential to evaluate the effectiveness of LSVT for dysarthria.     

EEG oscillations and magnetically evoked motor potentials reflect motor system excitability in overlapping neuronal populations

ObjectiveTo understand the relationship between neuronal excitability reflected by transcranial magnetic stimulation (TMS) evoked motor potentials (MEPs) and spontaneous oscillation amplitude and phase.MethodsWe combined spontaneous EEG measurement with motor cortex TMS and recorded MEP amplitudes from abductor digiti minimi (ADM).ResultsMidrange-beta oscillations over the stimulated left motor cortex were, on average, weaker before large- than small-amplitude MEPs. The phase of occipital midrange-beta oscillations was related to the MEP amplitudes.ConclusionsThe present results support the view that MEP and Rolandic beta oscillation amplitudes are associated with motor cortical excitability. However, oscillations seen in EEG reflect the excitability of a large population of cortical neurons, and MEP amplitude is affected also by spinal excitability and action potential desynchronization. Thus, MEP and EEG oscillation amplitudes are not strongly correlated. In addition, even during rest, motor system excitability appears to be related to activity in occipital areas at frequency ranges associated with visuomotor processing.SignificanceThe ability of spontaneous oscillations and MEPs to inform us about cortical excitability is clarified. For example, it is suggested that oscillatory activity at non-motor sites might be related to motor system excitability at rest.     

Comparison of different baseline conditions in evaluating factors that influence motor cortex excitability

Identifying task-related changes in cortical excitability requires comparing motor evoked potentials (MEPs) measured under an experimental condition with that obtained in a baseline, control condition. The goal of this study was to compare two different procedures for measuring baseline that are commonly used in transcranial magnetic stimulation (TMS) studies. We hypothesized that baseline measurements obtained during task performance may be elevated due to an overall heightened state of arousal or task-specific fluctuations in excitability. Single-pulse TMS was used to elicit MEPs during an experimental task involving action observation. Baseline MEPs were recorded before (preblock) and during (intrablock) the experimental blocks. Intrablock baseline MEPs were modulated in a manner correlated with the effect of the experimental manipulation. Although there are advantages to obtaining baseline measurements during the experimental block, such measurements are biased by the experimental manipulation. Unbiased baseline measurements are best obtained between experimental blocks.     

Insights on the neural basis of motor plasticity induced by theta burst stimulation from TMS–EEG

Transcranial magnetic stimulation (TMS) is a useful tool to induce and measure plasticity in the human brain. However, the cortical effects are generally indirectly evaluated with motor‐evoked potentials (MEPs) reflective of modulation of cortico‐spinal excitability. In this study, we aim to provide direct measures of cortical plasticity by combining TMS with electroencephalography (EEG). Continuous theta‐burst stimulation (cTBS) was applied over the primary motor cortex (M1) of young healthy adults, and we measured modulation of (i) MEPs, (ii) TMS‐induced EEG evoked potentials (TEPs), (iii) TMS‐induced EEG synchronization and (iv) eyes‐closed resting EEG. Our results show the expected cTBS‐induced decrease in MEP size, which we found to be paralleled by a modulation of a combination of TEPs. Furthermore, we found that cTBS increased the power in the theta band of eyes‐closed resting EEG, whereas it decreased single‐pulse TMS‐induced power in the theta and alpha bands. In addition, cTBS decreased the power in the beta band of eyes‐closed resting EEG, whereas it increased single‐pulse TMS‐induced power in the beta band. We suggest that cTBS acts by modulating the phase alignment between already active oscillators; it synchronizes low‐frequency (theta and/or alpha) oscillators and desynchronizes high‐frequency (beta) oscillators. These results provide novel insight into the cortical effects of cTBS and could be useful for exploring cTBS‐induced plasticity outside of the motor cortex.     

Modulation of fronto‐parietal connections during the rubber hand illusion

Accumulating evidence suggests that parieto‐frontal connections play a role in adjusting body ownership during the Rubber Hand Illusion (RHI). Using a motor version of the rubber hand illusion paradigm, we applied single‐site and dual‐site transcranial magnetic stimulation (TMS) to investigate cortico‐spinal and parietal‐frontal connectivity during perceived rubber hand ownership. Healthy volunteers received a conditioning TMS pulse over left anterior intraparietal sulcus (aIPS) and a test TMS pulse over left primary motor cortex (M1). Motor Evoked Potentials (MEPs) were recorded at rest and during three RHI conditions: (i) agency and ownership, (ii) agency but no ownership and (iii) neither agency nor ownership. Parietal‐motor communication differed among experimental conditions. The induction of action ownership was associated with an inhibitory parietal‐to‐motor connectivity, which was comparable to the aIPS‐to‐M1 inhibition present at rest. This aIPS‐to‐M1 inhibition disappeared during movement conditions not inducing ownership. Cortico‐spinal excitability was not significantly modulated during the motor RHI as indicated by the task‐constant MEP amplitude elicited by the M1 test pulse alone. Our results indicate that the perceived ownership over the rubber hand is associated with normal parietal‐motor communication. This communication is disturbed if the sensorimotor conflict between one's own hand and the rubber hand is not resolved.