Dominant Primary Motor Cortex Research Articles

TIME COURSE AND VISUAL PRESENTATION EFFECTS ON THE MOTOR MIRROR NEURON SYSTEM INDUCED BY TRANSCRANIAL MAGNETIC STIMULATION

The study of mirror neurons (MN) has a long way since its discovery on monkeys and later on humans. However, there are inconsistencies on the way that stimuli are presented and on the time of stimuli presentation. Which is the optimal way to present motor movement stimuli? Is it possible to estimate the time course of the mirror neurons effect by using transcranial magnetic stimulation at specific time windows? In the current study we investigated different type of stimuli presentation (photo and video of hand movements) by using single pulse Transcranial Magnetic Stimulation of the dominant primary motor cortex (M1) at different time windows (0, 320, 640 ms). Motor evoked potentials from FDI (index finger muscle) and ADM (little finger muscle) were recorded on 11 healthy subjects at rest with their hands in orthogonal position while only observing the visual stimuli in three different presentation conditions. Our results showed that Video presentation induces the strongest mirror effect at 320 ms from the movement onset. This effect is muscle specific. The current evidence provides an optimal protocol for the investigation of the mirror neurons system in humans and pave the way for future clinical application and rehabilitation.

Aerobic exercise and action observation priming modulate functional connectivity.

Aerobic exercise and action observation are two clinic-ready modes of neural priming that have the potential to enhance subsequent motor learning. Prior work using transcranial magnetic stimulation to assess priming effects have shown changes in corticospinal excitability involving intra- and interhemispheric circuitry. The objective of this study was to determine outcomes exclusive to priming- how aerobic exercise and action observation priming influence functional connectivity within a sensorimotor neural network using electroencephalography. We hypothesized that both action observation and aerobic exercise priming would alter resting-state coherence measures between dominant primary motor cortex and motor-related areas in alpha (7-12 Hz) and beta (13-30 Hz) frequency bands with effects most apparent in the high beta (20-30 Hz) band. Nine unimpaired individuals (24.8 ± 3 years) completed a repeated-measures cross-over study where they received a single five-minute bout of action observation or moderate-intensity aerobic exercise priming in random order with a one-week washout period. Serial resting-state electroencephalography recordings acquired from 0 to 30 minutes following aerobic and action observation priming revealed increased alpha and beta coherence between leads overlying dominant primary motor cortex and supplementary motor area relative to pre- and immediate post-priming timepoints. Aerobic exercise priming also resulted in enhanced high beta coherence between leads overlying dominant primary motor and parietal cortices. These findings indicate that a brief bout of aerobic- or action observation-based priming modulates functional connectivity with effects most pronounced with aerobic priming. The gradual increases in coherence observed over a 10 to 30-minute post-priming window may guide the pairing of aerobic- or action observation-based priming with subsequent training to optimize learning-related outcomes.

Differences in neurometabolites and transcranial magnetic stimulation motor maps in children with attention-deficit/hyperactivity disorder.

Background:Although much is known about cognitive dysfunction in attention-deficit/hyperactivity disorder (ADHD), few studies have examined the pathophysiology of disordered motor circuitry. We explored differences in neurometabolite levels and transcranial magnetic stimulation (TMS)–derived corticomotor representations among children with ADHD and typically developing children.Methods:We used magnetic resonance spectroscopy (MRS) protocols to measure excitatory (glutamate + glutamine [Glx]) and inhibitory (γ-aminobutyric acid [GABA]) neurometabolite levels in the dominant primary motor cortex (M1) and the supplementary motor area (SMA) in children with ADHD and typically developing children. We used robotic neuronavigated TMS to measure corticospinal excitability and create corticomotor maps.Results:We collected data from 26 medication-free children with ADHD (aged 7–16 years) and 25 typically developing children (11–16 years). Children with ADHD had lower M1 Glx (p = 0.044, d = 0.6); their mean resting motor threshold was lower (p = 0.029, d = 0.8); their map area was smaller (p = 0.044, d = 0.7); and their hotspot density was higher (p = 0.008, d = 0.9). M1 GABA levels were associated with motor map area (p = 0.036).Limitations: Some TMS data were lost because the threshold of some children exceeded 100% of the machine output. The relatively large MRS voxel required to obtain sufficient signal-to-noise ratio and reliably measure GABA levels encompassed tissue beyond the M1, making this measure less anatomically specific.Conclusion:The neurochemistry and neurophysiology of key nodes in the motor network may be altered in children with ADHD, and the differences appear to be related to each other. These findings suggest potentially novel neuropharmacological and neuromodulatory targets for ADHD.

Does anodal tDCS improve basketball performance? A randomized controlled trial

Shooting precision as well as dribbling and agility are crucial components of performance in basketball. We examined the effects of anodal tDCS over the dominant primary motor cortex in supporting these basketball specific abilities. Fifty-two sports students were enrolled in a double-blind, randomized, placebo-controlled, crossover trial with two interventions. Twenty minutes of anodal 1 mA tDCS/sham tDCS were applied over the primary motor cortex of the dominant hemisphere. Basketball shooting precision (basketball shooting accuracy test) and basketball specific dribbling and agility (Illinois ball-dribbling test) were tested prior and after each intervention. Basketball shooting precision and basketball specific dribbling and agility improved after real tDCS but not after sham tDCS. ANOVAs show significant intervention*time effects on both the shooting accuracy test (F 1,51 = 5.6; P = 0.022) and on the Illinois ball-dribbling test (F 1,51 = 4.5; P = 0.038). Anodal 1 mA tDCS over the dominant primary motor cortex is effective in supporting short-term performance in basketball. However, the available data is insufficient for application of this novel method within the framework of conventional sports training.

TDCS Anodal tDCS increases bilateral corticospinal excitability irrespective of hemispheric dominance

Background: Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique that utilizes weak direct currents to induce polarity-dependent modulation of corticospinal excitability. Although tDCS exerts a modulatory effect over the stimulation region, several studies have also demonstrated that distal areas of the brain connected to the region of stimulation may also be affected, as well as the contralateral hemisphere. Objective: We examined the effect of a single session of anodal tDCS on corticospinal excitability and inhibition of both the stimulated and non-stimulated hemisphere and examined the influence of these responses by the brain-derived neurotrophic factor (BDNF) polymorphism. Methods: In a randomized cross-over design, changes in corticospinal excitability and inhibition of the stimulated and non-stimulated hemispheres were analysed in 13 participants in both the dominant and non-dominant primary motor cortex (M1). Participants were exposed to 20 min of anodal and sham tDCS and also undertook a blood sample for BDNF genotyping. Results: TMS revealed a bilateral increase in corticospinal excitability irrespective of which hemisphere (dominant vs non-dominant) was stimulated (all P < 0.05). Furthermore, the induction of corticospinal excitability was influenced by the BDNF polymorphism. Conclusion: This finding shows that anodal tDCS induces bilateral effects in corticospinal excitability irrespective of hemispheric dominance. This finding provides scientists and medical practitioners with a greater understanding as to how this technique may be used as a therapeutic tool for clinical populations.

Alterations of hand sensorimotor function and cortical motor representations over the adult lifespan.

Using a cross sectional design, we aimed to identify the effect of aging on sensorimotor function and cortical motor representations of two intrinsic hand muscles, as well as the course and timing of those changes. Furthermore, the link between cortical motor representations, sensorimotor function, and intracortical inhibition and facilitation was investigated. Seventy-seven participants over the full adult lifespan were enrolled. For the first dorsal interosseus (FDI) and abductor digiti minimi (ADM) muscle, cortical motor representations, GABAA-mediated short-interval intracortical inhibition (SICI), and glutamate-mediated intracortical facilitation (ICF) were assessed using transcranial magnetic stimulation over the dominant primary motor cortex. Additionally, participants’ dexterity and force were measured. Linear, polynomial, and piecewise linear regression analyses were conducted to identify the course and timing of age-related differences. Our results demonstrated variation in sensorimotor function over the lifespan, with a marked decline starting around the mid-thirties. Furthermore, an age-related reduction in cortical motor representation volume and maximal MEP of the FDI, but not for ADM, was observed, occurring mainly until the mid-forties. Area of the cortical motor representation did not change with advancing age. Furthermore, cortical motor representations, sensorimotor function, and measures of intracortical inhibition and facilitation were not interrelated.

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.

Task-related measures of short-interval intracortical inhibition and GABA levels in healthy young and older adults: A multimodal TMS-MRS study

Establishing the associations between magnetic resonance spectroscopy (MRS)-assessed gamma-aminobutyric acid (GABA) levels and transcranial magnetic stimulation (TMS)-derived ‘task-related’ modulations in GABAA receptor-mediated inhibition and how these associations change with advancing age is a topic of interest in the field of human neuroscience. In this study, we identified the relationship between GABA levels and task-related modulations in GABAA receptor-mediated inhibition in the dominant (left) and non-dominant (right) sensorimotor (SM) cortices. GABA levels were measured using edited MRS and task-related GABAA receptor-mediated inhibition was measured using a short-interval intracortical inhibition (SICI) TMS protocol during the preparation and premotor period of a choice reaction time (CRT) task in 25 young (aged 18–33 years) and 25 older (aged 60–74 years) adults. Our results demonstrated that GABA levels in both SM voxels were lower in older adults as compared to younger adults; and higher SM GABA levels in the dominant as compared to the non-dominant SM voxel pointed to a lateralization effect, irrespective of age group. Furthermore, older adults showed decreased GABAA receptor-mediated inhibition in the preparation phase of the CRT task within the dominant primary motor cortex (M1), as compared to young adults. Finally, results from an exploratory correlation analysis pointed towards positive relationships between MRS-assessed GABA levels and TMS-derived task-related SICI measures. However, after correction for multiple comparisons none of the correlations remained significant.

Motor Task-Dependent Dissociated Effects of Transcranial Random Noise Stimulation in a Finger-Tapping Task Versus a Go/No-Go Task on Corticospinal Excitability and Task Performance.

Background and Objective: Transcranial random noise stimulation (tRNS) is an emerging non-invasive brain stimulation technique to modulate brain function, with previous studies highlighting its considerable benefits in therapeutic stimulation of the motor system. However, high variability of results and bidirectional task-dependent effects limit more widespread clinical application. Task dependency largely results from a lack of understanding of the interaction between externally applied tRNS and the endogenous state of neural activity during stimulation. Hence, the aim of this study was to investigate the task dependency of tRNS-induced neuromodulation in the motor system using a finger-tapping task (FT) versus a go/no-go task (GNG). We hypothesized that the tasks would modulate tRNS’ effects on corticospinal excitability (CSE) and task performance in opposite directions.Methods: Thirty healthy subjects received 10 min of tRNS of the dominant primary motor cortex in a double-blind, sham-controlled study design. tRNS was applied during two well-established tasks tied to diverging brain states. Accordingly, participants were randomly assigned to two equally-sized groups: the first group performed a simple motor training task (FT task), known primarily to increase CSE, while the second group performed an inhibitory control task (go/no-go task) associated with inhibition of CSE. To establish task-dependent effects of tRNS, CSE was evaluated prior to- and after stimulation with navigated transcranial magnetic stimulation.Results: In an ‘activating’ motor task, tRNS during FT significantly facilitated CSE. FT task performance improvements, shown by training-related reductions in intertap intervals and increased number of finger taps, were similar for both tRNS and sham stimulation. In an ‘inhibitory’ motor task, tRNS during GNG left CSE unchanged while inhibitory control was enhanced as shown by slowed reaction times and enhanced task accuracy during and after stimulation.Conclusion: We provide evidence that tRNS-induced neuromodulatory effects are task-dependent and that resulting enhancements are specific to the underlying task-dependent brain state. While mechanisms underlying this effect require further investigation, these findings highlight the potential of tRNS in enhancing task-dependent brain states to modulate human behavior.

A method for assessing recovery of fine motor function of the hand in a rhesus monkey model of cortical injury: an adaptation of the Fugl–Meyer Scale and Eshkol–Wachman Movement Notation

Motor dysfunction of the upper extremity can result from stroke, cortical injury and neurological diseases and causes significant disruption of activities of daily living. While some spontaneous recovery in terms of compensatory movements does occur after injury to cortical motor areas, full recovery is rare. The distinction between complete recovery and compensatory recovery is important as the development of compensatory movements in the upper extremity may not translate into full functional use in human patients. However, current animal models of stroke do not distinguish full recovery from compensatory recovery. We have developed a Non-Human Primate Grasp Assessment Scale (GRAS) to quantify the precise recovery of composite movement, individual digit action, and finger-thumb pinch in our rhesus monkey model of cortical injury. To date, we have applied this GRAS scale to assess the recovery of fine motor function of the hand in young control and cell-therapy treated monkeys with cortical injury confined to the hand representation in the dominant primary motor cortex. We have demonstrated that with this scale we can detect and quantify significant impairments in fine motor function of the hand, the development of compensatory function during recovery and finally a return to full fine motor function of the hand in monkeys treated with a cell therapy.

Age-related changes in TMS-based gamma-aminobutyric acid (GABA) modulation during a unimanual simple and choice reaction time task.

Age-related changes in TMS-based gamma-aminobutyric acid (GABA) modulation during a unimanual simple and choice reaction time task.

Effects of transcranial direct-current stimulation on laparoscopic surgical skill acquisition.

BackgroundChanges in medical education may limit opportunities for trainees to gain proficiency in surgical skills. Transcranial direct‐current stimulation (tDCS) can augment motor skill learning and may enhance surgical procedural skill acquisition. The aim of this study was to determine the effects of tDCS on simulation‐based laparoscopic surgical skill acquisition.MethodsIn this double‐blind, sham‐controlled randomized trial, participants were randomized to receive 20 min of anodal tDCS or sham stimulation over the dominant primary motor cortex, concurrent with Fundamentals of Laparoscopic Surgery simulation‐based training. Primary outcomes of laparoscopic pattern‐cutting and peg transfer tasks were scored at baseline, during repeated performance over 1 h, and again at 6 weeks. Intent‐to‐treat analysis examined the effects of treatment group on skill acquisition and retention.ResultsOf 40 participants, those receiving tDCS achieved higher mean(s.d.) final pattern‐cutting scores than participants in the sham group (207·6(30·0) versus 186·0(32·7) respectively; P = 0·022). Scores were unchanged at 6 weeks. Effects on peg transfer scores were not significantly different (210·2(23·5) in the tDCS group versus 201·7(18·1) in the sham group; P = 0·111); the proportion achieving predetermined proficiency levels was higher for tDCS than for sham stimulation. Procedures were well tolerated with no serious adverse events and no decreases in motor measures.ConclusionThe addition of tDCS to laparoscopic surgical training may enhance skill acquisition. Trials of additional skills and translation to non‐simulated performance are required to determine the potential value in medical education and impact on patient outcomes. Registration number: NCT02756052 (https://clinicaltrials.gov/).

Age-related changes of cortical excitability and connectivity in healthy humans: non-invasive evaluation of sensorimotor network by means of TMS-EEG

The sensorimotor cortical system undergoes structural and functional changes across its lifespan. Some of these changes are physiological and parallel the normal aging process, while others might represent pathophysiological mechanisms underlying neurodegenerative disorders. In the last years, the study of possible age-related modifications in brain sensorimotor functional characteristics has been the focus of several research projects. Here we have used the transcranial magnetic stimulation (TMS)-electroencephalography (EEG) navigated co-registration to investigate the influence of physiological aging on the excitability and connectivity of the human sensorimotor cortical system. To this end, we compared the TMS-evoked EEG potentials (TEPs) collected after stimulating the dominant primary motor cortex (M1) in healthy young subjects (mean age 24.5years) with those collected in healthy older adults (mean age 67.6years). We have shown that, after stimulation of the left motor cortex, TEPs are significantly affected by physiological aging. This phenomenon has a clear spatio-temporal specificity and we speculate that normal aging per se leads to some changes in the excitability of specific cortical neural assemblies whereas other alterations could reflect compensatory mechanisms to such changes.

P029 Effects of dual-mode non-invasive brain stimulation on freezing of gait in patients with Parkinson’s disease

Purpose Our previous study demonstrated the favorable effect of repetitive transcranial magnetic stimulation (rTMS) over both the dominant primary motor cortex of lower leg (M1-LL) and the left dorsolateral prefrontal cortex (DLPFC). The aim of this study was to investigate the effects of dual-mode non-invasive brain stimulation (NBS) on FOG using both rTMS and tDCS in patients with PD. Methods This study was a randomized controlled double-blind study comparing the effect of single vs. dual-mode stimulation. Thirty-two patients with PD that featured FOG were included and divided into two groups. For the dual-mode stimulation, 10 Hz rTMS over the dominant M1-LL and the anodal tDCS over the left DLPFC were simultaneously applied for 20 min per session, 5 sessions in a week. For the single stimulation, rTMS were applied at the same manner. Behavioral, neurophysiologic and cognitive outcomes were measured before, after, and 1 week after the intervention by the Timed Up and Go (TUG) test, Standing Start 180° Turn (SS-180° Turn Step/Time) test, Unified Parkinson’s Disease Rating Scale (UPDRS) part III, FOG Questionnaire (FOG-Q), motor evoked potential, Korean version of Montreal Cognitive Assessment (K-MOCA), Digit span-Forward/Back and Trail Making-A/B. Results There were significant improvements in TUG, SS-180° Turn Step, UPDRS part III and FOG-Q in both the dual-mode and the single stimulation group (p 0.05). The dual-mode stimulation also resulted in significant improvements in SS-180° Turn Time (p = 0.008), K-MOCA (p = 0.004), Digit span-Forward (p = 0.015) and Trail making-B test (p = 0.010), whereas single stimulation did not. Furthermore, improvement of Trail making-B test was significantly greater after the dual-mode stimulation than the single stimulation (p = 0.024). Conclusion The dual-mode stimulation using the 10 Hz rTMS over the dominant M1-LL and the anodal tDCS over the left DLPFC was more effective than single stimulation for improving FOG in combination with cognitive improvement in patients with PD.

P110 Transcranial direct current stimulation of the brain motor area generates a transient increase of small worldnessy in connectivity: An EEG graph theoretical analysis

Introduction Transcranial direct current stimulation (tDCS) is a non-invasive method modulating cortical excitability in a polarity-dependent way. At present, only few studies investigated the effects of tDCS on the modulation of functional connectivity between remote cortical areas. Objective In the present study we aimed to investigate the impact of bipolar tDCS on cortical networks connectivity through graph theoretical analysis. Materials & methods High-density EEG recordings were acquired before and after bipolar anodal, cathodal and sham tDCS applied over the primary motor cortex of the dominant hemisphere in 14 healthy subjects. Results Results showed that, after bipolar anodal tDCS stimulation over the dominant primary motor cortex the related brain network presented a more small-worldnessy, meaning a global tendency to be more random in its functional connections respect to prestimulus condition in both hemispheres. Conclusions Our results suggest that tDCS is able to modulate globally the cortical connectivity of the brain, modifying the underlying functional organization via complex pattern of direct and indirect cortical activations or inhibitions of the stimulated networks, which might be related to changes in synaptic efficiency of the motor network and related brain areas.

No Effect of Anodal Transcranial Direct Current Stimulation Over the Motor Cortex on Response-Related ERPs during a Conflict Task.

Anodal transcranial direct current stimulation (tDCS) over the motor cortex is considered a potential treatment for motor rehabilitation following stroke and other neurological pathologies. However, both the context under which this stimulation is effective and the underlying mechanisms remain to be determined. In this study, we examined the mechanisms by which anodal tDCS may affect motor performance by recording event-related potentials (ERPs) during a cued go/nogo task after anodal tDCS over dominant primary motor cortex (M1) in young adults (Experiment 1) and both dominant and non-dominant M1 in older adults (Experiment 2). In both experiments, anodal tDCS had no effect on either response time (RT) or response-related ERPs, including the cue-locked contingent negative variation (CNV) and both target-locked and response-locked lateralized readiness potentials (LRP). Bayesian model selection analyses showed that, for all measures, the null effects model was stronger than a model including anodal tDCS vs. sham. We conclude that anodal tDCS has no effect on RT or response-related ERPs during a cued go/nogo task in either young or older adults.

EP 137. The influence of age on hemispheric connectivity, a combined TMS and DTI study

Background Age effects both functional and structural brain function. Here, we combine two different methods to assess the impact of age on the neurophysiological and structural measurements of interhemispheric motor connectivity. We expect to find a clear association between both connectivity parameters and age. Methods 15 participants between 22 and 72 years (median 36 years) participated in this study. Ipsilateral silent period (ISP) was collected from both dominant and non-dominant first dorsal interosseus (FDI) muscle. Structural M1-M1 connectivity was calculated using probabilistic tractography (fMRI software library, FSL). Interhemispheric M1-M1 tract volume and mean fractional anisotropy (FA) of the tract were calculated between dominant and non-dominant M1 and vice versa. We tested associations between ISP depth, tract volume and FA and age by calculating Pearson correlations. Results ISP of the dominant hand correlated negatively with age (r = −0.54; p Discussion As expected, we found an association of age on the interhemispheric connectivity in both neurophysiological and structural MRI measurements. Interestingly, the effect was only present from the non-dominant to the dominant hemisphere, and not in the other direction. In addition, interhemispheric inhibition was associated with tract volume, but not with averaged FA values of the tract, and again, only in the direction from the non-dominant to the dominant hemisphere. Our findings indicate that the age-related changes in interhemispheric connectivity are different between the dominant and non dominant primary motor cortex. Furthermore, the data suggest that the age-related interhemispheric tract volume loss may be the underlying cause of the age-related decrease of interhemispheric inhibition.

Anodal tDCS over the Motor Cortex on Prepared and Unprepared Responses in Young Adults.

Anodal transcranial direct current stimulation (tDCS) over the primary motor cortex (M1) has been proposed as a possible therapeutic rehabilitation technique for motor impairment. However, despite extensive investigation into the effects of anodal tDCS on motor output, there is little information on how anodal tDCS affects response processes. In this study, we used a cued go/nogo task with both directional and non-directional cues to assess the effects of anodal tDCS over the dominant (left) primary motor cortex on prepared and unprepared motor responses. Three experiments explored whether the effectiveness of tDCS varied with timing between stimulation and test. Healthy, right-handed young adults participated in a double-blind randomised controlled design with crossover of anodal tDCS and sham stimulation. In Experiment 1, twenty-four healthy young adults received anodal tDCS over dominant M1 at least 40 mins before task performance. In Experiment 2, eight participants received anodal tDCS directly before task performance. In Experiment 3, twenty participants received anodal tDCS during task performance. In all three experiments, participants responded faster to directional compared to non-directional cues and with their right hand. However, anodal tDCS had no effect on go/nogo task performance at any stimulation – test interval. Bayesian analysis confirmed that anodal stimulation had no effect on response speed. We conclude that anodal tDCS over M1 does not improve response speed of prepared or unprepared responses of young adults in a go/nogo task.

Effect of 30 Hz theta burst transcranial magnetic stimulation on the primary motor cortex in children and adolescents.

Fourteen healthy children (13.8 ± 2.2 years, range 10–16; M:F = 5:9) received 30 Hz intermittent theta burst transcranial magnetic stimulation (iTBS) with a stimulation intensity of 70% of resting motor threshold (RMT) with a total of 300 (iTBS300) pulses. All volunteers were free of neurologic, psychiatric and serious medical illnesses, not taking any neuropsychiatric medications, and did not have any contraindications to transcranial magnetic stimulation. Changes in the mean amplitudes of motor-evoked potentials from baseline following iTBS were expressed as a ratio and assessed from 1 to 10 min (BLOCK1) and 1–30 min (BLOCK2) using repeated-measures analysis of variance. All 14 subjects completed iTBS300 over the dominant primary motor cortex (M1) without any clinically reported adverse events. ITBS300 produced significant M1 facilitation [F(5, 65) = 3.165, p = 0.01] at BLOCK1 and trend level M1 facilitation at BLOCK2 [F(10, 129) = 1.69, p = 0.089]. Although iTBS300 (stimulation duration of 92 s at 70% RMT) delivered over M1 in typically developed children was well-tolerated and produced on average significant facilitatory changes in cortical excitability, the post-iTBS300 neurophysiologic response was variable in our small sample. ITBS300-induced changes may represent a potential neuroplastic biomarker in healthy children and those with neuro-genetic or neuro-psychiatric disorders. However, a larger sample size is needed to address safety and concerns of response variability.

116. Functional connectivity between cortical speech network and primary motor cortex is abnormal in spasmodic dysphonia

In healthy humans, the execution of linguistic tasks modifies the excitability of the hand area of the dominant primary motor cortex (M1), as tested by TMS. Our aim was to investigate the effect of linguistic tasks on the excitability of the M1 in patients with adductor type-spasmodic dysphonia (ASD), before and after Botulinum Neurotoxin Type A (BoNT-A) injections. We studied 10 patients with ASD and 10 age-matched healthy subjects. All participants were right handed. The excitability of either M1 hand area was evaluated at the baseline and during different linguistic and non-linguistic tasks: (1) reading aloud of single words; (2) silent reading; (3) looking at meaningless non-letter strings; (4) oral movements without vocalization; (5) producing simple syllabic phonation. In healthy controls, the motor evoked potential (MEP) elicited by TMS of the dominant M1 were significantly larger during reading aloud. In ASD patients, MEP enhancement in the dominant hand emerged not only during reading aloud but also during syllabic phonation. BoNT-A injections restored the neurophysiologic abnormalities. We conclude that ASD is characterized by an abnormal excitability of the hand area of the dominant M1 during specific linguistic tasks. This likely reflects an altered functional connectivity between cortical speech network and M1.