Pre-movement Period Research Articles

Simulated fire video collection for advancing understanding of human behavior in building fires.

The goal of the present research was to develop a video collection of simulated fires to investigate how people perceive growing building fires. In fire safety science, a critical factor to occupant responses to building fires is the pre-movement period, determined by how long it takes an individual to initiate taking protective action with an incipient fire. Key to studying the psychological processes that contribute to the duration of the pre-movement period is presenting human subjects with building fires. One approach used in previous research is to present videos of building fires to individuals via scenarios. The numerical simulations used to model fire dynamics can be used to render videos for these scenarios. However, such simulations have predominantly been used in fire protection engineering to design buildings and are relatively inaccessible to social scientists. The present study documents a collection of videos, based on numerical simulations, which can be used by researchers to study human behavior in fire. These videos display developing fires in different types of rooms, growing at different rates, different smoke thickness, among other characteristics. As part of a validation study, participants were presented with subsets of the video clips and were asked to rate the perceived risk posed by the simulated fire. We observed that ratings varied by the intensity and growth rate of the fires, smoke opacity, type of room, and where the viewpoint was located from the fire. These effects aligned with those observed in previous fire science research, providing evidence that the videos could elicit perceived risk using fire simulations. The present research indicates that future studies can utilize the video library of fire simulations to study human perceptions of developing building fires as situational factors are systematically manipulated.

Competition, Conflict and Change of Mind: A Role of GABAergic Inhibition in the Primary Motor Cortex.

Deciding between different voluntary movements implies a continuous control of the competition between potential actions. Many theories postulate a leading role of prefrontal cortices in this executive function, but strong evidence exists that a motor region like the primary motor cortex (M1) is also involved, possibly via inhibitory mechanisms. This was already shown during the pre-movement decision period, but not after movement onset. For this pilot experiment we designed a new task compatible with the dynamics of post-onset control to study the silent period (SP) duration, a pause in electromyographic activity after single-pulse transcranial magnetic stimulation that reflects inhibitory mechanisms. A careful analysis of the SP during the ongoing movement indicates a gradual increase in inhibitory mechanisms with the level of competition, consistent with an increase in mutual inhibition between alternative movement options. However, we also observed a decreased SP duration for high-competition trials associated with change-of-mind inflections in their trajectories. Our results suggest a new post-onset adaptive process that consists in a transient reduction of GABAergic inhibition within M1 for highly conflicting situations. We propose that this reduced inhibition softens the competition between concurrent motor options, thereby favoring response vacillation, an adaptive strategy that proved successful at improving behavioral performance.

Decoding Saccade Intention From Primate Prefrontal Cortical Local Field Potentials Using Spectral, Spatial, and Temporal Dimensionality Reduction.

Most invasive Brain Computer Interfaces (iBCIs) use spike and Local Field Potentials (LFPs) from the motor or parietal cortices to decode movement intentions. It has been debated whether harvesting signals from other brain areas that encode global cognitive variables, such as the allocation of attention and eye movement goals in a variety of spatial reference frames, may improve the outcome of iBCIs. Here, we explore the ability of LFP signals, sampled from the lateral prefrontal cortex (LPFC) of macaque monkeys, to encode eye-movement intention during the pre-movement fixation period of a delayed saccade task. We use spectral dimensionality reduction to examine the spatiotemporal properties of the extracted non-rhythmic broadband activity and explore its usefulness in decoding saccade goals. The dynamics of the broadband signal in low spatial dimensions across the pre-movement fixation period uncovered saccade target separation; its discriminative potential was confirmed using support vector machine classifications. These findings reveal that broadband LFP from the LPFC can be used to decode intended saccade target location during pre-movement periods. We further provide a general workflow that can be implemented in iBCIs and it is relatively robust to the loss of spikes in individual electrodes.

Altered Pallidocortical Low-Beta Oscillations During Self-Initiated Movements in Parkinson Disease.

BackgroundParkinson disease (PD) patients have difficulty with self-initiated (SI) movements, presumably related to basal ganglia thalamocortical (BGTC) circuit dysfunction, while showing less impairment with externally cued (EC) movements.ObjectivesWe investigate the role of BGTC in movement initiation and the neural underpinning of impaired SI compared to EC movements in PD using multifocal intracranial recordings and correlating signals with symptom severity.MethodsWe compared time-resolved neural activities within and between globus pallidus internus (GPi) and motor cortex during between SI and EC movements recorded invasively in 13 PD patients undergoing deep brain stimulation implantation. We compared cortical (but not subcortical) dynamics with those recorded in 10 essential tremor (ET) patients, who do not have impairments in movement initiation.ResultsSI movements in PD are associated with greater low-beta (13–20 Hz) power suppression during pre-movement period in GPi and motor cortex compared to EC movements in PD and compared to SI movements in ET (motor cortex only). SI movements in PD are uniquely associated with significant low-beta pallidocortical coherence suppression during movement execution that correlates with bradykinesia severity. In ET, motor cortex neural dynamics during EC movements do not significantly differ from that observed in PD and do not significantly differ between SI and EC movements.ConclusionThese findings implicate low beta BGTC oscillations in impaired SI movements in PD. These results provide a physiological basis for the strategy of using EC movements in PD, circumventing diseased neural circuits associated with SI movements and instead engaging circuits that function similarly to those without PD.

BCI-based sensorimotor rhythm training can affect individuated finger movements

ABSTRACT Brain-computer interface (BCI) technology can restore communication and control to people who are severely paralyzed. BCI technology might also be able to enhance rehabilitation of motor function. We have previously shown that pre-movement sensorimotor rhythm (SMR) amplitude affects reaction time and performance on a joystick-based cursor movement task. The present study explores in adults without motor impairment the possibility that pre-movement SMR amplitude affects performance of individuated finger movements. In Phase 1, 8 individuals performed a finger flexion task that was monitored by an exoskeleton. During a 1-sec preparatory period, two colored targets on a video monitor cued flexion of the index finger, middle finger, both fingers, or neither finger; sudden color change then triggered the movement (or non-movement). SMR features (i.e. EEG amplitudes in specific frequency bands at specific scalp locations) in the pre-movement EEG that correlated with movement versus no movement were identified. In Phase 2, the participants learned to increase or decrease these SMR features to control a two-target BCI task. Finally, in Phase 3, they were asked to increase or decrease the SMR features to initiate the finger flexion task of Phase 1 and the impact on finger flexion performance was assessed. After BCI training, pre-movement SMR feature amplitude affected performance in a subset of individuals: lower amplitude was associated with shorter movement onset. In a subset of individuals, the beneficial effect on performance of lower SMR amplitude was greater when both fingers were flexed than when one was flexed and the other remained extended; thus, the impact of SMR amplitude modulation depended on the specificity of the subsequent motor task. These results indicate that BCI-based training of SMR activity in the pre-movement preparatory period can affect finger movements in a subset of individuals. They encourage studies that integrate such training into rehabilitation protocols and examine its capacity to enhance restoration of useful hand function.

551-P: The Impact of Type 1 Diabetes on Motor Dynamics in the Brain

Type 1 diabetes affects the structure and function of the brain, with psychomotor speed as the most commonly reported deficit. The current study sought to uncover the dynamics underlying motor processing in the brain of adults with type 1 diabetes using an arrow-based Flanker task. Adults (ages 19-35, N = 39) with type 1 diabetes and no major complications and a matched control group (N = 40) underwent magnetoencephalography (MEG) while performing the task. During the task, participants were presented with a row of five arrows facing right or left, and participants were instructed to respond by button press to the direction of the middle arrow. Analyses focused on the time period around movement execution to examine motor-related dynamics. Time series analyses were performed on the peak beta and gamma responses from the motor cortices. An ANOVA model and follow-up regression analyses were used to delineate the predictive value of each neural response in driving behavioral outcomes. Subsequent t-tests between frequent (3+ episodes per week) and infrequent (0-1 episodes per week) hypoglycemic groups were performed to examine response differences within the adults with type 1 diabetes. Responses driving behavior differed between adults with and without type 1 diabetes. In adults with type 1 diabetes, beta frequency responses were significant predictors of reaction time, where greater ipsilateral recruitment led to faster reaction times (b = .58, t = 3.64, p = .001). In contrast, gamma drove behavioral outcomes in the control group (b = -.43, t = -2.96, p = .005). Further, within group analyses revealed that more frequent episodes of hypoglycemia were associated with alterations specific to beta responses during the pre-movement baseline period (p < .05). These results show frequency specific alterations in motor dynamics in adults with type 1 diabetes, with an added effect of increased hypoglycemia. These findings strongly indicate that diabetes directly impacts motor control components in the brain, regulating behavioral outcomes. Disclosure C.M. Embury: None. V.A. Were: None. G.H. Lord: None. A. Drincic: Board Member; Self; Corcept Therapeutics. C. Desouza: Consultant; Self; Novo Nordisk A/S, Sanofi US. T.W. Wilson: None. Funding National Institutes of Health (R01MH103220, R01MH116782)

T123. Amplitudes of motor evoked potentials are modulated by preceding a band oscillations: A closed-loop EEG-TMS study

Introduction The amplitudes of MEPs in the resting state are considerably variable in each TMS. This variability of MEP amplitudes may reflect the fluctuation of the excitability of the primary motor cortex (M1). The neural substrates of determining MEP amplitudes for each TMS are still under the debate. There have been a few reports that deals with the relationship between MEP amplitudes and EEG oscillations in the offline analysis (e.g. Maki and Ilmoniemi, 2010). However, an attempt to explore the link between M1 and neural oscillations by a closed-loop EEG-MEP system is scarce. We have developed the closed-loop system and examined the relationship between EEG oscillations and MEP amplitudes. Methods Eighteen healthy adults (21–47 y.o, M:F = 15:3) participated in this study. EEGs were recorded at C3 with four surrounding electrodes, referred to the linked earlobe. Then, EEG signals at the C3 electrode were remontaged by source derivation and Fourier analyzed in the online to obtain EEG power of α or β band. The individual peak frequency of each band was determined in each subject before the MEP sessions using EEGs for about one minute in the resting state. When the online EEG power during MEP sessions reached the predefined threshold of high or low EEG power, a TMS pulse was delivered to record MEPs. About 50 MEPs were obtained for each of high/low power conditions. After recording MEPs, the MEP amplitudes of the high EEG power were compared with those of low power. The analyses were conducted for each of α and β band, respectively. Results MEPs were successfully recorded by the closed-loop system using EEG at C3. MEP amplitudes of the high EEG power condition were significantly higher than those of the low power condition in the α band. On the contrary, MEP amplitudes of the closed-loop by the β band were not significantly different between the conditions of high EEG power and that of low power. Conclusion We demonstrated that the high EEG power in α band resulted in higher MEP amplitudes compared with those of the low power by the customized closed-loop EEG-TMS system. Thus, the higher α power at C3 can be indicative of the higher M1 excitability. Event-related desynchronization is often reported that α or β power decreases before the hand movement (Stancak and Pfurtscheller, 1995). However, this experiment was conducted under the resting state. Therefore, the mechanism that modulates M1 excitability may be different from that of the premovement period. The α power around the central region is reported to originate from the primary sensory cortex (S1) while β power from M1 (Salmelin et al., 1995). It is also well known that M1 and S1 are tightly linked and modulate excitability between each other. Therefore, S1 oscillations may play a more important role to determine M1 excitability through M1-S1 connectivity.

Movement-Related Sensorimotor High-Gamma Activity Mainly Represents Somatosensory Feedback.

Somatosensation plays pivotal roles in the everyday motor control of humans. During active movement, there exists a prominent high-gamma (HG >50 Hz) power increase in the primary somatosensory cortex (S1), and this provides an important feature in relation to the decoding of movement in a brain-machine interface (BMI). However, one concern of BMI researchers is the inflation of the decoding performance due to the activation of somatosensory feedback, which is not elicited in patients who have lost their sensorimotor function. In fact, it is unclear as to how much the HG component activated in S1 contributes to the overall sensorimotor HG power during voluntary movement. With regard to other functional roles of HG in S1, recent findings have reported that these HG power levels increase before the onset of actual movement, which implies neural activation for top-down movement preparation or sensorimotor interaction, i.e., an efference copy. These results are promising for BMI applications but remain inconclusive. Here, we found using electrocorticography (ECoG) from eight patients that HG activation in S1 is stronger and more informative than it is in the primary motor cortex (M1) regardless of the type of movement. We also demonstrate by means of electromyography (EMG) that the onset timing of the HG power in S1 is later (49 ms) than that of the actual movement. Interestingly, we show that the HG power fluctuations in S1 are closely related to subtle muscle contractions, even during the pre-movement period. These results suggest the following: (1) movement-related HG activity in S1 strongly affects the overall sensorimotor HG power, and (2) HG activity in S1 during voluntary movement mainly represents cortical neural processing for somatosensory feedback.

Demand on skillfulness modulates interhemispheric inhibition of motor cortices.

The role of primary motor cortex (M1) in the control of hand movements is still unclear. Functional magnetic resonance imaging (fMRI) studies of unimanual performance reported a relationship between level of precision of a motor task and additional ipsilateral M1 (iM1) activation. In the present study, we determined whether the demand on accuracy of a movement influences the magnitude of the inhibitory effect between primary motor cortices (IHI). We used transcranial magnetic stimulation (TMS) to measure active IHI (aIHI) of the iM1 on the contralateral M1 (cM1) in the premovement period of a left-hand motor task. Ten healthy participants manipulated a joystick to point to targets of two different sizes. For aIHI, the conditioning stimulus (CS) was applied to iM1, and the test stimulus (TS) to cM1, with an interstimulus interval of 10 ms. The amount of the inhibitory effect of the CS on the motor-evoked potential (MEP) of the subsequent TS was expressed as percentage of the mean MEP amplitude evoked by the single TS. Across different time points of aIHI measurements in the premovement period, there was a significant effect for target size on aIHI. Preparing to point to small targets was associated with weaker aIHI compared with pointing to large targets. The present findings suggest that, during the premovement period, aIHI from iM1 on cM1 is modulated by the demand on accuracy of the motor task. This is consistent with task fMRI findings showing bilateral M1 activation during high-precision movements but only unilateral M1 activity during low-precision movements.

Timing of Cortical Events Preceding Voluntary Movement.

We studied magnetic signals from the human brain recorded during a second before a self-paced finger movement. Sharp triangular peaks were observed in the averaged signals about 0.7 second before the finger movement. The amplitude of the peaks varied considerably from trial to trial, which indicated that the peaks were concurrent with much longer oscillatory processes. One can cluster trials into distinct groups with characteristic sequences of events. Prominent short trains of pulses in the beta frequency band were identified in the premovement period. This observation suggests that during preparation of the intended movement, cortical activity is well organized in time but differs from trial to trial. Magnetoencephalography can capture these processes with high temporal resolution and allows their study in fine detail.

Large-Scale Synchronization Related to Structures Manifesting Simultaneous EEG Baseline Shifts in the Pre-Movement Period

Abstract Several current data indicate that intracranial records of the Bereitschaftspotential from some brain loci manifest baseline shifts (EBS) in the early pre-movement period that are separated from the movement components by a distinct plateau. In this context, main purpose of this study was to assess whether structures generating the EBSs that are simultaneously widespread in various structures of the brain will be specifically linked to higher levels of large-scale integration in comparison to structures that were not involved in EBS generation. In this study were included 21 epilepsy surgery candidates (12 men, 9 women; aged from 18 to 49 years), who were measured during self-paced clenching movements of the hand. Brain activities during the task were recorded using intracerebral electrodes and were evaluated in pairs. Eighty two percent of the EBSs started in various distant brain structures at the same time, eighteen percent at different time. Approximately half of the EBSs of the first group started in the prefrontal regions; the second half was obtained from pairs located in parietal and temporal regions. The first, the second, and the third groups exhibited a special degree of activity synchronization. The simultaneous EBS onsets associated synchronization strongly suggests significantly higher functional coupling of these brain areas which is supposed to be a basic mechanism of integration of various areas of the brain participating in cognitive and intentional functions.

Local and remote effects of transcranial direct current stimulation on the electrical activity of the motor cortical network

We systematically investigated the effects of cathodal and anodal Transcranial Direct Current Stimulation (CtDCS, AtDCS) on the electric activity of primary motor cortex during a motor task. High-density electroencephalography was used to define the spatial diffusion of tDCS after effects. Ten healthy subjects performed a finger tapping task with the right hand before and after three separate sessions of 20 minutes of Sham, AtDCS or CtDCS over left primary motor cortex (M1). During movement, we found an increment of low alpha band Event-Related Desynchronization (ERD) in bilateral central, frontal areas and in the left inferior parietal region, as well as an increment of beta ERD in fronto-central and parieto-occipital regions, after AtDCs compared to Sham and CtDCS. In the rest pre-movement period, after Sham as well as AtDCS, we documented an increment of low alpha band power over the course of pre- and post-stimulation recording sessions, localized in the sensorimotor and parieto-occipital regions. On the contrary, after CtDCS no increment of low alpha power was found. Finally beta band coherence among signals from left sensorimotor cortex and activity of bilateral parietal, occipital and right frontal regions was higher after AtDCS compared with Sham condition. Similarly, theta coherence with parietal and frontal regions was enhanced after AtDCS. We hypothesize that the local modulation of membrane polarization, as well as long-lasting synaptic modification induced by tDCS over M1, could result in changes of both local band power and functional architecture of the motor network.

Understanding cortical networks involved in the preparation of voluntary movement using simultaneous EEG-fMRI

Event Abstract Back to Event Understanding cortical networks involved in the preparation of voluntary movement using simultaneous EEG-fMRI Vinh T. Nguyen1*, Michael Breakspear2, 3, 4, 5 and Ross Cunnington1, 6 1 The University of Queensland, Queensland Brain Institute, Australia 2 Queensland Institute of Medical Research, Australia 3 University of New South Wales, School of Psychiatry, Australia 4 The Black Dog Institute, Australia 5 The Royal Brisbane and Womans Hospital, Australia 6 The University of Queensland, School of Psychology, Australia Background The cortical correlates of voluntary actions precede movement by at least 1-2 seconds. This sustained activity is reflected in the widely studied readiness potential (RP), which provides insight into the brain processes underlying the preparation of actions. Key contributing regions have been identified, including the middle cingulate cortex (MCC) and the supplementary motor area (SMA), but the relationship of activity within and between these regions to the RP is not understood. We sought to examine this relationship by integrating simultaneously acquired EEG and fMRI through computational modelling. Method We acquired simultaneous EEG and fMRI data from 20 healthy participants as they performed a simple task of voluntary, self-paced finger movements made every 10–15 seconds. We applied an EEG-informed fMRI analysis to examine trial-by-trial correlation between BOLD signals and neural responses reflected in the RP and global field power (GFP) activity preceding movements. We then used dynamic causal modelling (DCM) to examine interactions between the network of SMA and MCC during the preparation and performance of actions. DCM models were therefore informed by movement events as well as contextual modulators derived from EEG activity. The latter accounts for the correlation shown by the EEG-informed fMRI analysis. Bayesian model selection with a random-effects analysis was employed to select the most likely model of cortical interactions for our data. Results and Discussion The EEG-informed fMRI analysis revealed a positive correlation between GFP over the period from 750 ms to 400 ms prior to movement and BOLD responses in MCC. Specifically, trials in which neural activity in the GFP was greater over this premovement period also involved greater activation of the MCC. The best fitting model to infer the interactions between MCC and SMA comprised the GFP regulating the self-feedback connection of MCC to itself, and MCC activity regulating the self-feedback connection of SMA. This result suggests that the MCC modulates its own activity, and this modulation is strongest on trials with greater premovement GFP activity. Together, our study suggests that the internal modulation of MCC is essential to sustain premovement activity over time, and drives SMA activity in preparation for actions. Keywords: voluntary movements, simultaneous EEG-fMRI, multimodal neuroimaging, readiness potential, dynamic causal modeling, middle cingulate cortex Conference: ACNS-2013 Australasian Cognitive Neuroscience Society Conference, Clayton, Melbourne, Australia, 28 Nov - 1 Dec, 2013. Presentation Type: Oral Topic: Motor Citation: Nguyen VT, Breakspear M and Cunnington R (2013). Understanding cortical networks involved in the preparation of voluntary movement using simultaneous EEG-fMRI. Conference Abstract: ACNS-2013 Australasian Cognitive Neuroscience Society Conference. doi: 10.3389/conf.fnhum.2013.212.00183 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 15 Oct 2013; Published Online: 25 Nov 2013. * Correspondence: Mr. Vinh T Nguyen, The University of Queensland, Queensland Brain Institute, Brisbane, QLD, Australia, vinh.nguyen@uq.edu.au Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Vinh T Nguyen Michael Breakspear Ross Cunnington Google Vinh T Nguyen Michael Breakspear Ross Cunnington Google Scholar Vinh T Nguyen Michael Breakspear Ross Cunnington PubMed Vinh T Nguyen Michael Breakspear Ross Cunnington Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Sex-related differences in the hemispheric laterality of slow cortical potentials during the preparation of visually guided movements

Previous work suggests the presence of sex differences in the laterality of brain activity in the premotor-parietal network during the preparation of visually guided reaching movements. In the current study, electroencephalography was used to test the hypothesis that women would have higher amplitude potentials over frontal and parietal regions ipsilateral to arm movements, relative to men. Event-related slow cortical potentials (SCPs) were collected from 30 participants (15 men and 15 women) during the performance of two visually guided reaching conditions (eyes and arm moved to the same spatial location or moved in opposite directions). The results of the study demonstrate that the amplitudes of SCPs were significantly higher overlying frontal regions of the right hemisphere of women relative to men. These differences were present both during an instructed-delay period prior to receiving a go-signal to initiate movement and during the period just prior to movement initiation. The study also revealed an interaction of Sex and Condition in the parietal region during the pre-movement period. These results suggest that motor preparatory activity in men mainly occurs in the hemisphere contralateral to reaching but that preparatory activity in women is distributed relatively more bilaterally. However, the nature of these differences changes over the time course of the preparatory period and is partially dependent on the type of visuomotor mapping being performed.

Pre-movement gating of somatosensory-evoked potentials by self-initiated movements: The effects of ageing and its implication

To study whether the gating effect of the self-initiated movements on the cortical somatosensory-evoked potentials (SEPs) is affected by ageing. The SEPs elicited by stimulating the right median nerve were recorded in 14 young and 16 older healthy subjects, while self-initiated movements of the right fingers were performed at 5-10 s intervals. The amplitudes of the major components of the SEPs at F3 and C3' (2 cm posterior to C3) during the pre-movement period were analysed as the resting condition subserving the baseline. The amplitudes at rest were significantly greater in the elderly than in the younger subjects. The amplitudes of P27, N35 and P45 at C3' as well as N30 at F3 decreased significantly during the pre-movement period. However, the ratio of amplitudes in the pre-movement period to the resting period in the elderly was not significantly different from that in the younger subjects, except for the interaction of N30. The effect of age on the gating of N30 at F3 may indicate an altered preparatory processing of self-initiated movement in the elderly. The gating effect of older subjects at C3' is almost comparable to that of young ones, which appears to be a compensatory mechanism to maintain the precise movements. Ageing affects the SEPs differently at rest and pre-movement gating.

Golf putt outcomes are predicted by sensorimotor cerebral EEG rhythms

It is not known whether frontal cerebral rhythms of the two hemispheres are implicated in fine motor control and balance. To address this issue, electroencephalographic (EEG) and stabilometric recordings were simultaneously performed in 12 right-handed expert golfers. The subjects were asked to stand upright on a stabilometric force platform placed at a golf green simulator while playing about 100 golf putts. Balance during the putts was indexed by body sway area. Cortical activity was indexed by the power reduction in spatially enhanced alpha (8-12 Hz) and beta (13-30 Hz) rhythms during movement, referred to as the pre-movement period. It was found that the body sway area displayed similar values in the successful and unsuccessful putts. In contrast, the high-frequency alpha power (about 10-12 Hz) was smaller in amplitude in the successful than in the unsuccessful putts over the frontal midline and the arm and hand region of the right primary sensorimotor area; the stronger the reduction of the alpha power, the smaller the error of the unsuccessful putts (i.e. distance from the hole). These results indicate that high-frequency alpha rhythms over associative, premotor and non-dominant primary sensorimotor areas subserve motor control and are predictive of the golfer's performance.

Intermanual Differences in Movement-related Interhemispheric Inhibition

Interhemispheric inhibition (IHI) between motor cortical areas is thought to play a critical role in motor control and could influence manual dexterity. The purpose of this study was to investigate IHI preceding movements of the dominant and nondominant hands of healthy volunteers. Movement-related IHI was studied by means of a double-pulse transcranial magnetic stimulation protocol in right-handed individuals in a simple reaction time paradigm. IHI targeting the motor cortex contralateral (IHI(c)) and ipsilateral (IHI(i)) to each moving finger was determined. IHI(c) was comparable after the go signal, a long time preceding movement onset, in both hands. Closer to movement onset, IHI(c) reversed into facilitation for the right dominant hand but remained inhibitory for left nondominant hand movements. IHI(i) displayed a nearly constant inhibition with a trough early in the premovement period in both hands. In conclusion, our results unveil a more important modulation of interhemispheric interactions during generation of dominant than nondominant hand movements. This modulation essentially consisted of a shift from a balanced IHI at rest to an IHI predominantly directed toward the ipsilateral primary motor cortex at movement onset. Such a mechanism might release muscles from inhibition in the contralateral primary motor cortex while preventing the occurrence of the mirror activity in ipsilateral primary motor cortex and could therefore contribute to intermanual differences in dexterity.

How does the brain respond to unimodal and bimodal sensory demand in movement of the lower extremity?

Numerous electroencephalography (EEG) studies have shown that neurophysiological signals change in response to visual and sensory adaptations in upper extremity tasks. However, this has not been clearly studied in the lower extremity. In this study, we evaluated how sensory loading affects brain activations related to knee movement. Thirty-two channel EEG was recorded while ten subjects performed knee extension in four different conditions: no weight and no visual target (NWNT), weight affixed to the ankle and no visual target (WNT), no weight and a visual target (NWT), and both weight and target (WT). Surface electromyography (EMG) was recorded from the vastus medialis and vastus lateralis muscles to determine onset of the movement. EEG was epoched from -4.5 s before to 1 s after EMG onset. Epochs were averaged to acquire movement-related cortical potentials (MRCPs) of each task condition. MRCP amplitude during the pre-movement period from -2 s to EMG onset was evaluated at electrodes over motor, sensory, frontal, and parietal areas. The amplitude of the pre-movement potentials for the conditions was different across areas of interest. Over the motor area, NWNT had lower amplitude than any other condition and WT had higher amplitude than any other condition. There was no difference between unimodal NWT and WNT conditions. Mesial frontal and parietal areas showed larger MRCP to the bimodal condition than either unimodal or NWNT conditions. The parietal cortex was the only region that showed a difference between unimodal conditions with greater amplitude for NWT condition. Information concerning added sensory demand is processed by the motor cortex in a way that may be indifferent to the type of modality, but is influenced by the quantity of modalities at the level of the knee. Other brain structures such as parietal and premotor cortices respond based on the modality type to help plan appropriate strategies for motor control in response to sensory manipulations. This suggests that additional task demands in motor training may create a rich sensory environment that may be beneficial in promoting optimal neuromotor recovery.

Disinhibition of upper limb motor area by voluntary contraction of the lower limb muscle

It is well known that monosynaptic spinal reflexes and motor evoked potentials following transcranial magnetic stimulation (TMS) are reinforced during phasic and intensive voluntary contraction in the remote segment (remote effect). However, the remote effect on the cortical silent period (CSP) is less known. The purpose of the present study is to determine to what extent the CSP in the intrinsic hand muscle following TMS is modified by voluntary ankle dorsiflexion and to elucidate the origin of the modulation of CSP by the remote effect. CSP was recorded in the right first dorsal interosseous while subjects performed phasic dorsiflexion in the ipsilateral side under self-paced and reaction-time conditions. Modulation of the peripherally-induced silent period (PSP) induced by electrical stimulation of the ulnar nerve was also investigated under the same conditions. In addition, modulation of the CSP was investigated during ischemic nerve block of the lower limb and during application of vibration to the tibialis anterior tendon. The duration of CSP was significantly shortened by phasic dorsiflexion, and the extent of shortening was proportional to dorsiflexion force. Shortening of the CSP duration was also observed during tonic dorsiflexion. In contrast, the PSP duration following ulnar nerve stimulation was not altered during phasic dorsiflexion. Furthermore, the remote effect on the CSP duration was seen during ischemic nerve block of the lower limb and the pre-movement period in the reaction-time paradigm, but shortening of the CSP was not observed during tendon vibration. These findings suggest that phasic muscle contraction in the remote segment results in a decrease in intracortical inhibitory pathways to the corticospinal tract innervating the muscle involved in reflex testing and that the remote effect on the CSP is predominantly cortical in origin.

Motor cortex excitability changes preceding voluntary muscle activity in simple reaction time task

The effect of transcranial magnetic stimulation (TMS) on reaction time (RT) and motor cortex excitability in the premovement period was investigated. Single and paired-pulse TMS with 3 and 13 ms interstimulus intervals (ISI) were applied to the left motor cortex at different delays after a visual command for isometric right hand index finger abduction. Motor evoked potentials (MEPs) recorded from the right first dorsal interosseous (FDI) were analysed to assess cortex excitability. The MEPs in response to single pulse TMS were gradually increased in the premovement period in general, but strongly augmented in a period of 90-100 ms before the voluntary myoelectrical activity (EMG) onset. In paired-pulse TMS (13 ms ISI), the MEP augmentation was smaller but started earlier before the EMG burst, and a gradual increase of MEP amplitudes was not evident. In case of 3 ms ISI, the expected intracortical inhibition (ICI) was evident only when TMS preceded the voluntary EMG by an interval of more than 60 ms, but at shorter intervals, rather some MEP augmentation was observed. Generally, the augmentation of MEPs in the premovement period was more pronounced in single pulse TMS. Most strikingly, a dead band period without MEP occurrences was observed within an interval of 30-50 ms before the voluntary EMG. In conclusion, parallel action of intracortical facilitation (ICF) and ICI as well as different dynamic behaviour of ICF and pre movement facilitation may explain the earlier mentioned effects. Moreover, this leads to an extended description of the rather subtle TMS influence on RT.