Active Threshold Research Articles

Corticospinal activity during a single-leg stance in people with chronic ankle instability

PurposeThe aim of the study was to determine whether corticospinal excitability and inhibition of the tibialis anterior during single-leg standing differs among individuals with chronic ankle instability (CAI), lateral ankle sprain copers, and healthy controls. MethodsTwenty-three participants with CAI, 23 lateral ankle sprain copers, and 24 healthy control participants volunteered. Active motor threshold (AMT), normalized motor-evoked potential (MEP), and cortical silent period (CSP) were evaluated by transcranial magnetic stimulation while participants performed a single-leg standing task. ResultsParticipants with CAI had significantly longer CSP at 100% of AMT and lower normalized MEP at 120% of AMT compared to lateral ankle sprain copers (CSP100%: p = 0.003; MEP120%: p = 0.044) and controls (CSP100%: p = 0.041; MEP120%: p = 0.006). ConclusionThis investigation demonstrate altered corticospinal excitability and inhibition of the tibialis anterior during single-leg standing in participants with CAI. Further research is needed to examine the effects of corticospinal maladaptations to motor control of the tibial anterior on postural control performance in those with CAI.

Preoperative pain neuroscience education for shoulder surgery: A case series.

BackgroundCentral sensitisation, in addition to high levels of fear-avoidance and pain catastrophisation may exist in a subgroup of patients with shoulder pain. Pain neuroscience education (PNE) has been shown to positively influence sensitivity of the nervous system, as well as reduce fear and catastrophisation prior to lumbar and total knee surgery. To date, no study has examined the application of PNE prior to shoulder surgery.ObjectivesThis study examined the response to preoperative PNE in patients preparing for shoulder surgery.MethodAn exploratory pre–post case series was conducted. Twelve patients scheduled for surgery completed various pre-education measurements including shoulder pain, fear-avoidance, pain catastrophisation, beliefs and expectations regarding surgery, active shoulder flexion and pressure pain thresholds for the involved and uninvolved shoulder and the dominant-sided knee. Patients underwent a standard 30-min, one-on-one PNE session with a physiotherapist prior to surgery.ResultsFollowing education, all measures improved with some failing to reach significance: self-reported pain (p = 0.125), pain catastrophisation (p = 0.250) and pain pressure threshold of the uninvolved shoulder (p = 0.68) and knee (p = 0.097). Fear-avoidance (p = 0.013), active shoulder flexion (p = 0.013) and pain pressure threshold for the involved shoulder (p = 0.004) significantly improved.ConclusionA small patient group improved beyond minimal detectable change and/or minimal clinical important difference after education. No significant shifts of the preoperative beliefs occurred after education.Clinical implicationsPreoperative PNE may be beneficial to a subgroup of patients scheduled for shoulder surgery.

Low-intensity repetitive paired associative stimulation targeting the motor hand area at theta frequency causes a lasting reduction in corticospinal excitability

ObjectiveSub-motor threshold 5 Hz repetitive paired associative stimulation (5 Hz-rPAS25ms) produces a long-lasting increase in corticospinal excitability. Assuming a spike-timing dependent plasticity-like (STDP-like) mechanism, we hypothesized that 5 Hz-rPAS at a shorter inter-stimulus interval (ISI) of 15 ms (5 Hz-rPAS15ms) would exert a lasting inhibitory effect on corticospinal excitability. Methods20 healthy volunteers received two minutes of 5 Hz-rPAS15ms. Transcranial magnetic stimulation (TMS) was applied over the motor hotspot of the right abductor pollicis brevis muscle at 90% active motor threshold. Sub-motor threshold peripheral electrical stimulation was given to the left median nerve 15 ms before each TMS pulse. We assessed changes in mean amplitude of the unconditioned motor evoked potential (MEP), short-latency intracortical inhibition (SICI), intracortical facilitation (ICF), short-latency afferent inhibition (SAI), long-latency afferent inhibition (LAI), and cortical silent period (CSP) before and for 60 minutes after 5-Hz rPAS15ms. ResultsSubthreshold 5-Hz rPAS15ms produced a 20–40% decrease in mean MEP amplitude along with an attenuation in SAI, lasting at least 60 minutes. A follow-up experiment revealed that MEP facilitation was spatially restricted to the target muscle. ConclusionsSubthreshold 5-Hz rPAS15ms effectively suppresses corticospinal excitability. Together with the facilitatory effects of subthreshold 5-Hz rPAS25ms (Quartarone et al., J Physiol 2006;575:657–670), the results show that sub-motor threshold 5-Hz rPAS induces STDP-like bidirectional plasticity in the motor cortex. SignificanceThe results of the present study provide a new short-time paradigm of long term depression (LTD) induction in human sensory-motor cortex.

A time-efficient method to determine parameters for measurement of short-interval intracortical inhibition for quadriceps.

Short-interval intracortical inhibition (SICI) is often assessed to investigate inhibitory responses in the primary motor cortex representation of the quadriceps. However, determining appropriate paired-pulse transcranial magnetic stimulation (TMS) parameters to optimise SICI measurement can be impractical and time-consuming. This study investigated the intensity required to elicit maximal and 50% of maximum inhibition, and the test-retest reliability of a time-efficient approach for SICI measurement in quadriceps. Nine men and six women (26.6±4.4years) underwent single and paired-pulse (3-ms interval) TMS during 10% maximal voluntary isometric contraction on two days. Responses were recorded from vastus lateralis (VL), rectus femoris (RF) and vastus medialis (VM). Test stimulus intensity was 140% of active motor threshold (AMT), and conditioning stimulus intensities (CSIs) ranged from 55% to 90% (eight intensities) of AMT (five test and five paired responses for each intensity). With CSI of 55% AMT, SICI was minimal (conditioned:test motor evoked potential [MEP]; 1.00, 0.96 and 0.95 for VL, RF and VM, respectively, <1.00 indicates inhibition). Inhibition was greater at 70%-90% AMT for VL (0.67-0.85), at 75%-90% AMT for RF (0.70-0.78) and at 80%-90% AMT for VM (0.59-0.68) when compared to 55% AMT. The CSIs that elicited maximal and 50% maximal inhibition were ~84% and ~75% AMT, respectively. Reliability for individual CSIs ranged from "poor-to-good" for all muscles. SICI averaged across all CSIs demonstrated "moderate" reliability for VL and VM, but "poor" reliability for RF. This method may offer a practical approach to individualise and select CSIs to investigate quadriceps inhibitory networks in neurophysiological studies.

TMS coil orientation and muscle activation influence lower limb intracortical excitability

IntroductionPrevious research with transcranial magnetic stimulation (TMS) indicates that coil orientation (TMS current direction) and muscle activation state (rest or active) modify corticospinal and intracortical excitability of upper limb muscles. However, the extent to which these factors influence corticospinal and intracortical excitability of lower limb muscles is unknown. This study aimed to examine how variations in coil orientation and muscle activation affect corticospinal and intracortical excitability of tibialis anterior (TA), a lower leg muscle. MethodsIn 21 young (21.6 ± 3.3 years, 11 female) adults, TMS was administered to the motor cortical representation of TA in posterior-anterior (PA) and mediolateral (ML) orientations at rest and during muscle activation. Single-pulse TMS measures of motor evoked potential amplitude, in addition to resting and active motor thresholds, were used to index corticospinal excitability, whereas paired-pulse TMS measures of short-interval intracortical inhibition (SICI) and facilitation (SICF), and long-interval intracortical inhibition (LICI), were used to assess excitability of intracortical circuits. ResultsFor single-pulse TMS, motor thresholds and test TMS intensity were lower for ML stimulation (all P < 0.05). In a resting muscle, ML TMS produced greater SICI (P < 0.001) and less SICF (both P < 0.05) when compared with PA TMS. In contrast, ML TMS in an active muscle resulted in reduced SICI but increased SICF (both P ≤ 0.001) when compared with PA TMS. ConclusionTMS coil orientation and muscle activation influence measurements of intracortical excitability recorded in the tibialis anterior, and are therefore important considerations in TMS studies of lower limb muscles.

Effect of psychotropic drugs on cortical excitability of patients with major depressive disorders: A transcranial magnetic stimulation study

Transcranial magnetic stimulation (TMS) can be used to evaluate the effects of pharmacological interventions. The aim of this study was to assess the impact of the selective serotonin reuptake inhibitor, sertraline, and the atypical antipsychotic drugs quetiapine and olanzapine, on cortical excitability in unmedicated patients with major depressive disorder (MDD). The study included 45 medication-free MDD patients diagnosed according to DSM V. They were divided randomly into three groups who received a single oral dose of one of the three drugs sertraline (50 mg), quetiapine (100 mg) and olanzapine (10 mg). Psychological evaluation was conducted using the Mini-Mental State Examination (MMSE) and Beck Depression Inventory Scale (BDI). Resting and active motor thresholds (rMT and aMT) together with contralateral and ipsilateral cortical silent periods (cSP, and iSP) were measured for each participant before and at the time of maximum concentration of drug intake. There was significant increase in excitability of motor cortex after sertraline without changes in GABAB neurotransmission. Quetiapine and olanzapine potentiated inhibitory GABAB neurotransmission (prolongation of cSP); olanzapine additionally prolonged the iSP. Thus TMS can differentiate between the impact of different psychotropic drugs on excitatory and inhibitory transmission in motor cortex.

Stratifying chronic stroke patients based on the influence of contralesional motor cortices: An inter-hemispheric inhibition study

ObjectiveA recent “bimodal-balance recovery” model suggests that contralesional influence varies based on the amount of ipsilesional reserve: inhibitory when there is a large reserve, but supportive when there is a low reserve. Here, we investigated the relationships between contralesional influence (inter-hemispheric inhibition, IHI) and ipsilesional reserve (corticospinal damage/impairment), and also defined a criterion separating subgroups based on the relationships. MethodsTwenty-four patients underwent assessment of IHI using Transcranial Magnetic Stimulation (ipsilateral silent period method), motor impairment using Upper Extremity Fugl-Meyer (UEFM), and corticospinal damage using Diffusion Tensor Imaging and active motor threshold. Assessments of UEFM and IHI were repeated after 5-week rehabilitation (n = 21). ResultsRelationship between IHI and baseline UEFM was quadratic with criterion at UEFM 43 (95%conference interval: 40–46). Patients less impaired than UEFM = 43 showed stronger IHI with more impairment, whereas patients more impaired than UEFM = 43 showed lower IHI with more impairment. Of those made clinically-meaningful functional gains in rehabilitation (n = 14), more-impaired patients showed further IHI reduction. ConclusionsA criterion impairment-level can be derived to stratify patient-subgroups based on the bimodal influence of contralesional cortex. Contralesional influence also evolves differently across subgroups following rehabilitation. SignificanceThe criterion may be used to stratify patients to design targeted, precision treatments.

Electrophysiological differences in cortical excitability in different forms of dementia: A transcranial magnetic stimulation and laboratory biomarkers study

The aim of the present study was to identify neurophysiologic markers to differentiate between Alzheimer dementia (AD), Vascular dementia (VaD), and Parkinson's disease dementia (PDD), and to examine their relationship to levels of transforming growth factor β1 (TGFβ1). The study included 15 patients with each type of dementia (AD, VaD, PDD) and 25 control subjects. Dementia patients were diagnosed according to the DiagnosticandStatisticalManualofMentalDisorders4thedition-revised(DSM-IV-R). Modified Mini Mental State Examination (MMMSE), motor cortex excitability including resting and active motor thresholds (rMT, aMT), input-output (I/O) curve, contralateral and ipsilateral silent periods (cSP, iSP), short-interval intracortical inhibition (SICI) at 1,2 and 4ms, and serum levels of TGFβ1 were examined. There were no significant differences between groups with regards to age, sex, education or socioeconomic level. There was significant neuronal hyperexcitability in the form of reduced rMT and aMT and a shallower I/O curve in all three groups of dementia compared with the control group. The durations of cSP and iSP were longer in AD and PDD groups compared with the control group, whereas there were no significant differences in VaD. SICI was less effective in the three dementia groups than in the control group at intervals of 4ms. Serum levels of TGFβ1 were significantly elevated in all dementia groups in comparison with the control group. There was a significant negative correlation between serum level of TGFβ1 and cSP, iSP, and SICI across all patients and a significant negative correlation between serum level of TGFβ1 and iSP duration in AD. Although motor thresholds were reduced in all patients, measures of SICI, cSP and iSP could distinguish between dementia groups. Serum level of TGFβ1 negatively correlated with iSP specifically in the AD group. This suggests that levels of TGFβ1 may relate to GABAergic dysfunction in dementia.

Randomising stimulus intensity improves the variability and reliability of the assessment of corticospinal excitability

BackgroundAdvances in the control of transcranial magnetic stimulation (TMS) have enabled greater randomisation of stimulus intensity. It is unclear if such randomisation improves assessments of corticospinal excitability. New methodWe recorded the amplitude of TMS-induced motor evoked potentials (MEPs) from the first dorsal interosseous muscle of eleven participants, during three TMS protocols: blocks of increasing intensity (IB), randomised blocks (RB) and inter-stimulus randomisation (IR). Stimulus intensities from 90 to 140% of active motor threshold described corticospinal input-output (I/O) properties. The experiment was repeated in five participants. ResultsAlthough MEP amplitudes did not differ between IB, RB and IR stimulation protocols, variability was lowest in the IR protocol, compared to IB and RB protocols. Reliability was highest in the IR protocol, compared to IB and IR protocols. Comparison with existing methodsRandomising TMS intensity between each trial produces less variable and more reliable estimates of corticospinal excitability than previously used blocked protocols and produces the same I/O measures. ConclusionsInter-trial randomization of TMS intensities appears to be the most reliable method for constructing I/O curves at multiple time points and decreases the variability of responses.

Walking Training Enhances Corticospinal Excitability in Progressive Multiple Sclerosis—A Pilot Study

Background: Inflammatory lesions and neurodegeneration lead to motor, cognitive, and sensory impairments in people with multiple sclerosis (MS). Accumulation of disability is at least partially due to diminished capacity for neuroplasticity within the central nervous system. Aerobic exercise is a potentially important intervention to enhance neuroplasticity since it causes upregulation of neurotrophins and enhances corticospinal excitability, which can be probed using single-pulse transcranial magnetic stimulation (TMS). Whether people with progressive MS who have accumulated substantial disability could benefit from walking rehabilitative training to enhance neuroplasticity is not known.Objective: We aimed to determine whether 10 weeks of task-specific walking training would affect corticospinal excitability over time (pre, post, and 3-month follow-up) among people with progressive MS who required walking aids.Results: Eight people with progressive MS (seven female; 29–74 years old) with an Expanded Disability Status Scale of 6–6.5 underwent harness-supported treadmill walking training in a temperature controlled room at 16°C (10 weeks; three times/week; 40 min at 40–65% heart rate reserve). After training, there was significantly higher corticospinal excitability in both brain hemispheres, reductions in TMS active motor thresholds, and increases in motor-evoked potential amplitudes and slope of the recruitment curve (REC). Decreased intracortical inhibition (shorter cortical silent period) after training was noted in the hemisphere corresponding to the stronger hand only. These effects were not sustained at follow-up. There was a significant relationship between increases in corticospinal excitability (REC, area under the curve) in the hemisphere corresponding to the stronger hand and lessening of both intensity and impact of fatigue on activities of daily living (Fatigue Severity Scale and Modified Fatigue Impact Scale, respectively).Conclusion: Our pilot results support that vigorous treadmill training can potentially improve neuroplastic potential and mitigate symptoms of the disease even among people who have accumulated substantial disability due to MS.

Improved performance of impulse active noise control using active function threshold with absolute harmonic variable step-size algorithm

The Standard (conventional) adaptive algorithms exhibits low convergence rate and minimum noise suppression, or else the system becomes unstable under Gaussian and non-Gaussian (impulsive noise SαS distributions) noise environments. In order to overcome the drawback of traditional algorithms (i.e., to eliminate unwanted noise), the popular algorithm Filtered Cross Minimum Square (FxLMS) is used in Active Noise Control (ANC), not only to improve its efficiency but also to improve its performance. In this paper, we proposed two improvements: first, we proposed a novel method Active threshold function FxLMS (ATFxLMS) being employed in ANC in the paths of primary (reference) and error signals; a second proposal is employing the Variable Step-Size based on Absolute Harmonic Mean (AHMVSS) of error signal. The idea behind this method is that the step-size of the algorithm varies depending on the harmonic mean of error signal obtained from the error location. In comparison to the fixed step-size algorithm, the proposed ATF-AHMVSS provided an improved convergence rate for the desired ANC efficiency. Moreover computational complication of the proposed method was examined as it was found that the proposed algorithm provided stable condition for ANC systems. Computer simulation results are revealed that the proposed (AT & AHMVSS-FxLMS) algorithm have attained excellent performance in terms of convergence speed, noise reduction and minimum steady state error as compared to other existing algorithms under different noise inputs. The results obtained from the proposed algorithm show outperformance compared to traditional adaptive algorithms.

Connectivity of Ephemeral and Intermittent Streams in a Subtropical Atlantic Forest Headwater Catchment

Stream network extension and contraction depend on landscape features and the characteristics of precipitation events. Although this dependency is widely recognized, the interaction among overland-flow generation processes, drainage active length, and frequency in temporary streams remains less understood. We studied a forest headwater catchment with wide variation in soil depth to investigate the runoff generation processes that lead to the occurrence of ephemeral and intermittent flow and connectivity between hillslope and outlet. We used low-cost equipment to monitor the variation in the length of the active drainage network and to measure the water table development. The flow in the channels can develop even under light rainfall conditions, while the connectivity is controlled by antecedent wetness, total precipitation, and active contribution area thresholds. Runoff permanence and fragmentation were related to soil depth variation; flow being usually more disconnected due to deeper water tables in deeper soil locations. Our findings emphasized the impact of soil structure on runoff generation in hillslopes and can be useful in the management of the most active areas and their impact on the quality of available water.

Wilderness and conservation policies needed to avoid a coral reef fisheries crisis

Conservation and management policies rely on the perceived status of marine ecosystems, which are influenced by proxies and estimation methods. These include the number of protected areas, the percent coverage of nearshore areas, frequency or area relative to other ecosystems, and a diverse set of possible but often poorly evaluated impacts. Based on the emerging studies of the geographic distribution of reef fish biomass, I used two metrics of travel time to human settlements (>4-h) and major markets (>9-h) to estimate the percentage of passive conservation as remote wilderness in 99 tropical ecoregions. Randomly selecting >25,000 tropical coral reefs from a current coral reef map, 2.5% of the random reefs were classified as active conservation or high compliance marine reserves. Passive conservation was considerably larger at ~12% using the >4-h and 48% by the >9-h travel time thresholds. Marine reserves were more frequently located >4-h than <4-h travel times, indicating their inadequate usage as fisheries management tools. Therefore, travel distance or passive conservation and possibly fishing restrictions are the main mechanisms protecting coral reefs. Evaluating the distribution of an active plus passive conservation threshold of 30% protection indicated that 35% of the ecoregions did not achieve this level while 15% had a 100% deficit. When human dependency on fisheries was evaluated, most of Africa, Asia, and Caribbean ecoregions lacked significant refuge and therefore vulnerable to fisheries collapses. Estimates of passive plus active conservation deficits provides a path to prioritize actions to increase active conservation and restricting human and market demands.

Stimulus Intensity Affects Variability of Motor Evoked Responses of the Non-Paretic, but Not Paretic Tibialis Anterior Muscle in Stroke.

Background: Transcranial magnetic stimulus induced motor evoked potentials (MEPs) are quantified either with a single suprathreshold stimulus or using a stimulus response curve. Here, we explored variability in MEPs influenced by different stimulus intensities for the tibialis anterior muscle in stroke. Methods: MEPs for the paretic and non-paretic tibialis anterior (TA) muscle representations were collected from 26 participants with stroke at seven intensities. Variability of MEP parameters was examined with coefficients of variation (CV). Results: CV for the non-paretic TA MEP amplitude and area was significantly lower at 130% and 140% active motor threshold (AMT). CV for the paretic TA MEP amplitude and area did not vary with intensity. CV of MEP latency decreased with higher intensities for both muscles. CV of the silent period decreased with higher intensity for the non-paretic TA, but was in reverse for the paretic TA. Conclusion: We recommend a stimulus intensity of greater than 130% AMT to reduce variability for the non-paretic TA. The stimulus intensity did not affect the MEP variability of the paretic TA. Variability of MEPs is affected by intensity and side tested (paretic and non-paretic), suggesting careful selection of experimental parameters for testing.

Detecting cortical circuits resonant to high-frequency oscillations in the human primary motor cortex: a TMS-tACS study

Corticospinal volleys evoked by transcranial magnetic stimulation (TMS) over the primary motor cortex (M1) consist of high-frequency bursts (≈667 and ≈333 Hz). However, intracortical circuits producing such corticospinal high-frequency bursts are unknown. We here investigated whether neurons activated by single TMS pulses over M1 are resonant to high-frequency oscillations, using a combined transcranial alternating current stimulation (tACS)-TMS approach. We applied 667, 333 Hz or sham-tACS and, concurrently, we delivered six single-pulse TMS protocols using monophasic or biphasic pulses, different stimulation intensities, muscular states, types and orientations of coils. We recorded motor evoked potentials (MEPs) before, during and after tACS. 333 Hz tACS facilitated MEPs evoked by biphasic TMS through a figure-of-eight coil at active motor threshold (AMT), and by monophasic TMS with anterior-to-posterior-induced current in the brain. 333 Hz tACS also facilitated MEPs evoked by monophasic TMS through a circular coil at AMT, an effect that weakly persisted after the stimulation. 667 Hz tACS had no effects. 333 Hz, but not 667 Hz, tACS may have reinforced the synchronization of specific neurons to high-frequency oscillations enhancing this activity, and facilitating MEPs. Our findings suggest that different bursting modes of corticospinal neurons are produced by separate circuits with different oscillatory properties.

Impaired motor cortical plasticity associated with cannabis use disorder in young adults.

Maladaptive cortical plasticity has been described in individuals with heroin and methamphetamine addiction and may mediate other substance abuse disorders. It is unknown whether cannabis dependence in humans alters the capacity for induction of cortical plasticity. The aim of this study was to non-invasively investigate cortical plasticity with transcranial magnetic stimulation in young adults who meet DSM-5 criteria for cannabis use disorder (CUD). Thirty men (ages 20- 30) who used cannabis daily over the previous 6 months (15 diagnosed of CUD) and 15 demographically matched non-users were enrolled in this study. All participants underwent two sessions of theta burst stimulation (TBS) in which either continuous TBS (cTBS; 600 pulses, 80% active motor threshold) or intermittent TBS (iTBS; 2-s train of cTBS repeated every 10 s for a total of 190 s, 600 pulses) was applied over the primary motor cortex. The effects of these protocols were assessed by analysing the contralateral motor evoked potentials (MEPs). The relationships between cortical plasticity and problematic cannabis use, degree of dependence, and nicotine addiction were also investigated. Significant MEP inhibition after cTBS was observed in both cannabis users without CUD and non-users, while this inhibition was not seen in cannabis users with CUD. Strikingly, less motor cortical plasticity was observed in subjects with severe problematic cannabis use. No significant differences between users and non-users were found in the iTBS-induced cortical plasticity measures. Our study provides the first evidence of maladaptive cortical plasticity associated with cannabis use disorder and problematic cannabis use in humans.

The active butanol detection threshold remains the same during exercise

The active butanol detection thresholds (B-DT), determined using the sniffin' sticks, show a high intra- and inter-individual test-retest reliability, although the internal stimulus concentration may vary considerably depending on the dilution of the external stimulus concentration with odorless ambient air during active sniffing. There are various hypotheses for this surprising result. In this study, it should be tested whether a larger respiratory effort (vigor) under physical stress changes the active B-DT. In 28 young, healthy, normosmic adults, sitting on a stationary bicycle ergometer at rest phase, during aerobic exercise and in the recovery phase, the monorhinal B-DT using Sniffin' Sticks were determined. Various vital parameters such as blood pressure, heart frequency, body temperature, respiratory frequency and blood lactate characterized the three test phases. The individual stress perception was estimated according to the Borg scale. The B-DT did not change in the three test phases. All examined vital parameters were significantly larger in theloading phase than in the resting phase. In the case of a moderate to severe stress sensation (Borg-scale: 13-15), an aerobic physical stress could be confirmed on the basis of the vital parameters. The investigations support the hypothesis that vigor is not the decisive factor for a constant olfactory perception of external equal stimulus concentrations. The integration of internal stimulus concentration and nasal flow velocity and the empirical evaluation of the current odor concentration probably play a greater role.

Exercise-Induced Brain Excitability Changes in Progressive Multiple Sclerosis: A Pilot Study.

Even a single bout of aerobic exercise (AE) enhances corticospinal excitability (CSE), a biomarker of neuroplasticity. Because neurodegeneration limits capacity for neuroplasticity, it is not clear whether AE would induce CSE changes in people with progressive multiple sclerosis (MS). People with progressive MS (n = 10) requiring ambulatory assistive devices completed a graded maximal exercise test. Dual-energy x-ray absorptiometry was used to quantify body fat and lean mass. Before and following one 40-minute AE session using body weight-supported (<10% support) treadmill at moderate intensity, CSE was measured using transcranial magnetic stimulation. Variables included resting and active motor thresholds, motor evoked potential (MEP) amplitudes, recruitment curves, and length of the cortical silent period (CSP). Aerobic exercise reduced inhibition (shorter CSP) and increased excitation (increased MEP amplitude) only in the hemisphere corresponding to the stronger hand. Controlling for age, higher fitness and lower body fat significantly predicted exercise-induced reduction in resting motor threshold (ΔR = +0.458, P = 0.046) and CSP (ΔR = +0.568, P = 0.030), respectively. Despite high levels of disability, capacity for exercise-induced neuroplasticity was retained among people with progressive MS. The hemisphere contralateral to the weaker hand was resistant to exercise-induced CSE changes, suggesting less neuroplastic potential. Lower fitness and higher body fat were associated with diminished exercise-induced CSE benefits, suggesting that therapists should consider interventions aimed at improving fitness and combating sedentarism to ultimately enhance the benefits of exercise on the brain.Video Abstract available for more insights from the authors (see the Video, Supplemental Digital Content 1, available at: http://links.lww.com/JNPT/A302).

Interhemispheric and Intrahemispheric Connectivity From the Left Pars Opercularis Within the Language Network Is Modulated by Transcranial Stimulation in Healthy Subjects.

Neural activity related to language can be modulated within widespread networks following learning or in response to disruption—including the experimental application of noninvasive brain stimulation. However, the spatiotemporal characteristics of such modulation remain insufficiently explored. The present study combined transcranial magnetic stimulation (TMS) and electroencephalography (EEG) to explore the modulation of activity across the language network following continuous theta-burst stimulation (cTBS) of the left pars opercularis. In 10 healthy subjects (21 ± 2 years old, four females), neuronavigated cTBS was delivered over the left pars opercularis of the frontal operculum (part of the traditional Broca’s area) at 80% of active motor threshold (AMT) stimulation intensity. Real cTBS and sham cTBS were performed in two different visits separated by at least 48 h. Before, immediately, and 10 min after cTBS, 30 single pulses of TMS were delivered to the left pars opercularis at 80% of the resting motor threshold (RMT), whereas EEG was simultaneously recorded. We examined the cTBS-induced modulation of phase locking values (PLVs) between the TMS-evoked potentials (TEPs) recorded over the pars opercularis and those recorded over its right-hemispheric homolog area, the left supramarginal area, and the left superior temporal area in different EEG frequency bands and different time windows following cTBS. cTBS to the left pars opercularis induced within the gamma band: (1) a significant increase in TEP phase synchronization between the left and right pars opercularis at an early time window (250–350 ms) following cTBS; and (2) significantly increased PLV with the left supramarginal area and the left superior temporal area at a later time window (600–700 ms). In the theta and delta band, cTBS to the left pars opercularis induced significantly increased phase synchronization of TEPs between the left pars opercularis and the posterior left hemispheric language areas at a late time window. In sham condition, there was a significant decrease in TEP phase synchronization of the high beta band between left pars opercularis and left superior temporal area at 200–300 ms. These results contribute to characterize the dynamics of the language network and may have implications in the development of noninvasive stimulation protocols to promote the language rehabilitation in aphasia patients.

GPU accelerated study of a dual-frequency driven single bubble in a 6-dimensional parameter space: The active cavitation threshold.

The active cavitation threshold of a dual-frequency driven single spherical gas bubble is studied numerically. This threshold is defined as the minimum intensity required to generate a given relative expansion (Rmax-RE)/RE, where RE is the equilibrium size of the bubble and Rmax is the maximum bubble radius during its oscillation. The model employed is the Keller-Miksis equation that is a second order ordinary differential equation. The parameter space investigated is composed by the pressure amplitudes, excitation frequencies, phase shift between the two harmonic components and by the equilibrium bubble radius (bubble size). Due to the large 6-dimensional parameter space, the number of the parameter combinations investigated is approximately two billion. Therefore, the high performance of graphics processing units is exploited; our in-house code is written in C++ and CUDA C software environments. The results show that for (Rmax-RE)/RE=2, the best choice of the frequency pairs depends on the bubble size. For small bubbles, below 3μm, the best option is to use just a single frequency of a low value in the giant response region. For medium sized bubbles, between 3μm and 6μm, the optimal choice is the mixture of low frequency (giant response) and main resonance frequency. For large bubbles, above 6μm, the main resonance dominates the active cavitation threshold. Increasing the prescribed relative expansion value to (Rmax-RE)/RE=3, the optimal choice is always single frequency driving with the lowest value (20kHz here). Thus, in this case, the giant response always dominates the active cavitation threshold. The phase shift between the harmonic components of the dual-frequency driving (different frequency values) has no effect on the threshold.