Altered cortical excitability in patients with untreated obstructive sleep apnea syndrome

ObjectiveTo investigate cortical excitability in patients with obstructive sleep apnea syndrome (OSAS) during wakefulness.MethodsThe authors recruited 45 untreated severe OSAS (all males, mean age 47.2 years, mean apnea–hypopnea index = 44.6 h^?1) patients and 44 age-matched healthy male volunteers (mean apnea–hypopnea index = 3.4 h^?1). The TMS parameters measured were resting motor threshold (RMT), motor evoked potential (MEP) amplitude, cortical silent period (CSP), and short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF). These parameters were measured in the morning (9–10 am) more than 2 h after arising and the parameters of patients and controls were compared. The Epworth Sleepiness Scale (ESS) and the Stanford Sleepiness Scale (SSS) were also measured before the TMS study.ResultsOSAS patients had a significantly higher RMT and a longer CSP duration (t-test, p < 0.001) compared to healthy volunteers. No significant difference was observed between MEP amplitudes at any stimulus intensity or between the SICI (2, 3, 5 ms) and ICF (10, 15, 20 ms) values of OSAS patients and healthy volunteers (p > 0.05).ConclusionsThis TMS-based study suggests that untreated severe OSAS patients have imbalanced cortical excitabilities that enhanced inhibition or decreased brain excitability when awake during the day.     

Chronic treatment with rivastigmine in patients with Alzheimer's disease: a study on primary motor cortex excitability tested by 5 Hz-repetitive transcranial magnetic stimulation

ObjectiveTo investigate changes in cortical excitability and short-term synaptic plasticity we delivered 5 Hz repetitive transcranial magnetic stimulation (rTMS) over the primary motor cortex in 11 patients with mild-to-moderate Alzheimer’s disease (AD) before and after chronic therapy with rivastigmine.MethodsResting motor threshold (RMT), motor evoked potential (MEP), cortical silent period (CSP) after single stimulus and MEP facilitation during rTMS trains were tested three times during treatment. All patients underwent neuropsychological tests before and after receiving rivastigmine. rTMS data in patients were compared with those from age-matched healthy controls.ResultsAt baseline, RMT was significantly lower in patients than in controls whereas CSP duration and single MEP amplitude were similar in both groups. In patients, rTMS failed to induce the normal MEP facilitation during the trains. Chronic rivastigmine intake significantly increased MEP amplitude after a single stimulus, whereas it left the other neurophysiological variables studied unchanged. No significant correlation was found between patients’ neuropsychological test scores and TMS measures.ConclusionsChronic treatment with rivastigmine has no influence on altered cortical excitability and short-term synaptic plasticity as tested by 5 Hz-rTMS.SignificanceThe limited clinical benefits related to cholinesterase inhibitor therapy in patients with AD depend on factors other than improved plasticity within the cortical glutamatergic circuits.     

Cortical excitability in drug naive juvenile myoclonic epilepsy

PurposeTo evaluate the effect of diurnal variability on cortical excitability using single pulse transcranial magnetic stimulation (TMS), in drug naive patients with juvenile myoclonic epilepsy (JME) and to look for any differences in cortical excitability between males and females.MethodsThirty drug-naive patients with JME and 10 healthy controls were studied. Resting motor threshold (RMT), motor evoked potential (MEP), the duration of central motor conduction time (CMCT) and cortical silent period (CSP) were measured, twice, first early in the morning and again in the afternoon of the same day.ResultsDiurnal variation with higher evening values of CMCT and CSP were observed in the control group. In the study group, diurnal variation in RMT, CMCT and CSP was found with higher values in the morning than in control group. However, only the raised values of CSP [mean, 110.7 ms, morning and 96.44 ms, evening] were of statistical significance [p = 0.005, morning and 0.039, evening] as compared to controls. In the study group, males had higher values of RMT, CMCT and CSP than in females. However, the CMCT in males was lower in the evening study than in females. Further, RMT and morning CMCT was lower in females than in controls. In females, the morning CSP [mean, 100.91 ms, morning versus 87.86 ms, evening] was significantly prolonged [p = 0.017, morning versus 0.221, evening] as compared to controls.ConclusionThe study is suggestive of the existence of impaired supraspinal/intracortical inhibitory circuits which may account for the hyperexcitability of the motor system being prominent in the morning among drug naïve patients with JME. In this study, increased activity of cortical inhibitory networks, as evidenced by prolonged cortical silent period existed among drug naïve JME patients, but was found to be significant only in female patients. This may explain the increased seizure susceptibility in this cohort, at this time of the day and an increased manifestation of JME in females.     

The effect of modafinil on cortical excitability in patients with narcolepsy: A randomized,placebo-controlled,crossover study

ObjectiveTo investigate the effect of modafinil on cortical excitability in patients with narcolepsy using transcranial magnetic stimulation (TMS).MethodsNineteen drug-naïve narcolepsy patients with cataplexy (10 males, 9 females, and mean age 28.5 years) and 25 age- and sex-matched healthy controls were recruited. In this double-blind, randomized, crossover study, patients and controls received a single dose of 400 mg modafinil or placebo. Modafinil and placebo administrations were separated by a 2-week washout period. TMS parameters, such as resting motor thresholds (RMT), motor-evoked potential (MEP) amplitudes, cortical silent periods (CSP), short-interval intracortical inhibition (SICI), and intracortical facilitation (ICF), were measured before and 3 h after administering modafinil or placebo. The differences of TMS parameters were statistically tested between patients and controls and between before and after modafinil or placebo administration.ResultsNarcolepsy patients had significantly increased CSP durations compared to controls (independent t-test, P < 0.05), indicating decreased excitability of cortical networks in human narcolepsy. In patients after modafinil administration, MEP amplitudes, SICI, and ICF increased, and CSP duration shortened significantly, meaning enhanced motor excitability, whereas in controls modafinil did not change TMS parameters significantly. Placebo administration did not affect TMS parameters both in patients or controls.ConclusionsNarcolepsy patients with cataplexy showed decreased cortical excitability than normal healthy controls. Single dose modafinil significantly increased motor excitability in narcolepsy patients but had no effect in healthy controls.     

Determining optimal rTMS parameters through changes in cortical inhibition

ObjectivesEvidence shows that repetitive transcranial magnetic stimulation (rTMS) changes cortical inhibition (CI) and excitability and that these changes may relate to its therapeutic effects. This study aimed to investigate the effects of differing durations or ‘doses’ of rTMS on cortical inhibition and excitability in healthy subjects.MethodsFour different experiments were conducted: 1 session of 1200 pulses of 1 or 20 Hz active or sham rTMS; 10 sessions of 1 or 20 Hz active or sham rTMS, 1200 pulses/session; 1 session of 3600 pulses of 1 or 20 Hz active or sham rTMS; 1 session of 6000 pulses of 20 Hz active or sham rTMS. Measures of cortical inhibition and excitability included short-interval intracortical inhibition, long interval cortical inhibition, cortical silent period (CSP), motor evoked potential amplitude, resting motor threshold and intracortical facilitation.ResultsOnly 6000 pulses of 20 Hz rTMS lead to a significant lengthening of the CSP and therefore potentiation of CI. There were no changes to excitability measures.ConclusionOnly high frequency rTMS potentiated CI. Longer treatment durations are required to produce such changes.SignificanceStudies investigating the therapeutic effects of rTMS may benefit from extended dosing with increased number of pulses per session. CSP lengthening may be used to guide treatment response.     

Zonisamide decreases cortical excitability in patients with idiopathic generalized epilepsy.

ObjectiveTo evaluate changes in cortical excitability after long-term zonisamide (ZNS) administration.MethodsFifteen drug-naïve idiopathic generalized epilepsy (IGE) patients (8 male, mean age 24.9 years) were enrolled. The transcranial magnetic stimulation (TMS) parameters obtained using two Magstim 200 stimulators were resting motor threshold (RMT), motor evoked potential (MEP) amplitudes, cortical silent period (CSP), intracortical inhibition (ICI), and intracortical facilitation (ICF). TMS parameters were compared before and after ZNS administration.ResultsAll patients were administered ZNS monotherapy (200 mg/day) for 8 weeks. No patient reported seizures during the study period. After ZNS treatment MEP amplitudes were significantly reduced in right (−34.2%) and left hemispheres (−37.0%) (Wilcoxon’s signed rank test after Bonferroni’s correction for multiple comparisons, P < 0.05). Mean RMT, CSP, and ICI/ICF were not changed by ZNS (P > 0.05).ConclusionsThese findings suggest that ZNS decreases cortical excitability in patients with IGE and a MEP amplitude is a useful TMS parameter for evaluating changes in cortical excitability induced by ZNS.SignificanceThe findings in this study are helpful to understand how ZNS affects the excitability of the motor cortex in patients with IGE.     

Effect of cued training on motor evoked potential and cortical silent period in people with Parkinson’s disease

ObjectiveTo examine whether training under visual cues could enhance motor cortical excitability and intracortical inhibition in individuals with Parkinson’s disease (PD).MethodsThis was a single blinded cross-over study. Eight individuals with PD received two sessions of 30-min pinch-grip training with and without visual cues. The visual cue was given in form of an arrow that indicated the pre-set force level on a computer screen. Outcome measures consisted of peak motor evoked potential (MEP) and cortical silent period (CSP) of the first dorsal interosseus as well as behavioural tests including Purdue pegboard test, tapping speed in 30 s, and the maximum pinch grip force exerted by the thumb and index finger.ResultsAfter cued training, there were significant increases in the peak MEP, CSP duration and tapping speed (all p < 0.05). In contrast, there was no change in all outcome measures after training under the non-cued condition.ConclusionsThirty minutes of pinch-grip training with visual cues could enhance motor cortical excitability and intracortical inhibition in individuals with PD.SignificanceThe findings on the neurophysiological changes after cued-training may inform further clinical application of visual cues to maximize motor improvement and corticomotor plasticity in people with PD.     

Effect of slow rTMS of motor cortex on the excitability of the Blink Reflex: A study in healthy humans

ObjectiveTo evaluate the after-effects of low frequency, sub-threshold repetitive Transcranial Magnetic Stimulation (rTMS) of primary motor cortex, on the excitability of Blink Reflex (BR) in healthy subjects.MethodsThe BR recovery cycle was carried out in 10 healthy volunteers in basal conditions, immediately after rTMS (30 s), 15 and 60 min later. A paired electric supraorbital stimulus paradigm with inter-stimulus intervals (ISI) of 100–600–1000–1500 ms was used. The “real” rTMS consisted of a 200 stimuli long train delivered at 1 Hz and intensity 80% of rest Motor Threshold of the FDI muscle, using a focal coil applied over the primary motor cortex region. The basal BR recovery cycle was also compared with that obtained after a “sham” rTMS.ResultsThe recovery of the R2 component of the BR was significantly suppressed 30 s after rTMS. This effect was also observed at 15 min, though of lower magnitude and only at long ISIs (1000-1500 ms). No significant effect on R2 recovery was observed 60 min after real rTMS as well as after sham rTMS.ConclusionsrTMS of motor cortex modulates the excitability of BR through its action on cortical excitability and on the cortical facilitatory drive to the brainstem reflex pathways.SignificanceSlow (1 Hz), sub-threshold rTMS of motor cortex determines a long-lasting reduction of excitability of BR.     

Effects of continuous theta burst transcranial magnetic stimulation on cortical excitability in patients with idiopathic generalized epilepsy

IntroductionTranscranial magnetic stimulation (TMS) is a noninvasive technique for investigating cortical physiologic functions in the brain. In this study, the effects of continuous theta burst stimulation (cTBS) on motor evoked potential (MEP) parameters in patients with idiopathic generalized epilepsy (IGE) were investigated.Materials and methodsFifteen patients with IGE were included. Motor threshold (MT) and cortical silent period (CSP) were determined before cTBS application. Next, cTBS was applied to the dominant (left) hemisphere M1 hand area as the first application. After 1 day, cTBS was applied first to the left M1 hand area and then to the right lateral cerebellar area as the second application. Parameters were again determined after the applications.ResultsThere was no difference in resting MT values before and after cTBS application (p > 0.05). Although CSP increased after stimulation (p < 0.05), it was not significantly different between applications (p > 0.05).ConclusionFor patients with epilepsy, cTBS is a safe technique when applied at a low intensity. The inhibitory effect of cTBS, a noninvasive technique, on cortical excitability in patients with IGE was determined using MEP parameters. The effect lasted at least 1 h. To our knowledge, this is the first study to assess the effect of cTBS on cortical excitability in patients with IGE. Our findings indicate that cTBS decreases cortical excitability in patients with IGE.     

Functional repetitive transcranial magnetic stimulation increases motor cortex excitability in survivors of stroke

ObjectiveTo determine if repetitive transcranial magnetic stimulation (rTMS) applied to the motor cortex with simultaneous voluntary muscle activation, termed functional-rTMS, will promote greater neuronal excitability changes and neural plasticity than passive-rTMS in survivors of stroke.MethodsEighteen stroke survivors were randomized into functional-rTMS (EMG-triggered rTMS) or passive-rTMS (rTMS only; control) conditions. Measures of short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF), force steadiness (coefficient of variation, CV) at 10% of maximum voluntary contraction, and pinch task muscle activity were assessed before and after rTMS. Functional-rTMS required subjects to exceed a muscle activation threshold to trigger each rTMS train; the passive-rTMS group received rTMS while relaxed.ResultsSignificant interactions (time × condition) were observed in abductor pollicis brevis (APB) SICI, APB ICF, CV of force, and APB muscle activity. Functional-rTMS decreased APB SICI (p < 0.05) and increased ICF (p < 0.05) after stimulation, whereas passive-rTMS decreased APB muscle activity (p < 0.01) and decreased CV of force (p < 0.05). No changes were observed in FDI measures (EMG, ICF, SICI).Conclusion(s)Functional-rTMS increased motor cortex excitability, i.e., less SICI and more ICF for the APB muscle. Passive stimulation significantly reduced APB muscle activity and improved steadiness.SignificanceFunctional-rTMS promoted greater excitability changes and selectively modulated agonist muscle activity.     

Motor cortex dysfunction in complex regional pain syndrome

ObjectiveMost patients with complex regional pain syndrome (CRPS) exhibit debilitating motor symptoms. The effect of continuous pain on motor system in CRPS, however, is not well known. We searched for signs of motor cortex dysfunction in chronic CRPS type 1 patients with motor impairment.MethodsWe recorded rhythmic brain activity with magnetoencephalography (MEG) during noxious thulium–laser stimulation of both hands in eight CRPS patients and eight control subjects. We measured excitability of the motor cortex by monitoring the reactivity of the ∼20-Hz motor cortex rhythm to laser stimuli. The reactivity was defined as a sum of the stimulus-induced suppression and the subsequent rebound of the ∼20-Hz rhythm.ResultsIn CRPS, the reactivity of the ∼20-Hz rhythm in the hemisphere contralateral to the painful hand was significantly weaker than in control subjects. The reactivity correlated with the mean level of the spontaneous pain (r = −0.64, P = 0.04). Suppression of the ∼20-Hz rhythm correlated with the grip strength in the painful hand (r = 0.66, P = 0.04).ConclusionContinuous pain in CRPS is associated with attenuated motor cortex reactivity.SignificanceAbnormal motor cortex reactivity may be linked with motor dysfunction of the affected hand in CRPS.     

High frequency repetitive transcranial magnetic stimulation decreases cerebral vasomotor reactivity

ObjectiveRepetitive Transcranial Magnetic Stimulation (rTMS) has been recently employed as a therapeutic strategy for stroke, although its effects on cerebral hemodynamics has been poorly investigated. This study aims to examine the impact of high frequency rTMS on cerebral vasomotor reactivity (VMR).MethodsTwenty-nine healthy subjects were randomly assigned to real (19) or sham 17-Hz rTMS, applied on primary motor cortex (M1) of the dominant hemisphere. All subjects underwent Transcranial Doppler of the middle cerebral arteries to evaluate mean flow velocity and VMR before (T₀) and within 10 min (T₁) following rTMS. Four subjects underwent further VMR evaluations at 2 (T₂), 5 (T₃) and 24 h (T₄) after rTMS. As a control condition, 10 subjects underwent real (5) or sham rTMS on calcarine cortex. In addition, five acute stroke patients underwent five daily rTMS sessions on the affected hemisphere mimicking a therapeutic trial.ResultsFollowing real rTMS on M1 (p = 0.002) and calcarine cortex (p < 0.001) VMR decreased with respect to T₀ in both hemispheres, while no change was observed after sham rTMS (p > 0.6). VMR tended to remain lower than T₀ until T_3. Cerebral VMR decreased independently of the stimulated side also in the patients’ group.ConclusionsHigh frequency rTMS reduces cerebral VMR, possibly as a secondary effect on autonomic control of cerebral hemodynamics.SignificanceThe effect of rTMS on cerebral hemodynamics should be carefully considered before proceeding toward a therapeutic application in stroke patients.     

Inverse Correlation Between Resting Motor Threshold and Corticomotor Excitability After Static Magnetic Stimulation of Human Motor Cortex

BackgroundHigh-strength static magnetic field stimulation (SMS) results in a period of reduced corticomotor excitability that may be mediated through a decrease in membrane excitability.ObjectiveAs resting motor threshold (RMT) is thought to reflect membrane excitability, we hypothesized that SMS may increase RMT and that there would be an inverse relationship between RMT and motor-evoked potential (MEP) amplitude.MethodsTen healthy subjects (aged 20–29; 4 females) participated in a double-blinded crossover design comparing MEP amplitude and RMT before and after a 15-min period of SMS or sham stimulation over primary motor cortex (M1).ResultsMEP amplitude was initially significantly reduced post-SMS (～20%), and returned to baseline by 6 min post-intervention. MEP amplitude and RMT were inversely correlated (r² = 0.924; P = 0.001). Sham stimulation had no effect on MEP amplitude (P = 0.969) or RMT (P = 0.549).ConclusionAfter SMS, corticomotor excitability is transiently reduced in association with a correlated modulation of RMT. SMS after effects may be mediated in part by a reduction in membrane excitability, suggesting a possible role for non-synaptic (intrinsic) plasticity mechanisms.     

Repetitive transcranial magnetic stimulation reveals abnormal plastic response to premotor cortex stimulation in schizophrenia.

BACKGROUND: Schizophrenia may be characterized by abnormal plastic modulation in cortical neuronal circuits. Activation of premotor cortex using repetitive transcranial magnetic stimulation (rTMS) produces suppression of cortical excitability in primary motor cortex. We hypothesized that premotor rTMS would cause less suppression of motor cortical excitability in patients with schizophrenia than in control subjects. METHODS: Twelve patients diagnosed with schizophrenia and twelve healthy control subjects underwent subthreshold rTMS to the premotor area in a 15-min conditioning train. Measurements of primary motor cortical excitability (motor evoked potential; MEP), the resting motor threshold (RMT), and cortical inhibition (CI) were taken before and after the rTMS. RESULTS: There was no difference in RMT between groups at baseline, although the patient group had less CI than the control group at baseline. Following rTMS, the change in both MEP size and RMT between groups was significant. After rTMS, MEP size was suppressed in the control group and increased in the patient group, whereas RMT increased in the normal control group and decreased in the patient group. CONCLUSIONS: Patients with schizophrenia demonstrate abnormal brain responses to rTMS applied to the premotor cortex that appear to relate to reduced motor cortical inhibition.     

Effects of theta burst stimulation on motor cortex excitability in Parkinson's disease

ObjectiveLong-term potentiation (LTP)-like plasticity induced by paired associative stimulation (PAS) is impaired in Parkinson’s disease (PD). Intermittent theta burst stimulation (iTBS) is another rTMS protocol that produces LTP-like effects and increases cortical excitability but its effects are independent of afferent input. The aim of the present study was to examine the effects of iTBS on cortical excitability in PD.MethodsiTBS was applied to the motor cortex in 10 healthy subjects and 12 PD patients ON and OFF dopaminergic medications. Motor evoked potential (MEP) before and for 60 min after iTBS were used to examine the changes in cortical excitability induced by iTBS. Paired-pulse TMS was used to test whether intracortical circuits, including short interval intracortical inhibition, intracortical facilitation, short and long latency afferent inhibition, were modulated by iTBS.ResultsAfter iTBS, the control, PD ON and OFF groups had similar increases in MEP amplitude compared to baseline over the course of 60 min. Changes in intracortical circuits induced by iTBS were also similar for the different groups.ConclusionsiTBS produced similar effects on cortical excitability for PD patients and controls.SignificanceSpike-timing dependent heterosynaptic LTP-like plasticity induced by PAS may be more impaired in PD than frequency dependent homosynaptic LTP-like plasticity induced by iTBS.     

A meta-analysis of cortical inhibition and excitability using transcranial magnetic stimulation in psychiatric disorders

ObjectiveTo evaluate transcranial magnetic stimulation (TMS) measures of inhibition and excitation in obsessive–compulsive disorder (OCD), major depressive disorder (MDD) and schizophrenia (SCZ).MethodsParadigms included: short-interval cortical inhibition (SICI), cortical silent period (CSP), resting motor threshold, intracortical facilitation, and motor evoked potential amplitude. A literature search was performed using PubMed, Ovid Medline, Embase Psychiatry and PsycINFO 1990 through April 2012.ResultsA significant Hedge’s g was found for decreased SICI (g = 0.572, 95% confidence interval [0.179, 0.966], p = 0.004), enhanced intracortical facilitation (g = 0.446, 95% confidence interval [0.042, 0.849], p = 0.030) and decreased CSP (g = ?0.466, 95% confidence interval [?0.881, ?0.052], p = 0.027) within the OCD population. For MDD, significant effect sizes were demonstrated for decreased SICI (g = 0.641, 95% confidence interval [0.384, 0.898], p = 0.000) and shortened CSP (g = ?1.232, 95% confidence interval [?1.530, ?0.933], p = 0.000). In SCZ, a significant Hedge’s g was shown for decreased SICI (g = 0.476, 95% confidence interval [0.331, 0.620], p = 0.000).ConclusionInhibitory deficits are a ubiquitous finding across OCD, MDD, SCZ and enhancement of intracortical facilitation is specific to OCD.SignificanceProvides a clear platform from which diagnostic procedures can be developed.     

Increased motor cortical excitability after whole-hand electrical stimulation: A TMS study

ObjectiveTo examine the neuromodulatory effect of whole-hand mesh-glove (MG) stimulation on motor cortical pathways, we explored motor cortical excitability before and after suprathreshold whole-hand MG stimulation using transcranial magnetic stimulation (TMS).MethodsTwenty-eight healthy volunteers (14 controls) were studied at baseline, immediately post and 1 h post-MG stimulation for 30 min. Motor thresholds (MTs), motor evoked potentials (MEPs) recruitment curve, short intracortical inhibition (SICI) and intracortical facilitation (ICF) after paired magnetic stimuli were evaluated.ResultsAfter MG stimulation the MTs were significantly reduced and slope of MEP recruitment curve significantly increased; furthermore, the stimulation led to a sustained decrease of SICI and increase of ICF in the contralateral motor cortex. These effects lasted for at least 60 min and were stronger 1 h post-stimulation compared with testing immediately after stimulation. A sham group did not show any differences before and after MG stimulation.ConclusionsWe provide a first demonstration that MG whole-hand stimulation induces increases in motor cortical excitability lasting at least 1 h. Both the strength of the corticospinal projections and the inhibitory and facilitatory intracortical mechanisms are involved. Synaptic modifications such as long-term potentiation mechanisms may underlie this stimulation-induced cortical plasticity changes.SignificancePresent results prove the MG stimulation to be a promising tool in neurorehabilitation.     

Automated-parameterization of the motor evoked potential and cortical silent period induced by transcranial magnetic stimulation

ObjectiveTo standardize the characterization of motor evoked potential (MEP) and cortical silent period (CSP) recordings elicited with transcranial magnetic stimulation (TMS).MethodsA computer-based, automated-parameterization program (APP) was developed and tested which provides a comprehensive set of electromyography (EMG) magnitude and temporal measures. The APP was tested using MEP, CSP, and isolated CSP (iCSP) TMS stimulus–response data from a healthy adult population (N = 13).ResultsThe APP had the highest internal reliability (Cronbach’s alpha = .98) for CSP offset time compared with two prominent automated methods. The immediate post-CSP EMG recovery level was 49% higher than the pre-TMS EMG level. MEP size (peak amplitude, mean amplitude, peak-to-peak amplitude, and area) correlated higher with effective E-field (E_eff) than other intensity measures (r ≈ 0.5 vs. r ≈ 0.3) suggesting that E_eff is better suited for standardizing MEP stimulus–response relationships.ConclusionsThe APP successfully characterized individual and mean epochs containing MEP, CSP, and iCSP responses. The APP provided common signal and temporal measures consistent with previous studies and novel additional parameters.SignificanceWith the use of the APP modeling method and the E_eff, a standard approach for the analysis and reporting of MEP–CSP complex and iCSP measurements is achievable.     

Reduced motor cortex plasticity following inhibitory rTMS in older adults

ObjectiveAgeing is accompanied by diminished practice-dependent plasticity. We investigated the effect of age on another plasticity inducing paradigm, repetitive transcranial magnetic stimulation (rTMS).MethodsHealthy young (n = 15; 25 ± 4 years) and old (n = 15; 67 ± 5 years) adults participated in two experiments. Motor evoked potentials (MEPs) were measured in the target muscle (first dorsal interosseus, FDI) and a remote muscle (abductor digiti minimi) during a set of single stimuli. Subjects then received real or sham inhibitory rTMS (intermittent subthreshold trains of 6 Hz stimulation for 10 min). MEPs were measured for 30 min after rTMS.ResultsIn young adults, MEPs in the target FDI muscle were ∼15% smaller in the real rTMS experiment than in the sham rTMS experiment (P < 0.026). In old adults, FDI MEP size did not differ between experiments.ConclusionsAdvancing age is associated with reduced efficacy of inhibitory rTMS.SignificanceThis work has important implications for the potential therapeutic use of rTMS in stroke and neurological disease.