TMS-EEG signatures of the effects of transcranial static magnetic field stimulation (tSMS) on cortical excitability.

In transcranial static magnetic field stimulation (tSMS), a strong and small magnet placed over the head can modulate cortical functions below the magnet as well as those in the region remote from the magnet. We studied the neuromodulation induced by tSMS using transcranial magnetic stimulation (TMS) combined with simultaneous electroencephalography (EEG) to clarify the neurophysiological underpinnings of tSMS. tSMS or sham stimulation was applied over the left primary motor cortex (M1) for 20 min in 15 healthy subjects. Single pulse TMS was delivered over the left M1 before and after the intervention, while recording EEG. The amplitude around the P30 of the TMS-evoked potentials (TEPs) in the left primary sensorimotor area (SM1) significantly decreased after the real tSMS, and that around the N60 of the TEPs in the right SM1 significantly increased after the real tSMS. In addition, the alpha power of the TMS-induced oscillatory responses (IORs) in the left and right SM1 significantly decreased after the real tSMS. TMS-EEG is a powerful tool for studying local and global cortical reactivity to external stimuli at high temporal resolution. tSMS altered TEPs and IORs both at the stimulated cortex and at the contralateral cortex. These findings would be related to the neurophysiological mechanisms underlying the neuromodulation induced by tSMS.

Acute aerobic exercise modulates cognition and cortical excitability in adults with attention-deficit hyperactivity disorder (ADHD) and healthy controls.

Evidence suggests aerobic exercise has beneficial effects on cognitive performance in adults with attention-deficit hyperactivity disorder (ADHD). The underlying mechanisms might depend on mechanisms of exercise-mediated brain physiology. The study aims to investigate the effects of acute aerobic exercise on cortical excitability and cognitive performance, and the correlation between these phenomena in adults with ADHD. Twenty-six drug-naïve ADHD adults, and twenty-six age-, and gender-matched healthy controls were assessed with respect to cortical excitability and cognitive performance before and after acute aerobic exercise (a single session for 30 min) or a control intervention. The results show significantly enhanced intracortical facilitation (ICF) and decreased short intracortical inhibition (SICI) after aerobic exercise in healthy subjects. In contrast, SICI was significantly enhanced following acute aerobic exercise in ADHD. In ADHD, furthermore inhibitory control and motor learning were significantly improved after the acute aerobic exercise intervention. Alterations of SICI induced by aerobic exercise, and inhibitory control and motor learning improvement were significantly positively correlated in the ADHD group. Aerobic exercise had partially antagonistic effects in healthy controls, and ADHD patients. Furthermore, aerobic exercise-induced cognition-enhancing effects in ADHD depend on specific alterations of brain physiology, which differ from healthy humans.

Spatial sensorimotor mismatch between the motor command and somatosensory feedback decreases motor cortical excitability. A transcranial magnetic stimulation-virtual reality study.

Effective control of movement predominantly depends on the exchange and integration between sensory feedback received by our body and motor command. However, the precise mechanisms governing the adaptation of the motor system's response to altered somatosensory signals (i.e., discrepancies between an action performed and feedback received) following movement execution remain largely unclear. In order to address these questions, we developed a unique paradigm using virtual reality (VR) technology. This paradigm can induce spatial incongruence between the motor commands executed by a body district (i.e., moving the right hand) and the resulting somatosensory feedback received (i.e., feeling touch on the left ankle). We measured functional sensorimotor plasticity in 17 participants by assessing the effector's motor cortical excitability (right hand) before and after a 10-min VR task. The results revealed a decrease in motor cortical excitability of the movement effector following exposure to a 10-min conflict between the motor output and the somatosensory input, in comparison to the control condition where spatial congruence between the moved body part and the area of the body that received the feedback was maintained. This finding provides valuable insights into the functional plasticity resulting from spatial sensorimotor conflict arising from the discrepancy between the anticipated and received somatosensory feedback following movement execution. The cortical reorganization observed can be attributed to functional plasticity mechanisms within the sensorimotor cortex that are related to establishing a new connection between somatosensory input and motor output, guided by temporal binding and the Hebbian plasticity rule.

'Remote inhibition' of motor cortex in Epileptic encephalopathy with spike-wave activation in sleep (EE-SWAS): A TMS based cortical excitability study.

OBJECTIVES: The study compared real-time motor cortex excitability using transcranial magnetic stimulation (TMS)-derived parameters between children with epileptic encephalopathy with spike-wave activation in sleep (EE-SWAS) and age-matched neurotypical controls. The EE-SWAS group received steroids as standard of care and were longitudinally followed for three months. MATERIALS & METHODS: Children aged 5-12 years with immunotherapy-naive EE-SWAS (spike-wave-index≥50 %) and neurotypical controls were enrolled. Cognitive and behavioral assessments were performed using valid psychometric tools. Real-time motor cortex excitability was assessed by measuring resting motor threshold (RMT), short intra-cortical inhibition (SICI) and long intra-cortical inhibition (LICI) in both groups. In EE-SWAS group, a follow up evaluation with TMS at 4- and 12-week intervals, EEG, and neurobehavioral assessments at 12-weeks were performed to assess the effect of steroids on cortical excitability and to determine electroclinical outcome. RESULTS: Forty-eight children with suspected EE-SWAS and 26 neurotypical controls were screened; 20 were enrolled in each group. Children with EE-SWAS (mean age: 8.05 ± 1.76 years) had cognitive and behavioral problems (20/20), and ongoing seizures (12/20). At baseline, the dominant motor cortex was significantly inhibited in the EE-SWAS group compared to neurotypical children{RMT(%)[86.3 ± 6.96 vs 58.05 ± 4.71(p < 0.0001)]; LICI(%)[55.05 ± 4.39 vs 73.9 ± 3.75(p < 0.0001)]; SICI(%)[39.2 ± 4.36 vs 55.45 ± 4.78(p < 0.0001)]}. Reversal of motor cortex inhibition was sequentially observed in EE-SWAS group at 4- and 12-week follow-ups{(RMT[4, 12 weeks]: 71.45 ± 9.83, 63.45 ± 8.48); (LICI[4, 12 weeks]: 66.00 ± 6.26, 74.50 ± 5.36); (SICI[4, 12 weeks]: 49.35 ± 6.24, 56.05 ± 5.57)}[repeated-measures ANOVA: p < 0.0001]. CONCLUSION: Motor cortex is remotely inhibited in EE-SWAS, which may contribute to neurobehavioral impairment. Steroids can disinhibit/reverse the epilepsy-induced motor cortex inhibition leading to improvement in neurobehavior.

Effects of DLPFC tDCS Followed by Treadmill Training on Dual-Task Gait and Cortical Excitability in Parkinson's Disease: A Randomized Controlled Trial.

BACKGROUND: Gait disturbances are exacerbated in people with Parkinson's disease (PD) during dual-task walking (DTW). Transcranial direct current stimulation (tDCS) has been shown to exert beneficial effects on gait performance and cortical excitability in PD; however, its combined effects with treadmill training (TT) remain undetermined. OBJECTIVE: To investigate the effects of tDCS followed by TT on DTW performance and cortical excitability in individuals with PD. METHODS: Thirty-four PD participants were randomized to dorsal lateral prefrontal cortex (DLPFC) tDCS and TT group (DLPFC tDCS + TT group) or sham tDCS and TT group (sham tDCS + TT group) for 50 minutes per session (20 minutes tDCS followed by 30 minutes TT), 12 sessions within 5 weeks (2-3 sessions each week). Outcome measures included cognitive dual-task walking (CDTW), motor dual-task walking (MDTW), usual walking performance, cortical excitability, functional mobility, cognitive function, and quality of life. RESULTS: The DLPFC tDCS + TT group exerted significantly greater improvement in CDTW velocity (P = .046), cadence (P = .043), and stride time (P = .041) compared to sham tDCS + TT group. In addition, DLPFC tDCS + TT group demonstrated a significant increase in resting motor threshold of stimulated hemisphere compared with sham tDCS + TT group (P = .026). However, no significant differences between groups were found in MDTW performance and other outcomes. CONCLUSION: Twelve-session DLPFC tDCS followed by TT significantly improved CDTW performance and decreased cortical excitability more than TT alone in individuals with PD. Applying DLPFC tDCS prior to TT could be suggested for gait rehabilitation in individuals with PD. CLINICAL TRIAL REGISTRATION NUMBER: Australian New Zealand Clinical Trials Registry ACTRN12622000101785.

Fluctuation in cortical excitation/inhibition modulates capability of attention across time scales ranging from hours to seconds.

Sustained attention, as the basis of general cognitive ability, naturally varies across different time scales, spanning from hours, e.g. from wakefulness to drowsiness state, to seconds, e.g. trial-by-trail fluctuation in a task session. Whether there is a unified mechanism underneath such trans-scale variability remains unclear. Here we show that fluctuation of cortical excitation/inhibition (E/I) is a strong modulator to sustained attention in humans across time scales. First, we observed the ability to attend varied across different brain states (wakefulness, postprandial somnolence, sleep deprived), as well as within any single state with larger swings. Second, regardless of the time scale involved, we found highly attentive state was always linked to more balanced cortical E/I characterized by electroencephalography (EEG) features, while deviations from the balanced state led to temporal decline in attention, suggesting the fluctuation of cortical E/I as a common mechanism underneath trans-scale attentional variability. Furthermore, we found the variations of both sustained attention and cortical E/I indices exhibited fractal structure in the temporal domain, exhibiting features of self-similarity. Taken together, these results demonstrate that sustained attention naturally varies across different time scales in a more complex way than previously appreciated, with the cortical E/I as a shared neurophysiological modulator.

Impact of Acute High-intensity Interval Training on Cortical Excitability, M1-related Cognitive Functions, and Myokines: A Randomized Crossover Study.

High-intensity interval training (HIIT) is a time-efficient, safe, and feasible exercise type that can be utilized across different ages and health status. This randomized cross-over study aimed to investigate the effect of acute HIIT on cortical excitability, M1-related cognitive functions, cognition-related myokines, brain-derived neurotrophic factor (BDNF), and Cathepsin B (CTSB). Twenty-three sedentary young adults (mean age: 22.78 years ± 2.87; 14 female) participated in a cross-over design involving two sessions: either 23 min of HIIT or seated rest. Before and after the sessions, cortical excitability was measured using transcranial magnetic stimulation, and M1-related cognitive functions were assessed by the n-back test and mental rotation test. Serum levels of BDNF and CTSB were assessed using the ELISA method before and after the HIIT intervention. We demonstrated that HIIT improved mental rotation and working memory, and increased serum levels of BDNF and CTSB, whereas cortical excitability did not change. Our findings provide evidence that one session of HIIT is effective on M1-related cognitive functions and cognition-related myokines. Future research is warranted to determine whether such findings are transferable to different populations, such as cognitively at-risk children, adults, and older adults, and to prescribe effective exercise programs.

Mapping cortical excitability in the human dorsolateral prefrontal cortex.

BACKGROUND: Transcranial magnetic stimulation (TMS) to the dorsolateral prefrontal cortex (dlPFC) is an effective treatment for depression, but the neural effects after TMS remains unclear. TMS paired with electroencephalography (TMS-EEG) can causally probe these neural effects. Nonetheless, variability in single pulse TMS-evoked potentials (TEPs) across dlPFC subregions, and potential artifact induced by muscle activation, necessitate detailed mapping for accurate treatment monitoring. OBJECTIVE: To characterize early TEPs anatomically and temporally (20-50 ms) close to the TMS pulse (EL-TEPs), as well as associated muscle artifacts (<20 ms), across the dlPFC. We hypothesized that TMS location and angle influence EL-TEPs, and specifically that conditions with larger muscle artifact may exhibit lower observed EL-TEPs due to over-rejection during preprocessing. Additionally, we sought to determine an optimal group-level TMS target and angle, while investigating the potential benefits of a personalized approach. METHODS: In 16 healthy participants, we applied single-pulse TMS to six targets within the dlPFC at two coil angles and measured EEG responses. RESULTS: Stimulation location significantly influenced observed EL-TEPs, with posterior and medial targets yielding larger EL-TEPs. Regions with high EL-TEP amplitude had less muscle artifact, and vice versa. The best group-level target yielded 102% larger EL-TEP responses compared to other dlPFC targets. Optimal dlPFC target differed across subjects, suggesting that a personalized targeting approach might boost the EL-TEP by an additional 36%. SIGNIFICANCE: EL-TEPs can be probed without significant muscle-related confounds in posterior-medial regions of the dlPFC. The identification of an optimal group-level target and the potential for further refinement through personalized targeting hold significant implications for optimizing depression treatment protocols.

Exercise effects on cortical excitability in pain populations: A systematic review and meta-analysis.

BACKGROUND: Transcranial Magnetic Stimulation (TMS) studies examining exercise-induced neuroplasticity in pain populations have produced contradictory findings. We conducted a systematic review to explore how exercise impacts cortical excitability in pain populations using TMS metrics. This review aims to summarize the effect sizes and to understand their sources of heterogeneity. METHODS: We searched multiple databases from inception to December 2022. We included randomized controlled trials (RCTs) with any type of pain population, including acute and chronic pain; exercise interventions were compared to sham exercise or other active interventions. The primary outcomes were TMS metrics, and pain intensity was the secondary outcome. Risk of bias assessment was conducted using the Cochrane tool. RESULTS: This review included five RCTs (n = 155). The main diagnoses were fibromyalgia and cervical dystonia. The interventions included submaximal contractions, aerobic exercise, physical therapy, and exercise combined with transcranial direct current stimulation. Three studies are considered to have a high risk of bias. All five studies showed significant pain improvement with exercise. The neurophysiological data revealed improvements in cortical excitability measured by motor-evoked potentials; standardized mean difference = 2.06, 95% confidence interval 1.35-2.78, I2 = 19%) but no significant differences in resting motor threshold. The data on intracortical inhibition/facilitation (ICI/ICF) was not systematically analyzed, but one study (n = 45) reported higher ICI and lower ICF after exercise. CONCLUSIONS: These findings suggest that exercise interventions positively affect pain relief by modifying corticospinal excitability, but their effects on ICI/ICF are still unclear. While the results are inconclusive, they provide a basis for further exploration in this area of research; future studies should focus on establishing standardized TMS measurements and exercise protocols to ensure consistent and reliable findings. A large-scale RCT that examines various exercise interventions and their effects on cortical excitability could offer valuable insights to optimize its application in promoting neuroplasticity in pain populations.

Phosphene and motor transcranial magnetic stimulation thresholds are correlated: A meta-analytic investigation.

Transcranial magnetic stimulation (TMS) is commonly delivered at an intensity defined by the resting motor threshold (rMT), which is thought to represent cortical excitability, even if the TMS target area falls outside of the motor cortex. This approach rests on the assumption that cortical excitability, as measured through the motor cortex, represents a 'global' measure of excitability. Another common approach to measure cortical excitability relies on the phosphene threshold (PT), measured through the visual cortex of the brain. However, it remains unclear whether either estimate can serve as a singular measure to infer cortical excitability across different brain regions. If PT and rMT can indeed be used to infer cortical excitability across brain regions, they should be correlated. To test this, we systematically identified previous studies that measured PT and rMT to calculate an overall correlation between the two estimates. Our results, based on 16 effect sizes from eight studies, indicated that PT and rMT are correlated (ρ = 0.4), and thus one measure could potentially serve as a measure to infer cortical excitability across brain regions. Three exploratory meta-analyses revealed that the strength of the correlation is affected by different methodologies, and that PT intensities are higher than rMT. Evidence for a PT-rMT correlation remained robust across all analyses. Further research is necessary for an in-depth understanding of how cortical excitability is reflected through TMS.

Investigating cortical excitability and inhibition in patients with schizophrenia: A TMS-EEG study.

BACKGROUND: Transcranial magnetic stimulation (TMS) combined with electromyography (EMG) has widely been used as a non-invasive brain stimulation tool to assess excitation/inhibition (E/I) balance. E/I imbalance is a putative mechanism underlying symptoms in patients with schizophrenia. Combined TMS-electroencephalography (TMS-EEG) provides a detailed examination of cortical excitability to assess the pathophysiology of schizophrenia. This study aimed to investigate differences in TMS-evoked potentials (TEPs), TMS-related spectral perturbations (TRSP) and intertrial coherence (ITC) between patients with schizophrenia and healthy controls. MATERIALS AND METHODS: TMS was applied over the motor cortex during EEG recording. Differences in TEPs, TRSP and ITC between the patient and healthy subjects were analysed for all electrodes at each time point, by applying multiple independent sample t-tests with a cluster-based permutation analysis to correct for multiple comparisons. RESULTS: Patients demonstrated significantly reduced amplitudes of early and late TEP components compared to healthy controls. Patients also showed a significant reduction of early delta (50-160 ms) and theta TRSP (30-250ms),followed by a reduction in alpha and beta suppression (220-560 ms; 190-420 ms). Patients showed a reduction of both early (50-110 ms) gamma increase and later (180-230 ms) gamma suppression. Finally, the ITC was significantly lower in patients in the alpha band, from 30 to 260 ms. CONCLUSION: Our findings support the putative role of impaired GABA-receptor mediated inhibition in schizophrenia impacting excitatory neurotransmission. Further studies can usefully elucidate mechanisms underlying specific symptoms clusters using TMS-EEG biometrics.

Always expect the unexpected: eye position modulates visual cortex excitability in a stimulus-free environment.

Stimuli that potentially require a rapid defensive or avoidance action can appear from the periphery at any time in natural environments. de Wit et al. (Cortex 127: 120-130, 2020) recently reported novel evidence suggestive of a fundamental neural mechanism that allows organisms to effectively deal with such situations. In the absence of any task, motor cortex excitability was found to be greater whenever gaze was directed away from either hand. If modulation of cortical excitability as a function of gaze location is a fundamental principle of brain organization, then one would expect its operation to be present outside of motor cortex, including brain regions involved in perception. To test this hypothesis, we applied single-pulse transcranial magnetic stimulation (TMS) to the right lateral occipital lobe while participants directed their eyes to the left, straight-ahead, or to the right, and reported the presence or absence of a phosphene. No external stimuli were presented. Cortical excitability as reflected by the proportion of trials on which phosphenes were elicited from stimulation of the right visual cortex was greater with eyes deviated to the right as compared with the left. In conjunction with our previous findings of change in motor cortex excitability when gaze and effector are not aligned, this eye position-driven change in visual cortex excitability presumably serves to facilitate the detection of stimuli and subsequent readiness to act in nonfoveated regions of space. The existence of this brain-wide mechanism has clear adaptive value given the unpredictable nature of natural environments in which human beings are situated and have evolved.NEW & NOTEWORTHY For many complex tasks, humans focus attention on the site relevant to the task at hand. Humans evolved and live in dangerous environments, however, in which threats arise from outside the attended site; this fact necessitates a process by which the periphery is monitored. Using single-pulse transcranial magnetic stimulation (TMS), we demonstrated for the first time that eye position modulates visual cortex excitability. We argue that this underlies at least in part what we term "surveillance attention."

Acute aerobic exercise at different intensities modulates inhibitory control and cortical excitability in adults with attention-deficit hyperactivity disorder (ADHD).

BACKGROUND: This study aimed to investigate the effects of different aerobic exercise intensities on inhibitory control and cortical excitability in adults with attention-deficit/hyperactivity disorder (ADHD). METHODS: The study was conducted in a within-subject design. Twenty-four adults with ADHD completed a stop signal task and received cortical excitability assessment by transcranial magnetic stimulation (TMS) before and after a single session of low-, moderate-, high-intensity aerobic exercise or a control intervention. RESULTS: Acute moderate-, and high-intensity aerobic exercise improved inhibitory control in adults with ADHD. Moreover, the improving effect was similar between moderate-, and high-intensity aerobic exercise conditions. As shown by the brain physiology results, short interval intracortical inhibition was significantly increased following both, moderate- and high-intensity aerobic exercise intervention conditions. Additionally, the alteration of short interval intracortical inhibition and inhibitory control improvement were positively correlated. CONCLUSIONS: The moderate-, and high-intensity aerobic exercise-dependent alterations of cortical excitability in adults with ADHD might partially explain the inhibitory control-improving effects of aerobic exercise in this population.

Assessing cortical excitability with electroencephalography: A pilot study with EEG-iTBS.

BACKGROUND: Cortical excitability measures neural reactivity to stimuli, usually delivered via Transcranial Magnetic Stimulation (TMS). Excitation/inhibition balance (E/I) is the ongoing equilibrium between excitatory and inhibitory activity of neural circuits. According to some studies, E/I could be estimated in-vivo and non-invasively through the modeling of electroencephalography (EEG) signals and termed 'intrinsic excitability' measures. Several measures have been proposed (phase consistency in the gamma band, sample entropy, exponent of the power spectral density 1/f curve, E/I index extracted from detrend fluctuation analysis, and alpha power). Intermittent theta burst stimulation (iTBS) of the primary motor cortex (M1) is a non-invasive neuromodulation technique allowing controlled and focal enhancement of TMS cortical excitability and E/I of the stimulated hemisphere. OBJECTIVE: Investigating to what extent E/I estimates scale with TMS excitability and how they relate to each other. METHODS: M1 excitability (TMS) and several E/I estimates extracted from resting state EEG recordings were assessed before and after iTBS in a cohort of healthy subjects. RESULTS: Enhancement of TMS M1 excitability, as measured through motor-evoked potentials (MEPs), and phase consistency of the cortex in high gamma band correlated with each other. Other measures of E/I showed some expected results, but no correlation with TMS excitability measures or strong consistency with each other. CONCLUSIONS: EEG E/I estimates offer an intriguing opportunity to map cortical excitability non-invasively, with high spatio-temporal resolution and with a stimulus independent approach. While different EEG E/I estimates may reflect the activity of diverse excitatory-inhibitory circuits, spatial phase synchrony in the gamma band is the measure that best captures excitability changes in the primary motor cortex.

Effect of neuronavigated repetitive Transcranial Magnetic Stimulation on pain, cognition and cortical excitability in fibromyalgia syndrome.

BACKGROUND: Fibromyalgia syndrome is a widespread chronic pain condition identified by body-wide pain, fatigue, cognitive fogginess, and sleep issues. In the past decade, repetitive transcranial magnetic stimulation has emerged as a potential management tool.. In the present study, we enquired whether repetitive transcranial magnetic stimulation could modify pain, corticomotor excitability, cognition, and sleep. METHODS: Study is a randomized, sham-controlled, double-blind, clinical trial; wherein after randomizing thirty-four fibromyalgia patients into active or sham therapy (n = 17 each), each participant received repetitive transcranial magnetic stimulation therapy. In active therapy was given at 1 Hz for 20 sessions were delivered on dorsolateral prefrontal cortex (1200 pulses, 150 pulses per train for 8 trains); while in sham therapy coil was placed at right angle to the scalp with same frequency. Functional magnetic resonance imaging was used to identify the therapeutic site. Pain intensity, corticomotor excitability, cognition, and sleep were examined before and after therapy. RESULTS: Baseline demographic and clinical parameters for both active and sham groups were comparable. In comparison to sham, active repetitive transcranial magnetic stimulation showed significant difference in pain intensity (P < 0.001, effect size = 0.29, large effect) after intervention. Other parameters of pain perception, cognition, and sleep quality also showed a significant improvement after the therapy in active therapy group only, as compared to sham. CONCLUSIONS: Findings suggest that repetitive transcranial magnetic stimulation intervention is effective in managing pain alongside cognition and sleep disturbances in patients of fibromyalgia. It may prove to be an important tool in relieving fibromyalgia-associated morbidity.

Decoding the clinical effects of low-grade glioma-induced cortical excitability.

OBJECTIVE: Patients with low-grade glioma (LGG) in eloquent regions often present with seizures, and findings on detailed neuropsychological testing are often abnormal. This study evaluated the association between cortical excitability, seizures, and cognitive function in patients with LGG. METHODS: LGG patients who underwent transcranial magnetic stimulation (TMS) from January 2021 to December 2022 were studied. Cortical excitability was measured using the resting motor thresholds (RMTs) of the upper and lower extremities. Early postoperative seizures served as the seizure endpoint. Neuropsychological assessment was completed prior to surgery contemporaneous with the TMS studies. RESULTS: A total of 31 patients were analyzed for seizure outcome. Median (interquartile range [IQR]) upper-extremity RMT was 39% (34%-46%) of maximum stimulator output, and the median (IQR) lower-extremity RMT was 69% (51%-79%). Lower-extremity RMT was higher in patients with early postoperative seizures, especially in those with motor region tumors (p = 0.02); however, RMT was not associated with seizures at presentation or long-term seizure control. A total of 26 patients completed neuropsychological assessment. There were significant negative correlations between upper-extremity RMT and psychomotor processing speed (Wechsler Adult Intelligence Scale-Fourth Edition [WAIS-IV] Processing Speed Index r = -0.42, p = 0.031; WAIS-IV Coding r = -0.41, p = 0.036; WAIS-IV Symbol Search r = -0.39, p = 0.048), executive function (Trail Making Test Part B r = -0.41, p = 0.036), and hand dexterity (Grooved Pegboard Test r = -0.50, p = 0.047). CONCLUSIONS: RMT was positively correlated with early postoperative seizure risk and negatively correlated with psychomotor processing speed, executive function, and hand dexterity. These findings support the theory of local and regional resting oscillatory network dysfunction from a glioma-brain network.

Corticospinal excitability is highest at the early rising phase of sensorimotor µ-rhythm.

Alpha oscillations are thought to reflect alternating cortical states of excitation and inhibition. Studies of perceptual thresholds and evoked potentials have shown the scalp EEG negative phase of the oscillation to correspond to a short-lasting low-threshold and high-excitability state of underlying visual, somatosensory, and primary motor cortex. The negative peak of the oscillation is assumed to correspond to the state of highest excitability based on biophysical considerations and considerable effort has been made to improve the extraction of a predictive signal by individually optimizing EEG montages. Here, we investigate whether it is the negative peak of sensorimotor µ-rhythm that corresponds to the highest corticospinal excitability, and whether this is consistent between individuals. In 52 adult participants, a standard 5-channel surface Laplacian EEG montage was used to extract sensorimotor µ-rhythm during transcranial magnetic stimulation (TMS) of primary motor cortex. Post-hoc trials were sorted from 800 TMS-evoked motor potentials (MEPs) according to the pre-stimulus EEG (estimated instantaneous phase) and MEP amplitude (as an index of corticospinal excitability). Different preprocessing transformations designed to improve the accuracy by which µ-alpha phase predicts excitability were also tested. By fitting a sinusoid to the MEP amplitudes, sorted according to pre-stimulus EEG-phase, we found that excitability was highest during the early rising phase, at a significant delay with respect to the negative peak by on average 45° or 10 ms. The individual phase of highest excitability was consistent across study participants and unaffected by two different EEG-cleaning methods that utilize 64 channels to improve signal quality by compensating for individual noise level and channel covariance. Personalized transformations of the montage did not yield better prediction of excitability from µ-alpha phase. The relationship between instantaneous phase of a brain oscillation and fluctuating cortical excitability appears to be more complex than previously hypothesized. In TMS of motor cortex, a standard surface Laplacian 5-channel EEG montage is effective in extracting a predictive signal and the phase corresponding to the highest excitability appears to be consistent between individuals. This is an encouraging result with respect to the clinical potential of therapeutic personalized brain interventions in the motor system. However, it remains to be investigated, whether similar results can be obtained for other brain areas and brain oscillations targeted with EEG and TMS.

Increased intrinsic and synaptic excitability of hypothalamic POMC neurons underlies chronic stress-induced behavioral deficits.

Chronic stress exposure induces maladaptive behavioral responses and increases susceptibility to neuropsychiatric conditions. However, specific neuronal populations and circuits that are highly sensitive to stress and trigger maladaptive behavioral responses remain to be identified. Here we investigate the patterns of spontaneous activity of proopiomelanocortin (POMC) neurons in the arcuate nucleus (ARC) of the hypothalamus following exposure to chronic unpredictable stress (CUS) for 10 days, a stress paradigm used to induce behavioral deficits such as anhedonia and behavioral despair [1, 2]. CUS exposure increased spontaneous firing of POMC neurons in both male and female mice, attributable to reduced GABA-mediated synaptic inhibition and increased intrinsic neuronal excitability. While acute activation of POMC neurons failed to induce behavioral changes in non-stressed mice of both sexes, subacute (3 days) and chronic (10 days) repeated activation of POMC neurons was sufficient to induce anhedonia and behavioral despair in males but not females under non-stress conditions. Acute activation of POMC neurons promoted susceptibility to subthreshold unpredictable stress in both male and female mice. Conversely, acute inhibition of POMC neurons was sufficient to reverse CUS-induced anhedonia and behavioral despair in both sexes. Collectively, these results indicate that chronic stress induces both synaptic and intrinsic plasticity of POMC neurons, leading to neuronal hyperactivity. Our findings suggest that POMC neuron dysfunction drives chronic stress-related behavioral deficits.

Effects of transcranial direct current stimulation on visuospatial attention in air traffic controllers.

Visuospatial attention is a cognitive skill essential to the performance of air traffic control activities. We evaluated the effect of an anodic session of transcranial low-intensity direct current stimulation (tDCS) right parietal associated with cognitive training of visuospatial attention of 21 air traffic controllers. Within-subject designs were used, with all volunteers undergoing two tDCS sessions; an experimental (2 mA anodic) and control (sham) performed concomitantly with the cognitive training (2-Back). Visuospatial performance was measured using the Attention Network Test for Interactions and Vigilance pre- and post-intervention. The results indicate that after an active parietal tDCS session, the ATCOs showed faster responses, but not more accurate, for visuospatial attention in its aspects of orientation and reorientation. This result was significant when comparing baseline and post-tests in the active tDCS group. Comparing the post-tests between the tDCS active and sham groups, it is possible to infer a trend of improvement in the results based on faster and more accurate responses, which suggests a possible refinement of the ATCO's attentional orientation. However, this population may eventually have reached a plateau in the performance of this skill. From the analysis of the results we arrive at the following hypotheses: (I) the increase in cortical excitability mediated by anodic tDCS frequently recorded may not be accompanied by improvements in behavioural measures; (II) the interaction between anodic tDCS with another event of increased excitability-execution of a cognitive task, may have hindered the occurrence of neuroplasticity; (III) the air traffic control activity may be associated with a high level of attention, which may have contributed to a ceiling effect for the development of this skill; (IV) online assessments may be more relevant to identify acute effects; (V) repeated sessions may be more efficient to find cumulative effects; (VI) the analysis of interactions between attentional networks can contribute to the study of visuospatial attention; (VII) tDCS protocols aimed at ATCO need to consider the specifics of this audience, such as circadian rhythm and sleep and fatigue conditions.