Showing papers in "Neurophysiologie Clinique-clinical Neurophysiology in 2019"

Using EEG-based brain computer interface and neurofeedback targeting sensorimotor rhythms to improve motor skills: Theoretical background, applications and prospects.

Abstract: Many Brain Computer Interface (BCI) and neurofeedback studies have investigated the impact of sensorimotor rhythm (SMR) self-regulation training procedures on motor skills enhancement in healthy subjects and patients with motor disabilities. This critical review aims first to introduce the different definitions of SMR EEG target in BCI/Neurofeedback studies and to summarize the background from neurophysiological and neuroplasticity studies that led to SMR being considered as reliable and valid EEG targets to improve motor skills through BCI/neurofeedback procedures. The second objective of this review is to introduce the main findings regarding SMR BCI/neurofeedback in healthy subjects. Third, the main findings regarding BCI/neurofeedback efficiency in patients with hypokinetic activities (in particular, motor deficit following stroke) as well as in patients with hyperkinetic activities (in particular, Attention Deficit Hyperactivity Disorder, ADHD) will be introduced. Due to a range of limitations, a clear association between SMR BCI/neurofeedback training and enhanced motor skills has yet to be established. However, SMR BCI/neurofeedback appears promising, and highlights many important challenges for clinical neurophysiology with regards to therapeutic approaches using BCI/neurofeedback.

How can the stimulation of plantar cutaneous receptors improve postural control? Review and clinical commentary.

Abstract: Postural control requires constant and subconscious postural sway to manage balance and achieve postural stability. These movements of regulation are based in particular on cutaneous plantar information. The foot constitutes a functional whole that participates in the mechanisms of postural control and regulation. It represents the direct interface between the body and the ground during quiet standing, and plantar cutaneous information contributes to postural control. Upright balance mechanically depends on the gravitational torque produced by the forces of gravity and reaction of the ground. In this context, the foot behaves like a sensory system for postural regulation whose objective is to maintain a state of stability within a changing and constraining environment. There is a relation between balance improvement and the facilitation of sensory feedback related to the activation of the plantar cutaneous mechanoreceptors. From a clinical point of view, the application of additional tactile cues may have therapeutic benefits in relation to fall prevention, or to improve specific types of chronic pain.

A practical algorithm for using rTMS to treat patients with chronic pain

Abstract: High-frequency repetitive transcranial magnetic stimulation (rTMS) of the primary motor cortex has a good level of evidence of efficacy as a method for providing analgesic effects in patients with chronic pain. However, there is still no consensus regarding the parameters of stimulation to use and the detailed protocol to apply for therapeutic practice. In this article, we review the main technical points to address, and we propose a practical algorithm of how to use rTMS for chronic pain treatment in daily clinical practice.

Individual recovery profiles of manual dexterity, and relation to corticospinal lesion load and excitability after stroke –a longitudinal pilot study

Abstract: Summary Objectives In this longitudinal pilot study, we investigated how manual dexterity recovery was related to corticospinal tract (CST) injury and excitability, in six patients undergoing conventional rehabilitation. Methods Key components of manual dexterity, namely finger force control, finger tapping rate and independence of finger movements, were quantified. Structural MRI was obtained to calculate CST lesion load. CST excitability was assessed by measuring rest motor threshold (RMT) and the amplitude of motor evoked potentials (MEPs) using transcranial magnetic stimulation (TMS). Measurements were obtained at two weeks, three and six months post-stroke. Results At six months post-stroke, complete recovery of hand gross motor impairment (i.e., maximal Fugl-Meyer score for hand) had occurred in three patients and four patients had recovered ability to accurately control finger force. However, tapping rate and independence of finger movements remained impaired in all six patients at six months. Recovery in hand gross motor impairment and finger force control occurred in patients with smaller CST lesion load and almost complete recovery of CST excitability, although RMT or MEP size remained slightly altered in the stroke-affected hemisphere compared to the unaffected hemisphere. The two patients with poorest recovery showed persistent absence of MEPs and greatest structural injury to CST. Discussion The findings support good motor recovery being overall correlated with smaller CST lesion, and with almost complete recovery of CST excitability. However, impairment of manual dexterity persisted despite recovery in gross hand movements and grasping abilities, suggesting involvement of additional brain structures for fine manual tasks.

Three repeated sessions of transcranial random noise stimulation (tRNS) leads to long-term effects on reaction time in the Go/No Go task.

Abstract: Summary Objective We aimed to investigate whether the number of sessions delivered within one day influences the acute and long-term effects of transcranial random noise stimulation (tRNS) applied over the dorsolateral prefrontal cortex (DLPFC) on inhibitory control. Methods Thirty-six healthy participants were randomly assigned to receive either (i) 3 active (3A), (ii) 1 active and 2 sham (1A2S) or (iii) 3 sham (3S) tRNS sessions. The 3 tRNS were delivered consecutively in the same half-day separated by 30 min with the anode over the right and the cathode over the left DLPFC. The effects of tRNS on inhibitory control were assessed 5 times using a Go/No Go task: at baseline (T0), after one tRNS session (T1), after the 3 sessions (T3), 1 (D1) and 8 (D8) days after. Results As compared to sham, active tRNS did not acutely modulate accuracy in the Go/No Go task but decreased reaction times at Go trials. At D1, participants who received at least one active tRNS sessions (3A and 1A2S groups) were faster than those who received 3 sessions of sham. At D8, only the participants who received 3 active tRNS sessions were faster to successfully respond to Go trials as compared to sham. Discussion Three active tRNS sessions induced longer effects on reaction times than a single session of active tRNS, compared to sham. These findings suggested that delivering repeated tRNS sessions on the same day induces more sustained effects than delivering a single session.

Prognostic value of post-acute EEG in severe disorders of consciousness, using American Clinical Neurophysiology Society terminology.

Abstract: Summary Objective To evaluate whether electroencephalographic (EEG) features recorded during the post-acute stage in patients with severe disorders of consciousness (DoC) after acute brain injury (ABI), contribute to neurological outcome prediction of these patients at discharge from the intensive rehabilitation unit (IRU). Methods We retrospectively evaluated all patients consecutively admitted to the IRU from August 2012 to December 2016. Inclusion criteria were: 1) age > 18years, 2) patients with unresponsive wakefulness syndrome (UWS) or in a minimally conscious state (MCS), and 3) EEG and a coma recovery scale-revised (CRS-R) score available within the first week after admission. Clinical evaluation was performed using the Italian version of the CRS-R score. EEGs were classified according to American Clinical Neurophysiology Society (ACNS) terminology. Clinical state at final discharge was evaluated using the CRS-R score. Results In total, 102 patients were included in the analysis. After a mean of five months of IRU stay, among the 61 UWS subjects, 19 transitioned to MCS and 11 recovered to exit-MCS (E-MCS); twenty-three of the 41 subjects in MCS progressed to E-MCS. Using logistic regression, consciousness level (UWS/MCS-OR = 13.4), CRS-R score at admission (OR = 1.33) and use of activating drugs (OR = 4.7) were significant predictors of clinical improvement. Multivariable analysis showed that specific EEG patterns were independent predictors of improved consciousness at discharge in UWS patients. Discussion EEG performed within the first week after IRU admission, classified according to ACNS-terminology in patients with UWS at admission, can provide useful prognostic contribution.

Twice-daily neuronavigated intermittent theta burst stimulation for bipolar depression: A Randomized Sham-Controlled Pilot Study.

Abstract: The safety and efficacy of neuronavigated intermittent theta burst stimulation (iTBS) in patients with bipolar depression has not yet been investigated. We hypothesized the superiority of active iTBS over sham. Twenty-six patients were randomly allocated to receive either active (n=12) or sham (n=14) iTBS. Response and remission rates according to changes in depression MADRS score were high following active iTBS (72% and 42% for response and remission rates, respectively), but no significant difference was found after sham stimulation (42%and 25%). No adverse events were observed. This study revealed the safety and tolerability of twice daily iTBS in patients with bipolar depression. Larger controlled studies are warranted to prove iTBS superiority in treatment-resistant bipolar depression.

Postural responses to emotional visual stimuli.

Abstract: Postural control is a motor skill that allows individuals to interact with their environment. Indeed, in all species, development of postural control is a prerequisite for acquiring further motor abilities. In humans, the maintenance of a bipedal posture plays an important role in interaction with the environment, as it provides a stable postural basis allowing upper limbs and hands to be used to manipulate objects. On the other hand, this bipedal posture induces a constraint in terms of balance, as individuals have to deal with a relatively small base of support enclosed by the surface of the two feet. Biomechanical principles underlying postural control have been studied in great depth, but the effect of emotion on postural control seems to be an emergent topic. Over the last two decades, an exponential number of studies have been published at the interface of affective and social neurosciences. Moreover, the interactions between motor and affective processes are increasingly documented in the scientific literature. In this article, we try to synthetize main recent empirical results that have allowed exploration of the link between body posture and emotional processing.

Hospital production cost of transcranial direct current stimulation (tDCS) in the treatment of depression.

Abstract: Summary Objectives Due to its ease of use, tolerance, and cost of acquisition, transcranial direct current stimulation (tDCS) could constitute a credible therapeutic option for non-resistant depression in primary care, when combined with drug management. This indication has yet to receive official recognition in France. The objective of this study is to evaluate the production cost of tDCS for the treatment of depression in hospitals, under realistic conditions. Methods The methodology adopted is based on cost accounting and was validated by a multidisciplinary working group. It includes equipment, staff, and structural costs to obtain the most realistic estimate possible. We first estimated the cost of producing a tDCS session, based on our annual activity objective, and then estimated the cost of a 15-session treatment program. This was followed up with a sensitivity analysis applying appropriate parameters. Results The hospital production cost of a tDCS depression treatment program for a single patient was estimated at €1555.60 euros: €99 in equipment costs, €1076.95 in staff costs, and €379.65 in structural costs. Conclusion This cost analysis should make it possible to draw up pricing proposals in compliance with regulations and health policy choices and to develop health-economic studies. This would ultimately lead to official recognition of tDCS treatment for depression in France and pave the way for studying various scenarios of coverage by the French national health insurance system.

Investigating the effect of anticipating a startling acoustic stimulus on preparatory inhibition.

Abstract: Summary Objectives Motor-evoked potentials (MEPs) to transcranial magnetic stimulation (TMS) show a profound suppression when elicited during the instructed-delay of reaction time (RT) tasks. One predominant hypothesis is that this phenomenon, called “preparatory inhibition”, reflects the operation of processes that suppress motor activity to withhold prepared (but delayed) responses, a form of impulse control. In addition, a startling acoustic stimulus (SAS) – a loud and narrow sound – can trigger the release of prepared responses in RT tasks. We predicted that, if such premature release is clearly forbidden, then anticipating a SAS during delay periods may be associated with increased preparatory inhibition for greater impulse control. Methods Subjects performed a behavioural (n = 16) and TMS (n = 11) experiment. Both used a choice RT task that required subjects to choose a response based on a preparatory cue but to only release it after an imperative signal. SAS and TMS pulses were elicited at the end of the delay period and subjects were asked to do their best to only release their response after the imperative signal, even in the presence of SAS. SAS could be either rare or frequent, in separate blocks. Results Consistent with the literature, SAS shortened RTs, especially when they occurred frequently. Moreover, MEPs were suppressed when subjects delayed prepared responses but this preparatory inhibition did not depend on whether SAS were frequent or rare. Discussion The stronger RT shortening with frequent rather than rare SAS may be due to increased attention and/or reduced reactive inhibition to SAS, leaving preparatory inhibition unaffected.

Potential impact of bifrontal transcranial random noise stimulation (tRNS) on the semantic Stroop effect and its resting-state EEG correlates.

Abstract: Summary Objective The Stroop effect performance reflects cognitive resistance to interference We aimed to investigate the effect of a single transcranial random noise stimulation session (tRNS) applied over the dorsolateral prefrontal cortex (DLPFC) on the semantic Stroop effect and its resting electroencephalography (EEG) correlates (β/α ratio) Methods In a randomized, double-blind study, healthy volunteers were allocated to receive either one session of active tRNS (n = 8) or one session of sham tRNS (n = 11) The anode pad was placed on the scalp over the right-DLPFC and the cathode pad was placed over the left-DLPFC A computerized adaptation of the French Stroop Color-Word Test (Victoria version) and a resting-state continuous EEG recording were administered before and after the tRNS Results No significant difference were observed for either Stroop Interference/Congruent (F(1,15) = 05, P = 5, BF = 19) or Interference/Cross (F(1,14) = 32, P = 1, BF = 025) ratios No significant effect of tRNS was observed on EEG β/α ratios across electrodes (F(5,95) = 06, P = 7, BF = 059e−05) Under active stimulation, Pearson's tests showed significant correlations with moderate evidence between post–pre differences of Stroop Interference/Congruent and Fz-β/α ratios (r = 088, P = 02, BF = 405), and Stroop Interference/Crosses and Cz-β/α ratios (r = 089, P = 008, BF = 825), while the same correlations did not reach significance under sham conditions Discussion We observed no significant changes in either semantic Stroop task reaction time or its EEG correlates after tRNS However, we provide the original finding that fronto-central β/α activity becomes related to cognitive resistance to interference when the DLPFC is stimulated with random noise current The results suggest a potential resynchronization of relevant brain frequency patterns into Stroop-related cortical involvement

Reliability of maximum isometric hip and knee torque measurements in children with cerebral palsy using a paediatric exoskeleton - Lokomat.

Abstract: Summary Background The Lokomat (by L-Force tool) allows the measurement of the maximum voluntary isometric torque (MVIT) at the knee and hip joints in a standing position, as close as possible to the posture adopted during walking. However, the reliability of this measurement in children with cerebral palsy (CP) remains unknown. The main goal of this study was to evaluate inter and intra-tester reliability of a novel tool (L-Force) in CP population. Procedure L-Force reliability was determined in 17 children with CP by two experienced therapists. We collected MVITs in hip and knee flexors and extensors. Relative and absolute reliability of maximum joint torques were estimated using the intra-class correlation coefficient (ICC) and standard error of measurement (SEM), respectively. The correlation between L-Force and hand-held dynamometer (HHD) was also reported. Findings ICCs were good to excellent for intra and inter-tester reliability (all P ≤ 0.001). The SEM ranged from 2.0 to 4.1 Nm (12.1 to 21.7%) within-tester and from 2.1 to 3.5 Nm (11.9 to 22.5%) between testers. The correlation was fair to good between L-Force and HHD measures (r = [0.50–0.75]; all P ˂ 0.01) with higher values for flexors than extensors. Conclusion The L-Force is a reliable tool for quantifying the hip and knee flexors and extensors torques in children with cerebral palsy with an important timesaving and in a more functional posture than traditional HHD.

A single session of anodal transcranial direct current stimulation applied over the affected primary motor cortex does not alter gait parameters in chronic stroke survivors

Abstract: Summary Objectives The excitability of some neural circuits involved in walking and affected in individuals with chronic stroke can be modulated during and/or immediately after anodal transcranial direct current stimulation (a-tDCS). This study was designed to investigate the effects of a-tDCS during and immediately after application on leg muscle activity during gait, and on spatiotemporal and kinematic gait parameters in patients with chronic stroke. Methods This study was randomized, sham-controlled and double-blinded with a cross-over design and included 24 individuals with chronic stroke. Each participant underwent one 30-minute session each of effective a-tDCS at 2 mA and sham tDCS. In both sessions, the anode was placed over the leg motor cortex of the affected hemisphere and the cathode over the contralateral orbit. Six gait trials were performed before, during and immediately after each effective/sham tDCS session. Electromyographic activity of leg muscles, as well as spatiotemporal (e.g. gait speed) and kinematic (e.g. peak knee flexion and ankle dorsiflexion in the swing phase of gait) gait parameters were recorded. Genotyping for the brain-derived neurotrophic factor (BDNF) Val66Met polymorphism was undertaken since this gene may influence motor skill learning and the effects of tDCS. Results No significant effects of a-tDCS on gait parameters were found either for the total group or for the Val66Met (N = 10) and Val66Val (N = 14) subgroups. Conclusion A single session of a-tDCS delivered to the leg motor cortex did not immediately improve gait parameters in individuals with chronic stroke, regardless of their BDNF genotype.

Repetitive transcranial magnetic stimulation (rTMS) fails to increase serum brain-derived neurotrophic factor (BDNF)

Abstract: Summary Objectives Brain-derived neurotrophic factor (BDNF) plays an important role in neuronal plasticity and in the pathophysiology of various brain disorders. Repetitive transcranial magnetic stimulation (rTMS) has been widely used in neuropsychiatric disease. It is presumed that BDNF mediates the therapeutic benefits of rTMS, but previous results are contradictory. We therefore conducted a meta-analysis to examine the efficacy of rTMS to increase serum BDNF. Methods We performed a comprehensive literature search for clinical trials evaluating the efficacy of rTMS and addressing serum BDNF level. To pool effect size estimate (Hedges’ g) of serum BDNF across studies, a meta-analysis was performed according to the Cochrane guideline. Results rTMS failed to increase serum BDNF level with effect size of −0.12 (95% CI: −0.30, 0.06) (P = 0.193). Multilevel mixed-effects models analysis showed that overall effect of rTMS on BDNF levels was influenced by group of participants (healthy vs. disease) (P Conclusions Repetitive rTMS fails to increase serum BDNF, and it seems that serum BDNF level is related to frequency and duration of rTMS, as well as age and health status of population.

Split-hand phenomenon quantified by the motor unit number index for distinguishing cervical spondylotic amyotrophy from amyotrophic lateral sclerosis.

Abstract: Summary Objectives To investigate and compare split-hand phenomenon quantified by motor unit number index (MUNIX) between patients with cervical spondylotic amyotrophy (CSA) and those with amyotrophic lateral sclerosis (ALS). Methods MUNIX was performed on abductor pollicis brevis (APB), abductor digiti minimi (ADM) and first dorsal interosseous (FDI) in 46 CSA patients, 39 ALS patients and 41 healthy subjects. Split-hand measurements including split-hand index (SHI = ABP × FDI/ADM), ratio of APB to ADM (AA), ratio of FDI to ADM (FA) were measured by compound muscle action potential (CMAP) and MUNIX. Results There was a significant difference in both AA and SHI measured by two different methods between ALS and CSA patients (P Conclusions Both AA and SHI measured by two different methods are useful in distinguishing ALS from CSA, and those quantified by MUNIX may be a better differential diagnostic marker to provide an accurate and noninvasive additional test for distinguishing CSA from ALS, even in their early stages.

Cold evoked potentials: Acquisition from cervical dermatomes

Abstract: Summary Introduction Cold evoked potentials (CEPs) represent a novel technique to assess the integrity of cold-specific pathways within the somatosensory system. So far an objective assessment of these pathways has not been implemented into the clinical routine. Specifically, CEPs may help to elucidate the pathophysiological underpinnings of altered cold processing in neurological diseases. Objective To test feasibility and test-retest reliability of CEPs within two cervical dermatomes, including recording sites in glabrous and hairy skin, in order to facilitate the transition into clinical practice. Methods Twenty healthy subjects received 15 cold stimuli applied by a thermode either at the hand dorsum (C6 dermatome, hairy skin), the shoulder (C4 dermatome, hairy skin) or the thenar eminence (C6 dermatome, glabrous skin). Stimuli were applied from a baseline temperature of 30°C down to a destination temperature of 25 °C at a rate of 20 °C/s. N2 latencies and N2P2 amplitudes were recorded at the vertex using a surface electroencephalogram and test-retest statistics were calculated. Results Slight, innocuous cooling (Δ5 °C) from a baseline temperature of 30 °C elicited a brief percept of cooling and generated a vertex potential (N2P2) in most subjects. The latency of the vertex response is consistent with A-delta fiber activation. Based on test-retest analyses (i.e., intraclass correlation coefficients (ICCs) and Bland-Altman analyses) reliability is best within the C4 dermatome and for stimulation of hairy skin. ICCs display fair to substantial (ICCs from 0.51–0.81) reliability for amplitudes across all stimulation sites, possibly due to floor effects. CEPs latencies, however, were only poorly reliable (ICCs from −0.13 to 0.31). Conclusion The acquisition of CEPs from cervical dermatomes is feasible. Since involvement of cold-specific pathways is relevant for several pathologies in clinical neurology, the application of CEPs may complement existing techniques like contact heat and laser stimulation in the assessment of peripheral and central nervous system disorders. Future studies employing different stimulation paradigms using faster cooling are warranted in order to improve the signal-to-noise ratio.

Pattern electroretinography and retinal changes in patients with diabetes mellitus type 2

Abstract: Summary Objectives To objectively explore retinal neuronal function by pattern electroretinography (PERG) in patients with diabetes mellitus (DM) type 2 at different stages of diabetic retinopathy (DR). Methods A group of 84 patients with DM was studied, divided into three subgroups according to the degree of retinal changes. The first subgroup consisted of patients without DR (n = 28), the second patients with initial DR (n = 27) and the third patients with advanced DR (n = 29). Controls were 47 healthy individuals. PERG was performed and latency and amplitude were analyzed. Results PERG results were affected in DM patients including the group without DR; abnormalities were more severe in patients with advanced DR. Conclusion PERG could be used as an objective method providing evidence of early changes in retinal neuron function in DM patients, including at preclinical stages. It is useful for monitoring disease progression, as it is non-invasive, harmless, rapid, inexpensive and readily repeatable.

Posturo-locomotor markers of preclinical Parkinson's disease.

Abstract: Parkinson's disease (PD) is known to have a long prodromal stage due to the degeneration of dopaminergic neurons of the substantia nigra pars compacta over the course of many years without clinical manifestations of PD. When the diagnosis is made, the neuropathological process is already well entrenched. Consequently, identifying individuals during this prodromal period could be very helpful for future trials of neuroprotective or disease-modifying therapies, which might slow or prevent the degeneration of dopaminergic neurons. Thus, efforts are needed to determine appropriate early markers of PD. Gait and balance disorders are frequent during the early stages of PD. This systematic review aims to determine if gait and balance disorders occur before the diagnosis of PD and if so, whether they could be used as markers of preclinical PD. Findings reveal that, at the presymptomatic stage of PD, impaired basal ganglia function leads to disorders in gait and balance. Both clinical and instrumental assessments allow early detection of these disorders, particularly when performed under challenging conditions (e.g. dual-task). Among all studied parameters, temporal gait variability and arm kinematics appear to be promising markers of preclinical PD.

Contribution of transcranial magnetic stimulation in assessing parietofrontal connectivity during gesture production in healthy individuals and brain-injured patients.

Abstract: Summary Parietofrontal (PF) networks link the posterior parietal cortex to premotor and prefrontal areas, and are involved in the control of many motor and cognitive behaviors in healthy humans. In recent years, electrophysiological experiments have provided a better understanding of the functional specificity and temporal involvement of the PF networks’ different components during the planning of visually guided upper limb movements. In particular, transcranial magnetic stimulation has been used to temporarily inactivate a cortical area (virtual lesions) or to assess connectivity using paired-pulse protocols)). This approach has shed new light on the neural mechanisms that underlie the planning stages of the reaching and grasping phases of transitive movements. Reaching and grasping were often presented as two distinct processes; in fact, the respective involvement of dorsolateral and dorsomedial networks may depend on the movement's complexity and the need for precise coordination between the two phases. The dorsolateral parietofrontal network (linking the anterior part of the intraparietal sulcus to the ventral premotor cortex) is involved in the grasping phase (i.e. hand shape and grip force scaling), whereas the dorsomedial part (from the posterior part of the intraparietal sulcus and the superior parieto-occipital cortex to the dorsal premotor cortex) appears to be involved not only in the reaching phase but also in more complex visually guided grasping movements. Changes in parietofrontal connectivity following brain injury might explain the impairments in visually guided upper limb movements observed in patients (such as optic ataxia and the motor component of spatial neglect). Lastly, parietofrontal changes may reflect neuronal plasticity in motor function recovery.

Gait quantification in multiple sclerosis: A single-centre experience of systematic evaluation.

Abstract: Gait disorders can be disabling in persons with multiple sclerosis (PMS). Different gait parameters have been used to evaluate gait disorders according to the International classification of functioning. Some authors have reported a direct relation between evaluations over short distances and long-term outcomes. This relationship is of interest for the purposes of clinical research, as it enables short-distance evaluations to be used as a primary endpoint for trials. However, these endpoints are not always particularly relevant for PMS, and furthermore, all evaluations do not present the same metrological characteristics, especially with regards to reproducibility. However, it is essential to have good reproducibility in order to be able to test the effect of a therapeutic strategy on walking parameters in PMS. Using a range of walk tests (timed 25-foot walk in different conditions, namely comfortable walking, fast walking and dual-task walking; the Timed Up and Go test; the 6minute walk test) associated with neuromotor analysis of the lower limbs, we describe the advantages and limitations of gait evaluation in MS. Based on clinical experience accumulated over 4 years, we propose a minimum set of measurements to be used in clinical practice and also for research purposes.

Changes in recruitment of motor cortex excitation and inhibition in patients with drug-induced tardive syndromes.

Abstract: Summary Objectives It has recently been suggested that drug-induced tardive syndromes (TS) might be due to maladaptive plasticity, which increases motor excitability in cerebral cortex and basal ganglia. In order to test this hypothesis, we performed the first measurements of cortical excitability in TS. Methods Motor cortex excitability was examined using transcranial magnetic stimulation (TMS) in 22 TS patients and compared with that in 20 age and sex-matched healthy individuals. Resting and active motor threshold (RMT, AMT) and input–output curves (I/O curves) assessed corticospinal excitability. The duration of the contralateral silent period (cSP) at a range of stimulation intensities and ipsilateral silent period (iSP) were used as measures of inhibition. Results There were no significant differences in RMT and AMT between patients and controls, although the input–output curves were significantly steeper in patients. The cSP (at different stimulus intensities) and iSP were both longer in the patients compared to the control group. However, most of this difference could be accounted for by increased recruitment of motor evoked potentials (MEPs) in patients. Conclusion TS is characterized by hyperexcitability of corticospinal output that might contribute to the lack of selectivity in muscle recruitment and contribute to excess involuntary movement. The findings are opposite to those in naturally-occurring hyperkinesia such as Sydenham's and Huntington's chorea, suggesting a fundamental difference in the pathophysiology.

Efficacy of high-frequency (15 Hz) repetitive transcranial magnetic stimulation (rTMS) of the left premotor cortex/dorsolateral prefrontal cortex in decreasing cocaine intake (the MagneTox study): A study protocol for a randomized placebo-controlled pilot trial

Abstract: Summary Background Cocaine use disorder (CUD) is very common and has psychological and physical consequences. Patients with CUD present hypoactivity of the prefrontal cortical area. Thus, excitatory repetitive transcranial magnetic stimulation (rTMS) targeting the premotor cortex/dorsolateral prefrontal cortex (PMC/DLPFC), given its ability to increase prefrontal area excitability and to modulate cortico-limbic activity, could result in a decrease in cocaine intake. Methods We designed a protocol for a monocentric, randomized, double-blind, placebo-controlled, parallel-group pilot trial, with the principal aim of assessing the efficacy of rTMS on the reduction of cocaine intake. Patients with CUD will be recruited according to inclusion and exclusion criteria, and then randomized to undergo active or sham rTMS. Our rTMS protocol will consist of 15 days of 15 Hz rTMS targeting the left PMC/DLPFC. Toxicological and psychiatric assessments, urine drug tests, the Cocaine Craving Questionnaire (CCQ) and the Visual Analogic Scale (VAS) will be used to assess changes from baseline in cocaine intake and craving, mood and quality of life. Discussion Only a few studies have evaluated the efficacy of rTMS for CUD treatment in humans, with limitations concerning small sample size, short treatment duration, different rTMS protocols and the absence of a placebo-controlled group. Our study will attempt to overcome these shortcomings and will provide data that can be used for future larger studies of non-invasive left PMC/DLPFC stimulation as a treatment for CUD.

Temporal Characteristics of Attentional Disengagement from Emotional Facial Cues in Depression.

Abstract: Summary Objectives Studies have reported that depressed patients have difficulties in disengaging attention from negative information, but knowledge of the temporal characteristics of this disengagement is still rudimentary. Our objective is to reveal the temporal characteristics of attentional disengagement from emotional facial cues in depression. Methods We recruited 22 depressed patients and 22 healthy controls to participate in a cued target-response task with emotional facial expressions (happy, natural, and sad) as cues and three types of cue-target intervals (CTIs: 350 ms, 1000 ms, and 1500 ms). Both behavioral and electroencephalography (EEG) data were collected from each subject while performing the task. Then, both behavioral results and event-related potentials (ERPs) were analyzed across groups (depressed patients and normal controls), emotional types of facial cues (happy, natural, and sad), and CTIs. Results Both depressed patients and healthy controls had shorter response times in the conditions of CTI = 1000 ms and 1500 ms than in the condition of CTI = 350 ms but had no significant difference in response time between the conditions of CTI = 1000 ms and CTI = 1500 ms. The contingent negative variation (CNV), a well-documented ERP marker of cue-induced expectation of the forthcoming target, clearly appeared about 1000 ms following cue onset for normal controls and 1300 ms following cue onset for depressed patients. Statistical analysis by repeated-measures Anova showed that a main group effect exists for the average amplitudes of ERPs at electrode Cz 930 ms after cue onset, while there was no main effect of cue or interaction effect between cue and group. Discussion These results suggest that normal controls complete their attentional disengagement from emotional facial expression between 350 ms to 1000 ms after cue offset, while depressed patients complete their attentional disengagement later than that of normal controls but earlier than 1500 ms from the perspective of CNV onset, though the two groups have no significant difference in response time in the conditions of CTI = 1000 ms and CTI = 1500 ms respectively.

Motor unit number index (MUNIX) in myopathic disorders: Clinical correlations and potential pitfalls.

Abstract: Our aim was to study motor unit number index (MUNIX) in myopathic disorders. We studied 11 patients with myopathy, and healthy controls. We obtained MUNIX, compound muscle action potential (CMAP), motor unit size index (MUSIX) and alpha (α, power exponent from MUNIX equation) measurements from three different muscles. MUNIX and CMAP were significantly lower in one muscle. This MUNIX decrease may not be related to motor neuron loss, but rather to muscle fiber atrophy. MUSIX and α did not change and may be useful in determining whether the MUNIX decrease is indeed due to motor unit loss.

Identification of components from distant fibers in a recorded single muscle fiber potential (SFP) - a new approach to the SFP criteria.

Abstract: Summary Objectives The aim of our study was to verify the effectiveness of single fiber potential (SFP) criteria in cases when the potential recorded using single fiber electrode (SFE) or concentric needle electrode (CNE) is contaminated by distant fibers. Methods Morphological counterparts of SFP were studied using computer simulations. In this study, we examined triphasic potentials using a model of a linear source of SFP. The criteria defining SFP in the case of SFP contaminated by distant fibers were analyzed, and the effect of second fiber contamination on jitter and fiber diameter determination evaluated. Results We found that SFP criteria prevent detection of SFP from fibers smaller than about 30 μm in diameter, but do not prevent classification of a potential as an SFP even though it is formed by two or more fibers. This suggests that the presently used criteria may lead to incorrect interpretation of SFP potentials. SFPs contaminated by fibers of diameters differing by a few percent fulfill the criteria but a negative peak may be shifted in time and therefore impact jitter and diameter measurements. This contamination generally tends to decrease both the jitter and the determined diameter. A new approach to the identification of SFP is presented, determining fiber diameter and distance from the electrode to enable maximum sensitivity to potential contamination by the effect of a second fiber. Conclusion A new parameter characterizing SFP shape changes is introduced. This parameter is used in the method by which additional fibers affecting the SFP may be detected.

Visual event-related potentials in external emotional conditions in bipolar disorders I and II.

Abstract: Summary Objectives Mutual influences of cognitive and emotional functions occur in bipolar disorder, but specific alterations in relation to external emotional stimuli in bipolar I (BD I) and II (BD II) subtypes remain unknown. This study aimed to explore the effects of external emotional stimuli on cerebral attentional function in BD I and BD II. Methods We tested visual oddball event-related potentials (ERPs) during various external emotional stimuli (Disgust, Fear, Erotica, Happiness, Neutral and Sadness) in 31 patients with BD I, 19 BD II and 47 healthy volunteers. Participants’ concurrent affective states were also evaluated. Results The ERP N2 latencies during Fear and Happiness were prolonged, P3 amplitudes during Disgust and Erotica were decreased in BD I; P3 amplitudes during Disgust, Erotica, Happiness and Neutral conditions were decreased in BD II. Increased frontal and parietal and decreased temporal and occipital activations were found in BD I, while increased occipital and parietal and decreased frontal and limbic activations in BD II in relation to different external emotions. ERP components were not correlated with concurrent affective states in patients. Conclusions Automatic attention during Happiness and Fear, and voluntary attention during Disgust and Erotica conditions were impaired in BD I; and voluntary attention during Disgust, Happiness, Erotica and Neutral conditions was impaired in BD II. Our study illustrates different patterns of visual attentional deficits associated with different external emotional stimuli in BD I and BD II.

Brainstem evoked potentials and magnetic resonance imaging abnormalities in differential diagnosis of intracranial hypotension.

Abstract: Summary Objective To compare brainstem acoustic evoked potentials (BAEP) and magnetic resonance imaging (MRI) in the differential diagnosis of intracranial hypotension (IH), Chiari malformation (CM) and sensorineural hearing loss (SNHL). Methods BAEP were recorded in 18 IH, 18 CM, 20 SNHL patients and 52 controls. MRI were acquired in all IH and CM patients. Results Abnormal BAEP were observed in 94% of IH patients, in 33% of CM and 70% of SNHL patients. After recovery from IH, BAEP abnormalities disappeared. Internal auditory canal (IAC) MRI abnormalities were described in 88% of IH patients. MRI signs of IH were observed in 33–78% in IH patients, but the most frequent MRI sign was 8th nerve T2 hyperintensity, with contrast enhancement in T1 sequences. This finding, combined with wave I latency, yielded highest specificity and sensitivity for IH diagnosis. Conclusions Our study points out how IH can be effectively distinguished from CM and SNHL through the contribution of neurophysiology and MRI; in particular, evaluation of the 8th nerve achieves a high sensitivity and specificity in patients with IH. Further studies are required to examine the combined use of BAEP recordings ad MRI in diagnosis and monitoring of patients affected by IH.