Examining the Overlap Between ADHD and Autism Spectrum Disorder (ASD) Using Candidate Endophenotypes of ADHD

Objective: Recent discussions of aetiological overlap between ADHD and Autism Spectrum Disorder (ASD) require comparative studying of these disorders.

METHOD

We examined performance of ASD patients with (ASD+) and without (ASD-) comorbid ADHD, ADHD patients, and controls for selected putative endophenotypes of ADHD: Intrasubject Variability (ISV) of reaction times, working memory (WM), inhibition, and temporal processing.

RESULTS

We found that patients with ADHD or ASD+, but not ASD-, had elevated ISV across the entire task battery and temporal processing deficits, and that none of the groups were impaired in WM or inhibition. High levels of ISV and generally poor performance in ASD+ patients were only partially due to additive effects of the pure disorders.

CONCLUSION

Overall, we conclude that, within our limited but heterogeneous task battery, ISV and temporal processing deficits are most sensitive to ADHD symptomatology and that controlling for ADHD comorbidity is mandatory when assessing ISV in autism.

The impact of the COMT genotype and cognitive demands on facets of intra-subject variability

Intra-Subject Variability (ISV), a potential index of catecholaminergic regulation, is elevated in several disorders linked with altered dopamine function. ISV has typically been defined as reaction time standard deviation. However, the ex-Gaussian and spectral measures capture different aspects and may delineate different underlying sources of ISV; thus reflecting different facets of the construct. We examined the impact of factors associated with dopamine metabolism, namely, Catechol-O-Methyltransferase Val158Met (COMT) genotype and Working Memory (WM) and response-switching on ISV facets in young healthy adults. The Met allele was associated with overall increased variability. The rather exclusive sensitivity of ex-Gaussian tau to frequencies below 0.025 Hz and the quasi-periodic structure of particularly slow responses support the interpretation of tau as low frequency fluctuations of neuronal networks. Sigma, by contrast, may reflect neural noise. Regarding cognitive demands, a WM load-related increase in variability was present for all genotypes and all ISV facets. Contrastingly, ISV facets reacted differently to variations in response-switching as, across genotypes, sigma was elevated for rare target trials whereas tau was elevated for frequent standard trials, particularly for Met homozygotes. Our findings support the significant role of COMT in regulating behavioural ISV with its facetted structure and presumed underlying neural processes.

Electro-cortical correlates of multisensory integration using ecologically valid emotional stimuli: Differential effects for fear and disgust

Multisensory integration (MSI) is crucial for human communication and social interaction and has been investigated in healthy populations and neurodevelopmental disorders. However, the use of stimuli with high ecological validity is sparse, especially in event-related potential (ERP) studies. The present study examined the ERP correlates of MSI in healthy adults using short (500 ms) ecologically valid professional actor-produced emotions of fear or disgust as vocal exclamation or facial expression (unimodal conditions) or both (bimodal condition). Behaviourally, our results show a general visual dominance effect (similarly fast responses following bimodal and visual stimuli) and an MSI-related speedup of responses only for fear. Electrophysiologically, both P100 and N170 showed MSI-related amplitude increases only following fear, but not disgust stimuli. Our results show for the first time that the known differential neural processing of fear and disgust also holds for the integration of dynamic auditory and visual information.

Post-stroke insomnia in community-dwelling patients with chronic motor stroke: Physiological evidence and implications for stroke care

Questionnaire studies suggest that stroke patients experience sustained problems with sleep and daytime sleepiness, but physiological sleep studies focussing specifically on the chronic phase of stroke are lacking. Here we report for the first time physiological data of sleep and daytime sleepiness obtained through the two gold-standard methods, nocturnal polysomnography and the Multiple Sleep Latency Test. Data from community-dwelling patients with chronic right-hemispheric stroke (>12 months) were compared to sex- and age-matched controls. Behavioural and physiological measures suggested that stroke patients had poorer sleep with longer sleep latencies and lower sleep efficiency. Patients further spent more time awake during the night, and showed greater high-frequency power during nonREM sleep than controls. At the same time the Multiple Sleep Latency Test revealed greater wake efficiency in patients than controls. Importantly these findings were not due to group differences in sleep disordered breathing or periodic limb movements. Post-stroke insomnia is presently not adequately addressed within the care pathway for stroke. A holistic approach to rehabilitation and care provision, that includes targeted sleep interventions, is likely to enhance long-term outcome and quality of live in those living with chronic deficits after stroke.

Empathy training in medical students - a randomized controlled trial

AIM

Empathy is a core element in the doctor-patient relationship. This study examined whether empathy in medical students can be improved by specific training.

METHODS

158 medical students were randomized into two groups. The intervention group participated in an empathy skills training with simulated patients (SPs). The control group participated in a history course. After the intervention, empathy was assessed by blinded SPs and experts in an Objective Structured Clinical Examination (OSCE). Students also filled out a self-assessment concerning their attitude on empathy (Jefferson Scale of Physician Empathy Student Version, JSPE-S-S).

RESULTS AND CONCLUSIONS

Participants of the intervention group showed significantly higher levels of empathy when rated by SPs and experts than the control group. In contrast to that, no significant group differences were observed in self-rated empathy. The results underpin the value of empathy skills trainings in medical school study programs.

[Insomnia--state of the science]

Diagnostic systems such as the international classification of diseases (ICD-10) or the diagnostic and statistical manual of mental disorders (DSM IV) have frequently been criticized as not adequately reflecting the complexity and heterogeneity of insomnia. Progress was made through the introduction of the international classification of sleep disorders (ICSD-2) and the research diagnostic criteria (RDC). The DSM-5 introduced the new category of insomnia disorder, thus relinquishing the traditional dichotomy of primary versus secondary insomnia. Recent basic research indicates that genetic and epigenetic factors are involved in the etiology of insomnia; the so-called three P model (i.e. predisposing, precipitating and perpetuating factors) and the hyperarousal concept have gained much attention in trying to explain the pathophysiology of insomnia. With respect to the cognitive-behavioral therapy of insomnia (CBT-I), a plethora of empirical evidence supports the first-line character of this type of treatment for insomnia. Unfortunately, CBT-I is still administered to only a minority of afflicted patients, probably due to a lack of resources in the healthcare system. As a consequence, stepped-care models to improve insomnia therapy encompass self-help programs, internet-based treatment avenues, community-centered activities (specially trained nurses) and as a last resort medical specialists/psychotherapists and sleep experts to deal with insomnia.

Altered cingulate and amygdala response towards threat and safe cues in attention deficit hyperactivity disorder

BACKGROUND

Emotional dysregulation is becoming increasingly recognized as an important feature of attention deficit hyperactivity disorder (ADHD). In this study, two experiments were conducted investigating the neural response to either verbally instructed fear (IF) or uninstructed (classically conditioned) fear (UF) using the skin conductance response (SCR) and functional magnetic resonance imaging (fMRI).

METHOD

In the conditioning phase of the UF experiment (17 ADHD and 17 healthy controls), subjects experienced an unconditioned stimulus (UCS, unpleasant electrodermal stimulation) paired with a former neutral conditioned stimulus (CS+), whereas a control stimulus (CS-) was never paired with the UCS. In the subsequent test phase, only the CS+ and the CS- were presented. In the IF experiment (13 ADHD and 17 healthy controls), subjects were only told that an independently experienced UCS might occur together with the CS+ but not the CS- during testing. No UCS was presented.

RESULTS

Groups did not detectably differ in SCR or neural responses to UF. In IF, ADHD patients showed a trend-line decreased SCR and significantly decreased activation of the dorsal anterior cingulate cortex (dACC), a region prominently involved in fear responding, to the CS+. This was accompanied by higher amygdala activation to the CS-.

CONCLUSIONS

During IF, ADHD patients showed deficits in regions centrally involved in fear learning and expression in terms of diminished CS+-related dACC and increased CS--related amygdala signals. This suggests an impaired processing of verbally transmitted aversive information, which is central for conveying fear information in social contexts. This result extends the growing literature on emotional alterations in ADHD.

REM sleep instability--a new pathway for insomnia?

Chronic insomnia afflicts approximately 10% of the adult population and is associated with daytime impairments and an elevated risk for developing somatic and mental disorders. Current pathophysiological models propose a persistent hyperarousal on the cognitive, emotional and physiological levels. However, the marked discrepancy between minor objective alterations in standard parameters of sleep continuity and the profound subjective impairment in patients with insomnia is unresolved. We propose that "instability" of REM sleep contributes to the experience of disrupted and non-restorative sleep and to the explanation of this discrepancy. This concept is based on evidence showing increased micro- and macro-arousals during REM sleep in insomnia patients. As REM sleep represents the most highly aroused brain state during sleep it seems particularly prone to fragmentation in individuals with persistent hyperarousal. The continuity hypothesis of dream production suggests that pre-sleep concerns of patients with insomnia, i. e., worries about poor sleep and its consequences, dominate their dream content. Enhanced arousal during REM sleep may render these wake-like cognitions more accessible to conscious perception, memory storage and morning recall, resulting in the experience of disrupted and non-restorative sleep. Furthermore, chronic fragmentation of REM sleep might lead to dysfunction in a ventral emotional neural network, including limbic and paralimbic areas that are specifically activated during REM sleep. This dysfunction, along with attenuated functioning in a dorsal executive neural network, including frontal and prefrontal areas, might contribute to emotional and cognitive alterations and an elevated risk of developing depression.

Local area network inhibition: a model of a potentially important paraepileptic pathomechanism in neuropsychiatric disorders

Electroencephalographic abnormalities in the absence of any other major laboratory or imaging findings are a frequently encountered phenomenon in many psychiatric disorders. In some cases, clear-cut interictal epileptiform EEG abnormalities in patients with classic primary psychiatric disorders lead to referrals to epilepsy departments for diagnostic evaluation. Although video/EEG telemetry in these cases generally proves that there is no direct temporal link between the EEG pathologies and psychiatric symptoms, and therefore the psychiatric syndrome cannot be regarded as epilepsy, the relevance of the EEG abnormalities remains open to discussion. In this article we put forward the model of a paraepileptic pathomechanism, which might explain the pathogenetic role of such EEG pathologies, at least in subgroups of such patients. We propose that ictal or nonictal epileptic neurophysiological activity can lead to local area neuronal network inhibition (LANI). In this model clinical symptoms are related not to the excitatory epileptiform abnormalities themselves, but to the extent, site, and dynamics of the resulting local neuronal network inhibition. The LANI hypothesis is capable of explaining the complex relationship between EEG abnormalities and clinical symptoms in different neuropsychiatric syndromes and can be verified and falsified in empirical research.

Reduced cingulate glutamate/glutamine-to-creatine ratios in adult patients with attention deficit/hyperactivity disorder -- a magnet resonance spectroscopy study

BACKGROUND

The dopaminergic system is thought to be essentially involved in the pathogenesis of attention deficit/hyperactivity disorder (ADHD). However, there is also evidence for abnormalities in the glutamatergic system and recent theories focus on a disturbed interaction between the two systems as the essential pathogenetic mechanism of ADHD. In the present study, we wanted to test the hypothesis that prefrontal glutamate signals indirectly indicate dopaminergic dysfunction in adult patients with ADHD.

METHODS

Twenty-eight adult patients with ADHD and 28 group-matched healthy volunteers were studied clinically and using chemical-shift MR spectroscopy (MRS) of the prefrontal cortex covering the anterior cingulate gyrus.

RESULTS

A significant reduction of the combined glutamate/glutamine to creatine ratio in the right anterior cingulate cortex in patients with ADHD was found.

DISCUSSION

Glutamatergic alterations as measured with MRS might play a role in the pathogenesis of adult patients with ADHD.

Impact of Experimentally Induced Serotonin Deficiency by Tryptophan Depletion on Saliva Cortisol Concentrations

BACKGROUND

Tryptophan depletion (TD) has been shown to induce a transient mood-lowering effect in psychiatric patients and susceptible healthy subjects. We investigated the effects of TD on cortisol secretion in psychiatric patients and healthy subjects based on the hypothesis that the potential mood-lowering effects may be associated with increased activity of the hypothalamic-pituitary-adrenal axis, thus leading to a rise of cortisol secretion.

METHODS

After TD at 18.00 h, salivary cortisol was sampled in the evening and on the following morning. The first study was a randomized, placebo-controlled, crossover study in healthy subjects. Two further open trials in patients with obsessive-compulsive disorder (OCD) and primary insomnia compared the effects of TD on cortisol with baseline conditions.

RESULTS

In healthy subjects, TD significantly diminished cortisol the next morning compared with placebo. In OCD patients and primary insomniacs, cortisol the morning after TD was lowered compared with baseline. Evening cortisol was not affected by TD in any of the groups.

CONCLUSIONS

Contrary to expectation, TD led to a comparable decrease of morning cortisol in all groups investigated. However, these findings are consistent with former studies analyzing the impact of antiserotonergic drugs on cortisol secretion. The results underline that the antiserotonergic effects caused by TD may influence cortisol secretion.

Polysomnography during withdrawal with clomethiazole or placebo in alcohol dependent patients--a double-blind and randomized study

INTRODUCTION

The present study was designed to assess if the routine application of clomethiazole to ameliorate withdrawal symptoms in chronic alcohol dependent patients perpetuates sleep disturbances.

METHODS

Twenty inpatients with alcohol dependence according to DSM-IV criteria received clomethiazole or placebo in a double-blind, randomized design upon admission. 11 patients were randomized to the clomethiazole group and 9 patients to the placebo group. During the first 5 days of treatment the patients received either clomethiazole (1st day: 3 x 384 mg, 2nd day: 4 x 384 mg, 3rd day: 3 x 384 mg, 4th day: 2 x 384 mg and 5th day: 1 x 384 mg) or placebo capsules at constant intervals. The patients spent two consecutive nights in the sleep laboratory at each of three assessment times: the first time at the beginning of abstinence (night 1 and 2, T0), the second time 6 days later (i. e. after 5 days of treatment and one day of discontinuation of clomethiazole or placebo: nights 6 and 7, T1) and the third time after 13 days (nights 13 and 14, T2). The first night at each of the three assessment times was an adaptation night.

RESULTS

During the first two weeks of abstinence, the analysis of variance demonstrated a significant variation of Rapid Eye Movement (REM) sleep variables in the clomethiazole group. The placebo group showed no such variation. Clomethiazole evidently had a pronounced REM sleep suppressing effect, whereas the discontinuation of clomethiazole led to a REM sleep rebound. Furthermore, analysis of sleep continuity and sleep architecture variables showed that the clomethiazole group had significantly disturbed sleep at T1 in comparison to the placebo group. Simultaneous statistical testing with alcohol intake as covariate reduced the test power so that contrasts between the groups became nonsignificant.

CONCLUSIONS

The REM sleep results are in line with earlier findings that REM sleep disinhibition in primary alcohol dependency is partly due to a REM sleep rebound after withdrawal from medication. Differences in the polysomnographic variables of sleep continuitiy and sleep architecture at T0 and T1 found between the clomethiazole and the placebo patients correspond to rebound insomnia following discontinuation of clomethiazole. Our findings indicate that drugs enforcing GABAergic neurotransmission may perpetuate the neuroadaptative effects caused by chronic alcohol consumption.

[The importance of sleep for healthy alcohol consumers and alcohol dependent patients]

This article deals with the effects of alcohol on sleep and sleep EEG of healthy individuals and alcohol-dependent patients during different phases of alcohol dependency. Healthy individuals initially experience an improvement in sleep, although a greater quantity of alcohol can lead to problems of sleep maintenance during the second half of the night. Pre-existing sleep deprivation or sleep restriction potentiates the effects of alcohol. Alcohol-dependent patients are found to be more prone to sleep problems than healthy individuals, which can facilitate the development of alcoholism. These patients experience difficulty falling asleep and suffer from a reduced total sleep time during all phases of the disorder, often accompanied by other sleep disorders such as sleep apnea syndrome or periodic leg movements during sleep. Certain predictors for the risk of relapse in abstinent alcoholics have been identified. Neurobiological findings in sleep and alcohol dependency are discussed. The cholinergic-aminergic reciprocal interaction model of REM and non-REM sleep regulation is significant in this context. Therapeutic implications are discussed.

Event-related potential correlates selectively reflect cognitive dysfunction in schizophrenics

Schizophrenics show event-related potential (ERP) and particularly P3 abnormalities. To study the more detailed relationships between these ERP alterations and cognitive dysfunction we recorded and analyzed ERPs using a particular experimental approach. In 34 schizophrenics and 25 controls ERPs were obtained by a visual Go/Nogo task requiring response inhibition and were decomposed into temporally independent topographical components using Independent Component Analysis (ICA). ICA disentangled different subcomponents of P3. Subcomponent P3b with a parietal maximum amplitude was significantly reduced in the schizophrenics, probably reflecting their attentional deficits. Subcomponent P3ng with a frontal maximum amplitude and enhanced during Nogo condition appeared as an electrophysiological index of response inhibition. A significantly reduced P3ng enhancement, found in schizophrenics, probably reflects their impaired response control.

CONCLUSIONS

ICA can successfully identify ERP subcomponents with distinct scalp topographies representing significant differential indices of normal and abnormal cognitive processing. Involvement of frontal brain areas in disturbed executive control in schizophrenics is supported by our ICA findings.

Sleep and the cholinergic rapid eye movement sleep induction test in patients with primary alcohol dependence

BACKGROUND

The present study investigated polysomnographically assessed sleep parameters in alcohol-dependent patients after withdrawal and in healthy control subjects during baseline and after a cholinergic stimulation paradigm. The aim of the study was to test whether sleep parameters, especially rapid eye movement (REM) sleep variables, may serve as predictors for relapse in alcohol-dependent patients.

METHODS

Forty patients diagnosed with alcohol dependence were admitted to a specialized ward for alcohol withdrawal and were investigated by polysomnography at three time points: 2-3 weeks after withdrawal (T0) and at follow-up investigations 6 (T1) and 12 (T2) months after discharge from the hospital. A subgroup of patients (n = 17) was studied at T0 after challenge with galanthamine, a reversible cholinesterase inhibitor (cholinergic REM induction test, CRIT). Patients were compared with two control groups: a) 30 healthy control subjects (matched for age- and gender-distribution) for comparison at baseline conditions; and b) 17 age- and gender-matched control subjects for comparison with the CRIT.

RESULTS

At baseline the patients showed significant disturbances of sleep continuity and sleep architecture (decreased slow-wave sleep, SWS) and exhibited an increase of "REM sleep pressure" (a combined index of REM latency, REM density, and REM sleep percent). Galanthamine provoked significant alterations of sleep continuity, sleep architecture (reduced SWS), and increased most of the components of REM pressure, taking patients and control subjects together. Apart from SWS %SPT (sleep period time) no significant drug-group interactions occurred. Patients who remained abstinent (n = 11) for at least 6 months at follow-up exhibited significantly less abnormalities of REM sleep at T0 compared to the group of patients that relapsed at 6 months follow-up.

CONCLUSIONS

It is concluded that increased REM sleep pressure after alcohol withdrawal is a robust predictor of vulnerability to relapse. Thus, a subgroup of alcoholic patients appears to exhibit distinct neurobiological abnormalities assessable by polysomnography that are related to an increased vulnerability for alcoholism and early relapse.

Auditory and visual event-related potentials in alcoholics: abnormalities of components and brain electrical field

Alterations of ERPs recorded over midline scalp sites have frequently been reported in alcoholics. To assess the P3 and other ERP components topographically, auditory and visual ERPs were recorded from 33 scalp electrodes in abstinent alcoholics and healthy controls using an oddball paradigm. At the Cz electrode the alcoholics showed decreased visual N1 and increased auditory N2 amplitudes. Topographically, the negative centroids of the visual N1 and P3 and the auditory N2 differed between groups, and the positive centroid of the visual P3 was displaced toward the right hemisphere. While no valid diagnostic classification could be obtained by using the traditional ERP component P3 recorded from Pz, the combination of visual N1 and auditory N2 amplitudes at Cz with centroid parameters amounted to 51% explained variance and 92% correct discrimination of alcoholics from controls. Abnormalities of N1 amplitude and P3 topography similar to the current findings in alcoholics have previously been described for schizophrenics.

A double-blind, randomized and placebo-controlled study on the polysomnographic withdrawal effects of zopiclone, zolpidem and triazolam in healthy subjects

Rebound effects after withdrawal from hypnotics are believed to trigger their chronic use and to enhance the risk of tolerance and dependence. It was the purpose of this study to investigate the acute polysomnographic withdrawal effects after a 4 week treatment with standard doses of the non-benzodiazepine hypnotics zopiclone and zolpidem compared with triazolam and placebo. Healthy male subjects between 22 and 35 years of age participated in a parallel study design. They received either zopiclone 7.5 mg (n=11), zolpidem 10 mg (n=11), triazolam 0.25 mg (n=10) or placebo (n=7) over 4 weeks in randomized and double-blind order. Sleep EEG was registered during 2 nights before treatment under placebo, on days 1, 27 and 28 of treatment and on days 29,30,41 and 42 under placebo. Total sleep time and sleep efficiency were lower in the 1st night after discontinuation of triazolam (p < 0.05, t-test). After withdrawal from zopiclone or zolpidem slight but not significant rebound effects concerning sleep continuity were observed. Self-rating scales showed minimal rebound insomnia after discontinuation of all three hypnotics. In the placebo group no changes of sleep parameters were observed. Assuming that rebound insomnia is part of a withdrawal reaction, this study indicates that the risks of tolerance and dependency are low when administering zopiclone or zolpidem at the recommended doses.

Delta sleep ratio as a predictor of sleep deprivation response in major depression

The fast but short-lasting improvement of depressive symptoms by sleep deprivation (SD) in about 60% of patients with a major depressive disorder is well established, but the mechanisms of action are still not clear. Recent studies suggest that changes in non rapid eye movement (NREM) sleep, especially in slow wave activity (SWA), could be associated with the therapeutic outcome of SD. In the current study, spectral analysis of NREM sleep EEG directly prior to SD was performed to determine if automatically derived sleep parameters predict SD response. Sixteen pair matched and drug free patients with a major depressive disorder, 8 SD responders and 8 non-responders (response criterion: 50% reduction on the 6-item HAMD score), were included. Average EEG spectral power was calculated for the whole night before SD and for single NREM episodes. While whole-night averages of spectral power did not differ significantly between subgroups, SD responders showed a steady decrease of SWA across successive NREM episodes, whereas in non-responders an increase from the first to the second episode was observed. The different distribution of SWA was significantly expressed in the delta sleep ratio (quotient of SWA in the first to the second NREM episode). In conclusion, a high delta sleep ratio is a positive predictor for SD response. Referred to psycho- and pharmacotherapeutic results it is hypothesized that low and high values of the delta sleep ratio characterize subgroups of depressed patients with different neurobiological alterations, which could be relevant for further scientific and therapeutic approaches.

Dynamic synchronization between multiple cortical motor areas and muscle activity in phasic voluntary movements

To study the functional role of synchronized neuronal activity in the human motor system, we simultaneously recorded cortical activity by high-resolution electroencephalography (EEG) and electromyographic (EMG) activity of the activated muscle during a phasic voluntary movement in seven healthy subjects. Here, we present evidence for dynamic beta-range (16-28 Hz) synchronization between cortical activity and muscle activity, starting after termination of the movement. In the same time range, increased tonic activity in the activated muscle was found. During the movement execution a low-frequency (2-14 Hz) synchronization was found. Using a novel analysis, phase-reference analysis, we were able to extract the EMG-coherent EEG maps for both, low- and high-frequency beta range synchronization. The electrical source reconstruction of the EMG-coherent EEG maps was performed with respect to the individual brain morphology from magnetic resonance imaging (MRI) using a distributed source model (cortical current density analysis) and a realistic head model. The generators of the beta-range synchronization were not only located in the primary motor area, but also in premotor areas. The generators of the low-frequency synchronization were also located in the primary motor and in premotor areas, but with additional participation of the medial premotor area. These findings suggest that the dynamic beta-range synchronization between multiple cortical areas and activated muscles reflects the transition of the collective motor network into a new equilibrium state, possibly related to higher demands on attention, while the low-frequency synchronization is related to the movement execution.

Effects of repetitive transcranial magnetic stimulation on movement-related cortical activity in humans

Several lines of evidence suggest that low-rate repetitive transcranial magnetic stimulation (rTMS) of the motor cortex at 1 Hz reduces the excitability of the motor cortex and produces metabolic changes under and at a distance from the stimulated side. Therefore, it has been suggested that rTMS may have beneficial effects on motor performance in patients with movement disorders. However, it is still unknown in what way these effects can be produced. The aim of the present study is to investigate whether rTMS of the motor cortex (15 min at 1 Hz) is able to modify the voluntary movement related cortical activity, as reflected in the Beretischaftspotential (BP), and if these changes are functionally relevant for the final motor performance. The cortical movement-related activity in a typical BP paradigm of five healthy volunteers has been recorded using 61 scalp electrodes, while subjects performed self-paced right thumb oppositions every 8-20 s. After a basal recording, the BP was recorded in three different conditions, counterbalanced across subjects: after rTMS stimulation of the left primary motor area (M1) (15 min, 1 Hz, 10% above motor threshold), after 15 min of sham rTMS stimulation and following 15 min of voluntary movements performed with spatio-temporal characteristics similar to those induced by TMS. The tapping test was used to assess motor performance before and after each condition. Only movement-related trials with similar electromyographic (onset from muscular 'silence') and accelerometric patterns (same initial direction and similar amplitudes) were selected for computing BP waveforms. TMS- evoked and self-paced thumb movements had the same directional accelerometric pattern but different amplitudes. In all subjects, the real rTMS, but neither sham stimulation nor prolonged voluntary movements, produced a significant amplitude decrement of the negative slope of the BP; there was also a shortening of the BP onset time in four subjects. The effect was topographically restricted to cortical areas which were active in the basal condition, irrespective of the basal degree of activation at every single electrode. No changes in the tapping test occurred. These findings suggest that rTMS of the motor cortex at 1 Hz may interfere with the movement related brain activity, probably through influence on cortical inhibitory networks.

Oscillatory cortical activity and movement-related potentials in proximal and distal movements

OBJECTIVES

Event-related desynchronization (ERD) of alpha- and beta-rhythms, the post-movement beta-synchronization and the cortical movement-related potentials were analyzed in distal (finger) and proximal (shoulder) movements.

METHODS

EEG was recorded in 7 healthy right-handed men using a 59-channel whole-head EEG system while subjects performed self-paced movements.

RESULTS

The amplitude of the Bereitschaftspotential (BP) was greater over the central midline area and smaller over the contralateral sensorimotor hand area in shoulder than in finger movements. The maximal alpha- and beta-ERD was localized at parietal electrodes in shoulder movements and over the left and right sensorimotor hand area in finger movements. The post-movement beta-ERS was greater in shoulder than in finger movements, especially at the electrode located 3.5 cm left of the central midline electrode. A significant correlation between the slope of the terminal portion of the BP (negative slope) and amplitude of the post-movement beta-synchronization was observed in shoulder but not in finger movements.

CONCLUSIONS

Enhancement of BP over the central midline electrode suggests increased activation of the supplementary motor area in proximal movements. The spatial distribution of the alpha- and beta-ERD and of the post-movement beta-ERS shows topographic differences which may refer to the somatotopic organization of the primary sensorimotor cortex with shoulder representation medial to hand and fingers. The correlation between the negative slope and the post-movement beta-ERS in proximal movements supports the view that the brief post-movement inhibition over the motor cortical area is related to the pre-movement activation of that area.

The role of higher-order motor areas in voluntary movement as revealed by high-resolution EEG and fMRI

In the human motor cortex structural and functional differences separate motor areas related to motor output from areas essentially involved in higher-order motor control. Little is known about the function of these higher-order motor areas during simple voluntary movement. We examined a simple finger flexion movement in six healthy subjects using a novel brain-imaging approach, integrating high-resolution EEG with the individual structural and functional MRI. Electrical source reconstruction was performed in respect to the individual brain morphology from MRI. Highly converging results from EEG and fMRI were obtained for both executive and higher-order motor areas. All subjects showed activation of the primary motor area (MI) and of the frontal medial wall motor areas. Two different types of medial wall activation were observed with both methods: Four of the subjects showed an anterior type of activation, and two of the subjects a posterior type of activation. In the former, activity started in the anterior cingulate motor area (CMA) and subsequently shifted its focus to the intermediate supplementary motor area (SMA). Approximately 120 ms before the movement started, the intermediate SMA showed a drop of source strength, and simultaneously MI showed an increase of source strength. In the posterior type, activation was restricted to the posterior SMA. Further, three of the subjects investigated showed activation in the inferior parietal lobe (IPL) starting during early movement preparation. In all subjects showing activation of higher-order motor areas (anterior CMA, intermediate SMA, IPL) these areas became active before the executive motor areas (MI and posterior SMA). We suggest that the early activation of the anterior CMA and the IPL may be related to attentional functions of these areas. Further, we argue that the intermediate part of the SMA triggers the actual motor act via the release of inhibition of the primary motor area. Our results demonstrate that a noninvasive, multimodal brain imaging technique can reveal individual cortical brain activity with high temporal and spatial resolution, independent of a priori physiological assumptions.

Independent sleep EEG slow-wave and spindle band dynamics associated with 4 weeks of continuous application of short-half-life hypnotics in healthy subjects

OBJECTIVES

Habituation and adverse withdrawal reactions after prolonged medication with benzodiazepine (BZ) hypnotics are believed to play a role in dose escalation and the development of dependence.

METHODS

In the current sleep EEG study in 43 healthy male subjects, the known property of BZ- and similar hypnotics to change the NREM sleep EEG spectrum is utilized for a detailed quantitative analysis across 4 weeks of continuous medication and a subsequent two-week withdrawal period. The BZ hypnotic triazolam and the non-BZ hypnotics zopiclone and zolpidem, differing in pharmacological properties and reported adverse effects, were examined in parallel to a placebo group.

RESULTS

Reliably occurring spectral effects in the sleep stage 2 EEG were found in the 3 frequency bands 0.8-5 Hz, 5-10 Hz and 10-15 Hz. All 3 hypnotics showed the typical 'benzodiazepine signature', a 10-15 Hz increase and lower-frequency (<10 Hz) suppression relative to the preceding drug-free night. However, these effects developed differently across the first medication night, across the 4 medication weeks and after withdrawal: While the 5-10 Hz effect covaried with the blood presence of the drugs as estimated from the known plasma half-lifes, showed habituation and a rebound after withdrawal, the 10-15 Hz power increased across medication days and showed no rebound. Effects in the 0.8-5 Hz band in the first medication night correlated with the decrease of sleep efficiency at later withdrawal for triazolam and zolpidem.