Standard Montage Research Articles

Behavioral entrainment to rhythmic auditory stimulation can be modulated by tACS depending on the electrical stimulation field properties.

Synchronization between auditory stimuli and brain rhythms is beneficial for perception. In principle, auditory perception could be improved by facilitating neural entrainment to sounds via brain stimulation. However, high inter-individual variability of brain stimulation effects questions the usefulness of this approach. Here we aimed to modulate auditory perception by modulating neural entrainment to frequency modulated (FM) sounds using transcranial alternating current stimulation (tACS). In addition, we evaluated the advantage of using tACS montages spatially optimized for each individual's anatomy and functional data compared to a standard montage applied to all participants. Across two different sessions, 2 Hz tACS was applied targeting auditory brain regions. Concurrent with tACS, participants listened to FM stimuli with modulation rate matching the tACS frequency but with different phase lags relative to the tACS, and detected silent gaps embedded in the FM sound. We observed that tACS modulated the strength of behavioral entrainment to the FM sound in a phase-lag specific manner. Both the optimal tACS lag and the magnitude of the tACS effect were variable across participants and sessions. Inter-individual variability of tACS effects was best explained by the strength of the inward electric field, depending on the field focality and proximity to the target brain region. Although additional evidence is necessary, our results also provided suggestive insights that spatially optimizing the electrode montage could be a promising tool to reduce inter-individual variability of tACS effects. This work demonstrates that tACS effectively modulates entrainment to sounds depending on the optimality of the electric field. However, the lack of reliability on optimal tACS lags calls for caution when planning tACS experiments based on separate sessions.

Behavioral entrainment to rhythmic auditory stimulation can be modulated by tACS depending on the electrical stimulation field properties

Synchronization between auditory stimuli and brain rhythms is beneficial for perception. In principle, auditory perception could be improved by facilitating neural entrainment to sounds via brain stimulation. However, high inter-individual variability of brain stimulation effects questions the usefulness of this approach. Here we aimed to modulate auditory perception by modulating neural entrainment to frequency modulated (FM) sounds using transcranial alternating current stimulation (tACS). In addition, we evaluated the advantage of using tACS montages spatially optimized for each individual’s anatomy and functional data compared to a standard montage applied to all participants. Across two different sessions, 2 Hz tACS was applied targeting auditory brain regions. Concurrent with tACS, participants listened to FM stimuli with modulation rate matching the tACS frequency but with different phase lags relative to the tACS, and detected silent gaps embedded in the FM sound. We observed that tACS modulated the strength of behavioral entrainment to the FM sound in a phase-lag specific manner. Both the optimal tACS lag and the magnitude of the tACS effect were variable across participants and sessions. Inter-individual variability of tACS effects was best explained by the strength of the inward electric field, depending on the field focality and proximity to the target brain region. Although additional evidence is necessary, our results also provided suggestive insights that spatially optimizing the electrode montage could be a promising tool to reduce inter-individual variability of tACS effects. This work demonstrates that tACS effectively modulates entrainment to sounds depending on the optimality of the electric field. However, the lack of reliability on optimal tACS lags calls for caution when planning tACS experiments based on separate sessions.

Measurement of Ocular Vestibular Evoked Myogenic Potentials: Nasion Reference Montage as an Alternative to the Clinical Standard Montage.

To compare two novel electrode montages for ocular, vestibular evoked myogenic potential using single-nasion reference electrodes with the clinical standard montage. Randomized crossover experiment. Tertiary referral center. Sixty healthy participants. Normal hearing and vestibular function were confirmed with an extensive test-battery. All ocular, vestibular evoked myogenic potential settings were measured with air-conducted tone bursts at 100-dB normal hearing level and a frequency of 500 Hz. Three electrode montages were measured in randomized order: the clinical standard montage ("S"), the nasion reference montage ("N"), and the nasion reference montage with a more lateral active electrode ("L"). Upgaze was standardized to 35 degrees. Detection rate, latency of N1 and P1, peak-to-peak amplitude of N1 and P1, signal-to-noise ratio (SNR), asymmetry ratio (AR), concordance of expert assessment, and reliability. All electrode montages showed detection rates greater than 90%. Latencies for "L" were shorter than for "S" and "N." Amplitudes and SNR for "S" and "N" were higher than for "L," whereas the values for "S" and "N" did not differ significantly. For AR, no significant differences between the montages were assessed. Concordance of experts ranged from 78% for "L" and 89.8% for "N." All montages provided excellent day-to-day reliability (intraclass correlation coefficient ≥0.9) for amplitudes and SNR. Montage N could be a useful alternative to the clinical standard montage: although results are roughly equivalent, montage N requires one less electrode to do so.

Targeted density electrode placement achieves high concordance with traditional high-density EEG for electrical source imaging in epilepsy

ObjectiveHigh-density (HD) electroencephalography (EEG) is increasingly used in presurgical epilepsy evaluation, but it is demanding in time and resources. To overcome these issues, we compared EEG source imaging (ESI) solutions with a targeted density and HD-EEG montage. MethodsHD-EEGs from patients undergoing presurgical evaluation were analyzed. A low-density recording was created by selecting the 25 electrodes of a standard montage from the 83 electrodes of the HD-EEG and adding 8–11 electrodes around the electrode with the highest amplitude interictal epileptiform discharges. The ESI solution from this “targeted” montage was compared to that from the HD-EEG using the distance between peak vertices, sublobar concordance and a qualitative similarity measure. ResultsFifty-eight foci of forty-three patients were included. The median distance between the peak vertices of the two montages was 13.2 mm, irrespective of focus’ location. Tangential generators (n = 5/58) showed a higher distance than radial generators (p = 0.04). We found sublobar concordance in 54/58 of the foci (93%). Map similarity, assessed by an epileptologist, had a median score of 4/5. ConclusionsESI solutions obtained from a targeted density montage show high concordance with those calculated from HD-EEG. SignificanceRequiring significantly fewer electrodes, targeted density EEG allows obtaining similar ESI solutions as traditional HD-EEG montage.

Cinematographic continuity edits across shot scales and camera angles: an ERP analysis.

Film editing has attracted great theoretical and practical interest since the beginnings of cinematography. In recent times, the neural correlates of visual transitions at edit cuts have been at the focus of attention in neurocinematics. Many Event Related Potential (ERP) studies studies have reported the consequences of cuts involving narrative discontinuities, and violations of standard montage rules. However, less is known about edits that are meant to induce continuity. Here, we addressed the neural correlates of continuity editing involving scale, and angle variations across the cut within the same scene, two of the most popular devices used for continuity editing. We recorded the electroencephalographic signal obtained from 20 viewers as they watched four different cinematographic excerpts to extract ERPs at edit points. First, we were able to reproduce the general time and scalp distribution of the typical ERPs to filmic cuts in prior studies. Second, we found significant ERP modulations triggered by scale changes (scale out, scale in, or maintaining the same scale). Edits involving an increase in scale (scale out) led to amplification of the ERP deflection, and scale reduction (scale in) led to decreases, compared to edits that kept scale across the cut. These modulations coincide with the time window of the N300 and N400 components and, according to previous findings, their amplitude has been associated with the likelihood of consciously detecting the edit. Third, we did not detect similar modulations as a function of angle variations across the cut. Based on these findings, we suggest that cuts involving reduction of scale are more likely to go unnoticed, than ones that scale out. This relationship between scale in/out and visibility is documented in film edition manuals. Specifically, in order to achieve fluidity in a scene, the edition is designed from the most opened shots to the most closed ones.

Moving toward standardization: physician reporting of sleep studies.

Lastra AC, Ingram D, Park J, etal. Moving toward standardization: physician reporting of sleep studies. J Clin Sleep Med. 2023;19(3):595-603.

Modulation of cortical oscillations using 10hz near-infrared transcranial and intranasal photobiomodulation: a randomized sham-controlled crossover study

Abstract Objective: Transcranial Photobiomodulation (tPBM) provides a safe and noninvasive brain stimulation to intervene with brain functions. Despite the large body of reported clinical and behavioral outcomes, there is still need for a fuller understanding regarding NIR penetration and mechanisms. In this study, we investigated the effect of tPBM on cortical oscillations using power spectrum analysis. Methods: Twenty five healthy volunteers (9M/16F; mean age ± SD= 68.3± 6.63 years) received 20 minutes of active tPBM using 810 nm light-emitting diodes(LEDs), pulsed at 10 Hz with 50% duty cycle. In a randomized cross-over design, all participants received four arms of stimulation: (1) active (standard montage; LEDs irradiating the 4 hubs of default mode network), (2) active (non-standard montage - rearrangement of LEDs over right temporal-occipital regions, (3) active intranasal diode only, (4) sham (standard montage). Resting state EEG data was collected 10 minutes before (pre-tPBM), and at 10 and 30 minutes after (post10-tPBM; post30-tPBM) each stimulation session. The artifact-free resting-state data were used for power spectrum analysis. Results: Our power spectrum analysis showed significant changes in most frequency bands with all active stimulations (P<0.01). However, this modulation depended on the type and the location of stimulation. Namely, in type (1), a significant increase in theta, alpha, beta and gamma both post10-tPBM and post30-tPBM. For type (2), we found a significant increase in theta post30-tPBM, and alpha both post10 and post30-tPBM. For type (3) we found a significant increase in beta and gamma post10-tPBM and post30-tPBM, prominent in the posterior channels. Type (4) showed no significant change in any frequency bands. Conclusion: Findings from this study provide novel evidence that tPBM modulates neural oscillations in a frequency and location dependent manner. This is also the first investigation to measure the significant effect of an intranasal NIR LED on brain oscillation with EEG. Keywords: tPBM, EEG, power spectrum, cortical oscillation

Simplified frontal EEG in adults under veno-arterial extracorporeal membrane oxygenation

BackgroundEEG-based prognostication studies in intensive care units often rely on a standard 21-electrode montage (stdEEG) requiring substantial human, technical, and financial resources. We here evaluate whether a simplified 4-frontal electrode montage (4-frontEEG) can detect EEG patterns associated with poor outcomes in adult patients under veno-arterial extracorporeal membrane oxygenation (VA-ECMO).MethodsWe conducted a reanalysis of EEG data from a prospective cohort on 118 adult patients under VA-ECMO, in whom EEG was performed on admission to intensive care. EEG patterns of interest included background rhythm, discontinuity, reactivity, and the Synek’s score. They were all reassessed by an intensivist on a 4-frontEEG montage, whose analysis was then compared to an expert’s interpretation made on stdEEG recordings. The main outcome measure was the degree of correlation between 4-frontEEG and stdEEG montages to identify EEG patterns of interest. The performance of the Synek scores calculated on 4-frontEEG and stdEEG montage to predict outcomes (i.e., 28-day mortality and 90-day Rankin score {ge {4}}) was investigated in a secondary exploratory analysis.ResultsThe detection of EEG patterns using 4-frontEEG was statistically similar to that of stdEEG for background rhythm (Spearman rank test, ρ = 0.66, p < 0.001), discontinuity (Cohen’s kappa, kappa = 0.955), reactivity (kappa = 0.739) and the Synek’s score (ρ = 0.794, p < 0.001). Using the Synek classification, we found similar performances between 4-frontEEG and stdEEG montages in predicting 28-day mortality (AUC 4-frontEEG 0.71, AUC stdEEG 0.68) and for 90-day poor neurologic outcome (AUC 4-frontEEG 0.71, AUC stdEEG 0.66). An exploratory analysis confirmed that the Synek scores determined by 4 or 21 electrodes were independently associated with 28-day mortality and poor 90-day functional outcome.ConclusionIn adult patients under VA-ECMO, a simplified 4-frontal electrode EEG montage interpreted by an intensivist, detected common EEG patterns associated with poor outcomes, with a performance similar to that of a standard EEG montage interpreted by expert neurophysiologists. This simplified montage could be implemented as part of a multimodal evaluation for bedside prognostication.

Fully objective hearing threshold estimation in cochlear implant users using phase-locking value growth functions

Cochlear implant users require fitting of electrical threshold and comfort levels for optimal access to sound. In this study, we used single-channel cortical auditory evoked responses (CAEPs) obtained from 20 participants using a Nucleus device. A fully objective method to estimate threshold levels was developed, using growth function fitting and the peak phase-locking value feature. Results demonstrated that growth function fitting is a viable method for estimating threshold levels in cochlear implant users, with a strong correlation (r = 0.979, p < 0.001) with behavioral thresholds. Additionally, we compared the threshold estimates using CAEPs acquired from a standard montage (Cz to mastoid) against using a montage of recording channels near the cochlear implant, simulating recording from the device itself. The correlation between estimated and behavioural thresholds remained strong (r = 0.966, p < 0.001), however the recording time needed to be increased to produce a similar estimate accuracy. Finally, a method for estimating comfort levels was investigated, and showed that the comfort level estimates were mildly correlated with behavioral comfort levels (r = 0.50, p = 0.024).

Brain-state dependent TMS triggered by individual cortical source activity using online beamforming

EEG synchronized TMS is a powerful tool to investigate the role of brain oscillations in the modulation of excitability and plasticity by enabling specific phases to be differentially targeted in a closed-loop TMS paradigm. Using a 5-channel sensor level Laplacian montage centered on the EEG electrode C3 to isolate ongoing sensorimotor μ-oscillations, a correspondence between the negative peak of the μ-oscillation and states of high corticospinal excitability gating the induction of LTP like effects has been previously demonstrated but this standard montage is arbitrary and not always effective.

T88. Optimizing lower limb Somatosensory Evoked Potentials (SEPs) with additional derivations

SEPs recorded over the scalp serve as surrogate markers of dorsal column proprioceptive pathway integrity during surgery. Changes in SEP amplitude and/or latency meeting “alarm criteria” can indicate neural injury and prompt the surgical team to take action. Alarm criteria (e.g. 50% drop in amplitude) lose specificity when SEP measurement variability is high (e.g. ⩾25%). Lower limb scalp SEPs has vary dipole vectors between individuals. Standard recording electrode derivations of SEPs have been shown to be suboptimal when compared to a derivation individually optimized for each patient. Scalp lower limb SEPs were monitored from a consecutive sample of 51 patients during non-emergent procedures at Mayo Clinic Rochester. Two additional scalp electrodes at Cz and Pz were setup beside the standard scalp electrodes (CPz, Fz, CPi and CPc). Two standard derivations (CPz-Fz and CPi-CPc) and five expanded derivations (CPz-CPc, Cz-CPc, Pz-CPc, CPz-CPi and Pz-Fz) were recorded. P38 amplitudes were measured for all derivations; the derivation with the lowest coefficient of variation (CV) and highest amplitude from each group (standard vs. expanded montage) were determined. The P38 with highest amplitude and lowest CV were found in the expanded montage in 78 (76%) and 71 (70%) out of 102 limbs from 51 patients. The expanded montage significantly lowered the minimum CV by 1.75% (P < 0.0001, linear regression) and increased the maximal amplitude by 0.13 μV (P < 0.0001, linear regression) as compared to the standard montage. The CPz-CPc was the most frequent derivation with lowest CV and highest amplitude among all seven derivations. The effort to implement an expanded scalp montage should be balanced with the potential improvements, which by our data, are only incremental. An expanded scalp montage may be highest yield in patients where recordings from a conventional montage are of poor quality.

Evaluating the Effect of Repetitive Transcranial Magnetic Stimulation in Cerebral Palsy Children by Employing Electroencephalogram Signals.

Introduction:Transcranial magnetic stimulation is a new tool that has been employed to modulate the neuronal activity of brain by its excitatory and inhibitory property. In cerebral palsy (CP) learning of any new task is an extremely slow process due to damage in sensory and motor areas of brain affecting the cognitive ability of the child and putting constraints in achieving timely developmental milestones. For such patients the electroencephalogram (EEG) is one of the most cost effective diagnostic tools used that minimizes hospital stay. Its analysis helps to identify various neurological disorders determining the role of brain waves outlining the present status of mind.Materials and Methods:This study evaluated the EEG power spectrum density (PSD) of CP children both pre and post rTMS intervention to identify significance changes in signal patterns arising from different brain regions. thirty CP children participated in this study. Fifteen individuals underwent repetitive TMS (rTMS) therapy for 20 session comprising of 10 Hz frequency for 5 days a week for 4 weeks and another fifteen individual participated in activities of daily living for 20 sessions where they were administered mandatory standard therapy only. pre- EEG versus post EEG data recorded and analyzed employing the standard montage configuration. PSD was extracted employing fast fourier transform post acquisition of artifact free signal to undermine changes in signal pattern.Discussion and Conclusion:The results revealed that rTMS improves learning ability in CP children and it shows higher power peak at frequency of 50 Hz and lower power peak frequency at 100 Hz. The power intensity in gamma wave region shows significant reduction post-rTMS therapy between 38-24 power peak frequency and 7-4 range in 100 Hz power peak frequency. In future, it will be used as effective tool as memory enhancers, especially for children with neurological disorders.

P169 Does anodal transcranial direct current stimulation elicit consistent effects?

Introduction It is well known that transcranial direct current stimulation (tDCS) is capable of modulating cortical excitability. However, a source of growing concern has been the observed inter-individual variability of tDCS responses, and more recently, the intra-individual variability over repeated expositions. Few studies have investigated the reproducibility of tDCS effects over repeated sessions by assessing whether individuals respond in a predictable manner. The findings of these investigations showed to be inconsistent, and lack control groups to determine whether variability was related to the measuring tool (i.e. TMS). Objective The main objective of this study was to determine inter- and intra-individual variability of anodal tDCS (atDCS) effects on primary motor cortex (M1) excitability when applied over multiple sessions. In addition, we assessed whether tDCS response consistency was dependent on the stimulation parameters (i.e. current intensities). Subjects & methods Twelve subjects participated in a randomized crossover counterbalanced study, in which they received atDCS over M1 in three separate conditions (2 mA, 1 mA, sham) each repeated three times separated by 48 h. tDCS was delivered using a standard montage with the active electrode centered over M1 and the reference over the right supra-orbital area. Motor evoked potentials were recorded before and after stimulation (up to 30 min). Time and day of testing was maintained consistent within participants. To estimate the reliability of tDCS effects across multiple sessions, the Intra-class Correlation Coefficient (ICC) was calculated. Results AtDCS significantly increased cortical excitability at the group level in all sessions, except for the 1 mA condition. The ICC revealed fair to good reliability of tDCS effects. Given the distribution of individual responses showed important variability for the sham condition, we established a cut-off value based on this data to classify responses and to track individual changes across sessions for all conditions. Using this value, an intra-individual consistent response pattern was observed only in the 2 mA condition. Conclusion 2 mA anodal tDCS results in consistent intra- and inter-individual increases of M1 excitability.

Treatment-resistant obsessive-compulsive disorder: Insights from an open trial of transcranial direct current stimulation (tDCS) to design a RCT

The present study collected preliminary data testing the hypothesis that a lengthy transcranial direct current stimulation (tDCS) protocol reduces obsessive-compulsive disorder symptoms and strengthens executive control. Five patients presenting with treatment-resistant obsessive-compulsive disorder (TR-OCD) underwent neurocognitive and clinical testing prior to (baseline assessment) and after completing three weeks of tDCS (post-treatment evaluation). Four TR-OCD patients participated in 15 daily tDCS sessions during the three-week trial. One patient participated in 13 sessions. Scalp electrodes were situated using the standard montage for DLPFC stimulation: anode over left DLPFC (F3) and cathode over right frontopolar region (Fp2). We gained significant insights with this extensive testing: (1) TR-OCD patients demonstrated significant OCD symptom reduction following the course of tDCS; however, gains were not maintained at 1-month follow-up; (2) there were changes in depressive and schizotypal (positive) symptoms following three weeks of tDCS; however, baseline/post-treatment differences did not reach significance; (3) TR-OCD patients significantly lowered their daily ratings of depressive and generalized anxiety symptoms; (4) TR-OCD patients obtained a significant and specific improvement in Trail Making Test-part B (TMT-B) performance; and (5) there was a significant and robust correlation between TMT-B improvement and OCD symptom reduction. Although practice and placebo effects cannot be ruled out, the specific effects found in the study support further testing in a randomized controlled trial. Our results provide data to design further randomized clinical trials as to test whether and how tDCS induces a relevant clinical benefit in OCD. We discuss important design considerations for such a trial.

Tibial nerve F-wave recordings.

Tibial F-wave recordings are remarkable for their complexity and persistence. We postulate that the signal recorded by the E2 (reference) electrode causes this pattern. Tibial F-wave recordings were made from the abductor hallucis (AH) muscle using the standard montage in 10 subjects. Additional far-field simultaneous F-wave recordings were made from the AH, the base of the large toe, and the base of the small toe with the E2 placed on the contralateral foot. F-wave recordings made in the standard manner and from the base of the large or small toes showed complex waveforms and similar latencies. Recordings made from the AH-contralateral foot had simple waveforms in most subjects; in 2 subjects the latencies were longer, and 1 showed reduced persistence. The tibial F-waves are composed primarily of volume conducted recordings of the tibial-innervated foot muscles from the E2 electrode.

Prevalence of sleep disorders among ESRD patients

Sleep disorders are common among the patients undergoing dialysis in end stage renal disease (ESRD). Although variable, their prevalence has been reported to be higher when compared to the general population. The most frequently reported complaints are insomnia, restless leg syndrome (RLS), sleep-disordered breathing and excessive daytime sleepiness (EDS). The aim of this study was to assess the prevalence of sleep disorders in end stage renal disease patients on regular hemodialysis (group I with 30 patients) and CKD patients (group II with 30 patients) in comparison to 30 normal population (control group). In addition to laboratory investigations which included creatinine clearance using Cockroft and Gault formula, hemoglobin level (Hb), blood urea, serum creatinine, serum albumin, serum calcium and phosphorus and lipid profile, all subjects underwent one night of laboratory-based polysomnography (PSG) consisting of a standard montage of electroencephalography (EEG) (C3/A1 and O2/C3 or O1/C4), monopolar left and right electrooculography (EOG) referenced to the opposite mastoid, surface mentalis electromyography (EMG), respiratory airflow (measured by thermistor) and effort (piezoelectric sensors), electrocardiography (ECG), anterior tibialis EMG and pulse oximetry. For hemodialysis subjects, this study was performed on a night immediately following hemodialysis treatment. The results showed that patients on hemodialysis have sleep disorders, and that sleep disorders are common in group I and II than control group. The percentage of sleep disorders in hemodialysis patients were as follows: insomnia (69%), followed by obstructive sleep apnea syndrome OSAS (24%), RLS and periodic limb movement PLM (18%), nightmares (13%), EDS (12%), sleepwalking (2%), possible rapid eye movement behavior disorders RED (2%), possible narcolepsy (1.4%). While the percentage of sleep disorders in CKD patients were as follows: insomnia (54%), followed by RLS (19%), PLM (12%), OSAS (16%), nightmares (15%), EDS (15%), sleepwalking (4%), possible RBD (3%), possible narcolepsy (1%). There was inverse correlation between sleep disorders and Hb, albumin and creatinine clearance; also there was positive correlation between sleep disorder and phosphorus. We concluded that the sleep disorders are common in CKD patients either on conservative management or on regular hemodialysis. Treatment of anemia, hyperphosphatemia and hypoalbuminemia may improve sleep disorders among those patients.

Optimizing Ocular Vestibular Evoked Myogenic Potential Testing for Superior Semicircular Canal Dehiscence Syndrome: Electrode Placement

Objective: To compare the sensitivity and specificity of ocular vestibular evoked myogenic potentials (oVEMPs) using 2 electrode montages for the diagnosis of superior canal dehiscence syndrome (SCDS). Subjects: 16 SCDS patients (17 affected-SCDS ears, 15 contralateral-SCDS ears) and 12 controls (24 ears). Methods: oVEMPs were recorded in response to 500-Hz tone bursts using 2 electrode montages. For both montages the active electrode was placed approximately 5 mm below each eye and a ground electrode on the sternum. For montage 1 (standard), the reference electrode was centered 2 cm below each active electrode. For montage 2, the reference electrode was placed on the chin. Results: For either montage, the separation between oVEMP amplitudes in affected-SCDS ears and controls was significant (p < 0.001), with excellent sensitivity and specificity (>90%). Conclusion: oVEMP recordings with the standard montage remain a reliable method for evaluation of SCDS.

Does agomelatine block 5-HT2C receptors in humans?

receptor antagonist properties to healthy volunteersproduces reliable increases in slow wave sleep (SWS) in thepolysomnogram (see Sharpley et al. 1994; Sharpley andCowen 1995). The aim of the present study was to test thehypothesis that agomelatine would also increase SWS inhumans.We studied 15 healthy subjects (eight female, sevenmale; mean age 25.9 years, range 19–47 years) who weredetermined by clinical interview (non-patient version of theStructured Clinical Interview for DSM-IV) to have nocurrent history of psychiatric disorder or sleep disorder andwho were not taking any other medication. Each subjecttook matching capsules of placebo and agomelatine(25 mg) once, orally, 30 min before retiring to sleep in adouble blind, balanced order, crossover design with a 7- to14-day washout period between each sleep polysomno-gram. Subjective ratings of sleep (on a five-point scale) andside effects (on a four-point scale) were elicited themorning after each sleep study.On each study night, polysomnograms were recorded aseach participant slept at home, using the Embla A10 digitaldata recording system (Medcare, Broomfield, CO, USA).Participants retired and rose at their usual time, and this waskept constant for all study nights and all preceding nights.Polysomnography involved a standard montage: four electro-encephalogram channels (C3/A2, C4/A1, O1/A2, O2/A1),two electro-oculogram channels, and a submentalis electro-myogram. Polysomnograms were staged in 30-s epochs usingthe Embla diagnostic software, Somnologica Studio. Thissoftware provides measures for all aspects of sleep architec-ture according to standard criteria. In addition, the polysomno-grams were edited by an experienced sleep physiologist blindto treatment status. The polysomnograms of two participantswere excluded due to technical difficulties. However, theirsubjective ratings were available and were included. Differ-ences between the pairs of sleep nights were assessed usingStudent’spairedt test (two-tailed).Agomelatine produced no change in any polysomno-graphic parameter including SWS (Table 1). Separate exam-ination of sequential cycles of SWS also failed to reveal anyeffect of agomelatine (data not shown). Following agomela-tine, participants rated their sleep quality as improved, butthey also experienced more nausea (Table 1).Our findings suggest that initiation of a standard clinicaldose of agomelatine does not cause functional blockade ofbrain 5-HT

Altered sleep architecture and higher incidence of subsyndromal depression in low endogenous melatonin secretors

Melatonin secretion is synchronized to the sleep/wake cycle and has been suggested to have somnogenic properties. Sleep/wake cycle disruption and alterations in the secretary pattern of melatonin is present in various psychiatric disorders. The objective of this study was to investigate the sleep architecture and the presence of depression in individuals with low endogenous melatonin levels. The study included 16 participants (mean age 30.3 +/- 14.9 years). The first night of testing included psychiatric evaluation followed by melatonin secretion profile evaluation by Dim Light Melatonin Onset test and then standard montage polysomnographic testing. On the second night, only polysomnographic testing was carried out with an imposed sleep period of 8 h. Low endogenous melatonin secretors (LEMS) showed no discernible peaks in melatonin secretion compared to normal secretors (controls). LEMS demonstrated significant alterations in rapid eye movement sleep but not in non-rapid eye movement sleep along with poor sleep initiation and quality compared to controls. 55.6% of the low melatonin secretors group presented with subsyndromal depression. Melatonin has significant bearing on sleep architecture and a lack of melatonin may desynchronize endogenous rhythms allowing subsyndromal depression to manifest.

Disturbance of rapid eye movement sleep in spinocerebellar ataxia type 2

Five genetically confirmed spinocerebellar ataxia type 2 (SCA2) patients were admitted to our sleep laboratory for two all-night video-polysomnographies. A standard montage was used, including electroencephalography, vertical and horizontal electrooculography, electromyography of mental, submental, and tibialis anterior muscles, and respiratory monitoring. Four of five SCA2 patients had insufficient muscle atonia during rapid eye movement (REM) sleep. All patients exhibited myoclonic jerks during REM sleep, while elaborated behavior was not observed in the video. Abnormal motor control during sleep with periodic leg movements and REM sleep without atonia occurs frequently in SCA2. This finding may reflect a dysfunction of dopaminergic and/or brainstem and cerebellar outflow pathways.