Description

As of January 1999, The journal Electroencephalography and Clinical Neurophysiology,and its two sections Electromyography and Motor Control and Evoked Potentialshave amalgamated to become this journal - Clinical Neurophysiology Clinical Neurophysiology is the official journal of the International Federation of Clinical Neurophysiology. It is dedicated to fostering research and disseminating information on all aspects of Clinical Neurophysiology, both normal and abnormal. The journal aims at publishing scholarly reports on human physiology and pathophysiology of both the central and the peripheral nervous system. The journal is interested in manuscripts reporting data on integrated neuroimaging of central nervous functions including, but not limited to, functional MRI, MEG, EEG, PET and other aspects of neuroimaging. Electromyography, motor control and somatosensory physiopathology are covered by the journal, as well as evoked potentials with special emphasis on studies of cognitive functions. Studies on animals and technical notes must have clear relevance and applicability to humans.

Publisher details

Elsevier

Publications in this journal

• Cortical Activation To Voluntary Movement In Amyotrophic Lateral Sclerosis Is Related To Corticospinal Damage: Electrophysiological Evidence

  Authors: Riva N, Falini A, Inuggi A, Gonzalez-Rosa JJ, Amadio S, Cerri F, Fazio R, Del Carro U, Comola M, Comi G, Leocani L

  Clinical Neurophysiology.

  OBJECTIVES: The time course of mu and beta sensorimotor rhythms, with event-related desynchronisation (ERD) to preparation and execution of voluntary movement followed by synchronisation (ERS) afterOBJECTIVES: The time course of mu and beta sensorimotor rhythms, with event-related desynchronisation (ERD) to preparation and execution of voluntary movement followed by synchronisation (ERS) after movement, is considered to indicate cortical activation and idling, respectively. We investigated ERD and ERS in amyotrophic lateral sclerosis (ALS) patients and the relationship with anatomical and neurophysiological measures of corticospinal tract damage. METHODS: Pre-movement mu and beta ERD, and post-movement beta ERS were analysed in 16 ALS patients and 15 healthy controls performing self-paced brisk right thumb extensions. Apparent diffusion coefficient (ADC) of corticospinal tract was measured with magnetic resonance imaging (MRI). Motor-evoked potentials (MEPs) to the right abductor pollicis brevis were obtained using transcranial magnetic stimulation (TMS). RESULTS: Movement-related electromyographic activity was similar in the two groups. Post-movement ERS was significantly reduced in ALS group and negatively correlated with the amount of corticospinal damage as from MRI and TMS measures. ERD did not significantly differ between groups. CONCLUSIONS: Alterations of cortical activity in ALS patients were limited to the post-movement phase, as indicated by reduced ERS, and could be linked to reduced cortical inhibition rather than to generalised hyperexcitability. SIGNIFICANCE: The correlation between ERS and corticospinal damage severity might be interpreted as a functional compensation or dysfunction of inhibitory systems paralleling corticospinal damage.

• Spinal associative stimulation: A non-invasive stimulation paradigm to modulate spinal excitability

  Authors: Mar Cortes, Gary Thickbroom, Alvaro Pascual-Leone, Josep Valls-Sole, Dylan J Edwards

  Clinical Neurophysiology.

• The EEG patterns of drowsiness that are related to abnormal cognitive decline in elderly

  Authors: Masanori Saito, Megumi Takahashi, Hirokuni Tagaya, Hitoshi Miyaoka

  Clinical Neurophysiology. 121(S1):324.

  (Proceeding of XXIX International Congress of Clinical Neurophysiology, Kobe)

• Temporal coupling of rapid eye movements and cerebral activities during REM sleep.

  Authors: Keiko Ogawa, Takashi Abe, Hiroshi Nittono, Katuo Yamazaki, Tadao Hori

  Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology.

  OBJECTIVES: We investigated event-related potentials time locked to the onset and offset of rapid eye movements during rapid eye movement (REM) sleep. METHOD: Nine healthy university studentsOBJECTIVES: We investigated event-related potentials time locked to the onset and offset of rapid eye movements during rapid eye movement (REM) sleep. METHOD: Nine healthy university students participated in this study. Data were collected in a sleep laboratory. Rapid eye movements during REM sleep were recorded during natural nocturnal sleep. Saccades during wakefulness were recorded during a visually triggered task. Event-related potentials were averaged, time-locked to the onset and offset of eye movements. RESULTS: During REM sleep, a lambda-like response occurred over the occipital region, time-locked to the offset of rapid eye movements (similar to what occurs during wakefulness). Moreover, we found that a positive potential (P200r) occurred at about 200ms, with the maximal amplitude over the central region and time-locked to the onset of rapid eye movements during REM sleep; this potential was not observed during wakefulness. CONCLUSIONS: During REM sleep, the P200r occurs with the start of rapid eye movements, and then the lambda-like response occurs after termination of the movements. SIGNIFICANCE: We demonstrated temporal coupling of rapid eye movements and cerebral activities during REM sleep. These activities might provide a useful basis for future investigations of brain functions during REM sleep.

• Carpal tunnel syndrome: Demyelinative or ischemic conduction block?

  Authors: Satoshi Kuwabara

  Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology.

• Do children with ADHD and/or PDD-NOS differ in reactivity of alpha/theta ERD/ERS to manipulations of cognitive load and stimulus relevance?

  Authors: H Karin Gomarus, Albertus A Wijers, Ruud B Minderaa, Monika Althaus

  Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology.

  OBJECTIVE: We examined whether the method of event-related (de-)synchronization (ERD/ERS) revealed differential effects of selective attention and working memory load in children (8-11 years) withOBJECTIVE: We examined whether the method of event-related (de-)synchronization (ERD/ERS) revealed differential effects of selective attention and working memory load in children (8-11 years) with pervasive developmental disorder - not otherwise specified (PDD-NOS) or attention-deficit/hyperactivity disorder (ADHD). METHODS: Fifteen healthy controls and three equally large groups of children with symptoms of PDD-NOS, ADHD or both (PDD/HD) performed a visual selective memory search task. The EEG was recorded from which occipital alpha and frontal theta were derived. RESULTS: The effects of the overall task manipulations of task load, relevance and target/nontarget were clearly present in the overall analyses of alpha and theta ERD/ERS. However, no significant differences with respect to these manipulations existed between any of the subject groups. CONCLUSIONS: The results supply no evidence for a distinction in information processing abilities of selective attention and working memory as reflected by alpha and theta ERD/ERS between children diagnosed with either ADHD, PDD-NOS or healthy controls. SIGNIFICANCE: Alpha and theta ERD/ERS are sensitive to manipulations of task load, relevance and target/nontarget, but supply no additional information on possible group differences in comparison to the more frequently used method of event-related potentials.

• A longitudinal study of tremor frequencies in Parkinson's disease and essential tremor.

  Authors: B Hellwig, P Mund, B Schelter, B Guschlbauer, J Timmer, C H Lücking

  Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology.

  OBJECTIVE: There is evidence that the tremor frequency in essential tremor (ET) decreases with time. Longitudinal studies on the evolution of tremor frequencies in Parkinson's disease (PD) have soOBJECTIVE: There is evidence that the tremor frequency in essential tremor (ET) decreases with time. Longitudinal studies on the evolution of tremor frequencies in Parkinson's disease (PD) have so far not been published. Here, we present a longitudinal analysis of tremor frequencies in PD and ET. METHODS: We analyzed the standardized accelerometric and electromyographic tremor recordings of 53 patients with PD and 38 patients with ET who underwent repeated routine tremor recordings between 1991 and 2002. RESULTS: In an average follow-up period of 44.9 months in PD and 50.6 months in ET, the average number of tremor recordings was 3.3 in PD and 3.7 in ET. In both disorders, tremor frequencies tended to decrease with time. The average annual decrease of the tremor frequency was 0.09Hz/year in Parkinsonian rest tremor, 0.08Hz/year in Parkinsonian postural tremor and 0.12Hz/year in ET. CONCLUSIONS: The tremor frequency decreases with time in both PD and ET. The similarity of this decrease in PD and ET may point to a common underlying pathophysiological mechanism. SIGNIFICANCE: Decreasing tremor frequencies with time may be functionally important by inducing larger tremor amplitudes due to the low-pass filtering properties of muscles and limbs.

• Determining the time course of lexical frequency and age of acquisition using ERP.

  Authors: Fernando Cuetos, Analía Barbón, Mabel Urrutia, Alberto Domínguez

  Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology.

  OBJECTIVE: The main goal of the present study was to dissociate the effects on reading of frequency, age of acquisition (AoA) and imageability using the evoked response potential paradigm. METHOD:OBJECTIVE: The main goal of the present study was to dissociate the effects on reading of frequency, age of acquisition (AoA) and imageability using the evoked response potential paradigm. METHOD: Twenty participants read words from three experimental conditions: high and low frequency, late and early age of acquisition and high and low imageability. RESULTS: High frequency words produced more positive mean amplitude than low frequency words in the 175-360ms post-stimulus onset time window and late AoA produced more negative amplitudes than early AoA in the 400-610ms window. Imageability did not produce any effect in any time window tested. Brain electromagnetic tomography showed the most activated cortical areas for each category of stimuli. CONCLUSIONS: The lexical frequency of words seems to affect an early phase in the recognition process, perhaps at the level of the orthographic input lexicon, while AoA was observed at a later stage, indicating that this variable influence processing at a semantic level or at the links between semantics and phonology. SIGNIFICANCE: EEG permits the researcher to investigate the time course, and approximate location in the brain, of psycholinguistic variables.

• Feedback-related processes during a time-production task in young and older adults.

  Authors: Nele Wild-Wall, Rita Willemssen, Michael Falkenstein

  Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology.

  OBJECTIVE: We examined whether the age-related decline in the integrity of the mid-brain dopamine system plays a role in the adaptation of precisely timed motor responses by feedback information.OBJECTIVE: We examined whether the age-related decline in the integrity of the mid-brain dopamine system plays a role in the adaptation of precisely timed motor responses by feedback information. METHODS: Participants performed a time-production task with feedback given after each trial. They were encouraged to use the feedback for improving temporal response accuracy. Event-related potentials to the feedback were analyzed. RESULTS: Older participants performed poorer than the young. Overall, high response accuracy was more favoured following positive than negative feedback. Older participants performed even worse after negative feedback than the younger. The feedback-related negativity (FRN) was of lower amplitude for older vs. young participants. FRN amplitude correlated significantly with response accuracy only for the young group. CONCLUSIONS: The decreased response accuracy during time production of the older group may be related to a weakened fronto-striatal dopamine system and thus a reduced ability to use feedback information for improving temporal aspects of the motor response. SIGNIFICANCE: The study points to difficulties especially for older participants to process error feedback, and it underlines the importance of positive feedback in order to improve temporal response accuracy. Suggestions can be drawn for the design of feedback information especially for older adults in motor learning environments.

• Choice of multivariate autoregressive model order affecting real network functional connectivity estimate.

  Authors: Camillo Porcaro, Filippo Zappasodi, Paolo Maria Rossini, Franca Tecchio

  Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology.

  OBJECTIVE: A realistic simulation exploiting real cortical sources identified from non-invasive extra-cranial recordings in healthy subjects has been considered in order to select the most robustOBJECTIVE: A realistic simulation exploiting real cortical sources identified from non-invasive extra-cranial recordings in healthy subjects has been considered in order to select the most robust procedure for choosing the correct order of multivariate autoregressive (MVAR) models. Different signal-to-noise ratios filter settings and sampling rates were also tested on the estimate of functional connectivity among the network nodes, in simulated and real cases. METHODS: Starting from magnetoencephalographic recordings, cortical sources in primary sensorimotor areas of the hand were obtained by functional source separation (FSS). Different criteria for the choice of the model order were compared in the simulated network constructed through one of the FSS-extracted sources and its noise-added delayed copies. In two real cases, a validation of the model order (not known a priori) choice was obtained by comparing the time-frequency properties as depicted by classical non-parametric and MVAR methods at rest, during isometric contraction (stationary states) and while dynamically responding to a sensory stimulation (transient state). For completeness, the whole set of MVAR functional connectivity measures was taken into account, to assess the most suitable for our network description. RESULTS: That the use of an incorrect model order distorts network functional connectivity estimate was documented both in the realistic simulation and in the two real cases. The Minimal Description Length and Schwartz Bayesian Criterion were selected as the most robust for MVAR model order choice. Partial directed coherence (PDC) was the most suitable method for time-frequency connectivity estimate in the simulated as well as in the real cases, both in stationary and transient states. Moreover, the results of MVAR-based connectivity estimate depend on filter setting in the real case. CONCLUSIONS: The most robust procedure for choosing the correct MVAR model order was provided. The adjunctive comparison of MVAR to classical methods is recommended to validate the choice in the real case. SIGNIFICANCE: Correct MVAR model order choice and band filtering play an important role for the correct network connectivity estimate.

• Electrophysiological evidence of functional integration between the language and motor systems in the brain: A study of the speech Bereitschaftspotential.

  Authors: J J McArdle, Z Mari, R H Pursley, G M Schulz, A R Braun

  Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology.

  OBJECTIVE: We investigated whether the Bereitschaftspotential (BP), an event related potential believed to reflect motor planning, would be modulated by language-related parameters prior to speech.OBJECTIVE: We investigated whether the Bereitschaftspotential (BP), an event related potential believed to reflect motor planning, would be modulated by language-related parameters prior to speech. We anticipated that articulatory complexity would produce effects on the BP distribution similar to those demonstrated for complex limb movements. We also hypothesized that lexical semantic operations would independently impact the BP. METHODS: Eighteen participants performed 3 speech tasks designed to differentiate lexical semantic and articulatory contributions to the BP. EEG epochs were time-locked to the earliest source of speech movement per trial. Lip movements were assessed using EMG recordings. Doppler imaging was used to determine the onset of tongue movement during speech, providing a means of identification and elimination of potential artifact. RESULTS: Compared to simple repetition, complex articulations produced an anterior shift in the maximum midline BP. Tasks requiring lexical search and selection augmented these effects and independently elicited a left lateralized asymmetry in the frontal distribution. CONCLUSIONS: The findings indicate that the BP is significantly modulated by linguistic processing, suggesting that the premotor system might play a role in lexical access. SIGNIFICANCE: These novel findings support the notion that the motor systems may play a significant role in the formulation of language.

• Ethnic differences regarding sensory, pain, and reflex responses in the trigeminal region.

  Authors: Osamu Komiyama, Kelun Wang, Peter Svensson, Lars Arendt-Nielsen, Misao Kawara, Antoon De Laat

  Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology.

  OBJECTIVE: The present study evaluated ethnic differences in sensory, pain responses, and the exteroceptive suppression reflex (ES) in the trigeminal region. METHODS: Twenty-eight Caucasian (14 menOBJECTIVE: The present study evaluated ethnic differences in sensory, pain responses, and the exteroceptive suppression reflex (ES) in the trigeminal region. METHODS: Twenty-eight Caucasian (14 men and 14 women, age from 20 to 31) and 28 gender and age matched Japanese participated. Tactile detection thresholds and filament-prick pain detection thresholds were measured on the left cheek skin. Surface EMG was recorded from the left masseter muscle, and 13 different intensities of electrical stimuli were applied to the skin overlying the left mental nerve. The first stimulation intensity at which the late ES appeared was defined as the electrical reflex threshold. The duration and suppression degree of the ES were also determined. RESULTS: Japanese subjects had a significantly lower sensory and pain threshold then Caucasian subjects. Caucasian subjects had a significantly lower electrical reflex threshold in comparison to Japanese subjects. Caucasian subjects had significantly longer duration of the ES and larger suppression degree of the ES compared to Japanese subjects. CONCLUSIONS: Our results demonstrate that ethnic differences exist not only concerning sensory and pain responses but also regarding reflex (motor) responses. SIGNIFICANCE: The findings of this study have direct implications for studies evaluating different types of orofacial pain conditions and trigeminal reflexes.

• Ocular vestibular-evoked myogenic potentials elicited from monaural versus binaural acoustic stimulations.

  Authors: Shou-Jen Wang, Fu-Shan Jaw, Yi-Ho Young

  Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology.

  OBJECTIVE: This study compared the ocular vestibular-evoked myogenic potentials (oVEMPs) that are elicited (recorded) in response to monaural and separately, simultaneous binaural acousticOBJECTIVE: This study compared the ocular vestibular-evoked myogenic potentials (oVEMPs) that are elicited (recorded) in response to monaural and separately, simultaneous binaural acoustic stimulations. The optimal stimulation mode for oVEMPs was also determined. METHODS: Twenty healthy volunteers (14 men and 6 women, aged from 22 to 33years, mean 28years) without any previous ear disorders were enrolled in this study. Each subject underwent oVEMP testing using monaural acoustic stimulation (Mon-oVEMP) with different stimulus intensities, and with bilateral recording. On another day, the same volunteers underwent oVEMP testing using simultaneous binaural acoustic stimulation and bilateral recording (Bin-oVEMP). RESULTS: With 95dB nHL tone burst stimulation, the biphasic nI-pI waveforms were recorded with maximal amplitudes from the electrodes located below the eyes contralateral to the side of acoustic stimulation while the subject was gazing upward. Significant correlations were identified between Mon-oVEMPs and Bin-oVEMPs with respect to threshold, latencies and amplitude. However, no significant difference existed between Mon-oVEMPs and Bin-oVEMPs in terms of the response rate, threshold, latency or amplitude. CONCLUSIONS: The Bin-oVEMP test yields the same information as the Mon-oVEMP test, but the duration of recording in the former is shorter than the latter. SIGNIFICANCE: The Bin-oVEMP test may be a more convenient screening tool for evaluating the crossed vestibulo-ocular reflex.

• Combined cardiac sympathetic excitation and vagal impairment in patients with non-organic erectile dysfunction.

  Authors: Chih J Chen, Terry B J Kuo, Yi-Jhan Tseng, Cheryl C H Yang

  Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology.

  OBJECTIVE: Patients with non-organic erectile dysfunction (ED) frequently present with syndromes involving systemic sympathovagal dysfunction. The linkage of ED to cardiac autonomic regulation is notOBJECTIVE: Patients with non-organic erectile dysfunction (ED) frequently present with syndromes involving systemic sympathovagal dysfunction. The linkage of ED to cardiac autonomic regulation is not well understood. METHODS: Forty-four men with non-organic ED and 38 healthy age-matched control subjects with ages ranging from 40 years to 69 years were recruited. These two groups were divided into three distinct age categories at 10-year intervals. Patients were divided into three different severity categories, among whom 35 patients received a two-month oral treatment of trazodone. Power spectral analysis of successive R-R intervals (RR) was performed to evaluate the variance (variance of RR-interval values), the high-frequency power (HF), and the ratio of low-frequency power to HF (LF/HF) of their heart rate variability (HRV). RESULTS: Patients exhibited a significantly lower variance and HF, but a higher LF/HF compared to the control group across all age categories. The changes in variance and HF were severity dependent. In addition, all the HRV parameters of the patients with a satisfactory response after treatment have significantly improved. CONCLUSION: The results indicate that patients with non-organic ED had significant cardiac sympathetic hyperactivity and severity-dependent cardiac vagal impairment. SIGNIFICANCE: Non-organic ED may be accompanied by an abnormality in cardiac autonomic regulation.

• Effects of experimental focal compression on excitability of human median motor axons.

  Authors: Tatsunori Ikemoto, Toshikazu Tani, Shinichirou Taniguchi, Masahiko Ikeuchi, Jun Kimura

  Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology.

  OBJECTIVE: To characterize the effect of focal compression by threshold tracking and other excitability measures of human median motor axons. METHODS: We conducted a sequence of excitability studiesOBJECTIVE: To characterize the effect of focal compression by threshold tracking and other excitability measures of human median motor axons. METHODS: We conducted a sequence of excitability studies using a software written in BASIC (QTRAC version 4.0, (c)Institute of Neurology, London, UK, with multiple excitability protocol TRONDXM 2) in 24 healthy subjects, stimulating the median nerve at the wrist and recording compound muscle action potentials from the abductor pollicis brevis. Constant, localized compression was applied at the wrist by mechanically lowering a probe attached to a disk electrode, which also served as the stimulating cathode. RESULTS: Compared with the pre-compression values, measurements during compression showed a shift of threshold electrotonus waveforms toward the baseline (fanning-in), steeper current-threshold relationships, increased strength-duration time constants, prolonged relative refractory periods and reduced levels of superexcitability, but no alteration in late subexcitability. These excitability changes indicating depolarization reversed to hyperpolarization immediately after release of compression. The nerve compression altered none of the excitability measures when recorded 2cm distally from the pressure probe. CONCLUSIONS: Mild nerve compression produces a very localized axonal depolarization at the compression site followed by hyperpolarization upon release of compression, as expected from focal ischemia. SIGNIFICANCE: The current results imply that the sharply-localized conduction abnormalities demonstrated electrophysiologically in peripheral nerve entrapment syndromes and compression myelopathies may, in part, result from compression-induced focal nerve ischemia.

• Periodic leg movements during sleep and periodic limb movement disorder in patients presenting with unexplained insomnia.

  Authors: Raffaele Ferri, Viola Gschliesser, Birgit Frauscher, Werner Poewe, Birgit Högl

  Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology.

  OBJECTIVE: The aim of this study was to evaluate quantitatively the presence and the characteristics of periodic leg movements during sleep (PLMS) in a group of consecutive patients presenting withOBJECTIVE: The aim of this study was to evaluate quantitatively the presence and the characteristics of periodic leg movements during sleep (PLMS) in a group of consecutive patients presenting with daytime impairment related to insomnia of unknown etiology and whose polysomnographic features differ from those of healthy individuals only for a significantly increased arousal index in NREM sleep. METHODS: We recruited 20 consecutive adult patients with insomnia according to the ICSD-2 criteria, 20 patients with RLS, and 12 age-matched normal controls. The time structure of their polysomnographically recorded leg movements during sleep was analyzed by means of an approach particularly able to consider their periodicity. RESULTS: A subgroup of 12 patients with a relatively high number of periodic LM activity was detected with a statistically based approach using two indexes: total LM index and Periodicity index. This subgroup had high PLMS index, Periodicity index was also high and PLMS showed a progressive decrease during the night, being highest in the first hours of sleep. The characteristics of PLMS were identical within this insomnia subgroup and RLS patients. CONCLUSIONS: PLMS was a common finding in our patients with insomnia and a detailed analysis of their periodicity revealed that a subgroup of these patients had to be finally diagnosed with Periodic Limb Movement Disorder. SIGNIFICANCE: Polysomnography with the subsequent analysis of PLMS periodicity is able to differentiate between insomnia patient subgroups.

• Quantification of the auditory startle reflex in children.

  Authors: Mirte J Bakker, Frits Boer, Johan N van der Meer, Johannes H T M Koelman, Thijs Boerée, Lo Bour, Marina A J Tijssen

  Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology.

  OBJECTIVE: To find an adequate tool to assess the auditory startle reflex (ASR) in children. METHODS: We investigated the effect of stimulus repetition, gender and age on several quantifications ofOBJECTIVE: To find an adequate tool to assess the auditory startle reflex (ASR) in children. METHODS: We investigated the effect of stimulus repetition, gender and age on several quantifications of the ASR. ASR's were elicited by eight consecutive auditory stimuli in 27 healthy children. Electromyographic activity of orbicularis oculi, masseter, sternocleidomastoid, deltoid, abductor pollicis brevis, quadriceps muscles and the sympathetic skin response were recorded. ASR parameters (response probability in % and magnitude in area-under-the-curve) were: (1) combined response of all six muscles (2) blink response. RESULTS: Response probabilities were 78% in orbicularis oculi (median latency 41ms), 17% in sternocleidomastoid (median latency 66ms), 10% in masseter (median latency 66ms) and lower in other muscles. The ASR combined response probability and the sympathetic skin response significantly decreased with the repetitive stimuli, but the blink response probability did not. The magnitude (area-under-the-curve) of both the blink response and the combined response did not decrease with the repetitive stimuli. There were no gender or age effects. CONCLUSION: As in adults, the blink response and the combined response of multiple muscles show different habituation patterns in children. SIGNIFICANCE: Investigation of multiple muscles seems appropriate to quantify the ASR in children.

• Neurophysiological mechanisms of conduction impairment of the auditory nerve during cerebellopontine angle surgery.

  Authors: Sumito Sato, Masaru Yamada, Hiroyuki Koizumi, Yuya Onozawa, Naomi Shimokawa, Emi Kawashima, Kiyotaka Fujii

  Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology.

  OBJECTIVE: Intraoperative auditory brainstem response (ABR)-monitoring is useful for hearing preservation in patients undergoing cerebellopontine angle surgery. Prolongation of the latency of wave V,OBJECTIVE: Intraoperative auditory brainstem response (ABR)-monitoring is useful for hearing preservation in patients undergoing cerebellopontine angle surgery. Prolongation of the latency of wave V, for example, is observed under surgical stress such as cerebellar retraction. We analyzed intraoperative ABR findings to study the neurophysiological mechanism(s) underlying latency prolongation. METHODS: The ABR recorded during microvascular decompression surgery was studied in 18 patients with hemifacial spasm. We measured each trace of the ABR records, both the latency of each wave and some interpeak latencies. We also analyzed their waveforms especially in the early component, to assess changes during surgery. RESULTS: The latency of wave V varied with cerebellar retraction. The delayed latency of wave V was correlated with the prolonged interpeak latency of waves I-III. An additional wave (designated wave I') between waves I and II was appeared; it was accompanied by a prolongation in the latency of wave V. Wave I' contributed to prolongation of the interpeak latency of waves I-III, resulting in a delay in the latency of wave V. Chronological analysis revealed that the minimum latency of wave I' was the same as wave IN, suggesting that wave I' arose near the porus acusticus internus (PAI). CONCLUSION: Our study showed that cerebellar retraction may result in conduction impairment of the auditory nerve near the PAI, suggesting that the Obersteiner-Redlich zone is an electrophysiologically vulnerable site and wave I' is derived from the change in the vector of wave IN. SIGNIFICANCE: Our findings may provide neurophysiological evidence to support the theoretical model of ABR generators by Scherg and von Cramon.

• Variability of EMG patterns: A potential neurophysiological marker of Parkinson's disease?

  Authors: Julie A Robichaud, Kerstin D Pfann, Sue Leurgans, David E Vaillancourt, Cynthia L Comella, Daniel M Corcos

  Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology.

  OBJECTIVE: This study evaluated whether changes in the electromygraphic (EMG) pattern during rapid point-to-point movements in individuals diagnosed with PD can: (1) distinguish PD subjects fromOBJECTIVE: This study evaluated whether changes in the electromygraphic (EMG) pattern during rapid point-to-point movements in individuals diagnosed with PD can: (1) distinguish PD subjects from healthy subjects and (2) determine if differences in the EMG pattern reflect disease severity in PD. METHODS: Three groups of 10 PD subjects and 10 age/sex-matched healthy subjects performed rapid 72 degrees point-to-point elbow flexion movements. PD subjects were divided, a priori, into three groups based upon off medication motor UPDRS score. RESULTS: Measures related to the EMG pattern distinguished all PD subjects and 9 out of 10 healthy subjects, resulting in 100% sensitivity. Further, significant correlations were shown between EMG measures and the motor UPDRS score. After 30 months, the one healthy subject whose EMG pattern was abnormal was reexamined. The EMG measures remained abnormal and the motor UPDRS score went from 0 to 10. Parkinson's disease was diagnosed. CONCLUSION: Measures related to the variability of the EMG pattern during rapid point-to-point movements provide neurophysiological measures that objectively distinguish PD subjects from healthy subjects. These measures also correlate with disease severity. SIGNIFICANCE: EMG measures may provide a non-invasive measure that is sensitive and specific for identifying individuals with PD.

• The human sound-evoked vestibulo-ocular reflex and its electromyographic correlate.

  Authors: Miriam S Welgampola, Americo A Migliaccio, Oluwaseun A Myrie, Lloyd B Minor, John P Carey

  Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology.

  OBJECTIVE: Sound and vibration evoke a short-latency eye movement or "sound-evoked vestibulo-ocular reflex" (VOR) and an infraorbital surface potential: the "ocular vestibular-evoked myogenicOBJECTIVE: Sound and vibration evoke a short-latency eye movement or "sound-evoked vestibulo-ocular reflex" (VOR) and an infraorbital surface potential: the "ocular vestibular-evoked myogenic potential" (OVEMP). We examined their relationship by measuring the modulation of both responses by gaze and stimulus parameters. METHODS: In seven subjects with superior semicircular-canal dehiscence (SCD) and six controls, the sound-evoked VOR was measured in 3D using scleral search coils. OVEMPs were recorded simultaneously, using surface electromyography. RESULTS: Eye movement onset (11.6+/-0.8ms) coincided with the OVEMP peak (12.1+/-0.35ms). OVEMP and VOR magnitudes were 5-15 times larger in SCD compared with controls. OVEMP amplitudes were maximal on upgaze and abolished on downgaze; VOR magnitudes were unaffected. When stimulus type was changed from sound to vibration, OVEMP and VOR changed concordantly: increasing in controls and decreasing in SCD. OVEMP and VOR tuned to identical stimulus frequencies. OVEMP and VOR magnitudes on upgaze were significantly correlated (R=0.83-0.97). CONCLUSION: Selective decrease of the OVEMP upon downgaze is consistent with relaxation or retraction of the inferior oblique muscles. The temporal relationship of OVEMP and VOR and their identical modulation by external factors confirms a common origin. SIGNIFICANCE: Sound-evoked OVEMP and VOR represent the electrical and mechanical correlates of the same vestibulo-ocular response.

• Auditory-evoked potentials to frequency increase and decrease of high- and low-frequency tones.

  Authors: Hillel Pratt, Arnold Starr, Henry J Michalewski, Andrew Dimitrijevic, Naomi Bleich, Nomi Mittelman

  Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology.

  OBJECTIVE: To define cortical brain responses to large and small frequency changes (increase and decrease) of high- and low-frequency tones. METHODS: Event-Related Potentials (ERPs) were recorded inOBJECTIVE: To define cortical brain responses to large and small frequency changes (increase and decrease) of high- and low-frequency tones. METHODS: Event-Related Potentials (ERPs) were recorded in response to a 10% or a 50% frequency increase from 250 or 4000Hz tones that were approximately 3s in duration and presented at 500-ms intervals. Frequency increase was followed after 1s by a decrease back to base frequency. Frequency changes occurred at least 1s before or after tone onset or offset, respectively. Subjects were not attending to the stimuli. Latency, amplitude and source current density estimates of ERPs were compared across frequency changes. RESULTS: All frequency changes evoked components P(50), N(100), and P(200). N(100) and P(200) had double peaks at bilateral and right temporal sites, respectively. These components were followed by a slow negativity (SN). The constituents of N(100) were predominantly localized to temporo-parietal auditory areas. The potentials and their intracranial distributions were affected by both base frequency (larger potentials to low frequency) and direction of change (larger potentials to increase than decrease), as well as by change magnitude (larger potentials to larger change). The differences between frequency increase and decrease depended on base frequency (smaller difference to high frequency) and were localized to frontal areas. CONCLUSIONS: Brain activity varies according to frequency change direction and magnitude as well as base frequency. SIGNIFICANCE: The effects of base frequency and direction of change may reflect brain networks involved in more complex processing such as speech that are differentially sensitive to frequency modulations of high (consonant discrimination) and low (vowels and prosody) frequencies.

• Retinotopic mapping of the human visual cortex at a magnetic field strength of 7T.

  Authors: Michael B Hoffmann, Jörg Stadler, Martin Kanowski, Oliver Speck

  Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology.

  OBJECTIVE: fMRI-based retinotopic mapping data obtained at a magnetic field strength of 7T are evaluated and compared to 3T acquisitions. METHODS: With established techniques retinotopic mapping dataOBJECTIVE: fMRI-based retinotopic mapping data obtained at a magnetic field strength of 7T are evaluated and compared to 3T acquisitions. METHODS: With established techniques retinotopic mapping data were obtained in four subjects for 25 slices parallel to the calcarine sulcus at 7 and 3T for three voxel sizes (2.5(3), 1.4(3), and 1.1(3)mm(3)) and in two subjects for 49 slices at 7T for 2.5(3)mm(3) voxels. The data were projected to the flattened representation of T1 weighted images acquired at 3T. RESULTS: The obtained retinotopic maps allowed for the identification of visual areas in the occipito-parietal cortex. The mean coherence increased with magnetic field strength and with voxel size. At 7T, the occipital cortex could be sampled with high sensitivity in a short single session at high resolution. Alternatively, at lower resolution simultaneous mapping of a great expanse of occipito-parietal cortex was possible. CONCLUSION: Retinotopic mapping at 7T aids a detailed description of the visual areas. Here, recent findings of multiple stimulus-driven retinotopic maps along the intraparietal sulcus are supported. SIGNIFICANCE: Retinotopic mapping at 7T opens the possibility to detail our understanding of the cortical visual field representations in general and of their plasticity in visual system pathologies.

• ERP correlates of selective attention and working memory capacities in children with ADHD and/or PDD-NOS.

  Authors: H Karin Gomarus, Albertus A Wijers, Ruud B Minderaa, Monika Althaus

  Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology.

  OBJECTIVE: We examined whether children (8-11 years) diagnosed with Pervasive Developmental Disorder-Not Otherwise Specified (PDD-NOS) or Attention-Deficit/Hyperactivity Disorder (ADHD) showingOBJECTIVE: We examined whether children (8-11 years) diagnosed with Pervasive Developmental Disorder-Not Otherwise Specified (PDD-NOS) or Attention-Deficit/Hyperactivity Disorder (ADHD) showing primarily hyperactive behavior, differed in selective attention and working memory (WM) abilities. METHODS: Healthy controls and children with ADHD, PDD-NOS or symptoms of both disorders (PDD/HD) (n=15 in each group) carried out a visual selective memory search task while their EEG was recorded from which event-related potentials were derived. RESULTS: Compared to the control group, all patient groups made more omissions while hyperactive children also exhibited more false alarms. Regarding the process of WM-controlled search, significant group differences in ERP data were found between the control group and each of the clinical groups. CONCLUSIONS: The results point to less efficient WM-functioning in all patient groups. Whereas the clinical groups differed from each other at the behavioral level as measured by questionnaires, no distinction between the clinical groups could be made with respect to performance or ERP measures of WM capacity and selective attention. SIGNIFICANCE: The results suggest that a possible differentiation in selectivity and working memory capacities between PDD-NOS and ADHD is hard to find. This may agree with clinical practice, where differential diagnosis is a subject of discussion.

• Model comparison for automatic characterization and classification of average ERPs using visual oddball paradigm.

  Authors: A.C. Merzagora, M Butti, R Polikar, M. Izzetoglu, S. Bunce, S Cerutti, A M Bianchi, B. Onaral

  Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology.

  OBJECTIVE: To determine whether automated classifiers can be used for correctly identifying target categorization responses from averaged event-related potentials (ERPs) along with identifyingOBJECTIVE: To determine whether automated classifiers can be used for correctly identifying target categorization responses from averaged event-related potentials (ERPs) along with identifying appropriate features and classification models for computer-assisted investigation of attentional processes. METHODS: ERPs were recorded during a target categorization task. Automated classification of average target ERPs versus average non-target ERPs was performed by extracting different combinations of features from the P300 and N200 components, which were used to train six classifiers: Euclidean classifier (EC), Mahalanobis discriminant (MD), quadratic classifier (QC), Fisher linear discriminant (FLD), multi-layer perceptron neural network (MLP) and support vector machine (SVM). RESULTS: The best classification performance (accuracy: 91-92%; sensitivity: 85-86%; specificity: 95-99%) was provided by QC, MLP, SVM on feature vectors extracted from P300 recorded at multiple sites. In general, non-linear and non-parametric classifiers (QC, MLP, SVM) performed better than linear classifiers (EC, MD, FLD). The N200 did not explain variance beyond that of P300 recorded at multiple sites. CONCLUSIONS: The results suggest that automatic characterization and classification of average target and non-target ERPs is feasible. Features of P300 recorded at multiple sites used to train non-linear classifiers are recommended for optimal classification performance. SIGNIFICANCE: Automatic characterization of target ERPs can provide an objective approach for detecting and diagnosing abnormalities and evaluating interventions for clinical populations, paving the way for future real-time monitoring of attentional processes.

• Characteristics of generalised epileptiform activity.

  Authors: H Aurlien, I O Gjerde, G E Eide, J C Brøgger, N E Gilhus

  Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology.

  OBJECTIVE: To study the age-related occurrence of specific features of generalised epileptiform activity (GEA), their correlation with EEG background activity (BA), and their internal correlation.OBJECTIVE: To study the age-related occurrence of specific features of generalised epileptiform activity (GEA), their correlation with EEG background activity (BA), and their internal correlation. METHODS: 17,723 consecutive routine EEGs from 12,511 patients were annotated and categorised into a database. The first EEG containing GEA from all 325 patients with such activity were selected and categorised for GEA features. The BA was studied in multivariable fractional polynomial regression models including intervening variables. The GEA features were studied in similar models for age-dependency and internal correlation. RESULTS: High GEA-amplitude and low GEA-frequency correlated with BA slowing. The occurrence of 'irregular spike/sharp slow wave' pattern increased with age (p=0.003). Hyperventilation sensitivity was not age-related. There was no correlation between hyperventilation sensitivity and photoparoxysmal response. The age-related probability for specific GEA-types was established. CONCLUSIONS: High GEA-amplitude and low GEA-frequency correlate with BA slowing, indicating cerebral cortical dysfunction. Hyperventilation sensitivity and photoparoxysmal response independently increase the yield of EEG. There is no age-dependency for hyperventilation sensitivity showing that an upper age threshold for hyperventilation provocation is inappropriate. SIGNIFICANCE: The results extend our understanding of GEA and help the electroencephalographer in weighing the various GEA components.

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