Contingent Negative Variation Amplitude Research Articles

Phasic alertness in a cued double-choice reaction time task: A Contingent Negative Variation (CNV) study

A phasic change in alertness is produced every time that a warning stimulus precedes a target, and it enhances and maintains the response readiness to an impending stimulus. In the present study, we investigated the Contingent Negative Variation (CNV) phenomenon, as index of phasic alertness, during a S1–S2 paradigm in which the imperative stimulus was represented by a double-choice reaction time task, designed to increase the executive requests at S2. Subjects performed the task at three consecutive time points in order to explore the CNV activity over time. The repetition of a cued double-choice reaction time task reduced the reaction times (RTs), while CNV amplitude remained steady along the sessions. Our data suggest that the continuous recruitment of attentional resources does not undergo habituation when it is related to the brain activity required in the maintenance of working memory when the mental model of the stimulus environment is updated.

Slow cortical potential and theta/beta neurofeedback training in adults: effects on attentional processes and motor system excitability.

Neurofeedback (NF) is being successfully applied, among others, in children with attention deficit/hyperactivity disorder (ADHD) and as a peak performance training in healthy subjects. However, the neuronal mechanisms mediating a successful NF training have not yet been sufficiently uncovered for both theta/beta (T/B), and slow cortical potential (SCP) training, two protocols established in NF in ADHD. In the present, randomized, controlled investigation in adults without a clinical diagnosis (n = 59), the specificity of the effects of these two NF protocols on attentional processes and motor system excitability were to be examined, focusing on the underlying neuronal mechanisms. Neurofeedback training consisted of 10 double sessions, and self-regulation skills were analyzed. Pre- and post-training assessments encompassed performance and event-related potential measures during an attention task, and motor system excitability assessed by transcranial magnetic stimulation. Some NF protocol-specific effects have been obtained. However, due to the limited sample size medium effects did not reach the level of significance. Self-regulation abilities during negativity trials of the SCP training were associated with increased contingent negative variation amplitudes, indicating improved resource allocation during cognitive preparation. Theta/beta training was associated with increased response speed and decreased target-P3 amplitudes after successful theta/beta regulation suggested reduced attentional resources necessary for stimulus evaluation. Motor system excitability effects after theta/beta training paralleled the effects of methylphenidate. Overall, our results are limited by the non-sufficiently acquired self-regulation skills, but some specific effects between good and poor learners could be described. Future studies with larger sample sizes and sufficient acquisition of self-regulation skills are needed to further evaluate the protocol-specific effects on attention and motor system excitability reported.

Age-Related Psychophysiological Vulnerability to Phenylalanine in Phenylketonuria

Background: Phenylketonuria (PKU) is caused by the inherited defect of the phenylalanine hydroxylase enzyme, which converts phenylalanine (Phe) into tyrosine (Tyr). Neonatal screening programs and early treatment have radically changed the natural history of PKU. Nevertheless, an increased risk of neurocognitive and psychiatric problems in adulthood remains a challenging aspect of the disease. In order to assess the vulnerability of complex skills to Phe, we explored: (a) the effect of a rapid increase in blood Phe levels on event-related potentials (ERP) in PKU subjects during their second decade of life; (b) the association (if existing) between psychophysiological and neurocognitive features.Methods: Seventeen early-treated PKU subjects, aged 10–20, underwent ERP [mismatch negativity, auditory P300, contingent negative variation (CNV), and Intensity Dependence of Auditory Evoked Potentials] recording before and 2 h after an oral loading of Phe. Neurocognitive functioning, historical and concurrent biochemical values of blood Phe, Tyr, and Phe/Tyr ratio, were all included in the statistical analysis.Results: Event-related potential components were normally detected in all the subjects. In subjects younger than 13 CNV amplitude, W2-CNV area, P3b latency, and reaction times in motor responses were negatively influenced by Phe-loading. Independently from the psychophysiological vulnerability, some neurocognitive skills were more impaired in younger patients. No correlation was found between biochemical alterations and neurocognitive and psychophysiological findings.Conclusion: The vulnerability of the emerging neurocognitive functions to Phe suggests a strict metabolic control in adolescents affected by PKU and a neurodevelopmental approach in the study of neurocognitive outcome in PKU.

Changes in negative and positive EEG shifts during slow cortical potential training in children with attention-deficit/hyperactivity disorder: a preliminary investigation.

We examined the effects of self-regulation of slow cortical potentials (SCP) in nine children with attention-deficit/hyperactivity disorder (ADHD) by focusing on the changes in electroencephalographic (EEG) shifts during SCP sessions. In SCP training, individuals learn to increase and decrease their cortical excitabilities (enhancement of negative and positive cortical shifts). To examine the efficiency of SCP training, we conducted an attention task and measured contingent negative variation, which relates to the attention maintenance ability. Moreover, to assess training effects at the behavioral level, the Japanese ADHD rating scale (SNAP-J) was completed by the parents. In SCP training, we analyzed changes in EEG shifts during 16 training sessions by calculating the peak amplitudes of positive and negative shifts. The results of EEG data showed that peak amplitudes increased in sessions 11 and 12 for negative shifts and in sessions 9 and 13 for positive shifts. Moreover, we found an enhancement of contingent negative variation amplitude in the attention task before and after training, suggesting that the ability of these children to maintain attention could be modified by SCP training. However, significant behavioral improvements were not observed on the Japanese ADHD rating scale. It has been proposed that the number of additional training sessions may affect both physiological and behavioral improvements. Our present results, however, suggest the possibility that even low numbers of training sessions, such as 16, can bring about physiological improvement, whereas greater numbers of training sessions may be needed to have an influence on behavioral changes.

The Contingent Negative Variation – An Electrophysiological Correlate of Temporal Processing or Reference Memory?

In EEG research, the contingent negative variation (CNV) is considered to be strongly related to interval timing (e.g., Macar & Vidal, 2004; Macar, Vidal, & Casini, 1999). However, it is discussed controversially whether certain properties of the CNV (e.g., amplitude, peak latency and resolution) directly reflect the process of temporal accumulation or rather processes related to reference memory or decision stages in temporal information processing (van Rijn et al., 2011). This present study was designed in order to investigate the relationship between CNV mean amplitude, CNV resolution, and memory processes as well as processes of temporal accumulation. The task design aimed at dissociating between processes of reference memory and temporal accumulation. Three different categories of cognitive tasks were developed: temporal tasks related to reference memory, temporal tasks related to immediate memory and reference memory, and tasks without temporal components. Assuming correlations between post S2 CNV resolution and reference memory capacity (negative) as well as CNV amplitude and reference memory capacity (positive), no correlations were expected to be found between these CNV measures and performance in less reference memory related temporal tasks. The results do not support our hypotheses and methodological problems are discussed primarily.

Decoupling interval timing and climbing neural activity: a dissociation between CNV and N1P2 amplitudes.

It is often argued that climbing neural activity, as for example reflected by the contingent negative variation (CNV) in the electroencephalogram, is the signature of the subjective experience of time. According to this view, the resolution of the CNV coincides with termination of subjective timing processes. Paradoxically, behavioral data indicate that participants keep track of timing even after the standard interval (SI) has passed. This study addresses whether timing continues after CNV resolution. In Experiment 1, human participants were asked to discriminate time intervals while evoked potentials (EPs) elicited by the sound terminating a comparison interval (CI) were measured. As the amplitude of N1P2 components increases as a function of the temporal distance from the SI, and the latency of the P2 component followed the hazard rate of the CIs, timing processes continue after CNV resolution. Based on a novel experimental paradigm, statistical model comparisons and trial-by-trial analyses, Experiment 2 supports this finding as subjective time is more accurately indexed by the amplitude of early EPs than by CNV amplitude. These results provide the first direct evidence that subjective timing of multisecond intervals does not depend on climbing neural activity as indexed by the CNV and that the subjective experience of time is better reflected by distinct features of post-CI evoked potentials.

Physiological effect of olfactory stimuli inhalation in humans: an overview

The importance of odorants in human life has long been recognized. Literature contains different approaches of physiological and psychological effects of odorant compounds, fragrances and essential oils. This work discusses odorants inhalation effect, based on an overview of major studies in humans. Beneficial effect of fragrances is mainly related to human behaviour. Studies document odorants influence in sympathetic and parasympathetic nervous systems, and neurophysiological brain activity. Moreover, odours compounds can act on the neuroendocrine system, neurotransmitters and neuromodulators, influencing psychological behaviour as well as body function. Odorant inhalation modulates physiological pathways, and in some cases, results in skin function regulation. The mechanism is incompletely elucidated. These findings suggest that olfactory system plays a role in central nervous system function beyond that of smell. In this overview, it was observed that odour compounds influenced stress biomarkers, dehydroepiandrosterone, oxidative stress, estradiol, dopamine, cutaneous barrier, sebum secretion and cutaneous immune system in humans. Some can be related with skin function. As the skin is associated with an extensive biochemical cascade and has complex mechanisms, studies have far to go, as there are processes not yet investigated related to skin that may be affected through olfaction. Future researches are needed to further understand and describe the mechanisms of action of physiological effects in fragrance compounds.

Contingent negative variation is associated with cognitive dysfunction and secondary progressive disease course in multiple sclerosis.

Background and PurposeThe relationship between contingent negative variation (CNV), which is an event-related potential, and cognition in multiple sclerosis (MS) has not been examined previously. The primary objective of the present study was thus to determine the association between CNV and cognition in a sample of MS patients.MethodsThe subjects of this study comprised 66 MS patients [50 with relapsing-remitting MS (RRMS) and 16 with secondary progressive MS (SPMS)] and 40 matched healthy volunteers. A neuropsychological battery was administered to all of the subjects; CNV recordings were made from the Cz, Fz, and Pz electrodes, and the amplitude and area under the curve (AUC) were measured at each electrode.ResultsRRMS patients exhibited CNVs with lower amplitudes and smaller AUCs than the controls at Pz. SPMS patients exhibited CNVs with lower amplitudes and smaller AUCs than the controls, and CNVs with a smaller amplitude than the RRMS patients at both Cz and Pz. After correcting for multiple comparisons, a lower CNV amplitude at Pz was significantly associated with worse performance on measures of speed of information processing, verbal fluency, verbal learning, and verbal recall.ConclusionsCNV may serve as a marker for disease progression and cognitive dysfunction in MS. Further studies with larger samples and wider electrode coverage are required to fully assess the value of CNV in these areas.

EPA-0476 – Comparative study of P50 suppression, PPI and antisaccade measures in first episode and chronic schizophrenia patients

The aim of the study was to compare P50 suppression, prepulse inhibition (PPI) and antisaccade (AS) measures in first episode and chronic schizophrenia patients to assess the predictive validity and progressive changes of selected parameters. Unmedicated first-episode (15 subjects) and chronic (15 subjects) schizophrenia patients participated in the study. The patients’ symptomatology was rated with the Positive and Negative Syndrome Scale (PANSS). Control group included 21 healthy subjects. P50 suppression and acoustic startle prepulse inhibition (PPI) were estimated according to standard protocols (Olincy et al., 2010; Calkins et al., 2007). In AS task subjects had to look as quickly as possible at the horizontal mirror position of the peripheral target. Saccade and contingent negative variation (CNV) parameters were evaluated. Higher PANSS scales values were found in chronic patients compared to first episode ones. Both patients’ groups displayed significantly reduced P50 suppression (p<0,001) and prepulse inhibition deficit at 60 ms lead interval (p<0,05) compared to controls. Patients of both groups exhibited increase in the correct AS latency and larger number of errors in AS task compared to controls (p<0,05). The pronounced decline of CNV amplitude in frontal regions was found in chronic patients only ( Group x Area interaction , p<0,05). Results of the study corroborate the evidences of P50, PPI and AS measures predicting validity. The CNV analysis revealed pronounced prefrontal cortex dysfunction in chronic patients only. These data are compatible with the hypothesis of progressive brain changes in schizophrenia.

Differential Entrainment of Neuroelectric Delta Oscillations in Developmental Dyslexia

Oscillatory entrainment to the speech signal is important for language processing, but has not yet been studied in developmental disorders of language. Developmental dyslexia, a difficulty in acquiring efficient reading skills linked to difficulties with phonology (the sound structure of language), has been associated with behavioural entrainment deficits. It has been proposed that the phonological ‘deficit’ that characterises dyslexia across languages is related to impaired auditory entrainment to speech at lower frequencies via neuroelectric oscillations (<10 Hz, ‘temporal sampling theory’). Impaired entrainment to temporal modulations at lower frequencies would affect the recovery of the prosodic and syllabic structure of speech. Here we investigated event-related oscillatory EEG activity and contingent negative variation (CNV) to auditory rhythmic tone streams delivered at frequencies within the delta band (2 Hz, 1.5 Hz), relevant to sampling stressed syllables in speech. Given prior behavioural entrainment findings at these rates, we predicted functionally atypical entrainment of delta oscillations in dyslexia. Participants performed a rhythmic expectancy task, detecting occasional white noise targets interspersed with tones occurring regularly at rates of 2 Hz or 1.5 Hz. Both groups showed significant entrainment of delta oscillations to the rhythmic stimulus stream, however the strength of inter-trial delta phase coherence (ITC, ‘phase locking’) and the CNV were both significantly weaker in dyslexics, suggestive of weaker entrainment and less preparatory brain activity. Both ITC strength and CNV amplitude were significantly related to individual differences in language processing and reading. Additionally, the instantaneous phase of prestimulus delta oscillation predicted behavioural responding (response time) for control participants only.

Preparatory attention after lesions to the lateral or orbital prefrontal cortex – An event-related potentials study

The prefrontal cortex (PFC) plays a central role in preparatory and anticipatory attentional processes. To investigate whether subregions of the PFC play differential roles in these processes we investigated the effect of focal lesions to either lateral prefrontal (lateral PFC; n=11) or orbitofrontal cortex (OFC; n=13) on the contingent negative variation (CNV), an electrophysiological index of preparatory brain processes. The CNV was studied using a Go/NoGo delayed response task where an auditory S1 signaled whether or not an upcoming visual S2 was a Go or a NoGo stimulus. Neither early (500–1000ms) nor late (3200–3700ms) phase Go trial CNV amplitude was reduced for any of the patient groups in comparison to controls. However, the lateral PFC group showed enhanced Go trial early CNV and reduced late CNV Go/NoGo differentiation. These data suggests that normal orienting and evaluation as reflected by the CNV is intact after OFC lesions. The enhanced early CNV after lateral PFC damage may be due to failure in inhibition and the reduced late CNV difference wave confirms a deficit in preparatory attention after damage to this frontal subregion.

Attentional processing in bulbar- and spinal-onset amyotrophic lateral sclerosis: Insights from event-related potentials

Our objective was to evaluate attentional processing with respect to the clinical-onset subtype in amyotrophic lateral sclerosis (ALS) using event-related potentials (ERPs). Thirty-three non-demented ALS patients (22 spinal onset, 11 bulbar onset) and 32 age- and gender-matched controls underwent a psychophysiological evaluation. Mismatch Negativity (MMN), P300 components and Contingent Negative Variation (CNV) were obtained. Latencies and amplitudes of the MMN, P3a and P3b waves and CNV amplitude were then evaluated. Clinical parameters were correlated with ERP data. No differences emerged between ALS patients and controls with regard to the MMN and P3b components. N1-P3a inter-peak latency (Fz, p = 0.003; Cz, p = 0.001; Pz, p = 0.002) was longer in ALS-b than in ALS-s. Total CNV area (Cz, p = 0.01) and W1-CNV area were significantly reduced (Cz, p = 0.05; Pz, p = 0.03) in ALS-b with respect to the one of the controls, while no differences were found between ALS-s patients and controls. In conclusion, automatic pre-attentive processing of stimuli seems to be preserved in ALS. However, a significant delay in the time-course of selective attentive processing and a difficulty in initiating and sustaining attention may be present in ALS-b, which points to a possible dysfunction in the frontal neural network that responds to novelty and to abnormal integration of associative functions. This attentional impairment should be taken in account while developing alternative communicative strategies in ALS patients.

Multi‐components of evoked‐brain potentials in deficit and nondeficit schizophrenia

The present study aims to detect the specific and common impairment index relative to evoked brain potentials (EBPS ) in deficit schizophrenia (DS) and nondeficit schizophrenia (NDS), and investigates the relationship between EBPs and clinical variables. The study used EBPs in 21 patients with DS, 38 patients with NDS, and 50 healthy controls (HCs) to investigate P300 waves, mismatch negative (MMN), sensory gating (SG) P50 and contingent negative variation (CNV). A comparison of three groups and the relationship between EBPs and clinical variables were performed using general linear model analyses and partial correlation, respectively. Compared with HCs, both groups of patients showed delayed N1 , N2 , and P3a latency, and reduced N1 and N2 amplitude. The MMN showed delayed latency. The P50 ratios and the inhibited ratios were impaired, whereas SG loss ratios increased. CNV amplitude was reduced. Compared with HCs, NDS showed delayed latency of S2'-C in CNV, whereas DS showed shortened latency. Only NDS, when compared with HCs, showed delayed latency of P3b , Also, only DS, when compared with HCs, showed delayed latency of point A in CNV. Latency of point A in CNV of DS, correlated with a poorer Global Assessment of Functioning Scale (6 weeks) and was independent of clinical characteristics. Schizophrenia represents a clinical syndrome with shared impairments in brain function, whereas DS is a relatively homogeneous subgroup of schizophrenia with unique pathophysiological changes.

Clarifying Response Processes and Efficiency in a Cued Continuous Performance Test

Event Abstract Back to Event Clarifying Response Processes and Efficiency in a Cued Continuous Performance Test Robert J. Barry1, Diana Karamacoska1* and Genevieve Z. Steiner1 1 University Of Wollongong, School of Psychology, Australia Background The cued Continuous Performance Test (CPT) is known to elicit the contingent negative variation (CNV), which facilitates response preparation to upcoming Targets/NonTargets (imperative stimuli). Less prevalent in the literature is the examination of ERP responses to the cues, and how the preparatory activity these stimuli elicit influences the subsequent processing of imperative stimuli. Our study aimed to clarify whether the response processes to the imperatives were similar to those occurring to the cue, and determine if physiological and behavioural response efficiency was facilitated by this preparatory activity. Methods Continuous EEG was recorded from 70 participants during a computerised version of the Gordon-CPT that involved a fixed series of digits presented on a monitor with 1000 ms SOA. Subjects were required to press a button to the Target, 9, when cued by 1, and refrain from responses to cued NonTarget numbers. Single trial ERPs were extracted for the cue and two imperatives, and were analysed via Principal Components Analysis (PCA). Response components to cues and imperatives were assessed for similarity using the coefficient of congruence (rc); latencies were also assessed. For behavioural performance, reaction time (RT) was measured from Target onset and correlated with CNV amplitude. Results PCA identified 7 response components for the cue and imperatives: N1, PN, P2, N2c, N2b, P3, and SW. All were deemed to be similar between the stimulus types (rc > .80), except the N2cs, which showed little resemblance (rc < .80). Peak latencies strongly correlated between cue and imperatives (r = .99), with shorter latencies apparent for imperative components. RTs reduced as a function of increasing CNV amplitude. Discussion The response components to imperatives are strongly related to cue response components, suggesting that similar response processes are occurring for these stimuli during the task. The preparatory activity elicited by the cue enhances both electrophysiological and behavioural response efficiency in this cued paradigm. Keywords: Continuous Performance Test (CPT), event-related potentials (ERPs), Principal Components Analysis (PCA), response processes, response efficiency Conference: ACNS-2013 Australasian Cognitive Neuroscience Society Conference, Clayton, Melbourne, Australia, 28 Nov - 1 Dec, 2013. Presentation Type: Poster Topic: Attention Citation: Barry RJ, Karamacoska D and Steiner GZ (2013). Clarifying Response Processes and Efficiency in a Cued Continuous Performance Test. Conference Abstract: ACNS-2013 Australasian Cognitive Neuroscience Society Conference. doi: 10.3389/conf.fnhum.2013.212.00142 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 11 Sep 2013; Published Online: 25 Nov 2013. * Correspondence: Miss. Diana Karamacoska, University Of Wollongong, School of Psychology, Wollongong, Australia, d.karamacoska@westernsydney.edu.au Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Robert J Barry Diana Karamacoska Genevieve Z Steiner Google Robert J Barry Diana Karamacoska Genevieve Z Steiner Google Scholar Robert J Barry Diana Karamacoska Genevieve Z Steiner PubMed Robert J Barry Diana Karamacoska Genevieve Z Steiner Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

The contingent negative variation in remitted paediatric bipolar patients: no evidence of abnormality.

Although the Contingent Negative Variation (CNV) paradigm has been useful in schizophrenia, limited research involving such paradigm in subjects with Bipolar Disorder (BD) has produced contradictory findings. To the best of our knowledge, no study has investigated CNV in Paediatric Bipolar Disorder (PBD) subjects. Thirty remitted PBD patients and thirty matched healthy control group subjects participated in the study. No significant between group main effect could be found for either CNV latency or amplitude. We propose that CNV is unlikely to be a true endophenotype of BD. However, absence of CNV finding during euthymic phase in BD may help us in advancing our understanding of BD and such finding may, in fact, have some specificity with regard to differentiating BD from schizophrenia.

Differential Go/NoGo activity in both contingent negative variation and spectral power.

We investigated whether both the contingent negative variation (CNV), an event-related potential index of preparatory brain activity, and event-related oscillatory EEG activity differentiated Go and NoGo trials in a delayed response task. CNV and spectral power (4–100 Hz) were calculated from EEG activity in the preparatory interval in 16 healthy adult participants. As previously reported, CNV amplitudes were higher in Go compared to NoGo trials. In addition, event-related spectral power of the Go condition was reduced in the theta to low gamma range compared to the NoGo condition, confirming that preparing to respond is associated with modulation of event-related spectral activity as well as the CNV. Altogether, the impact of the experimental manipulation on both slow event-related potentials and oscillatory EEG activity may reflect coordinated dynamic changes in the excitability of distributed neural networks involved in preparation.

Higher, faster, stronger: The effect of dynamic stimuli on response preparation and CNV amplitude

The contingent negative variation (CNV) is a slow negative shift in the electroencephalogram (EEG), observed during response preparation. To optimalize the CNV paradigm, this study developed a task using dynamic stimuli and next combined this task with a Go/No-go test. In the first experiment, 19 healthy volunteers were subjected to the classic Traffic light (TL) task and the new dynamic Lines task. In the Lines task, response time was faster and CNV amplitude was larger compared to the TL task. In the second experiment, 20 healthy participants were tested on a Go/No-go version of the Lines task. Response times increased as the probability of response requirement decreased. CNV amplitude was larger when probability of response requirement was higher. In conclusion, the dynamic task promotes response preparation. The new tasks may be especially valuable in groups with attention difficulties (i.e. elderly or ADHD patients).

Allocation of attention in response to novel neutral stimuli and predictive negative stimuli in men and women: an event-related potentials research study

Hormonal cycle modulates arousal circuitry. Animal experiments suggested that progesterone enhanced fear-potentiated startle. At present, direct electrophysiological evidence of a gender difference in novel and unpredictive stimuli is still sparse. Ten men and 23 women at one of two different stages of the menstrual cycle (menses phase, WM, and luteal phase, WL) were examined for event-related potential evidence of attention allocation in the oddball task phase (OTP) and predictive task phase (PTP). We used two tones, 1 kHz 80% as standard stimuli and 2 kHz 20%, as novel stimuli presented randomly in OTP. In PTP, every novel stimuli fixed followed a white noise, but 1 kHz tones never followed white noise. The results showed: (1) In OTP, the P3 amplitude in the WL group during the 350–400-ms time window was higher than that of the other two groups. (2) In PTP, no difference was observed between the groups with respect to the amplitude of contingent negative variation during the 1080–1180 ms and 1320–1360 ms time windows. Thus, it is concluded that women in WL present modulated autonomic arousal, but no difference to predictive negative stimuli than women in WM and men.

Motor Planning in Chronic Upper-Limb Hemiparesis: Evidence from Movement-Related Potentials

BackgroundChronic hemiplegia is a common long-term consequence of stroke, and subsequent motor recovery is often incomplete. Neurophysiological studies have focused on motor execution deficits in relatively high functioning patients. Much less is known about the influence exerted by processes related to motor preparation, particularly in patients with poor motor recovery.Methodology/Principal FindingsThe current study investigates motor preparation using a modified response-priming experiment in a large sample of patients (n = 50) with moderate-to-severe chronic hemiparesis. The behavioural results revealed that hemiparetic patients had an increased response-priming effect compared to controls, but that their response times were markedly slower for both hands. Patients also demonstrated significantly enhanced midline late contingent negative variation (CNV) during paretic hand preparation, despite the absence of overall group differences when compared to controls. Furthermore, increased amplitude of the midline CNV correlated with a greater response-priming effect. We propose that these changes might reflect greater anticipated effort to respond in patients, and consequently that advance cueing of motor responses may be of benefit in these individuals. We further observed significantly reduced CNV amplitudes over the lesioned hemisphere in hemiparetic patients compared to controls during non-paretic hand preparation, preparation of both hands and no hand preparation. Two potential explanations for these CNV reductions are discussed: alterations in anticipatory attention or state changes in motor processing, for example an imbalance in inter-hemispheric inhibition.Conclusions/SignificanceOverall, this study provides evidence that movement preparation could play a crucial role in hemiparetic motor deficits, and that advance motor cueing may be of benefit in future therapeutic interventions. In addition, it demonstrates the importance of monitoring both the non-paretic and paretic hand after stroke and during therapeutic intervention.

Effects of magnitude and magnitude predictability of postural perturbations on preparatory cortical activity in older adults with and without Parkinson’s disease

The goal of this study was to identify whether impaired cortical preparation may relate to impaired scaling of postural responses of people with Parkinson's disease (PD). We hypothesized that impaired scaling of postural responses in participants with PD would be associated with impaired set-dependent cortical activity in preparation for perturbations of predictable magnitudes. Participants performed postural responses to backward surface translations. We examined the effects of perturbation magnitude (predictable small vs. predictable large) and predictability of magnitude (predictable vs. unpredictable-in-magnitude) on postural responses (center-of-pressure (CoP) displacements) and on preparatory electroencephalographic (EEG) measures of contingent negative variation (CNV) and alpha and beta event-related desynchronization (ERD). Our results showed that unpredictability of perturbation magnitude, but not the magnitude of the perturbation itself, was associated with increased CNV amplitude at the CZ electrode in both groups. While control participants scaled their postural responses to the predicted magnitude of the perturbation, their condition-related changes in CoP displacements were not correlated with condition-related changes in EEG preparatory activity (CNV or ERD). In contrast, participants with PD did not scale their postural responses to the predicted magnitude of the perturbation, but they did demonstrate greater beta ERD in the condition of predictably small-magnitude perturbations and greater beta ERD than the control participants at the CZ electrode. In addition, increased beta ERD in PD was associated with decreased adaptability of postural responses, suggesting that preparatory cortical activity may have a more direct influence on postural response scaling for people with PD than for control participants.