Changes In Oscillatory Activity Research Articles

Human cortical theta reactivity to high‐frequency repetitive transcranial magnetic stimulation

Electroencephalography (EEG) can directly monitor the temporal progression of cortical changes induced by repetitive Transcranial Magnetic Stimulation (rTMS) and facilitate the understanding of cortical and subcortical influences in the genesis of oscillations. In this combined rTMS/EEG study, we aimed to investigate changes in oscillatory activity after high-frequency (∼11 Hz) rTMS relative to the number of applied pulses. Twenty intermittent trains of 20 or 60 rTMS pulses were delivered over the human primary motor cortex at rest and tuned to individual mu frequency. The regional and interregional oscillatory neural activity after stimulation were evaluated using event-related power (ERPow) and event-related coherence (ERCoh) transformations. The most prominent changes for ERPow were observed in the theta band (4-7 Hz), as an increase in ERPow up to 20 s following 60 rTMS pulses, whereas ERPow increases were smaller in mu (10-12 Hz) and beta (13-30 Hz). ERCoh revealed that rTMS 60 modulated the connectivity in the theta band for up to 20 s. The topography of mu and theta changes were not identical; mu was more focal and theta was more global. Our data suggested the presence of independent cortical theta and mu generators with different reactivity to rTMS but could not rule out possible thalamocortical contributions in generating theta and mu over the motor network.

The effect of hypercapnia on resting and stimulus induced MEG signals

The effect of hypercapnia (an increase in CO(2) concentration in the blood) on the functional magnetic resonance imaging (fMRI) blood oxygenation level dependent (BOLD) haemodynamic response has been well characterised and is commonly used for BOLD calibration. However, relatively little is known of the effect of hypercapnia on the electrical brain processes that underlie the BOLD response. Here, we investigate the effect of hypercapnia on resting and stimulus induced changes in neural oscillations using a feed-forward low gas flow system to deliver a reliable and repeatable level of hypercapnia. Magnetoencephalography (MEG) is used in conjunction with beamformer source localisation algorithms to non-invasively image changes in oscillatory amplitude. At rest, we find robust oscillatory power loss in the alpha (8Hz-13Hz), beta (13Hz-30Hz) and low gamma (30Hz-50Hz) frequency bands in response to hypercapnia. Further, we show that the spatial signature of this power loss differs across frequency bands, with the largest effect being observed for the beta band in sensorimotor cortices. We also measure changes in oscillatory activity induced by visual and motor events, and the effect of hypercapnia on these changes; whilst the percentage change in oscillatory activity on activation was largely unaffected by hypercapnia, the absolute change in oscillatory amplitude differed between normocapnia and hypercapnia. This work supports invasive recordings made in animals, and the results have potential implications for calibrated BOLD studies.

Brain oscillatory activity during motor imagery in EEG-fMRI coregistration

The purpose of the present work was to investigate the correlation between topographical changes in brain oscillatory activity and the blood oxygenation level-dependent (BOLD) signal during a motor imagery (MI) task using electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) coregistration. EEG was recorded in 7 healthy subjects inside a 1.5 T MR scanner during the imagination of the kinesthetic experience of movement. A Fast Fourier Transform was applied to EEG signal in the rest and active conditions. We used the event-related-synchronization (ERS)/desynchronization (ERD) approach to characterize where the imagination of movement produces a decrease in alpha and beta power. The mean alpha map showed ERD decrease localized over the contralateral sensory motor area (SM1c) and a light desynchronization in the ipsilateral sensory motor area (SM1i); whereas the mean beta map showed ERD decrease over the supplementary motor area (SMA). fMRI showed significant activation in SMA, SM1c, SM1i. The correlation is negative in the contralateral side and positive in the ipsilateral side. Using combined EEG-fMRI signals we obtained useful new information on the description of the changes in oscillatory activity in alpha and beta bands during MI and on the investigation of the sites of BOLD activity as possible sources in generating these rhythms. By correlating BOLD and ERD/ERS we may identify more accurately which regions contribute to changes of the electrical response.

Frontal shift of posterior alpha activity is correlated with cognitive impairment in early Alzheimer's disease: A magnetoencephalography-beamformer study

Induced-oscillatory activity is considered a key factor for understanding functional processes in the brain. Magnetoencephalography (MEG) can measure oscillatory activity non-invasively with higher spatial resolution than electroencephalography (EEG). However, MEG has rarely been used to explore functional abnormalities that may represent state markers in patients with Alzheimer's disease (AD). Thirteen patients with early AD and 14 age-matched normal controls participated in the present study. Magnetoencephalography activity was acquired during eyes-open and eyes-closed states. Alpha event-related synchronization (ERS) after eye closing was calculated and its cortical sources superimposed on each individual's magnetic resonance imaging (MRI) scan. The resulting functional image was converted into a Talairach-transformed anatomical brain image and group comparisons were made. We also assessed correlations between cortical ERS sources showing significant between-group differences in alpha activity and external clinical parameters, especially measures of cognitive function. The averaged alpha ERS after eye closing appeared dominantly in posterior brain regions in both patients with AD and healthy controls. However, there was a significant increase in alpha ERS in frontal regions, maximal over the prefrontal cortex, in patients with AD relative to controls, indicating a frontal shift of the posterior dominant MEG alpha rhythm in AD patients. This frontal ERS source in the alpha band was negatively correlated with Mini-Mental State Examination scores in the AD patient group. The findings indicate that a frontal shift of alpha ERS elicited by an eyes-open/eyes-closed paradigm may be an early brain electromagnetic change in patients with AD, probably representing a physiological state marker of the disease. Furthermore, the results confirm that the beamformer with group comparison analysis is a useful tool with which to explore functional processes in the brain, as indicated by oscillatory activity changes.

Pollen-tube tip growth requires a balance of lateral propagation and global inhibition of Rho-family GTPase activity

Rapid tip growth allows for efficient development of highly elongated cells (e.g. neuronal axons, fungal hyphae and pollen tubes) and requires an elaborate spatiotemporal regulation of the growing region. Here, we use the pollen tube as a model to investigate the mechanism regulating the growing region. ROPs (Rho-related GTPases from plants) are essential for pollen tip growth and display oscillatory activity changes in the apical plasma membrane (PM). By manipulating the ROP activity level, we showed that the PM distribution of ROP activity as an apical cap determines the tip growth region and that efficient tip growth requires an optimum level of the apical ROP1 activity. Excessive ROP activation induced the enlargement of the tip growth region, causing growth depolarization and reduced tube elongation. Time-lapse analysis suggests that the apical ROP1 cap is generated by lateral propagation of a localized ROP activity. Subcellular localization and gain- and loss-of-function analyses suggest that RhoGDI- and RhoGAP-mediated global inhibition limits the lateral propagation of apical ROP1 activity. We propose that the balance between the lateral propagation and the global inhibition maintains an optimal apical ROP1 cap and generates the apical ROP1 activity oscillation required for efficient pollen-tube elongation.

Revisión crítica del comportamiento de la coherencia corticomuscular en el control motor fino de la fuerza

Understanding how the human motor control operates is an important issue to the neuroscience. One example is how the motor cortex controls muscle activity, which can be observed through corticomuscular coherence (CMC). Our study aimed to verify the influence of certain factors related to the fine motor control of force tasks on CMC. Our issue is if would be possible the strength of the coupling between the central and muscular systems measured by changes in oscillatory activity of beta- and gamma-band being influenced by these factors as much healthy subjects as patients. Beta-band CMC was especially important when executing sustaining accurate control tasks, which need more concentration and effort. However, we found that beta-band CMC was influenced by some factors. With regard to gamma-band CMC, apparently a complex and continuous dynamic integration of several mechanisms would be necessary to modulate gamma-band CMC, since it was not modulated by magnitude of force. Therefore, it seems these mechanisms would be required to an adequate and effective neural networks operation when a dynamic force output is required. Beta- and gamma-band CMC could enrich our understanding of the dynamic changes of the motor system not only in health subjects but also in neurological patients. It may serve as a sensitive index for quantifying dynamical changes in fine motor control of force. It has the potential to become a useful tool to characterize the patterns of changes in central nervous system's activities for the purposes of basic research, especially in restoring of motor function.

Cortical oscillations scan using chirp-evoked potentials in 6-hydroxydopamine rat model of Parkinson's disease

There has been a growing interest during the last years on the relationship between Parkinson's disease and changes in the oscillatory activity, mostly in the cortico-basal motor loop. As Parkinson's disease (PD) is not limited to motor symptoms, it is logical to assume that the changes in oscillatory activity are not limited to this loop. Steady-state responses (SSR) are the result of averaging individual responses to trains of rhythmic stimuli delivered at a constant frequency. The amplitude of the response varies depending on the stimulus modality and stimulation rate, with a frequency of maximal response that is probably associated to the working frequency of the pathway involved. The study of SSR may be of interest in PD as a non-invasive test of cortical oscillatory activity. Our aim was to study the changes in auditory steady-state responses (ASSR) in the 6-hydroxydopamine (6-OHDA) model of Parkinson's disease in rats. We recorded the ASSR over the auditory cortex in a group of 10 control and 17 6-OHDA lesioned rats (the latter before and after the administration of the dopaminergic agonist apomorphine) both awake and under anesthesia with ketamine/xylazine, using chirp-modulated stimuli. The three conditions (control, lesion, lesion plus apomorphine) were compared with special emphasis on the amplitude, inter-trial phase coherence, and frequency of maximal response. A reduction in the frequency of maximal response (between 40 and 60 Hz) was observed in the 6-OHDA lesioned rats that was normalized after apomorphine injection. The administration of this dopaminergic agonist also reduced the inter-trial phase coherence of the response in frequencies above 170 Hz. These findings suggest that the nigrostriatal dopaminergic system may be involved in the regulation of oscillatory activity not only in motor circuits, but also in sensory responses.

Local injection of MK801 modifies oscillatory activity in the nucleus accumbens in awake rats

Pharmacological blockade of NMDA receptors is used to model certain aspects of schizophrenia. It had been shown previously that ketamine dose dependently enhances high-frequency oscillations in the rodent nucleus accumbens, a structure implicated in schizophrenia. Here, the authors examined the effect of intra-accumbal and systemic administration of MK801 on delta, gamma and high-frequency oscillatory activity recorded in the nucleus accumbens of freely moving rats. In this study, rats were implanted with electrodes in the nucleus accumbens for chronic local field potential recording. Rats received either bilateral injections of MK801 (1 and 4 microg) or intraperitoneal injections of the drug (0.1 and 0.5 mg/kg). Saline was used as control in each instance. Both local and systemic injections significantly enhanced the power and frequency of high-frequency oscillations and caused an increase in the occurrence, duration and amplitude of high-frequency oscillatory bursts. In contrast, no effect or a decrease in the power of delta and gamma bands was observed following local or systemic administration of MK801, respectively. These findings suggest that the dominant change in oscillatory activity after administration of NMDA receptor antagonists affect high frequencies. Moreover, direct NMDA blockade in the accumbal circuitry is sufficient to generate increases in high-frequency oscillations. The presence of abnormal oscillatory activity in the accumbens may be associated with the psychomimetic effects of NMDA receptor antagonists.

Parkinsonism: evolving pathophysiologic concepts

The link between the hallmark pathology in Parkinson's disease, i.e., dopamine loss in the basal ganglia, and the behavioral signs of parkinsonism, remains mysterious. This presentation will review our knowledge of system-level changes in brain activity in parkinsonism. The most commonly discussed models of the changes in brain activity that lead to parkinsonism were developed twenty years ago, and were strongly based on anatomical considerations and changes in the firing rates of basal ganglia neurons in dopamine-depleted animals. The most important change noted was an increase in the activity of neurons in the basal ganglia output nuclei. A simple anatomic argument was used to link these changes to the striatal loss of dopamine. Since that time, a plethora of new findings has emerged, indicating that the changes in firing rate may be less important than changes in other aspects of basal ganglia activity. Changes in oscillatory activity in the beta- and gamma-bands of frequencies have been observed to be important, as have changes in non-linear firing characteristics such as increases in the bursting activity of individual basal ganglia neurons. Studies in animals and humans have also shown that the ensemble activity of basal ganglia neurons appears to be altered in parkinsonism, with the emergence of pathological levels of synchronization between neighboring neurons. Perhaps most importantly, parkinsonism has emerged as a circuit disorder in which the focal loss of dopamine in the basal ganglia has significant down-stream effects on the activity of other areas of the brain, specifically the thalamus, portions of the cortex, and the brainstem. Many questions in this field remain unanswered. The links between dopamine loss and the changes in firing patterns have not been identified, and the relationship between the electrical changes in the basal ganglia-thalamocortical circuitry and parkinsonian motor signs remains unclear. The significance of anatomical changes that are secondary to long-term dopamine loss, such as loss of the dendritic spines of striatal medium spiny neurons, and the role of non-dopaminergic or extra-basal ganglia pathology in parkinsonism also need to be elucidated. Addressing these questions will be essential for the development of more effective pharmacological and surgical strategies to treat parkinsonian patients.

Cortical oscillatory power changes during auditory oddball task revealed by spatially filtered magnetoencephalography

To investigate the neural sources and associated changes in oscillatory activity involved in auditory attention and memory updating processing using spatially filtered magnetoencephalography. We recorded magnetic responses during an auditory oddball task in 12 normal subjects. Synthetic aperture magnetometry (SAM)-permutation analysis was used to visualize the multiple brain regions associated with event-related magnetic fields (ERFs), and event-related oscillations during target detection processing. SAM-permutation results showed the topographical distribution of N1m over the bilateral primary auditory cortex. Post-stimulus delta (1.5-4 Hz) activity sources, likely related to the P300 slow-waveform, were distributed over the right frontocentral and parietal regions. Source locations of theta (4-8 Hz) and alpha (8-13 Hz) event-related synchronization (ERS) were identified over the dorsolateral and medial prefrontal cortex. We visualized bilateral central-Rolandic suppresions for mu (8-15 Hz), beta (15-30 Hz), and low-gamma (30-60 Hz) activities, more dominant in the hemisphere contralateral to the moving hand (button-pressing in response to target stimuli). Prefrontal theta and alpha ERS, and frontocentral-parietal delta ERS are functionally engaged in auditory attention and memory updating process. Spatially filtered MEG is valuable for detection and source localization of task-related changes in the ongoing oscillatory activity during oddball tasks.

238 CAFFEINE PREVENTS A LOSS OF CALCIUM OSCILLATORY RESPONSE ASSOCIATED WITH POSTOVULATORY AGING OF MOUSE OOCYTES

Numerous studies have demonstrated that postovulatory aging of oocytes prior to fertilization has detrimental effects on oocyte quality and developmental competence. Oocyte aging is accompanied by abnormal oocyte activation and subsequent development, suggesting a disruption of Ca2+ oscillations after fertilization. The inositol 1,4,5-trisphosphate receptor type 1 (IP3R1) in mammals is responsible for the majority of Ca2+ release during fertilization (Miyazaki S et al. 1993 Dev. Biol.). Previously, we reported that phosphorylation of IP3R1 at an MPM-2 epitope may play an important role in facilitating the induction of Ca2+ oscillations at the MII stage (Lee B et al. 2006 Development), indicating that IP3R1 phosphorylation may be a good indicator of the health of the oocyte. However, few studies have investigated the alteration of the Ca2+ signaling and IP3R1 function associated with oocyte aging. On the other hand, a previous report showed that caffeine increased MPF activity and suppressed fragmentation after parthenogenetic activation of aged oocytes (Kikuchi K et al. 2000 Biol. Reprod.). Therefore, the purpose of the present study was to examine whether and how Ca2+ oscillatory activity changes during oocyte aging and to test if caffeine prevents the negative effects of oocyte aging. MII mouse oocytes were collected 14 h after hCG injection and cultured in vitro for 8, 24 or 48 h with or without caffeine (5 or 10 mm). Oocyte quality was assessed by the occurrence of spontaneous fragmentation, monitoring of Ca2+ oscillations after exposure to 10 mm strontium chloride, Western blot analysis of IP3R1 phosphorylation and immunostaining of IP3R1. In oocytes in vitro aged for 8 h, the duration of the first Ca2+ rise was significantly decreased compared with fresh MII oocytes, although this reduction was not observed in MII oocytes treated with 5 mm caffeine. The phosphorylation of IP3R1 at the MPM-2 epitope was slightly decreased during oocyte aging in both caffeine and noncaffeine treatment. Importantly, whereas IP3R1 in MII oocytes treated for 8 h with 5 mm caffeine displayed the typical cortical cluster organization, IP3R1 in aged oocytes without caffeine became dispersed in the cytoplasm. In addition, caffeine significantly suppressed the spontaneous fragmentation that is normally observed by 48 h of in vitro culture. These results suggest that the Ca2+ oscillatory activity is compromised during oocyte aging and caffeine prevents the loss of integrity of Ca2+ signaling possibly by keeping the cortical distribution of IP3R1.

Changes in oscillatory activity of neurons in the medial septal area in animals with a model of chronic temporal epilepsy

Comparative studies of the activity of extracellularly recorded neurons in living slices of the medial septal area of healthy guinea pigs and animals with a model of chronic temporal epilepsy demonstrated differences between them in terms of the frequency and pattern of cell discharges. The brains of animals with experimental epilepsy showed a doubling of the total level of activity as compared with controls, due to increases in the discharge frequencies of irregular and regular non-volleying neurons. There was a sharp (three-fold) increase in the number of cells with rhythmic discharge volleys, along with changes in the parameters of volley activity - both in neurons with the endogenous (pacemaker) pattern and in cells with secondary involvement in rhythmic activity. The possible mechanisms for these changes are discussed. These data widen our understanding of the processes forming pathological synchronization in epilepsy and may assist in the creation of new approaches to the treatment of this disease.

Changes of oscillatory activity during visual oddball task (SEEG study)

Event Abstract Back to Event Changes of oscillatory activity during visual oddball task (SEEG study) Robert Roman1*, Milan Brázdil2, J. Chládek3, P. Jurák3, Ivan Rektor2 and M. Kukleta1 1 Department of Physiology, Medical Faculty, Masaryk University, Czechia 2 Department of Neurology, St. Anne Hospital, Masaryk University, Czechia 3 Institute of Scientific Instruments, Academy of Sciences, Czechia Objectives: To study intracerebral distribution and frequency spectrum of event-related desynchronization (ERD) and synchronization (ERS) recorded during discrimination task. Methods: EEG was recorded from 187 cerebral sites in 6 patients suffering from intractable epilepsy during visual oddball task. Patients were instructed to respond only to the target stimulus by pressing the microswitch button. The intertrial variance method of quantification of ERD and ERS was used separately for target and frequent stimuli in individually selected reactive frequency bands (in the theta, alfa, beta and gamma range). Results: ERD and ERS were observed both after target and frequent stimuli repeatedly in the amygdala, hippocampus, parahippocampal gyrus, cingulate gyrus, fusiform gyrus, rectus gyrus, orbitofrontal gyri, superior and middle temporal gyri, middle and inferior frontal gyri. ERD after target stimuli was found in 139 sites – 91 cases in alfa, 69 cases in theta, 86 cases in beta and 15 cases in gamma band. ERS was observed in 86 sites – 42 cases in alfa, 37 cases in theta, 42 cases in beta and 17 cases in gamma band. ERD after frequent stimuli was present in 53 sites – 21 cases in alfa, 9 cases in theta, 23 cases in beta and 5 cases in gamma band. ERS was found in 63 sites – 24 cases in alfa, 9 cases in theta, 39 cases in beta and 4 cases in gamma band. Conclusion: Widespread distribution of decreased and increased oscillatory activity in different frequency bands shows the complexity of neural networks involved in cognitive processing of visual stimuli. More frequent finding of ERD phenomena after target stimuli might probably reflect the enhanced information processing related to the executive functions. Conference: 10th International Conference on Cognitive Neuroscience, Bodrum, Turkey, 1 Sep - 5 Sep, 2008. Presentation Type: Poster Presentation Topic: Brain Electrical Oscillations in Cognition Citation: Roman R, Brázdil M, Chládek J, Jurák P, Rektor I and Kukleta M (2008). Changes of oscillatory activity during visual oddball task (SEEG study). Conference Abstract: 10th International Conference on Cognitive Neuroscience. doi: 10.3389/conf.neuro.09.2009.01.141 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: 05 Dec 2008; Published Online: 05 Dec 2008. * Correspondence: Robert Roman, Department of Physiology, Medical Faculty, Masaryk University, Brno, Czechia, roman@med.muni.cz 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 Roman Milan Brázdil J. Chládek P. Jurák Ivan Rektor M. Kukleta Google Robert Roman Milan Brázdil J. Chládek P. Jurák Ivan Rektor M. Kukleta Google Scholar Robert Roman Milan Brázdil J. Chládek P. Jurák Ivan Rektor M. Kukleta PubMed Robert Roman Milan Brázdil J. Chládek P. Jurák Ivan Rektor M. Kukleta 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.

Role of Synchronized Oscillatory Brain Activity for Human Pain Perception

The understanding of cortical pain processing in humans has significantly improved since the development of modern neuroimaging techniques. Non-invasive electrophysiological approaches such as electro- and magnetoencephalography have proven to be helpful tools for the real-time investigation of neuronal signals and synchronous communication between cortical areas. In particular, time-frequency decomposition of signals recorded with these techniques seems to be a promising approach because different pain-related oscillatory changes can be observed within different frequency bands, which are likely to be linked to specific sensory and motor functions. In this review we discuss the latest evidence on pain-induced time-frequency signals and propose that changes in oscillatory activity reflect an essential communication mechanism in the brain that is modulated during pain processing. The importance of synchronization processes for normal and pathological pain processing, such as chronic pain states, is discussed.

P3 and ERD/ERS in a Visual Oddball Paradigm

Abstract: Objective: The present study investigates intracerebrally the concurrent occurrence of event-related potentials (ERPs) and event-related desynchronization/synchronization phenomena (ERD/ERS) in subjects performing a visual oddball task. Methods: Evoked (P3) and induced ERD/ERS changes were studied in six subjects with drug-resistant epilepsy. Depth EEG activity from the mesiotemporal limbic structures (amygdala, hippocampus, and parahippocampal gyrus) was analyzed. We used an averaging of raw data to obtain ERPs, and an averaging of the amplitude/power envelope (complex demodulation) in five frequency bands: theta, α 1, α 2, beta, and gamma to obtain ERD/ERS. The P3 component of ERP and ERD/ERS in response to target and nontarget stimuli were evaluated. Results: Even though both P3 and ERD/ERS phenomena were observed in all of the investigated mesiotemporal regions, the most pronounced findings were revealed in the hippocampus. A P3 component of ERP was repeatedly observed in the hippocampus after target stimuli. Significant changes in the oscillatory hippocampal activity were found: ERD in the α 1 and α 2 frequency bands. Evident, near-significant changes were observed throughout the hippocampus in the theta band. No apparent ERD/ERS changes in the beta or in the gamma frequency band were seen in our intracerebral data. The distribution of the P3 and ERD/ERS maxima differed slightly in adjacent contacts, but occurred at the same time. Conclusions: The cognitive processing of visual information is simultaneously accompanied by several electrophysiological phenomena. In addition to ERPs, apparent changes in oscillatory activity were detected in the intracerebral recordings from mesiotemporal limbic structures. Timing of both neuronal processes seems to be simultaneous, but differing spatial distribution could reflect the involvement of different networks.

Movement‐related changes in oscillatory activity in the human subthalamic nucleus: ipsilateral vs. contralateral movements

A voluntary movement is accompanied by a series of changes in neuronal oscillatory activity in the subthalamic nucleus (STN). These changes can be recorded through electrodes implanted for deep brain stimulation to treat Parkinson's disease in the time interval between the surgery and the internalization of the connections to the batteries. Both baseline activity and movement-related changes are different in the 'on' and 'off' medication motor states. In the 'off' state a low frequency activity in the alpha-beta range (8-25 Hz) that dominates the spectrum is interrupted during the movement, while in the 'on' state baseline frequencies are higher and a peri-movement gamma increase (70-80 Hz) is usually observed. Similar changes have been described with electrocorticographic recordings over the primary motor cortex but the gamma increase was only present during contralateral movements. We compared ipsi- and contralateral movement-related changes in STN activity, using a time-frequency analysis of the recordings obtained simultaneously in both STN and the scalp (electroencephalography) during right and left hand movements. The movement-related changes observed in the STN in the 'on' and the 'off' states were similar to those described previously in terms of predominant frequency bands, but we found bilateral changes in the STN during movements of either hand. A contralateral earlier start of the beta STN changes was mostly observed when the moving hand corresponded to the less-affected side, irrespective of hand dominance. These results suggest that movement-related activity in the STN has, by and large, a bilateral representation and probably reflects cortical input.

Attentional shifts towards an expected visual target alter the level of alpha-band oscillatory activity in the human calcarine cortex

Neuronal operations associated with the top–down control process of shifting attention from one locus to another involve a network of cortical regions, and their influence is deemed fundamental to visual perception. However, the extent and nature of these operations within primary visual areas are unknown. In this paper, we used magnetoencephalography (MEG) in combination with magnetic resonance imaging (MRI) to determine whether, prior to the onset of a visual stimulus, neuronal activity within early visual cortex is affected by covert attentional shifts. Time/frequency analyses were used to identify the nature of this activity. Our results show that shifting attention towards an expected visual target results in a late-onset (600 ms postcue onset) depression of alpha activity which persists until the appearance of the target. Independent component analysis (ICA) and dipolar source modeling confirmed that the neuronal changes we observed originated from within the calcarine cortex. Our results further show that the amplitude changes in alpha activity were induced not evoked (i.e., not phase-locked to the cued attentional task). We argue that the decrease in alpha prior to the onset of the target may serve to prime the early visual cortex for incoming sensory information. We conclude that attentional shifts affect activity within the human calcarine cortex by altering the amplitude of spontaneous alpha rhythms and that subsequent modulation of visual input with attentional engagement follows as a consequence of these localized changes in oscillatory activity.

Emotionally Arousing Visual Stimuli Modulate Oscillatory alpha Activity Recorded from STN Area in PD Patients

High frequency stimulation (HFS) of the subthalamic nucleus (STN) has become a widely accepted therapy to treat motor symptoms in PD patients. In some patients however, stimulation may be accompanied by behavioral and cognitive side effects drawing attention to a possible influence of HFS on associative and limbic circuits within the STN area. To further elucidate the involvement of the human STN region in the processing of emotional information we investigated changes in oscillatory activity within the STN area in response to emotionally arousing visual stimuli. Local field potentials (LFP) were recorded through deep brain macroelectrodes (Medtronic, model 3389) from the STN area in 10 PD patients (6 men, 4 women; age 53.2±3.8 years; 19 sides) during a 1 second presentation of emotionally arousing stimuli (selected from the International Affective Picture System). Data were digitally pass-band filtered in the alpha (8–12Hz) range, squared and responses averaged across pleasant, unpleasant and neutral stimuli. Changes in alpha activity were defined as the percentage decrease (event-related desynchronization-ERD) or increase in band power during the test interval (0.5s to 3s post-stimulus) in comparison to the baseline period (2s before stimulus presentation) for each emotional category. A significant decrease in alpha power was found for all stimulus categories starting at about 0.5s after stimulus presentation. During the post-stimulus time period from 1–2s the ERD was significantly larger in trials of pleasant (mean ERD 21.6%±2.8; p<0.001) and unpleasant (mean ERD 15.0%±4.2; p=0.002) stimuli compared to neutral (mean ERD 4.4%±4.2). The modulation of late alpha activity recorded from the STN area in PD may reflect processing of emotional arousal as it followed both pleasant and unpleasant stimuli. These findings suggest that „limbic“ processing occurs in the region of STN and may offer an explanation for why STN-HFS may be complicated by affective disorders in PD patients.

EEG correlates of wrist kinematics as revealed by averaging techniques and Morlet wavelet transforms.

The question regarding the invariant movement properties the central nervous system may organize to accomplish different motor task demands as reflected in EEG remains unsolved. Surprisingly, no systematic electrocortical research in humans has related movement preparation with different movement distance, although this area has been widely investigated in the field of motor control. This study examined whether the amplitude of discrete wrist movements influences the various EEG components both in time and frequency domains. Time-domain averaging techniques and Morlet wavelet transforms of EEG single trials were applied in order to extract three components [BP(0), N1, and LPS] of movement related potentials (MRP) and to quantify changes in oscillatory activity of the movement-induced EEG waveforms accompanying 20, 40, and 60 unilateral wrist flexion movements. The experimental manipulations induced systematic changes in BP(0) and N1 amplitude along the midline (Fz, Cz, and Pz) with 20 movement showing the most negativity and 60 the least. The dominant energy within a 30-50 frequency cluster from bilateral precentral (C3, Cz, C4), frontal (F3, Fz, F4), and parietal (P3, Pz, P4) areas with maximum at vertex (Cz) also appeared to be sensitive to movement amplitude with the least power observed during 60 wrist flexion. This suggests that movement amplitude may be a controllable variable that is highly related with task-specific cortical activation primarily at frontocentral areas as reflected in EEG.