EEG theta dynamics within frontal and parietal cortices for error processing during reaching movements in a prism adaptation study altering visuo-motor predictive planning

Modulation of frontal midline theta (fmθ) is observed during error commission, but little is known about the role of theta oscillations in correcting motor behaviours. We investigate EEG activity of healthy partipants executing a reaching task under variable degrees of prism-induced visuo-motor distortion and visual occlusion of the initial arm trajectory. This task introduces directional errors of different magnitudes. The discrepancy between predicted and actual movement directions (i.e. the error), at the time when visual feedback (hand appearance) became available, elicits a signal that triggers on-line movement correction. Analysis were performed on 25 EEG channels. For each participant, the median value of the angular error of all reaching trials was used to partition the EEG epochs into high- and low-error conditions. We computed event-related spectral perturbations (ERSP) timelocked either to visual feedback or to the onset of movement correction. ERSP time-locked to the onset of visual feedback showed that fmθ increased in the high-but not in the lowerror condition with an approximate time lag of 200 ms. Moreover, when single epochs were sorted by the degree of motor error, fmθ started to increase when a certain level of error was exceeded and, then, scaled with error magnitude. When ERSP were time-locked to the onset of movement correction, the fmθ increase anticipated this event with an approximate time lead of 50 ms. During successive trials, an error reduction was observed which was associated with indices of adaptations (i.e., aftereffects) suggesting the need to explore if theta oscillations may facilitate learning. To our knowledge this is the first study where the EEG signal recorded during reaching movements was time-locked to the onset of the error visual feedback. This allowed us to conclude that theta oscillations putatively generated by anterior cingulate cortex activation are implicated in error processing in semi-naturalistic motor behaviours. © 2016 Arrighi et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Spectral parameters modulation and source localization of blink-related alpha and low-beta oscillations differentiate minimally conscious state from vegetative state/unresponsive wakefulness syndrome

Recently, the cortical source of blink-related delta oscillations (delta BROs) in resting healthy subjects has been localized in the posterior cingulate cortex/precuneus (PCC/PCu), one of the main core-hubs of the default-mode network. This has been interpreted as the electrophysiological signature of the automatic monitoring of the surrounding environment while subjects are immersed in self-reflecting mental activities. Although delta BROs were directly correlated to the degree of consciousness impairment in patients with disorders of consciousness, they failed to differentiate vegetative state/unresponsive wakefulness syndrome (VS/UWS) from minimally conscious state (MCS). In the present study, we have extended the analysis of BROs to frequency bands other than delta in the attempt to find a biological marker that could support the differential diagnosis between VS/UWS and MCS. Four patients with VS/UWS, 5 patients with MCS, and 12 healthy matched controls (CTRL) underwent standard 19-channels EEG recordings during resting conditions. Three-second-lasting EEG epochs centred on each blink instance were submitted to time-frequency analyses in order to extract the normalized Blink-Related Synchronization/Desynchronization (nBRS/BRD) of three bands of interest (low-alpha, high-alpha and low-beta) in the time-window of 50-550 ms after the blink-peak and to estimate the corresponding cortical sources of electrical activity. VS/UWS nBRS/BRD levels of all three bands were lower than those related to both CTRL and MCS, thus enabling the differential diagnosis between MCS and VS/UWS. Furthermore, MCS showed an intermediate signal intensity on PCC/PCu between CTRL and VS/UWS and a higher signal intensity on the left temporo-parieto-occipital junction and inferior occipito-temporal regions when compared to VS/UWS. This peculiar pattern of activation leads us to hypothesize that resting MCS patients have a bottom-up driven activation of the task positive network and thus are tendentially prone to respond to environmental stimuli, even though in an almost unintentional way

Pointing in cervical dystonia patients

IntroductionThe normal hemispheric balance can be altered by the asymmetric sensorimotor signal elicited by Cervical Dystonia (CD), leading to motor and cognitive deficits.MethodsDirectional errors, peak velocities, movement and reaction times of pointing towards out-of-reach targets in the horizontal plane were analysed in 18 CD patients and in 11 aged-matched healthy controls.ResultsCD patients displayed a larger scatter of individual trials around the average pointing direction (variable error) than normal subjects, whatever the arm used, and the target pointed. When pointing in the left hemispace, all subjects showed a left deviation (constant error) with respect to the target position, which was significantly larger in CD patients than controls, whatever the direction of the abnormal neck torsion could be. Reaction times were larger and peak velocities lower in CD patients than controls.DiscussionDeficits in the pointing precision of CD patients may arise from a disruption of motor commands related to the sensorimotor imbalance, from a subtle increase in shoulder rigidity or from a reduced agonists activation. Their larger left bias in pointing to left targets could be due to an increased right parietal dominance, independently upon the direction of head roll/jaw rotation which expands the left space representation and/or increases left spatial attention. These deficits may potentially extend to tracking and gazing objects in the left hemispace, leading to reduced skills in spatial-dependent motor and cognitive performance

Presupposti neurotrasmettitoriali del trattamento farmacologico dei disordini di coscienza

Vari report documentano il miglioramento dell'arousal, della responsività e delle performance cognitive in soggetti con disordini di coscienza dopo somministrazione di farmaci agenti sull'asse amino-acidico (glutammato/GABA) e monoaminico (dopamina, noradranalina e serotonina). Ciò avvalora l'ipotesi che deficit neurotrasmettitoriali abbiamo un ruolo fondamentale nel determinare disordini di vigilanza-coscienza. È noto infatti che la noradrenalina induce vigilanza e influenza i processi di attenzione, memoria, percezione del dolore, mentre la serotonina (5-HT) svolge una funzione importante nella regolazione dell’umore e del comportamento emozionale, oltre ad influenzare l'appetito ed il ritmo sonno-veglia. La dopamina ed in particolare il sistema mesocorticolimbicocorticale è connessa con il meccanismo del piacere e del rinforzo. Il sistema colinergico, insieme ai sistemi noradrenergico e serotoninergico, è coinvolto nel regolare l’eccitabilità generale dell’encefalo, e nella regolazione ciclo sonno-veglia. Ha un ruolo importante nell’apprendimento e la memoria

Do any blink-related EEG changes represent activation of consciousness mechanism?

Ruolo dell'ammiccamento spontaneo nel mantenimento del flusso di coscienz

Frontal Midline theta is related to error during reaching movements

Si studia l'attività EEg in banda teta durante movimenti di reachin

Data from: EEG theta dynamics within frontal and parietal cortices for error processing during reaching movements in a prism adaptation study altering visuo-motor predictive planning

Modulation of frontal midline theta (fmθ) is observed during error commission, but little is known about the role of theta oscillations in correcting motor behaviours. We investigate EEG activity of healthy partipants executing a reaching task under variable degrees of prism-induced visuo-motor distortion and visual occlusion of the initial arm trajectory. This task introduces directional errors of different magnitudes. The discrepancy between predicted and actual movement directions (i.e. the error), at the time when visual feedback (hand appearance) became available, elicits a signal that triggers on-line movement correction. Analysis were performed on 25 EEG channels. For each participant, the median value of the angular error of all reaching trials was used to partition the EEG epochs into high- and low-error conditions. We computed event-related spectral perturbations (ERSP) time-locked either to visual feedback or to the onset of movement correction. ERSP time-locked to the onset of visual feedback showed that fmθ increased in the high- but not in the low-error condition with an approximate time lag of 200 ms. Moreover, when single epochs were sorted by the degree of motor error, fmθ started to increase when a certain level of error was exceeded and, then, scaled with error magnitude. When ERSP were time-locked to the onset of movement correction, the fmθ increase anticipated this event with an approximate time lead of 50 ms. During successive trials, an error reduction was observed which was associated with indices of adaptations (i.e., aftereffects) suggesting the need to explore if theta oscillations may facilitate learning. To our knowledge this is the first study where the EEG signal recorded during reaching movements was time-locked to the onset of the error visual feedback. This allowed us to conclude that theta oscillations putatively generated by anterior cingulate cortex activation are implicated in error processing in semi-naturalistic motor behaviours

Alterazione del tempo di reazione motorio in pazienti affetti da sclerosi multipla con cinematica dell'arto superiore normale: disordine dell'attenzione o della pianificazione motoria?

Introduzione. A differenza del cammino, il movimento dell’arto superiore è stato relativamente poco indagato in pazienti con Sclerosi Multipla (SM). A questo scopo abbiamo analizzato alcuni parametri cinematici di pazienti con SM durante l’esecuzione di movimenti di puntamento effettuati con entrambi gli arti superiori, e abbiamo confrontato il Tempo di Reazione Motoria (TRM) con i tempi di esecuzione del Test di Stroop (TS) e del Trail Making Test (TMT). Materiali e metodi. Sono stati reclutati 35 pazienti (18 maschi, età media 46±9 anni) con diagnosi di SM, durata media di malattia 11,8±6,5 anni). I movimenti di entrambi gli arti sono stati monitorati utilizzando un sistema optoelettronico (ELITE, BTS, Milano) in grado di localizzare nello spazio markers posizionati su ciascun processo acromiale, gomito, polso e indice. Ciascun paziente eseguiva almeno 7 movimenti di puntamento verso ciascuno dei tre target (LEDs, diametro 5 mm) posizionati a 0°, 20° a sinistra e 20° a destra rispetto alla linea mediana, secondo una sequenza pseudo-randomizzata. Il segnale di GO consisteva nell’accensione di uno dei tre LED. Abbiamo calcolato i seguenti parametri cinematici: TRM, Durata del Movimento (DM), Picco di Velocità Tangenziale (PtgVel), e li abbiamo confrontati con quelli ottenuti da un campione uniforme per sesso e per età composto da 14 volontari sani. Ai pazienti sono poi stati proposti il TS ed il TMT. Risultati. Mentre PtgVel e DM risultavano nella norma nella maggior parte dei pazienti (25 per l’arto dx, 21 per il sn), TRM risultava superiore a quello del gruppo di controllo in 28 pazienti per l’arto dx e 31 per l’arto sn, fra i quali 20 per l’arto dx e 18 per l’arto sn presentavano una cinematica nella norma. È emersa una correlazione inversa statisticamente significativa fra PtgVel e DM per entrambi gli arti (dx:r=0,789p=0,0000000300; sn:r= 0,784 p=0,0000000680); e fra PtgVel e TRM medio (r=0,37 p=0,198). Il TS è risultato patologico in 10 pazienti su 35, mentre la performance del TMT è risultata essere nella norma in tutti i pazienti. Nessuna correlazione statisticamente significativa è emersa tra TRM ed i tempi di esecuzione di ciascuna prova del TS. Conclusioni. I presenti dati suggeriscono due conclusioni, a nostra conoscenza non ancora evidenziate in letteratura: 1. Il TRM risulta patologico nella quasi totalità dei pazienti, anche a fronte di una cinematica dell’arto superiore conservata. 2. Il TRM tuttavia non correla con i tempi di esecuzione del TS suggerendo una specifica alterazione della pianificazione del movimento indipendennte da processi attenzionali

A case of post-traumatic minimally conscious state reversed by midazolam: Clinical aspects and neurophysiological correlates

We describe the case of a subject in a post-traumatic Minimally Conscious State (MCS) who retrieved full interaction with the environment after midazolam infusion. We studied EEG correlates of the "awakening reaction" in the different domains of frequency, time and cortical topography, along with the intrinsic connectivity within both the task-positive and the linguistic network

Cortical source of blink-related delta oscillations and their correlation with levels of consciousness

Recently, blink-related delta oscillations (delta BROs) have been observed in healthy subjects during spontaneous blinking at rest. Delta BROs have been linked with continuous gathering of information from the surrounding environment, which is classically attributed to the precuneus. Furthermore, fMRI studies have shown that precuneal activity is reduced or missing when consciousness is low or absent. We therefore hypothesized that the source of delta BROs in healthy subjects could be located in the precuneus and that delta BROs could be absent or reduced in patients with disorders of consciousness (DOC). To test these hypotheses, electroencephalographic (EEG) activity at rest was recorded in 12 healthy controls and nine patients with DOC (four vegetative states, and five minimally conscious states). Three-second-lasting EEG epochs centred on each blink instance were analyzed in both time- (BROs) and frequency domains (event-related spectral perturbation or ERSP and intertrial coherence or ITC). Cortical sources of the maximum blink-related delta power, corresponding to the positive peak of the delta BROs, were estimated by standardized Low Resolution Electromagnetic Tomography. In control subjects, as expected, the source of delta BROs was located in the precuneus, whereas in DOC patients, delta BROs were not recognizable and no precuneal localization was possible. Furthermore, we observed a direct relationship between spectral indexes and levels of cognitive functioning in all subjects participating in the study. This reinforces the hypothesis that delta BROs reflect neural processes linked with awareness of the self and of the environment