Biomedical subjects

W Szurhaj

Publications and source records attributed to W Szurhaj.

10 recordsLinked to original sources

PubMed2006

Predominance of the contralateral movement-related activity in the subthalamo-cortical loop.

OBJECTIVE: Abnormal low- and high-frequency oscillatory activities have been linked to abnormal movement control in Parkinson's disease. We aimed to study how low- and high-frequency oscillatory activities are modulated by movement in the contralateral and ipsilateral subcorticocortical loops. METHODS: We studied mu, beta and gamma rhythm event-related desynchronisation (ERD) and synchronisation (ERS) recorded from electrode contacts in the subthalamic nucleus (STN) areas and over the primary sensorimotor (PSM) cortex. RESULTS: Mu and beta ERD/ERS patterns were very similar when comparing PSM cortex and STN areas and very different when comparing contralateral and ipsilateral structures. Beta rhythm ERS was more predominant over contralateral structures than over ipsilateral ones. Gamma rhythm ERS was only recorded from the contralateral STN area (particularly following administration of L-Dopa). For all patients, the best bipolar derivations - as defined by the earliest mu and beta ERD and the strongest beta and gamma ERS - always included the STN electrode contacts that produced the best clinical results. CONCLUSIONS: Movement-related activity is involved in the movement preparation in the contralateral subthalamo-cortical loop and in the movement execution in the bilateral subthalamo-cortical loops. SIGNIFICANCE: Contralateral beta rhythm ERD seemed to be related to bradykinesia of the limb performing the movement.

Cerebral Cortex↗

PubMed2006

Oscillatory cortical activity related to voluntary muscle relaxation: influence of normal aging.

OBJECTIVE: In this study we aimed to investigate if there are age-related differences in cortical oscillatory activity induced by self-paced muscular pure relaxation in comparison with muscle contraction as reference movement. METHODS: Event-related (de)synchronization (ERD/ERS) have been recorded related to voluntary muscle contraction and relaxation in 10 young and 10 elderly right-handed healthy subjects. The muscle relaxation task consisted in a voluntary relaxation of maintained wrist extension without any overt, associated muscle contraction. The muscle contraction task corresponded to a self-initiated brief wrist extension. RESULTS: In elderly subjects compared to young ones, mu and beta ERD preceding muscular relaxation was more widespread, beginning significantly earlier over contralateral frontocentral and parietocentral regions (p<0.05) as well as over ipsilateral regions (p<0.05). The beta synchronization was significantly attenuated (p<0.05). CONCLUSIONS: These results suggest an alteration of inhibitory motor systems and an altered post-movement somesthetic inputs processing with normal aging. These alterations were accompanied by compensatory mechanisms. SIGNIFICANCE: These age-related alterations during different phases of muscle relaxation could participate to explain global sensorimotor slowing observed with normal aging.

Adult↗

PubMed2004

Influence of aging on cortical activity associated with a visuo-motor task.

The aim of this study was to determine how cerebral aging influences the pattern of cortical oscillatory activity when a targeting movement with visual control is planned. Changes in cortical oscillatory activity were assessed by recording the event-related (de)synchronization (ERD/S) of micro and beta rhythms. Young and elderly subjects performed a distal movement, a proximal movement and a visuo-guided targeting movement. Our results demonstrated an increase in micro ERD over ipsilateral regions and showed the spatial extent of micro ERD over parietocentral and parietal regions during motor planning in elderly subjects compared to young ones. After the movement, the beta ERS was significantly modified (a decrease in slope and amplitude) in elderly subjects. The most pronounced age-related changes in ERD/S pattern were observed for the targeting movement. Our results suggest that motor planning is less efficient in elderly subjects. This deficit might result from impaired parietal integrative function and/or changes in inputs from subcortical structures. Subsequently, the changes observed in the post-movement phase might reflect a decrease in (reafferent) sensory inputs and hence impaired their input processing.

Adult↗

PubMed2004

[The role of the EEG in epilepsy management].

Diagnosis of epilepsy is based upon clinical data. But the electroencephalogram (EEG) remains absolutely necessary for proper management of epileptic patients by the neurologist both in consultation and in hospital practice. Nevertheless, it is very important to keep in mind the actions limit of EEG, especially its sensitivity and specificity. In this paper, we will emphasize the value of EEG in epilepsy, its interest for the management of patients in consultation, the situations when the neurologist can use EEG-monitoring, and what it can bring to the emergency management of epileptic patients in hospital. We will thus see that, in each of these situations, EEG must be interpreted with full knowledge of clinical data.

Electroencephalography↗

PubMed2004

[Management of patients after a first seizure].

Neuroimaging evaluation in patients after a first seizure could be easily determined on the basis of seizure history, neurological examination, blood sample analysis and electroencephalography. The main objectives of the initial work-up are to differentiate a true seizure event from seizure-like symptoms, to exclude a single seizure as a manifestation of non organic cause and finally to consider the seizure as a result of cerebral lesion or inaugurate epilepsy. When a new onset seizure is diagnosed, urgent neuroimaging is recommended only in patients with focal neurological deficit, persistent or worsening alteration in the level of consciousness and when clinical and biological data lead to a suspected vascular or infectious etiology. Brain CT scan is usually more available in emergency to identify the cause of seizure. It may have an important role for the therapeutic strategy and may defer MRI investigation. Nevertheless, brain MRI must be performed in emergency when CT scan is not conclusive despite a severe clinical condition or in case of cerebral venous thrombosis. Imaging modalities depend on clinical data, patient age and suspected epilepsy type.

Brain Diseases↗

PubMed2003

Changes in oscillatory cortical activity related to a visuomotor task in young and elderly healthy subjects.

OBJECTIVE: In order to better understand the spatio-temporal interaction of the activated cortical areas when the movement is visuo-guided and to assess the age effect on the spatio-temporal pattern of cortical activity, we have compared a proximo-distal movement with visual-motor control and hand-eye coordination (targeting movement) with a distal and a proximal movement. METHODS: Brain's electrical activity was studied using the analysis of event-related (de)synchronizations (ERD/S) of cortical mu and beta rhythms in 17 subjects, 8 young and 9 elderly subjects. RESULTS: In both populations, we found an earlier and broader mu and beta ERD during the preparation of the targeting movement compared to distal and proximal movements, principally involving the contralateral parietal region. During the execution, a spreading over the parietocentral region during proximal movement and over the parietal region during targeting movement was observed. After the execution of proximal and targeting movements, a wider and higher beta ERS was observed only in the young subjects. In the elderly subjects, our results showed a significant decrease of beta ERS during the targeting task. CONCLUSIONS: These results suggest there was a larger recruitment of cortical areas, involving notably the parietal cortex when the movement is visuo-guided. Moreover, cerebral aging-related changes in the spatio-temporal beta ERS pattern suggests an impaired sensory integration.

Adult↗

PubMed2003

[Clinical and electrophysiological features of "cortical tremor"].

The purpose of this paper is to draw attention to one particular variant of tremor named "cortical tremor," which corresponds to rhythmic cortical myoclonus whose principal differential diagnosis is essential tremor. Diagnosis may be established with electrophysiological explorations (electromyography, accelerometry, electroencelography with back averaging, long latency reflexes, giant somesthesic evoked potentials). Clinical and electrophysiological features of 15 patients are reported and compared to cases previously published. Association with generalized or partial seizures is possible. Other cases in the family are often mentioned with a dominant autosomal transmission. The therapeutic approach is based on the use of antiepileptic drugs.

Adolescent↗

PubMed2001

Does post-movement beta synchronization reflect an idling motor cortex?

After the completion of a voluntary movement, a synchronization of cortical beta rhythms is recorded over the contralateral central region, which is assumed to reflect the termination of the motor command. In order to test this hypothesis, we compared in eight healthy subjects the synchronization of EEG beta rhythms following active and passive index extension. The passive movement was also performed after deafferentation by ischaemic nerve block in three subjects. Beta synchronization was present in all subjects after both active and passive movements, and disappeared under ischaemia in all three subjects. Post-movement beta synchronization can not solely be explained by an idling motor cortex. It may also, at least in part, reflect a movement-related somatosensory processing.

Adult↗

PubMed2001

Event-related variations in the activity of EEG-rhythms. Application to the physiology and the pathology of movements.

The averaging of the ongoing activity of the electroencephalogram (EEG) allows extracting the potentials that are time-locked and phase-locked to an event. These potentials are described as evoked potentials. There is another type of change in the ongoing EEG, which is time-locked but not phase-locked to an event: the EEG rhythm reactivity, also called "Event-Related Desynchronization and Synchronization" (ERD/ERS) by Pfurtscheller. These changes are often visible to the naked eye but they cannot be extracted by the averaging technique. Their quantification requires another method, which was suggested by Pfurtscheller and Aranibar in 1977. This method consists in measuring the temporal evolution of the power of EEG signal within a given frequency band before, during, and after an event. ERD corresponds to the decrease in power of an EEG rhythm related to an event. Conversely, ERS corresponds to an increase in amplitude of an EEG rhythm related to the event. ERD represents the activation of the subjacent cortical areas. ERS would partly traduce the setting at rest of the cortex; it would also be related to the somesthetics afferents inputs. This method can be applied to the study of cortical activation in many situations: memory tasks, auditory processing, attention, anticipatory behavior, and voluntary movement. Thus, a voluntary self-paced movement of the dominant hand is preceded by an ERD of mu and beta rhythms occurring respectively 2 000 and 1 500 ms before the movement onset. This ERD is recorded over the contralateral central region. It becomes bilateral at the movement onset and reaches its maximum at the movement offset. It is then followed by an ERS of the beta rhythms. We show that ERD/ERS phenomena vary with the type of movement, and that their study allows exploring the modifications of cortical excitability that are observed in Parkinson's disease and in epilepsy with focal motor seizures.

Journal Article↗

PubMed2000

Brief and sustained movements: differences in event-related (de)synchronization (ERD/ERS) patterns.

OBJECTIVE: (1) To determine if there are changes in event-related desynchronization/event-related synchronization (ERD/ERS) patterns when the movement is sustained? (2) To determine, from a technical point of view for ERD calculation, if it is possible to take the reference period during muscular activation? METHODS: Eight healthy subjects performed two series of brief and sustained self-paced extensions with their dominant wrist. The end of the sustained movement was externally triggered by the examinator. ERD/ERS was calculated in mu and beta bands from 13 source derivations covering motor areas, computed from 29 scalp electrodes. Movement onset and offset were determined by electromyographic activity (EMG) of wrist extensors. RESULTS: When the movement was sustained, power in the mu and beta bands returned to baseline values within 4-5 s. Movement duration had little effect, if at all, on both pre and post-movement periods. Compared to brief movement, after the onset of the prolonged movement, mu ERD just returned to baseline, without synchronization. In contrast, beta ERS was still present though earlier and much lower. CONCLUSIONS: The reference period for ERD calculation may be taken during muscular activation if its duration is long enough. Beta synchronization may occur despite a non-deactivated motor cortex, suggesting a contribution from afferent somesthetic inputs.

Cortical Synchronization↗