Biomedical subjects

J L Bourriez

Publications and source records attributed to J L Bourriez.

At least 19 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↗

PubMed2006

Gait abnormalities induced by acquired bilateral pallidal lesions: a motion analysis study.

BACKGROUND: Bilateral pallidal lesions induce a range of cognitive and motor disorders, principally a parkinsonian syndrome in which severe disturbances of gait and gait initiation are frequently reported. However, the precise clinical features of these disorders (and the role of the pallidum therein) remain to be established. OBJECTIVES: The goal of this study was to characterise gait and gait initiation disorders within the context of a parkinsonian syndrome in patients with acquired, bilateral, pallidal lesions (PAL patients), to compare these disorders to those seen in Parkinson's disease (PD), and to assess the corresponding physiopathological implications. PATIENTS AND METHODS: By using a video motion analysis system (VICON), we studied gait kinematic parameters in two patients presenting with bilateral, pallidal lesions. Kinematic and kinetic parameters were also determined during gait initiation. The two patients were compared with a group of 17 PD patients and to 20 healthy controls. RESULTS: In both PAL and PD patients, kinematic parameters (gait and gait initiation) and kinetic parameters (gait initiation) were similarly impaired, evidenced by akinesia (difficulty in initiating gait characterized by impairment of anticipatory postural adjustments). Hypokinesia and bradykinesia (respectively reduced stride length and reduced speed during gait) were also noted. CONCLUSION: The gait and gait initiation disorders seen in cases of bilateral pallidal lesions (namely akinesia, hypokinesia and bradykinesia) are similar to those observed in PD. Subject to confirmation in more extensive studies, we hypothesize that bipallidal patients may present higher level gait disorders,with potential mediation by cognitive impairment.

Aged↗

PubMed2006

Relationship between event-related beta synchronization and afferent inputs: analysis of finger movement and peripheral nerve stimulations.

OBJECTIVE: We compared beta synchronization associated with voluntary finger movement with beta synchronization produced by sensory stimulation, in order to better understand the relationship between event-related beta synchronization (ERS) and the different afferent inputs. METHODS: Twenty-four subjects performed an index finger extension. They also received three types of electrical stimulation (cutaneous stimulation of the index finger, single and repetitive stimulation of the median nerve). An EEG was recorded using 38 scalp electrodes. Beta ERS was analyzed with respect to movement offset and the stimulus (or the last stimulus in the series, for repetitive stimulation). RESULTS: Median nerve stimulation and finger extension induced more intense beta ERS than cutaneous stimulation. The magnitude of beta ERS induced by movement or by single median nerve stimulation were not different but post movement beta synchronization duration was longer than beta ERS induced by single median nerve stimulation and cutaneous stimulation. CONCLUSIONS: This study demonstrates that beta ERS depends on the type and quantity of the afferent input. SIGNIFICANCE: This work reinforces the hypothesis of a relationship between beta ERS and processing of afferent inputs.

Adult↗

PubMed2005

[Pathophysiological mechanisms implicated by high-frequency stimulation in Parkinson's disease: the restoration of high and low frequency oscillatory systems].

INTRODUCTION: Increased neuronal activity in the internal pallidum (GPi) and the subthalamic nucleus (STN) has been clearly demonstrated in Parkinsonian models, and the two structures have thus been selected as therapeutic targets for functional neurosurgery. High-frequency electrical stimulation of the GPi or the STN improves the parkinsonian symptoms but also dyskinesias directly by GPi stimulation or indirectly by reduction of L-Dopa associated with STN stimulation. According to Alexander's model of the organisation of the basal ganglia, electrical stimulation of GPi or STN should have led to uncontrolled hyperkinesia. This apparent paradox could be explained on one hand by the involvement of different anatomo-functional areas within these structures and on the other by spatial and temporal changes in neuronal discharge patterns in the basal ganglia which in turn produce variations in synchronisation. RESULTS: Event-related (de)synchronisation (ERD) has enabled us to study variations in subcortico-cortical oscillatory activity: it has been shown that high-frequency electrical stimulation of the GPi/STN increases desynchronisation of low frequency rhythms (mu and beta,<30 Hz) during movement preparation and execution and augments post-movement synchronisation. Stimulation also decreases the abnormal frontocentral spreading of desynchronisation during movement preparation. CONCLUSIONS: In accordance with previous coherence analyses, electrical stimulation of STN is likely to restore the activity of high-frequency and low-frequency systems, as evidenced by a decrease in the hypersynchronisation of low-frequency rhythms at rest and restoral of a high-frequency rhythm during movement. Stimulation may improve spatial selectivity by activating the selected programs in conjunction with the primary sensorimotor cortex, whilst inhibiting competitive programs represented by abnormal spreading outside the primary sensorimotor cortex.

Basal Ganglia↗

PubMed2004

Statistical tools for clinical gait analysis.

Gait analysis studies involve continuous curves of data measured over a gait cycle. Curve analysis and interpretation require adequate statistical methods. Three principal problems may be encountered in clinical practice: (i) the reliability of gait curves for a given patient, (ii) classifying a new subject as belonging to a given population or not and (iii) comparison of two populations (independent or paired). This paper presents three statistical tools for solving these problems: (i) intra-class correlation coefficients, (ii) confidence bands for a population (iii) a combination of analysis of variance and confidence bands for the difference between the means and shows how they can be used in clinical practice.

Adult↗

PubMed2003

Subthalamic nucleus stimulation modulates motor cortex oscillatory activity in Parkinson's disease.

In Parkinson's disease, impaired motor preparation has been related to an increased latency in the appearance of movement-related desynchronization (MRD) throughout the contralateral primary sensorimotor (PSM) cortex. Internal globus pallidus (GPi) stimulation improved movement desynchronization over the PSM cortex during movement execution but failed to improve impaired motor preparation. PET studies indicate that subthalamic nucleus (STN) stimulation partly reverses the abnormal premotor pattern of brain activation during movement. By monitoring MRD, we aimed to assess changes in premotor and PSM cortex oscillatory activity induced by bilateral STN stimulation and to compare these changes with those induced by l-dopa. Ten Parkinson's disease patients and a group of healthy, age-matched controls performed self-paced wrist flexions in each of four conditions: without either stimulation or l-dopa (the 'off' condition), with stimulation and without l-dopa (On Stim), with l-dopa and without stimulation ('on drug'), and with both stimulation and l-dopa (On Both). Compared with the Off condition, in both the On Stim and the On Drug condition the Unified Parkinson's Disease Rating Scale (UPDRS) III score decreased by about 60% and in the On Both condition it decreased by 80%. The desynchronization latency over central regions contralateral to movement and the movement desynchronization over bilateral central regions were significantly increased by stimulation and by l-dopa, with a maximal effect when the two were associated. Furthermore, desynchronization latency significantly decreased over bilateral frontocentral regions in the three treatment conditions compared with the Off condition. In Parkinson's disease, STN stimulation may induce a change in abnormal cortical oscillatory activity patterns (similar to that produced by l-dopa) by decreasing the abnormal spreading of desynchronization over frontocentral regions and increasing PSM cortex activity during movement preparation and execution, with a correlated improvement in bradykinesia. Parkinsonians under treatment displayed a desynchronization pattern close to that seen in healthy, age-matched controls, although central latencies remained shorter. The study indicates that it is possible to influence cortical reactivity related to the planning and execution of voluntary movement through the basal ganglia, and furthermore that the oscillatory activity of the PSM cortex (in addition to that of premotor areas) could be of major importance in the control of movement-associated, neural activity in Parkinson's disease.

Aged↗

PubMed2003

Effect of L-Dopa on the pattern of movement-related (de)synchronisation in advanced Parkinson's disease.

In the early stages of Parkinson's disease (PD), impaired motor preparation has been related to a delay of mu rhythm movement-related desynchronisation, suggesting hypoactivation of the contralateral, primary sensorimotor (PSM) cortex. Following movement, a decrease in the amplitude of beta rhythm movement-related synchronisation was observed over the same region. This decrease--not seen in control subjects--was thus thought to be related to an impairment in cortical deactivation. By monitoring movement-related (de)synchronisation, we aimed (i) to extend to advanced PD the observations made in less-advanced situations and (ii) to test the effect of acute L-Dopa on these abnormalities. The United Parkinson's Disease Rating Scale (UPDRS) III score decreased by about 60% following acute L-Dopa administration, and we observed the following concurrent changes: a marked increase in mu desynchronisation pre-movement latency (thus reduced delay) during movement preparation over contralateral, central regions; an increase in mu desynchronisation during movement execution over bilateral central regions; a decrease in mu desynchronisation latency over bilateral frontocentral regions, and a significant increase in beta synchronisation over contralateral, central regions after movement. Changes of mu and beta rhythm parameters seemed to be inversely correlated with bradykinesia. Mu rhythm desynchronisation latency and beta synchronisation amplitude further decreased in advanced PD compared to earlier stages of the disease, suggesting greater impairment of cortical activation/deactivation as the disease progresses. L-Dopa partially restored the abnormal mu and beta rhythm cortical (de)synchronisation patterns over the PSM cortex.

Adult↗

PubMed2003

Subthalamic stimulation influences postmovement cortical somatosensory processing in Parkinson's disease.

In Parkinson's disease, poor motor performance (resulting primarily from abnormal cortical activation during movement preparation and execution) may also be due to impaired sensorimotor integration and defective cortical activity termination of the ongoing movement, thus delaying preparation of the following one. Reduced movement-related synchronization of the beta rhythm in Parkinson's disease compared to controls has been put forward as evidence for impaired postmovement cortical deactivation. We assessed the effects of subthalamic deep brain stimulation and l-dopa on beta rhythm synchronization over the premotor and primary sensorimotor cortex. Ten advanced patients performed self-paced wrist flexion in four conditions according to the presence or not of stimulation and l-dopa. Compared to without treatment, the motor score improved by approximately 60%; the beta synchronization was present over the contralateral frontocentral region and increased significantly over the contralateral central region under stimulation and under l-dopa, with a maximal effect when both treatments were associated. Our advanced patients displayed very focused and attenuated beta rhythm synchronization which, under stimulation, increased over the contralateral premotor and primary sensorimotor cortex. Stimulation and l-dopa both partly restored postmovement cortical deactivation in advanced Parkinson's disease, although the respective mechanisms probably differ. They may improve bradykinesia and cortical deactivation by reestablishing movement-related somatosensory processing at the end of the movement through the basal ganglia into the cortex.

Aged↗

PubMed2002

[Characterization of the functional relations between cerebral structures: the linear and non-linear].

Two kinds of methods are available in order to assess the functional relationships between different cerebral structures from the analysis of EEG signals: linear and non-linear methods. In this paper, we describe didactically the methodological bases of signal processing. After recalling the significance of the fundamental parameters of a sine wave: frequency, amplitude and phase, we show, from a first example about an epileptic seizure propagation, how a linear variation between phase and frequency can be interpreted as a small time difference between two EEG channels. This linear method hypothesises that these two signals are respectively the input and the output of a linear system. Then, we point out the limits of this method and we introduce non-linear methods. Among the latter, a recent approach introduces a realistic model of EEG which try to relate signal measured quantities to relations between underlying structures which produce them.

Algorithms↗

PubMed2002

Influence of internal globus pallidus stimulation on motor cortex activation pattern in Parkinson's disease.

OBJECTIVES: Indications of the functional neurosurgical treatments become more and more numerous, however, few methods were used to study the mechanism of action and some discrepancies came to light. We assessed the influence of internal globus pallidus (GPI) stimulation and L-Dopa on cortical activation during the preparation and execution phases of the movement compared to clinical improvement of Parkinson's disease. METHODS: We recorded the movement-related cortical potential and movement-related desynchronization. RESULTS: The Unified Parkinson's Disease Rating Scale was improved by 46% under stimulation and 64% under stimulation with L-Dopa. Premovement desynchronization was significantly increased on central contralateral derivation under stimulation with L-Dopa and decreased on frontocentral ipsilateral derivation under stimulation with and without L-Dopa. Movement desynchronization was improved on the contralateral motor cortex under stimulation with and without L-Dopa (benefit correlated with bradykinesia improvement). The movement-related postmotor potential was significantly increased under stimulation with L-Dopa. CONCLUSIONS: GPI stimulation alone influenced the premotor cortex activation during the planning and induced a selective and focal effect on the organisation of motor cortical activity during the movement execution which may explain bradykinesia improvement. The motor cortex activation improvement under stimulation with L-Dopa concerned both the movement preparation and execution but remained very localised to the contralateral motor cortex.

Aged↗

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

Chronic bilateral pallidal stimulation and levodopa do not improve gait in the same way in Parkinson's disease: a study using a video motion analysis system.

Chronic bilateral internal globus pallidus (GPi) stimulation allows control of levodopa induced dyskinesias (LID) and motor symptoms in severe Parkinson's disease (PD). The effect on gait has not been clearly established. Different results have been reported, mostly consisting of clinical data. The aim of this study was to evaluate, by means of a video motion analysis system (optoelectronic VICON system), the influence of bilateral GPi stimulation on gait in PD. Five patients underwent bilateral GPi stimulation. The preoperative and postoperative (3 months after surgery) clinical gait disturbances (items 29 and 30 of the motor UPDRS), as well as spatial and temporal gait measurements (namely cadence, velocity, stride and step times, single and double limb support times, stride and step lengths) were analysed in off condition (the patient had received no treatment for 12 hours or merely the lowest dose of levodopa allowing him to walk for the gait analysis) and in the on drug condition (after administration of 200 mg of levodopa). The gait analysis was performed with the VICON system. In off condition, there was a statistically significant improvement after surgery for UPDRS III and gait (clinically assessed). In on drug condition, there was a significant improvement for LID whereas UPDRS III and clinical assessment of gait were unchanged. The VICON system also showed that surgery improved gait especially in off condition, but also in on drug condition. Our method allowed exact quantification of the influence of surgery on gait characteristics. As compared with levodopa treatment, the effect of stimulation seems to be different. Indeed, the results suggest only limited effects of pallidal stimulation on the control of stride length and rather point to compensatory additional mechanisms.

Aged↗

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

[Neurophysiologic study of tremor].

Tremor is frequently encountered in neurologic practice. Clinical examination supplies information regarding its approximative frequency, regularity, amplitude, topography and activation conditions. The neurophysiological study helps in confirming the tremor, in differentiating it from other movement disorders like myoclonus, and may provide distinctive features which are important for the aetiological diagnosis. The neurophysiological investigation includes accelerometry, which analyses the mechanics of the movement. Spectral analysis with FFT allows the determination of frequency and amplitude. Accelerometry is always associated with surface EMG of at least two antagonistic muscles. It may show rhythmic bursts, their frequency, duration and activation pattern (alternating or synchronous). This neurophysiological approach to tremor has multiple interests. It may help in differentiating a true rest tremor from a postural tremor seemingly persisting at rest. Brief interruptions or rhythm breaks during distraction manoeuvers are seen in psychogenic tremors. Surface EMG may also demonstrate positive myoclonic bursts, or brief silent periods corresponding to negative myoclonus, sometimes pseudorhythmic, thus appearing clinically like a tremor, but investigations, aetiologies and treatment are different. Several features, especially slow frequency, may suggest a midbrain tremor, thus requiring brain imagery centered around the posterior fossa. Finally, the neurophysiological examination is the only way to demonstrate a primary writing tremor, or a primary orthostatic tremor, the frequency of which is pathognomonic while clinical symptoms are rather misleading.

Diagnosis, Differential↗

PubMed2000

[Thulium laser evoked potentials. Normative values for the arms and legs].

Laser somatosensory evoked potentials (LSEP) evaluate the functional integrity of thermoalgic pathways by the specific stimulation of A delta and C nociceptive afferences. As compared to a CO2 laser, the thulium Yttrium Aluminium Garnet (YAG) laser may be conducted by an optic fiber, which allows easier access to the stimulated body sites. We present normative data on thulium YAG LSEPs recorded after stimulation of upper and lower limbs (N = 15). LSEPs were obtained with a stimulation intensity that was twice the nociceptive threshold at the upper limbs (UL) and one and a half at the lower limbs (LL). To ensure a stable attentional level, subjects were asked to estimate stimulus intensity after each stimulation. The nociceptive thresholds at upper and lower limbs were respectively 319 +/- 65 mJ and 359 +/- 95, and with the above methodology the LSEPs could be obtained in every subject. The latencies of N2 and P2 were respectively 199 +/- 18 ms and 325 +/- 37 ms at the UL, 239 +/- 36 ms and 378 +/- 38 ms at the LL. This method produced robust and reproducible results and proved to be reliable for routine clinical use. To optimise response stability we propose that right/left stimulation be conducted following an 'A-B-B-A' procedure.

Adult↗

PubMed1999

Motor programming is more affected in progressive supranuclear palsy than in Parkinson's disease: a spatiotemporal study of event-related desynchronization.

To determine the benefit of motor programming analysis for distinguishing patients with parkinsonism, we compared the spatiotemporal pattern of event-related desynchronization (ERD) preceding a self-paced voluntary wrist flexion between two groups of 10 patients with progressive supranuclear palsy (PSP) and Parkinson's disease (PD) and 10 control subjects. ERD of the mu rhythm was computed from 11 source derivations covering the medial frontocentral, central, and parietocentral areas during two successive left and right experimental conditions (80 self-paced wrist flexions). ERD began in the control group 1750 ms before movement onset over the contralateral central area and then appeared bilaterally on movement execution. In both patient groups, spatiotemporal distribution differed from that in the control group. In the PSP group, ERD had a shorter latency over the contralateral primary sensorimotor area compared with the PD group (PSP: 375 ms before movement onset for both conditions; PD: right flexion 1125 ms before movement onset, left flexion 1000 ms). ERD was observed over the parietocentral area in both groups but also with a clear reduction of latency before movement onset in the PSP group. In both groups, a bilateral central pattern appeared 250 ms before movement execution. In conclusion, our study indicates that ERD analysis is a useful method for observing the changes in cortical activation and for measuring motor programming impairment in parkinsonism, which was more affected in PSP than in PD.

Aged↗

PubMed1999

[Event-related desynchronization and synchronization. Reactivity of electrocortical rhythms in relation to the planning and execution of voluntary movement].

Cortical electroencephalographic rhythms reactivity may be quantified using event-related desynchronization (ERD) and synchronization (ERS) methods. We therefore studied cortical activation occurring during programming and performance of voluntary movement in healthy subjects. EEG power evolution within the reactive frequency bands (mu and beta central rhythms) was averaged before, during and after a minimum of 50 self-paced flexions of the thumb. Recordings in 18 normal adults showed that ERD (decrease in power) of mu rhythm started 2,000 ms before movement onset, while ERD of beta rhythm started 1,500 ms before movement onset. Early ERD of mu and beta rhythms were located over the contralateral central region covering primary motor cortex. They were followed by bilateral ERD occurring over ipsilateral and contralateral central regions during performance of the movement. At the end of the movement, an ERS (increase in power) of beta rhythm occurred. These results suggest that programming of voluntary movement induces early activation in contralateral sensorimotor areas, while performance of the movement induces bilateral activation in sensorimotor areas. ERS of beta rhythm occurring at the end of the movement could correspond to inactivation of motor areas activated by movement. Based on EEG activity, ERD and ERS prove to be useful methods to analyze cortical activation during programming and performance of voluntary movements with good spatial and temporal resolution.

Adult↗