Biomedical subjects

Deborah J Serrien

Publications and source records attributed to Deborah J Serrien.

14 recordsLinked to original sources

PubMed2004

Motor inhibition in patients with Gilles de la Tourette syndrome: functional activation patterns as revealed by EEG coherence.

There is considerable evidence that Gilles de la Tourette syndrome (TS) is due to frontal-striatal dysfunction. Here we determine whether adaptive cortical changes occur that might ameliorate the effects of this dysfunction. Specifically we test the hypothesis that increased interactions between selected cortical areas may help compensate through strengthened inhibition of inappropriate motor responses. To this end we recorded EEG in nine unmedicated patients with TS and nine age-matched healthy subjects during a variety of behavioural tasks related to motor inhibition. Functional connectivity between cortical areas was assessed by means of EEG coherence in the alpha frequency band (8-12 Hz). Elevated coherence was found between sensorimotor areas and the prefrontal and mesial frontal cortex during the acute voluntary suppression of tics. The same frontomesial network was overactive in TS patients compared with healthy subjects even when suppression of voluntary movement rather than tics was required during a Go-NoGo task. Behavioural performance in the Go-NoGo task was not different between patients and controls, confirming that the elevated frontomesial coherence in TS was likely to be adaptive rather than functionally disruptive. It is concluded that the gain in inhibitory frontomesial cortical networks is adaptively heightened in TS, and that the same network can also be engaged in the voluntary suppression of tics.

Acoustic Stimulation↗

PubMed2004

Changes in functional coupling patterns during bimanual task performance.

Functional interaction between cortical areas may involve synchronization of activities, manifest as coherence between EEG signals. However, although EEG-EEG coherence changes when motor tasks are compared to each other or rest, there is little evidence that coherence is modulated within an action. To address this issue we used a bimanual drawer-opening task necessitating asymmetrical hand actions and comprising distinct movement phases. Pronounced modulations in EEG-EEG coherence in the beta band (>12-24 Hz) occurred with movement phase. Differences in coherence due to a switch in role of the hands were mainly observed in the alpha band (8-12 Hz). These findings suggest that inter-regional synchronization changes dynamically across task execution in line with behavioral performance.

Cerebral Cortex↗

PubMed2004

Cortico-cortical coupling patterns during dual task performance.

We investigated the neural correlates of dual task performance using EEG coherence as a measure of the functional coupling between cortical regions. Nine healthy participants performed a rhythmical movement with the right hand and an isometric contraction with the left hand, either initiated simultaneously or successively. EEG data revealed that dual task performance was associated with stronger coherence in left hemispheric and mesial areas than the sum of the tasks performed separately in the beta (>12-30 Hz), but not alpha (8-12 Hz), band. This effect was more pronounced when the two assignments were initiated simultaneously, as opposed to successively. The data demonstrate that the pattern of cortico-cortical coupling during bimanual actions is not just the sum of that associated with its component parts, but is increased according to coordinative demands and processing load.

Arm↗

PubMed2004

Functional significance of the ipsilateral hemisphere during movement of the affected hand after stroke.

Previous fMRI observations have suggested increased task-related activation of the ipsilateral cerebral motor cortex in patients recovering from stroke. This is generally taken to infer an increased output from this area, although the functional relevance of this has been questioned. Here, we use directed EEG coherence to reveal whether there is increased informational flow from the ipsilateral motor cortex following motor stroke, and through correlation with degree of recovery, establish that this pattern of activity is associated with limited functional improvement. Unrecovered (n = 14), recovered (n = 11) patients and healthy subjects (n = 16) performed an isometric grip task with either hand that corresponded to 25% of individual maximum force, while EEG was recorded. For unrecovered stroke patients, most task-related information flow between the sensorimotor cortices in the low beta band of the EEG came from the ipsilateral (undamaged) hemisphere during grip with the affected hand. This was not the case when they gripped with their unaffected hand, when cortical activity was driven from the contralateral sensorimotor cortex. The latter pattern was also seen in recovered patients and controls. These findings suggest a functional role for the ipsilateral hemisphere in organizing movement of the impaired limb following stroke, but only in those patients that do not make a good functional recovery. Patients making a fuller recovery organize movement-related cortical activity from the hemisphere contralateral to movement.

Adolescent↗

PubMed2004

The quest to understand bimanual coordination.

Many skillful manipulations engage both hands for goal achievement. Whereas the goal is planned consciously and achieved quasi-invariantly, the articulators are mobilized automatically, but in a flexible manner (Lashley's principle of motor equivalence). In brain disorders affecting hand functions, adaptive mechanisms are mobilized to improve goal achievement. Thus, chronic cerebellar patients were found to initiate a bimanual drawer task with marked intermanual desynchronization as compared to control subjects. This was partly compensated for, however, by adjusting the kinematics as the individual limbs move toward the goal, thereby improving the initial desynchronization. Adaptive strategies rarely correct deficits completely, however. Bimanual movement patterns, either in-phase or anti-phase are relatively stable in healthy human subjects, whereas brain pathology may preferentially impair the anti-phase pattern. This is the case in patients with acquired pathology of the corpus callosum, thereby suggesting that this structure is important for maintaining temporally independent limb and hand movements.

Animals↗

PubMed2003

Influence of working memory on patterns of motor related cortico-cortical coupling.

Working memory is implicated in various higher-order cognitive operations. We hypothesized that the availability of a temporal representation in working memory would limit the extent of cortico-cortical coupling necessary to undertake a self-paced rhythmic movement. To this end we examined modulations in cortico-cortical interactions as determined by EEG coherence during a delay interval and subsequent movement reproduction. Right hand movement was initially paced by a metronome beat every 0.9 s, followed by a delay interval, after which hand movement was repeated in an unpaced manner. Movement reproduction after a long (22.5 s, corresponding to 25 movement cycles) compared to a short (5.4 s, corresponding to 6 movement cycles) delay interval was associated with an increased degree of functional coupling in the beta frequency band (12-30 Hz) of the left (movement-driving) hemisphere (F3-FC3, F3-C3 and F3-P3 connections) as well as mesial regions (FCz-FC3, FCz-C3 and Cz-FC3 connections) even though overall behavioral characteristics were not influenced. In addition, analysis of the EEG coherence in the delay period revealed a bilateral frontal network (F3-F4, F3-FC4, F4-FC3 and FC3-FC4 connections). Activity in the latter tended to be synchronized in the theta band (4-8 Hz) and was significantly less strong at 22.5 s than 5.4 s. These data suggest that working memory may be partly subserved by synchronization in a bilateral frontal network and may provide an intrinsic contextual influence that shapes the pattern of cortico-cortical interaction during a given task.

Biomechanical Phenomena↗

PubMed2003

Anticipatory cortico-cortical interactions: switching the task configuration between effectors.

Cognitive regulation enables a subject to plan actions according to context and to respond in a flexible manner to environmental conditions. This implies that foreknowledge about a change in system configuration will trigger preparatory activity in anticipation of the impending transformation. In the present study, we evaluate a unimanual task under two performance conditions that affected the cognitive context, and examine modulations in cortico-cortical interactions as determined by EEG coherence. The right hand movement was performed in an experimental paradigm that necessitated in some trials a voluntary and predictable switch towards a left hand movement, whereas in other trials no switch was required and movement of the right hand continued. The data showed that execution of the right hand movement was associated with an increased degree of task-related coherence in the alpha frequency band (8-12 Hz) in the switching as compared to the no switching condition, and this was most apparent for fronto-parietal connections of the movement-driving (left) as well as for the primed (right) hemisphere. For the primed hemisphere, we observed that the information flow was driven from the F4 electrode overlying the prefrontal area, which suggests that anticipatory preplanning occurred. These data indicate that higher-order cognitive operations bias cortico-cortical interactions in respect of an upcoming switch of the task settings between effectors by recruiting neural resources proactively. Dynamic adjustments in the alpha band suggest that low frequency activity is a characteristic of distributed information processing related to movement planning.

Adult↗

PubMed2003

Transient increases of synchronized neural activity during movement preparation: influence of cognitive constraints.

The ability to prepare movement is an essential requirement for the control of goal-directed actions. It allows us to respond in an adaptable and swift manner to environmental conditions. In the present study, we manipulate cognitive context, by means of response probability, to modify the degree of movement preparation in a delayed cueing task performed with the right hand, and evaluate the neural dynamics (EEG coherence) and behavioural output (reaction time). Task-related coherence was stronger over the contralateral hemisphere. In particular, coherence between the left sensorimotor area and frontal (C3-F3, C3-FC3) and parietal (C3-P3) regions was increased during right-hand movement preparation as compared to rest in the alpha frequency band (8-12 Hz). Reducing response probability diminished the degree of functional coupling between C3-F3 and C3-FC3, and was associated with a prolonged reaction time. These findings suggest an association between neural dynamics and behavioural performance and emphasize that response predictability biases information processing in goal-oriented behaviour.

Adult↗

PubMed2003

The importance of the dominant hemisphere in the organization of bimanual movements.

The successful control of upper limb movements is an essential skill of the human motor system. Yet, the neural organization of bimanual actions remains an issue of debate. Their control can be directed from both hemispheres, or, coordinated motion might be organized from the dominant (left) hemisphere. In order to unravel the neural mechanisms of bimanual behavior, we analyzed the standard task-related and directed coherence between EEG signals picked up over the primary sensorimotor cortices in right-handed subjects during unimanual as well as bimanual in-phase (symmetrical) and anti-phase (asymmetrical) movements. The interhemispheric coherence in the beta frequency band (>13-30 Hz) was increased in both unimanual and bimanual patterns, compared to rest. During unimanual actions, the drive in the beta band from one primary sensorimotor cortex to the other was greater during movement of the contralateral as opposed to ipsilateral hand. In contrast, during bimanual actions, the drive from the dominant to the non-dominant primary sensorimotor cortex prevailed, unless task constraints induced by an external perturbation resulted in a substantial uncoupling of the hand movements, when interhemispheric coherence would also drop. Together, these results suggest that the contralateral hemisphere predominantly organizes unimanual movements, whereas coupled bimanual movements are mainly controlled from the dominant hemisphere. The close association between changes in interhemispheric coupling and behavioral performance indicates that synchronization of neural activity in the beta band is exploited for the control of goal-directed movement.

Adult↗

PubMed2003

The integration of cortical and behavioural dynamics during initial learning of a motor task.

Here we test the hypothesis that frequency and topographically specific changes in the strength of functional cortico-cortical coupling occur during the acquisition of a completely new task. To this end we studied the behavioural and cortical dynamics of a bimanual multifrequency coordination pattern during which one hand moved at twice the frequency of the other hand. This pattern represents a noninherent assignment and necessitates training before appropriate interlimb decoupling takes place. Results showed that acquisition of the multifrequency task was associated with an improved behavioural output that matched specific changes in the electroencephalogram dynamics. In particular, practice of the coordination pattern was accompanied by a decrease in coherence between the primary sensorimotor regions, and over the midline area in the alpha and beta bands, respectively, along with an increase in functional interhemispheric coupling between the prefrontal areas in the gamma band. These data suggest that the strength of cortico-cortical connectivity is adaptively modified across regions and across frequencies during early learning as the functional couplings are created and optimized for the purpose of movement execution.

Cerebral Cortex↗

PubMed2002

The functional role of interhemispheric synchronization in the control of bimanual timing tasks.

The aim of the present study was to investigate whether synchronized activity between the right and left primary sensorimotor cortices has a functional role in the organization of bimanual in-phase and anti-phase movement patterns, performed at different cycling frequencies. To this end we evaluated the cortical dynamics by means of task-related EEG. Both behavioral performance and coupling between the primary sensorimotor cortices in the beta frequency band were reduced with increasing movement speed, and this effect was far more powerful in the anti-phase than in-phase mode. Thus, a progressive degradation of interhemispheric connectivity with cycling rate was associated with a deteriorating behavioral output. Overall, these results support a significant role for interhemispheric synchronization in the control of bimanual movements.

Adult↗

PubMed2002

Repetitive transcranial magnetic stimulation of the supplementary motor area (SMA) degrades bimanual movement control in humans.

Moving the upper limbs at a common tempo according to an in-phase or anti-phase mode represents elementary coordination dynamics. Previously, the role of the supplementary motor area (SMA) has been emphasized for successful production of these patterns. The objective of this study was to investigate whether repetitive transcranial magnetic stimulation (rTMS) of the SMA at 5 Hz can interfere with these isofrequency configurations in the post-stimulation stage. Results showed a deterioration of temporal control as a function of coordinative complexity. This effect was associated with a decrease in the functional coupling between the primary motor cortices, as measured by electroencephalographic coherence. These data suggest that rTMS of the SMA can modify interhemispheric communication and accordingly modulate interlimb behavior.

Adult↗

PubMed2002

Control of manipulative forces during unimanual and bimanual tasks in patients with Huntington's disease.

The aim of the study was to investigate grip-load force regulation in Huntington's disease (HD) patients as compared to control subjects during the performance of a manipulative task that required rhythmical unimanual or bimanual isodirectional/non-isodirectional actions in the sagittal plane. Results showed that the profile of grip-load ratio force was characterized by maxima and minima that were attained at upward and downward hand positions, respectively. Minimum force ratio was higher in patients than in controls, which points to an elevated baseline that may be related to the inherent bradykinesia observed in HD. Maximum force ratio was also increased in patients, but this effect depended on the performance condition, with largest amplifications occurring during non-isodirectional movements. The latter rescaling may be associated with the complexity of the coordination mode and its asymmetrical load characteristics. In addition, the temporal delay between the grip and load force peaks was augmented in patients versus controls, indicating a disturbed coupled activation of both forces. Furthermore, the interval was largest during non-isodirectional movements followed by isodirectional and unimanual movements, which denotes that the grip-load force coupling deteriorated as a function of coordinative complexity. Together, these data indicate a deficit in the grip-load force constraint due to HD and illustrate the degrading effect of striatal dysfunction on (bi)manual manipulative function.

Adult↗

PubMed2002

Movement control of manipulative tasks in patients with Gilles de la Tourette syndrome.

When a hand-held object is moved, grip and load force are accurately coordinated for establishing grasp stability. In the present work, the question was raised whether patients with Gilles de la Tourette syndrome (TS), who show tic-like movements, are impaired in grip-load force control when executing a manipulative task. To this end, we assessed force regulation during action patterns that required rhythmical unimanual or bimanual (iso-directional/anti-directional) movements. Results showed that the profile of grip-load force ratio was characterized by maxima and minima that were realized at upward and downward hand positions, respectively. TS patients showed increased force ratios during unimanual and bimanual movements, compared with control subjects, indicative of an inaccurate specification of the precision grip. Functional imaging data complemented the behavioural results and revealed that secondary motor areas showed no (or greatly reduced) activation in TS patients when executing the movement tasks as compared with baseline conditions. This indicates that the metabolic level in the secondary motor areas was equal during rest and task performance. At the neuronal level, this observation suggests that these cortical areas were continuously involved in movement preparation. Based on these data, we conclude that the ongoing activation of secondary motor areas may be explained by the TS patients' involuntary urges to move. Accordingly, interference will prevent an accurate planning of voluntary behaviour. Together, these findings reveal modulations in movement organization in patients with TS and exemplify degrading consequences for manual function.

Adult↗