Biomedical subjects

Julie Duque

Publications and source records attributed to Julie Duque.

6 recordsLinked to original sources

PubMed2005

Formation of a motor memory by action observation.

Mirror neurons discharge with both action observation and action execution. It has been proposed that the mirror neuron system is instrumental in motor learning. The human primary motor cortex (M1) displays mirror activity in response to movement observation, is capable of forming motor memories, and is involved in motor learning. However, it is not known whether movement observation can lead directly to the formation of motor memories in the M1, which is considered a likely physiological step in motor learning. Here, we used transcranial magnetic stimulation (TMS) to show that observation of another individual performing simple repetitive thumb movements gives rise to a kinematically specific memory trace of the observed motions in M1. An extended period of observation of thumb movements that were oriented oppositely to the previously determined habitual directional bias increased the probability of TMS-evoked thumb movements to fall within the observed direction. Furthermore, the acceleration of TMS-evoked thumb movements along the principal movement axis and the balance of excitability of muscle representations active in the observed movements were altered in favor of the observed movement direction. These findings support a role for the mirror neuron system in memory formation and possibly human motor learning.

Adult↗

PubMed2005

Encoding a motor memory in the older adult by action observation.

The ability of motor training to encode a motor memory is reduced in older adults. Here, we tested the hypothesis that training-dependent memory encoding, an issue of relevance in neurorehabilitation, is enhanced in elder individuals by action observation which alone can contribute to learning processes. A group of 11 healthy older adults participated in this study, which consisted of three randomized counterbalanced sessions on different days testing the effects of motor training (MT) alone, action observation (AO) alone, and a combination of both (MT + AO) on motor memory encoding. The combination of MT + AO formed a motor memory in the primary motor cortex and differentially modulated motor cortical excitability in muscles that were agonist and antagonist with respect to the training task, but MT or AO alone did not. These results suggest that action observation can enhance the effects of motor training on memory encoding protocols in the older adult, possibly through Hebbian modulation of intracortical excitatory mechanisms.

Aged↗

PubMed2005

Transcallosal inhibition in chronic subcortical stroke.

Movements of the paretic hand in patients with chronic subcortical stroke are associated with high interhemispheric inhibition (IHI) targeting the motor cortex in the lesioned hemisphere relative to healthy controls. The purpose of this investigation was to determine whether this abnormality also involves IHI operating during movements of the non-paretic hand. Here, we studied IHI in the process of generation of voluntary index finger movements by the paretic and non-paretic hands in a simple reaction time paradigm in a group of patients with chronic subcortical stroke. With movements of the non-paretic index finger, IHI targeting the contralateral primary motor cortex ((c)M1) decreased progressively to turn into facilitation at around movement onset, similar to healthy controls. In contrast, movements of the paretic index finger resulted in significantly deeper inhibition at all premovement timings relative to the non-paretic hand. In conclusion, these results document a deeper premovement IHI with paretic than non-paretic hand movements of patients with chronic subcortical stroke, a possible mechanism underlying deficits in motor control.

Adult↗

PubMed2005

Paradoxical effect of digital anaesthesia on force and corticospinal excitability.

The role played by sensory information in maintaining motor cortical representations is still incompletely understood. We investigated the effect of digital anaesthesia of the index finger and thumb on the amplitude of motor evoked potentials to transcranial magnetic stimulation (TMS) recorded from the first dorsal interosseus, F-wave response probability and maximal key pinch force. Whereas digital anaesthesia led to a 29% decrease in maximal force, both motor evoked potential amplitudes and F-wave probability remained unchanged. This dramatic decrease in maximal voluntary contraction following digital anaesthesia may result from a lack of proper sensory feedback during the task.

Adult↗

PubMed2004

Influence of interhemispheric interactions on motor function in chronic stroke.

In patients with chronic stroke, the primary motor cortex of the intact hemisphere (M1(intact hemisphere)) may influence functional recovery, possibly through transcallosal effects exerted over M1 in the lesioned hemisphere (M1(lesioned hemisphere)). Here, we studied interhemispheric inhibition (IHI) between M1(intact hemisphere) and M1(lesioned hemisphere) in the process of generation of a voluntary movement by the paretic hand in patients with chronic subcortical stroke and in healthy volunteers. IHI was evaluated in both hands preceding the onset of unilateral voluntary index finger movements (paretic hand in patients, right hand in controls) in a simple reaction time paradigm. IHI at rest and shortly after the Go signal were comparable in patients and controls. Closer to movement onset, IHI targeting the moving index finger turned into facilitation in controls but remained deep in patients, a finding that correlated with poor motor performance. These results document an abnormally high interhemispheric inhibitory drive from M1(intact hemisphere) to M1(lesioned hemisphere) in the process of generation of a voluntary movement by the paretic hand. It is conceivable that this abnormality could adversely influence motor recovery in some patients with subcortical stroke, an interpretation consistent with models of interhemispheric competition in motor and sensory systems.

Adult↗

PubMed2003

Correlation between impaired dexterity and corticospinal tract dysgenesis in congenital hemiplegia.

One of the most devastating consequences of early corticospinal lesions is the impaired dexterity that results in a noticeable deficit while manipulating small objects. One purpose of the present study was to investigate the extent to which a deficit in the coordination of fingertip forces when grasping and lifting an object between the thumb and index finger could account for the impaired dexterity in patients with congenital hemiplegia (CH). A second objective was to examine whether, in these patients, deficits in skilled hand movements are correlated with the importance of structural damage to the corticospinal tract. The scaling and coordination of fingertip forces during precision grip was investigated in 16 CH patients (aged 8-19 years) and 16 age- and sex-matched control subjects. Proprioception, stereognosis, pressure sensitivity and motor upper limb function (including digital and manual dexterity) were also assessed quantitatively. The structural damage of the corticospinal tract was estimated by measuring the cross-sectional area of cerebral peduncles with MRI and by calculating an index of symmetry between the two peduncles. In CH patients, a large number of parameters measured during the grip-lift task were significantly different when compared with those found in control subjects. Among those, the duration of the preloading and loading phases was significantly longer in CH patients. In addition, both the dissimilarity and time-shift between the profiles of the grip and load force rates, quantified with the cross-correlation method, were also significantly larger in CH patients; the time-shift was strongly correlated with impaired dexterity. These findings suggest that impaired dextrous finger movements in CH patients may specifically result from their inability to ensure a precise synergy between fingertip forces while manipulating an object. Finally, the finding that the time-shift also correlated with the corticospinal tract dysgenesis, as estimated with the cerebral peduncle asymmetry, argues in favour of a critical role of the corticospinal system in the temporal coordination between different muscles involved in dextrous hand movements. Both digital and manual dexterity were also altered in the non-paretic hand of CH patients. This deficit may reveal the contribution of the lesioned hemisphere to the control of ipsilateral skilled finger movements.

Adolescent↗