APHP Service de medecine physique et readaptation

Garches, France

APHP Service de medecine physique et readaptation

Garches, France

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Roche N.,University Pierre and Marie Curie | Lackmy A.,University Pierre and Marie Curie | Achache V.,University Pierre and Marie Curie | Bussel B.,APHP Service de medecine physique et readaptation | Katz R.,University Pierre and Marie Curie
Clinical Neurophysiology | Year: 2012

Objective: It has recently been shown that transcranial direct current stimulation (tDCS) (1) can modify lumbar spinal network excitability and (2) decreases cervical propriospinal system excitability. Thus the purpose of this series of experiments was to determine if anodal tDCS applied over the leg motor cortex area induces changes in lumbar propriospinal system excitability. To that end, the effects of anodal tDCS and sham tDCS on group I and group II propriospinal facilitation of quadriceps motoneurones were studied in healthy subjects. Methods: Common peroneal nerve group I and group II quadriceps H-reflex facilitation was assessed in 15 healthy subjects in two randomised conditions: anodal tDCS condition and sham tDCS condition. Recordings were performed before, during and after the end of the cortical stimulation. Results: Compared to sham, anodal tDCS decreases significantly CPN-induced group I and II quadriceps H-reflex facilitation during and also after the end of the cortical stimulation. Conclusions: Anodal tDCS induces (1) modulation of lumbar propriospinal system excitability (2) post-effects on spinal network. Significance: These results open a new vista to regulate propriospinal lumbar system excitability in patients and suggest that anodal tDCS would be interesting for neuro-rehabilitation of patients with central nervous system lesions. © 2011 International Federation of Clinical Neurophysiology.


Roche N.,University Pierre and Marie Curie | Bussel B.,APHP Service de medecine physique et readaptation | Maier M.A.,University of Paris Descartes | Maier M.A.,University Paris Diderot | And 3 more authors.
Journal of Physiology | Year: 2011

Motor skill acquisition may induce modifications of spinal network excitability. We studied the impact of two different precision grip force control tasks on cervical spinal network excitability in healthy subjects. The results show that the nature of the motor task performed has a specific impact on the excitability of these cervical spinal circuits and that presynaptic Ia inhibition may play an important role for acquisition of a new motor task. The results strongly suggest that early motor adaptations induced by a motor task are not only cortical but also spinal in origin. Abstract Motor skill acquisition in the lower limb may induce modifications of spinal network excitability. We hypothesized that short-term motor adaptation in precision grip tasks would also induce modifications of cervical spinal network excitability. In a first series of experiments, we studied the impact of two different precision grip force control tasks (a visuomotor force-tracking task and a control force task without visual feedback) on cervical spinal network excitability in healthy subjects. We separately tested the efficacy of two key components of the spinal circuitry: (i) presynaptic inhibition on flexor carpi radialis (FCR) Ia terminals, and (ii) disynaptic inhibition directed from extensor carpi radialis (ECR) to FCR. We found that disynaptic inhibition decreased temporarily after both force control tasks, independently of the presence of visual feedback. In contrast, the amount of presynaptic inhibition on FCR Ia terminals decreased only after the visuomotor force tracking task. This temporary decrease was correlated with improved tracking accuracy during the task (i.e. short-term motor adaptation). A second series of experiments confirmed these results and showed that the visuomotor force-tracking task resulted also in an increase of the H max/M max ratio and the slope of the ascending part of the H-reflex recruitment curve. In order to address the role of presynaptic inhibition in the motor adaptation process, we conducted a third series of experiments during which presynaptic inhibition was recorded before and after two consecutive sessions of visuomotor force tracking. The results showed that (i) improved tracking accuracy occurred during both sessions, and (ii) presynaptic inhibition decreased only after the first session of visuomotor force tracking. Taken together, these results suggest thus that the nature of the motor task performed has a specific impact on the excitability of these cervical spinal circuits. These findings also suggest that early motor adaptation is associated with a modulation of presynaptic Ia inhibition in the upper limb. © 2011 The Authors. Journal compilation © 2011 The Physiological Society.


Klomjai W.,Paris-Sorbonne University | Klomjai W.,Mahidol University | Lackmy-Vallee A.,Paris-Sorbonne University | Katz R.,Paris-Sorbonne University | And 5 more authors.
Journal of Physiology | Year: 2014

During neural development in animals, GABAergic and glycinergic neurons are first excitatory, and then become inhibitory in the mature state. This developmental shift is due mainly to strong expression of the cation-chloride K-Cl cotransporter 2 (KCC2) and down-regulation of Na-K-Cl cotransporter 1 (NKCC1) during maturation. The down-regulation of co-transporter KCC2 after spinal cord transection in animals leads to the depolarising (excitatory) action of GABA and glycine and thus results in a reduction of inhibitory synaptic efficiency. Furosemide, a loop diuretic, has been shown to selectively and reversibly block inhibitory postsynaptic potentials without affecting excitatory postsynaptic potentials in animal spinal neurons. Moreover, this diuretic has been also demonstrated to block the cation-chloride co-transporters. Here, we used furosemide to demonstrate changes in spinal inhibitory networks in healthy human subjects. Non-invasive electrophysiological techniques were used to assess presynaptic inhibition, postsynaptic inhibition and the efficacy of synaptic transmission between muscle afferent terminals and soleus motoneurons in the spinal cord. Orally administered furosemide, at doses commonly used in the clinic (40 mg), significantly reduced spinal inhibitory interneuronal activity for at least 70 min from intake compared to control experiments in the same subjects while no changes were observed in the efficacy of synaptic transmission between muscle afferent terminals and soleus motoneurons. The reduction of inhibition was dose-dependent. Our results provide indirect evidence that reversible changes in the cation-chloride transport system induce modulations of inhibitory neuronal activity at spinal cord level in humans. © 2014 The Physiological Society.

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