Maxime Robert

Specific neural substrate linking respiration to locomotion

When animals move, respiration increases to adapt for increased energy demands; the underlying mechanisms are still not understood. We investigated the neural substrates underlying the respiratory changes in relation to movement in lampreys. We showed that respiration increases following stimulation of the mesencephalic locomotor region (MLR) in an in vitro isolated preparation, an effect that persists in the absence of the spinal cord and caudal brainstem. By using electrophysiological and anatomical techniques, including whole-cell patch recordings, we identified a subset of neurons located in the dorsal MLR that send direct inputs to neurons in the respiratory generator. In semi-intact preparations, blockade of this region with 6-cyano-7-nitroquinoxaline-2,3-dione and (2R)-amino-5-phosphonovaleric acid greatly reduced the respiratory increases without affecting the locomotor movements. These results show that neurons in the respiratory generator receive direct glutamatergic connections from the MLR and that a subpopulation of MLR neurons plays a key role in the respiratory changes linked to movement.

Exercise Intensity Levels in Children With Cerebral Palsy While Playing With an Active Video Game Console

Background Children with cerebral palsy (CP) are prone to secondary complications related to physical inactivity and poor cardiorespiratory capacity. This problem could be greatly attenuated through the use of video games that incorporate physical activity for 2 reasons: Video games already represent an important component of leisure time in younger people, and such games can lead to a high level of exercise intensity in people who are healthy. Objective The study objective was to evaluate exercise intensity in children with spastic diplegic CP and children who were typically developing while playing with an active video game console. Design This was a cross-sectional study. Methods Ten children (7–12 years old) with spastic diplegic CP (Gross Motor Function Classification System level I or II) and 10 children who were age matched and typically developing were evaluated in a movement analysis laboratory. Four games were played with the active video game console (jogging, bicycling, snowboarding, and skiing) for 40 minutes. Heart rate was recorded during the entire playing period with a heart rate belt monitor. Exercise intensity was defined as the percentage of heart rate reserve (HRR). In addition, lower extremity motion analysis was carried out during the final minute of the playing period for the jogging and bicycling games. Results No difference between groups was observed for any variables. A main effect of games was observed for the amount of time spent at an intensity greater than 40% of HRR. Specifically, more than 50% of the playing time for the jogging game and more than 30% of the playing time for the bicycling game were spent at an intensity greater than 40% of HRR. In addition, the jogging game produced a larger range of motion than the bicycling game. Limitations A limitation of this study was the relatively small and heterogeneous sample. Conclusions For all 4 games, similar exercise intensity levels were observed for children who were typically developing and children with CP, suggesting that children with CP could obtain exercise-related benefits similar to those obtained by children without CP while playing with an active video game console.

Impaired visually guided weight-shifting ability in children with cerebral palsy

The ability to control voluntary weight shifting is crucial in many functional tasks. To our knowledge, weight shifting ability in response to a visual stimulus has never been evaluated in children with cerebral palsy (CP). The aim of the study was (1) to propose a new method to assess visually guided medio-lateral (M/L) weight shifting ability and (2) to compare weight-shifting ability in children with CP and typically developing (TD) children. Ten children with spastic diplegic CP (Gross Motor Function Classification System level I and II; age 7-12 years) and 10 TD age-matched children were tested. Participants played with the skiing game on the Wii Fit game console. Center of pressure (COP) displacements, trunk and lower-limb movements were recorded during the last virtual slalom. Maximal isometric lower limb strength and postural control during quiet standing were also assessed. Lower-limb muscle strength was reduced in children with CP compared to TD children and postural control during quiet standing was impaired in children with CP. As expected, the skiing game mainly resulted in M/L COP displacements. Children with CP showed lower M/L COP range and velocity as compared to TD children but larger trunk movements. Trunk and lower extremity movements were less in phase in children with CP compared to TD children. Commercially available active video games can be used to assess visually guided weight shifting ability. Children with spastic diplegic CP showed impaired visually guided weight shifting which can be explained by non-optimal coordination of postural movement and reduced muscular strength.

Bilateral connectivity in the brainstem respiratory networks of lampreys

This study examines the connectivity in the neural networks controlling respiration in the lampreys, a basal vertebrate. Previous studies have shown that the lamprey paratrigeminal respiratory group (pTRG) plays a crucial role in the generation of respiration. By using a combination of anatomical and physiological techniques, we characterized the bilateral connections between the pTRGs and descending projections to the motoneurons. Tracers were injected in the respiratory motoneuron pools to identify pre‐motor respiratory interneurons. Retrogradely labeled cell bodies were found in the pTRG on both sides. Whole‐cell recordings of the retrogradely labeled pTRG neurons showed rhythmical excitatory currents in tune with respiratory motoneuron activity. This confirmed that they were related to respiration. Intracellular labeling of individual pTRG neurons revealed axonal branches to the contralateral pTRG and bilateral projections to the respiratory motoneuronal columns. Stimulation of the pTRG induced excitatory postsynaptic potentials in ipsi‐ and contralateral respiratory motoneurons as well as in contralateral pTRG neurons. A lidocaine HCl (Xylocaine) injection on the midline at the rostrocaudal level of the pTRG diminished the contralateral motoneuronal EPSPs as well as a local injection of 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX) and (2R)‐amino‐5‐phosphonovaleric acid (AP‐5) on the recorded respiratory motoneuron. Our data show that neurons in the pTRG send two sets of axonal projections: one to the contralateral pTRG and another to activate respiratory motoneurons on both sides through glutamatergic synapses. J. Comp. Neurol. 520:1442–1456, 2012.

Active video games and children with cerebral palsy: the future of rehabilitation?

The aim of this study was to compare the aerobic solicitation and the postural movements induced by an active video game console in children with cerebral palsy, and in typically developing children. Results showed that the response varied greatly between games, emphasizing the importance of choosing the adequate game in order to solicit specific motor functions. Also, children with CP demonstrated strong interest and usually showed similar responses than their healthy counterpart, suggesting that active video game playing might be appropriate for motor rehabilitation.

Agreement of spatio-temporal gait parameters between a vertical ground reaction force decomposition algorithm and a motion capture system

INTRODUCTION A ground reaction force decomposition algorithm based on large force platform measurements has recently been developed to analyze ground reaction forces under each foot during the double support phase of gait. However, its accuracy for the measurement of the spatiotemporal gait parameters remains to be established. OBJECTIVE The aim of the present study was to establish the agreement between the spatiotemporal gait parameters obtained using (1) a walkway (composed of six large force platforms) and the newly developed algorithm, and (2) an optoelectronic motion capture system. METHODS Twenty healthy children and adolescents (age range: 6-17 years) and 19 healthy adults (age range: 19-51 years) participated in this study. They were asked to walk at their preferred speed and at a speed that was faster than the preferred one. Each participant performed three blocks of three trials in each of the two walking speed conditions. RESULTS The spatiotemporal gait parameters measured with the algorithm did not differ by more than 2.5% from those obtained with the motion capture system. The limits of agreement represented between 3% and 8% of the average spatiotemporal gait parameters. Repeatability of the algorithm was slightly higher than that of the motion capture system as the coefficient of variations ranged from 2.5% to 6%, and from 1.5% to 3.5% for the algorithm and the motion capture system, respectively. CONCLUSION The proposed algorithm provides valid and repeatable spatiotemporal gait parameter measurements and offers a promising tool for clinical gait analysis. Further studies are warranted to test the algorithm in people with impaired gait.

Impact of Exercise-Induced Fatigue on the Strength, Postural Control, and Gait of Children with a Neuromuscular Disease

Objective Children with a neuromuscular disease are prone to early muscular fatigue. The objective of the present study was to evaluate the effects of fatigue induced by a walking exercise on the strength, postural control, and gait of children with a neuromuscular disease. Design Maximal isometric knee strength (extension and flexion), quiet standing postural control, and gait were evaluated in 12 children (8.8 [1.4] yrs) with a neuromuscular disease before and after a walking exercise. The participants were asked to stop walking when they considered themselves “very fatigued.” Results After the exercise-induced fatigue, a significant increase in range of motion in pelvis obliquity, hip abduction and adduction, and ankle flexion and extension during gait was reported along with an increase in stride length variability. Fatigue also reduced the knee flexor strength and had a detrimental effect on postural control. Conclusions Fatigue affects the strength, postural control, and gait of children with a neuromuscular disease and could notably increase the risks of falling and the occurrence of serious injuries.

Analysing gait using a force-measuring walkway: intrasession repeatability in healthy children and adolescents

The goal of this study was to determine the repeatability of gait parameters measured by a force plate gait analysis system (Leonardo Mechanograph® GW) in healthy children. Nineteen healthy children and adolescents (age range: 7–17 years) walked at a self-selected speed on an 11-m-long walkway. Vertical ground reaction forces were measured in the central 6 m of the walkway. Each participant performed three blocks of three trials while walking barefoot and three blocks of three trials while wearing shoes. There were no differences between trials within each condition. All force and spatiotemporal parameters had intraclass correlation coefficients above 0.87 and coefficients of variation in the order of 1–6%. In this group of healthy children and adolescents, gait analysis with a force plate system produced repeatable intra-day results.

Changes in physiological tremor associated with an epileptic seizure: a case report

IntroductionEpileptic seizures are associated with motor, sensory, somatosensory or autonomic symptoms that have all been described in varying detail over the years. Of interest in the present report is a case of normal physiological tremor, which to date has never been evaluated prior to and during an epileptic seizure. In fact, there is only anecdotal mention of pre-ictal and ictal changes in clinically noticeable tremor in the literature.Case presentationOur patient was a left-handed, 27-year-old Caucasian woman diagnosed seven years previously with partial epileptic seizures, secondarily generalized. Physiological tremor was measured simultaneously on the index finger of both hands of our patient. Electromyography as well as heart rate and respiration were also monitored. A previously performed electroencephalography examination revealed abnormal oscillations focalized to the left primary somatosensory cortex. She was also diagnosed with left frontal neuronal heterotopias. We detected subclinical changes in tremor characteristics, such as amplitude, median power frequency and power dispersion, contralateral to the localization of epileptic activity. Tremor characteristics remained relatively steady ipsilateral to the localization of the epileptic activity.ConclusionsChanges in physiological tremor characteristics should be considered as another possible pre-ictal or ictal manifestation. We propose that the network associated with physiological tremor might be more sensitive to abnormal oscillations generated within the central nervous system by epileptic activity from certain structures.