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Mercier, Catherine

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Mercier

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Catherine

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Université Laval. Département de réadaptation

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ncf13675366

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Voici les éléments 1 - 9 sur 9
  • PublicationAccès libre
    A virtual reality avatar interaction (VRai) platform to assess residual executive dysfunction in active military personnel with previous mild traumatic brain injury : proof of concept
    (Taylor & Francis Informa Healthcare, 2016-09-08) Jackson, Philip L.; Mercier, Catherine; Hébert, Luc J.; Robitaille, Nicolas; Richards, Carol Lillian; Fecteau, Shirley; Bouyer, Laurent; McFadyen, Bradford James
    Purpose: This proof of concept study tested the ability of a dual task walking protocol using a recently developed avatar-based virtual reality (VR) platform to detect differences between military personnel post mild traumatic brain injury (mTBI) and healthy controls. Methods: The VR platform coordinated motion capture, an interaction and rendering system, and a projection system to present first (participant-controlled) and third person avatars within the context of a specific military patrol scene. A divided attention task was also added. A healthy control group was compared to a group with previous mTBI (both groups comprised of six military personnel) and a repeated measures ANOVA tested for differences between conditions and groups based on recognition errors, walking speed and fluidity and obstacle clearance. Results: The VR platform was well tolerated by both groups. Walking fluidity was degraded for the control group within the more complex navigational dual tasking involving avatars, and appeared greatest in the dual tasking with the interacting avatar. This navigational behaviour was not seen in the mTBI group. Conclusions: The present findings show proof of concept for using avatars, particularly more interactive avatars, to expose differences in executive functioning when applying context-specific protocols (here for the military). Implications for rehabilitation Virtual reality provides a means to control context-specific factors for assessment and intervention. Adding human interaction and agency through avatars increases the ecologic nature of the virtual environment. Avatars in the present application of the Virtual Reality avatar interaction platform appear to provide a better ability to reveal differences between trained, military personal with and without mTBI.
  • PublicationAccès libre
    Is somatosensory excitability more affected by the perspective or modality content of motor imagery?
    (Elsevier, 2011-02-11) Jackson, Philip L.; Mercier, Catherine; Richards, Carol Lillian; Voisin, Julien; Malouin, Francine.
    Beneficial effects of mental practice likely arise because motor imagery involves largely similar neural networks as physical execution of the same movement. While it is known that the involvement of the motor system is favoured by focusing on the kinaesthetic modality and by the first person perspective, little is known about the impact of these factors on the somatosensory system. The present paper examines the effects on the somatosensory excitability of both perspective (the point of view of the person imagining a motor act) and modality (visual versus kinaesthetic) during mental practice. Seventeen healthy subjects participated. Quality of mental practice was controlled using chronometric tests and a subjective questionnaire. Excitability of the somatosensory system was assessed through the steady-state electroencephalographical response to a continuous train of electrical stimuli applied to the radial nerve, at the same time subjects were instructed to perform one of five tasks designed to separate the effects of perspective, modality and motor versus non-motor imagery. Kinaesthetic motor imagery exerts the largest effect on somatosensory excitability whereas visual motor imageries (1st and 3rd person perspectives) produce the same lower effect that static visual imagery does. Strikingly, specific effect of kinaesthetic motor imagery correlates with the selfselected speed to imagine and execute the same movement. These findings suggest a key role of the kinaesthetic content of motor imagery in recruiting the sensorimotor system.
  • PublicationRestreint
    Anodal transcranial direct current stimulation enhances the effects of motor imagery training in a finger tapping task
    (Oxford University Press, 2015-11-05) Jackson, Philip L.; Mercier, Catherine; Saimpont, Arnaud; Guillot, Aymeric; Doyon, Julien; Collet, Christian; Malouin, Francine.
    Motor imagery (MI) training and anodal transcranial direct current stimulation (tDCS) applied over the primary motor cortex can independently improve hand motor function. The main objective of this double-blind, sham-controlled study was to examine whether anodal tDCS over the primary motor cortex could enhance the effects of MI training on the learning of a finger tapping sequence. Thirty-six right-handed young human adults were assigned to one of three groups: (i) who performed MI training combined with anodal tDCS applied over the primary motor cortex; (ii) who performed MI training combined with sham tDCS; and (iii) who received tDCS while reading a book. The MI training consisted of mentally rehearsing an eight-item complex finger sequence for 13 min. Before (Pre-test), immediately after (Post-test 1), and at 90 min after (Post-test 2) MI training, the participants physically repeated the sequence as fast and as accurately as possible. An ANOVA showed that the number of sequences correctly performed significantly increased between Pre-test and Post-test 1 and remained stable at Post-test 2 in the three groups (P < 0.001). Furthermore, the percentage increase in performance between Pre-test and Post-test 1 and Post-test 2 was significantly greater in the group that performed MI training combined with anodal tDCS compared with the other two groups (P < 0.05). As a potential physiological explanation, the synaptic strength within the primary motor cortex could have been reinforced by the association of MI training and tDCS compared with MI training alone and tDCS alone.
  • PublicationRestreint
    Decreasing phantom limb pain through observation of action and imagery : a case series
    (Wiley, 2011-02-01) Jackson, Philip L.; Mercier, Catherine; Michon, Pierre-Emmanuel; Malouin, Francine.; Beaumont, Geneviève
    Background. Phantom limb pain is often resistant to treatment. Techniques based on visual-kinesthetic feedback could help reduce it. Objective. The objective of the current study was to test if a novel intervention combining observation and imagination of movements can reduce phantom limb pain. Methods. This single-case multiple baseline study included six persons with upper or lower limb phantom pain. Participants' pain and imagery abilities were assessed by questionnaires. After a 3–5-week baseline, participants received a two-step intervention of 8 weeks. Intervention 1 was conducted at the laboratory with a therapist (two sessions/week) and at home (three sessions/week); and Intervention 2 was conducted at home only (five times/week). Interventions combined observation and imagination of missing limb movements. Participants rated their pain level and their ease to imagine daily throughout the study. Results. Time series analyses showed that three participants rated their pain gradually and significantly lower during Intervention 1. During Intervention 2, additional changes in pain slopes were not significant. Four participants reported a reduction of pain greater than 30% from baseline to the end of Intervention 2, and only one maintained his gains after 6 months. Group analyses confirmed that average pain levels were lower after intervention than at baseline and had returned to baseline after 6 months. Social support, degree of functionality, and perception of control about their lives prior to the intervention correlated significantly with pain reduction. Conclusions. Persons with phantom limb pain may benefit from this novel intervention combining observation and motor imagery. Additional studies are needed to confirm our findings, elucidate mechanisms, and identify patients likely to respond.
  • PublicationRestreint
    Variability in the effector-specific pattern of motor facilitation during the observation of everyday actions : implications for the clinical use of action observation
    (Elsevier, 2010-07-13) Hétu, Sébastien; Jackson, Philip L.; Mercier, Catherine; Gagné, Martin
    Action observation is increasingly considered as a rehabilitation tool as it can increase the cortical excitability of muscles involved in the observed movements and therefore produce effector-specific motor facilitation. In order to investigate the action observation mechanisms, simple single joint intransitive movements have commonly been used. Still, how the observation of everyday movements which often are the prime target of rehabilitation affects the observer cortical excitability remains unclear. Using transcranial magnetic stimulations, we aimed at verifying if the observation of everyday movements made by the proximal or distal upper-limb produces effector-specific motor facilitation in proximal (arm) and distal (hand) muscles of healthy subjects. Results suggest that, similar to simple intransitive movements, observation of more complex everyday movements involving mainly the proximal or distal part of upper limb induces different patterns of motor facilitation across upper limb muscles (P=0.02). However, we observed large inter-individual variability in the strength of the effector-specific motor facilitation induced by action observation. Yet, subjects had similar types of response (strong or weak effector-specific effects) when watching proximal or distal movements indicating that the facilitation pattern was highly consistent within subjects (r=0.83-0.88, P<0.001). This suggests that some individuals are better than other at precisely mapping the observed movements on their motor repertoire and that this type of response holds for various types of everyday actions.
  • PublicationAccès libre
    Development and validation of open-source activity intensity count and activity intensity classification algorithms from raw acceleration signals of wearable sensors
    (Basel MDPI, 2020-11-26) Mercier, Catherine; Clouâtre, Jade; Routhier, François; Poitras, Isabelle; Campeau-Lecours, Alexandre; Bouyer, Laurent
    Background: A popular outcome in rehabilitation studies is the activity intensity count, which is typically measured from commercially available accelerometers. However, the algorithms are not openly available, which impairs long-term follow-ups and restricts the potential to adapt the algorithms for pathological populations. The objectives of this research are to design and validate open-source algorithms for activity intensity quantification and classification. Methods: Two versions of a quantification algorithm are proposed (fixed [FB] and modifiable bandwidth [MB]) along with two versions of a classification algorithm (discrete [DM] vs. continuous methods [CM]). The results of these algorithms were compared to those of a commercial activity intensity count solution (ActiLife) with datasets from four activities (n = 24 participants). Results: The FB and MB algorithms gave similar results as ActiLife (r > 0.96). The DM algorithm is similar to a ActiLife (r ≥ 0.99). The CM algorithm differs (r ≥ 0.89) but is more precise. Conclusion: The combination of the FB algorithm with the DM results is a solution close to that of ActiLife. However, the MB version remains valid while being more adaptable, and the CM is more precise. This paper proposes an open-source alternative for rehabilitation that is compatible with several wearable devices and not dependent on manufacturer commercial decisions.
  • PublicationAccès libre
    Modulation of the response to a somatosensory stimulation of the hand during the observation of manual actions
    (Springer, 2010-11-03) Hétu, Sébastien; Rodrigues, Erika C.; Jackson, Philip L.; Mercier, Catherine; Voisin, Julien; Vargas, Claudia D.; Malouin, Francine.; Chapman, C. Elaine
    Observation of hand movements has been repeatedly demonstrated to increase the excitability of the motor cortical representation of the hand. Little attention, however, has been devoted to its effect on somatosensory processing. Movement execution is well known to decrease somatosensory cortical excitability, a phenomenon termed ‘gating’. As executed and observed actions share common cortical representations, we hypothesized that action observation (hand movements) should also modulate the cortical response to sensory stimulation of the hand. Seventeen healthy subjects participated in these experiments in which electroencephalographic (EEG) recordings of the somatosensory steady-state response (SSSR) were obtained. The SSSR provides a continuous measure of somatosensory processing. Recordings were made during a baseline condition and five observation conditions in which videos showed either a: (1) hand action; (2) passive stimulation of a hand; (3) static hand; (4) foot action; or (5) static object. The method employed consisted of applying a continuous 25 Hz vibratory stimulation to the index finger during the six conditions and measuring potential gating effects in the SSSR within the 25 Hz band (corresponding to the stimulation frequency). A significant effect of condition was found over the contralateral parietal cortex. Observation of hand actions resulted in a significant gating effect when compared to baseline (average gating of 22%). Observation of passive touch of the hand also gated the response (17% decrease). In conclusion, the results show that viewing a hand performing an action or being touched interferes with the processing of somatosensory information arising from the hand.
  • PublicationAccès libre
    I am touched by your pain : limb-specific modulation of the cortical response to a tactile stimulation during pain observation
    (American Pain Society, 2011-09-10) Jackson, Philip L.; Mercier, Catherine; Voisin, Julien; Marcoux, Louis-Alexandre; Canizales, Dora Linsey
    The observation of pain in other individuals is known to impact the cerebral activity in regions dedicated to one’s nociception, as well as the behavior toward the person in pain. However, it remains unclear whether this shared representation for pain modulates somatosensory processing to nonpainful stimuli and whether this modulation is limb specific. Twenty right-handed healthy participants viewed a series of pictures depicting right hands or right feet in painful or nonpainful situations while light repetitive (25 Hz) mechanical stimuli were applied to the hand. The cortical excitability to these nonpainful stimuli was measured through the energy in the 25-Hz frequency band of electroencephalographic data. Following picture onset, a combination of nonspecific and specific modulation of cortical excitability was found. The former was widespread over the parieto-central region and likely related to factors such as attention. The latter was mostly restricted to 3 electrodes over the parietal cortex contralateral to the stimulation of the hand, and was specifically associated with the observation of others’ hand in painful scenarios. This result confirms that the observation of pain can modulate somatosensory cortical excitability in an effector-specific way. The findings add to the accumulating evidence that other people’s somatic pain is mapped onto the observer’s sensori-motor system and offers a new paradigm to investigate potential neurophysiological changes in care providers who are often overexposed to others' pain. Perspective This electroencephalography study demonstrates with a quick, easily implementable, and noninvasive paradigm that the change in cortical somatosensory excitability during pain observation is limb-specific, and confirms from a neuroscience perspective that being exposed to others’ pain implies more than the sharing of an affective experience.
  • PublicationAccès libre
    Modulation of brain activity during action observation : influence of perspective, transitivity and meaningfulness
    (Public Library of Science, 2011-09-12) Eugène, Fanny; Hétu, Sébastien; Jackson, Philip L.; Mercier, Catherine; Michon, Pierre-Emmanuel
    The coupling process between observed and performed actions is thought to be performed by a fronto-parietal perception-action system including regions of the inferior frontal gyrus and the inferior parietal lobule. When investigating the influence of the movements' characteristics on this process, most research on action observation has focused on only one particular variable even though the type of movements we observe can vary on several levels. By manipulating the visual perspective, transitivity and meaningfulness of observed movements in a functional magnetic resonance imaging study we aimed at investigating how the type of movements and the visual perspective can modulate brain activity during action observation in healthy individuals. Importantly, we used an active observation task where participants had to subsequently execute or imagine the observed movements. Our results show that the fronto-parietal regions of the perception action system were mostly recruited during the observation of meaningless actions while visual perspective had little influence on the activity within the perception-action system. Simultaneous investigation of several sources of modulation during active action observation is probably an approach that could lead to a greater ecological comprehension of this important sensorimotor process.