High frequency electrical stimulation (HFS) of the skin is an experimental procedure known to ind... more High frequency electrical stimulation (HFS) of the skin is an experimental procedure known to induce a robust central sensitization of nociceptive pathways in healthy volunteers [1]. HFS also induces an “enhancement” of the cortical responses to vibrotactile [2] and visual stimuli [3] projected in proximity of the sensitized body part. This enhancement is present 20 minutes after HFS, but disappears 45 minutes after. In this study we investigated if the enhanced cortical processing is mediated by an enhancement of attention towards the sensitized arm. To this aim, we used a temporal order judgment (TOJ) task that is based on the psychophysical law of prior entry, according to which the perception of attended stimuli is speeded up as compared to unattended ones. A prioritization of stimuli applied onto the HFS arm would indicate that HFS induces an attentional bias towards stimuli presented onto the sensitized arm. Our TOJ study does not provide any evidence for a possible perceptual bias towards the HFS arm during secondary hyperalgesia. Our results do not support the possibility that the enhanced cortical processing observed for non-nociceptive and non-somatosensory stimuli applied onto the sensitized arm is mediated by increased attention towards that arm
Recently, Vanden Bulcke, Crombez, Durnez, and Van Damme (2015) investigated whether the attention... more Recently, Vanden Bulcke, Crombez, Durnez, and Van Damme (2015) investigated whether the attentional prioritization of a specific location due to the anticipation of pain is modality specific or multisensory. They used a temporal order judgment task in which participants judged the order of either two tactile or two visual stimuli, one presented on each hand. Additionally, participants either expected the occurrence of a painful stimulus on one hand or the absence of any pain. Results showed that participants' judgments were biased to the advantage of the stimuli, tactile or visual, presented at the location where pain was expected. The authors concluded that the anticipation of pain leads to a multisensory prioritization of information presented at the threatened spatial location. Here, we would like to question their conclusion in terms of a genuine attentional modulation of multisensory nature, based on methodological and theoretical grounds.
Psychophysical and electrophysiological assessments of nociception using laser stimulation reveal... more Psychophysical and electrophysiological assessments of nociception using laser stimulation reveal a marked dysfunction of thermo-nociceptive pathways in the affected limb of patients with chronic CRPS.
For a long time, pain research has focused on understanding the mechanisms underlying the unpleas... more For a long time, pain research has focused on understanding the mechanisms underlying the unpleasant experience generated by a nociceptive stimulus. Cognitive theories emphasize the functional aspects of nociception by defining it as a warning process. Nociceptive inputs are processed in a multisensory processing system that prioritizes stimuli that are meaningful for the integrity of the body and integrates them into multi-frame representations of the body and the proximal space. The ultimate purpose of this multisensory system would be to guide defensive behaviors. Recent experimental evidence supports the role that cognitive functions such as selective attention, spatial perception and motor preparation play in nociceptive processing. In addition, the cognitive approach of pain offers new clinical perspectives by providing a framework for the treatment of chronic pain based on neuropsychological rehabilitation.
Several studies have used neuroimaging techniques in an attempt to characterize brain correlates ... more Several studies have used neuroimaging techniques in an attempt to characterize brain correlates of the attentional modulation of pain. Although these studies have advanced the knowledge in the field, important confounding factors such as imprecise theoretical definitions of attention, incomplete operationalization of the construct under exam, and limitations of techniques relying on measuring regional changes in cerebral blood flow have hampered the potential relevance of the conclusions. Here, we first provide an overview of the major theories of attention and of attention in the study of pain to bridge theory and experimental results. We conclude that load and motivational/affective theories are particularly relevant to study the attentional modulation of pain and should be carefully integrated in functional neuroimaging studies. Then, we summarize previous findings and discuss the possible neural correlates of the attentional modulation of pain. We discuss whether classical functional neuroimaging techniques are suitable to measure the effect of a fluctuating process like attention, and in which circumstances functional neuroimaging can be reliably used to measure the attentional modulation of pain. Finally, we argue that the analysis of brain networks and spontaneous oscillations may be a crucial future development in the study of attentional modulation of pain, and why the interplay between attention and pain, as examined so far, may rely on neural mechanisms shared with other sensory modalities.
Studies have suggested that, alongside sensory, motor and vegetative symptoms, patients with CRPS... more Studies have suggested that, alongside sensory, motor and vegetative symptoms, patients with CRPS also present unilateral cognitive deficits leading to impaired perception and utilization of the affected limb. This has led some authors to propose that CRPS patients present a neglect-like symptomatology similar to the left hemineglect that is classically observed in patients suffering from a lesion of the right hemisphere. In this presentation, we will review the data supporting the existence of neglect-like symptoms in CRPS. We will show that, even though it is clear that CRPS-related changes in cortical function do not only affect sensorimotor processes but also higher-order multisensory processing of spatial information, there is still no agreement as to whether patients with CRPS really present neglect symptoms and, if they do, what it is that they really neglect. Furthermore, we will discuss whether these neglect-like symptoms are specific for CRPS, or whether they can also be observed in other types of lateralized pain syndrome
Continuous theta burst stimulation (cTBS) applied over the primary motor cortex (M1) can alleviat... more Continuous theta burst stimulation (cTBS) applied over the primary motor cortex (M1) can alleviate pain although the neural basis of this effect remains largely unknown. Besides, the primary somatosensory cortex (S1) is thought to play a pivotal role in the sensori-discriminative aspects of pain perception but the analgesic effect of cTBS applied over S1 remains controversial. To investigate cTBS-induced analgesia we characterized, in two separate experiments, the effect of cTBS applied either over M1 or S1 on the event-related brain potentials (ERPs) and perception elicited by nociceptive (CO2 laser stimulation) and non-nociceptive (transcutaneous electrical stimulation) somatosensory stimuli. All stimuli were delivered to the ipsilateral and contralateral hand. We found that both cTBS applied over M1 and cTBS applied over S1 significantly reduced the percept elicited by nociceptive stimuli delivered to the contralateral hand as compared to similar stimulation of the ipsilateral hand. In contrast, cTBS did not modulate the perception of non-nociceptive stimuli. Surprisingly, this side-dependent analgesic effect of cTBS was not reflected in the amplitude modulation of nociceptive ERPs. Indeed, both nociceptive (N160, N240 and P360 waves) and late-latency non-nociceptive (N140 and P200 waves) ERPs elicited by stimulation of the contralateral and ipsilateral hands were similarly reduced after cTBS, suggesting an unspecific effect, possibly due to habituation or reduced alertness. In conclusion, cTBS applied over M1 and S1 reduces similarly the perception of nociceptive inputs originating from the contralateral hand, but this analgesic effect is not reflected in the magnitude of nociceptive ERPs.
High frequency electrical conditioning stimulation (HFS) is an experimental method to induce incr... more High frequency electrical conditioning stimulation (HFS) is an experimental method to induce increased mechanical pinprick sensitivity in the unconditioned surrounding skin (secondary hyperalgesia). Secondary hyperalgesia is thought to be the result of central sensitization, i.e. increased responsiveness of nociceptive neurons in the central nervous system. Vibrotactile and visual stimuli presented in the area of secondary hyperalgesia also elicit enhanced brain responses, a finding that cannot be explained by central sensitization as it is currently defined. HFS may recruit attentional processes, which in turn affect the processing of all stimuli. In this study we have investigated whether HFS induces perceptual biases towards stimuli presented onto the sensitized arm by using Temporal Order Judgment (TOJ) tasks. In TOJ tasks, stimuli are presented in rapid succession on either arm, and participants have to indicate their perceived order. In case of a perceptual bias, the stimuli presented on the attended side are systematically reported as occurring first. Participants performed a tactile and a visual TOJ task before and after HFS. Analyses of participants' performance did not reveal any prioritization of the visual and tactile stimuli presented onto the sensitized arm. Our results provide therefore no evidence for a perceptual bias towards tactile and visual stimuli presented onto the sensitized arm. Cutaneous tissue injury induces increased pain sensitivity (hyperalgesia) within the injured area ("primary" hyperalgesia) and also in the surrounding non-injured skin ("secondary" hyperalgesia). Secondary hyperalgesia is thought to be the result of central sensitization, defined by the International Association for the Study of Pain (IASP) as "an increased responsiveness of nociceptive neurons in the central nervous system to their normal or subthreshold afferent input" 1. Secondary hyperalgesia can also be induced experimentally, for example, after capsaicin treatment 2 or by high frequency electrical stimulation (HFS), which consists of five 1-second trains of painful electrical stimuli delivered on the skin 3,4. By using these methods, studies have showed that secondary hyperalgesia is characterized by increased pain sensitivity to mechanical pinprick stimuli but not heat stimuli 5,6 ; and by increased pinprick evoked potentials (PEPs) 7. Interestingly, previous studies have reported an increase in brain responses measured by event related potentials (ERPs) to non-nociceptive vibrotactile and visual stimuli presented into the area of secondary hyperalgesia 8,9 20 minutes after the end of HFS. This increase cannot be explained in terms of central sensitization as it is currently defined by the IASP 1 (for a debate about the concept of central sensitization please refer to 10,11) and may be considered a corollary HFS-induced effect involving supra-spinal cognitive mechanisms 9 , possibly attentional ones. Attention allocated towards a particular stimulus or location typically leads to a perceptual bias, meaning that the processing of attended stimuli is speeded up at the detriment of unattended ones 12,13. We hypothesized that HFS would increase attentional allocation towards the sensitized arm and consequently induce a perceptual bias towards the sensitized body part leading to a prioritization of the processing of the stimuli applied onto that body part. Indeed, if the aim of sensitization is to protect the body from further injury and promote healing, one might expect that, after inducing sensitization, all sensory stimuli presented on the sensitized body part could
Central sensitization refers to the increased responsiveness of nociceptive neurons in the centra... more Central sensitization refers to the increased responsiveness of nociceptive neurons in the central nervous system after repeated or sustained peripheral nociceptor activation. It is hypothesized to play a key role in the development of chronic pain. A hallmark of central sensitization is an increased sensitivity to noxious mechanical stimuli extending beyond the injured location, known as secondary hyperalgesia. For its ability to modulate the transmission and the processing of nociceptive inputs, attention could constitute a promising target to prevent central sensitization and the development of chronic pain. It was recently shown that the experimental induction of central sensitization at both forearms of healthy volunteers using bilateral high-frequency electrocutaneous stimulation (HFS), can be modulated by encouraging participants to selectively focus their attention to one arm, to the detriment of the other arm, resulting in a greater secondary hyperalgesia on the attended ar...
Part of the multifaceted pathophysiology of Complex Regional Pain syndrome (CRPS) has been ascrib... more Part of the multifaceted pathophysiology of Complex Regional Pain syndrome (CRPS) has been ascribed to a lateralized maladaptive neuroplasticity in sensorimotor cortices, a finding that has been corroborated by behavioral studies indicating that CRPS patients indeed present difficulties in mentally representing their painful limb. Hand laterality judgment tasks (HLT) are widely used to measure such difficulties, with the laterality of hand stimuli corresponding to the affected hand judged more slowly than the one of hand stimuli corresponding to the unaffected hand. Importantly, the HLT is also regularly used in the rehabilitation of CRPS and other chronic pain disorders, with the aim to activate motor imagery and, consequently, restoring the cortical representation of the limb. The potential of these tasks to elicit motor imagery is thus critical to their use in therapy. Yet, the influence of the biomechanical constraints (BMC) on HLT reaction time, supposed to reflect the activati...
Patients with complex regional pain syndrome (CRPS) report cognitive difficulties, affecting the ... more Patients with complex regional pain syndrome (CRPS) report cognitive difficulties, affecting the ability to represent, perceive and use their affected limb. Moseley, Gallace & Spence (2009) observed that CRPS patients tend to bias the perception of tactile stimulation away from the pathological limb. Interestingly, this bias was reversed when CRPS patients were asked to cross their arms, implying that this bias is embedded in a complex representation of the body that takes into account the position of body-parts. Other studies have failed to replicate this finding (Filbrich et al., 2017) or have even found a bias in the opposite direction (Sumitani et al., 2007). Moreover, perceptual biases in CRPS patients have not often been compared to these of other chronic pain patients. Chronic pain patients are often characterized by an excessive focus of attention for bodily sensations. We might therefore expect that non-CRPS pain patients would show a bias towards instead of away from their...
How we perceive our body is shaped by sensory experiences with our surrounding environment, as wi... more How we perceive our body is shaped by sensory experiences with our surrounding environment, as witnessed by poor performance in tasks during which participants judge with their hands crossed the temporal order between two somatosensory stimuli, one applied on each hand. This suggests that somatosensory stimuli are not only processed according to a somatotopic representation but also a spatiotopic representation of the body. We investigated whether the perception of stimuli occurring in external space, such as visual stimuli, can also be influenced by the body posture and somatosensory stimuli. Participants performed temporal order judgements on pairs of visual stimuli, one in each side of space, with their hands uncrossed or crossed. In Experiment 1, participants’ hands were placed either near or far from the visual stimuli. In Experiment 2, the visual stimuli were preceded, either by 60 ms or 360 ms, by tactile stimuli applied on the hands placed near the visual stimuli. Manipulati...
Simultaneous execution of cognitive and sensorimotor tasks is critical in daily life. Here, we ex... more Simultaneous execution of cognitive and sensorimotor tasks is critical in daily life. Here, we examined whether dexterous manipulation, a highly habitual and seemingly automatic behavior, involves high order cognitive functions. Specifically, we explored the impact of reducing available cognitive resources on the performance of a precision grip-lift task in healthy participants of three age groups (18-30, 30-60 and 60-75 years). Participants performed a motor task in isolation (M), in combination with a low-load cognitive task (M + L), and in combination with a high-load cognitive task (M + H). The motor task consisted in grasping, lifting and holding an apparatus instrumented with force sensors to monitor motor task performance. In the cognitive task, a list of letters was shown briefly before the motor task. After completing the motor task, one letter of the list was shown, and participants reported the following letter of the list. In M + L, letters in the list followed the alpha...
High frequency electrical stimulation (HFS) of the skin is an experimental procedure known to ind... more High frequency electrical stimulation (HFS) of the skin is an experimental procedure known to induce a robust central sensitization of nociceptive pathways in healthy volunteers [1]. HFS also induces an “enhancement” of the cortical responses to vibrotactile [2] and visual stimuli [3] projected in proximity of the sensitized body part. This enhancement is present 20 minutes after HFS, but disappears 45 minutes after. In this study we investigated if the enhanced cortical processing is mediated by an enhancement of attention towards the sensitized arm. To this aim, we used a temporal order judgment (TOJ) task that is based on the psychophysical law of prior entry, according to which the perception of attended stimuli is speeded up as compared to unattended ones. A prioritization of stimuli applied onto the HFS arm would indicate that HFS induces an attentional bias towards stimuli presented onto the sensitized arm. Our TOJ study does not provide any evidence for a possible perceptual bias towards the HFS arm during secondary hyperalgesia. Our results do not support the possibility that the enhanced cortical processing observed for non-nociceptive and non-somatosensory stimuli applied onto the sensitized arm is mediated by increased attention towards that arm
Recently, Vanden Bulcke, Crombez, Durnez, and Van Damme (2015) investigated whether the attention... more Recently, Vanden Bulcke, Crombez, Durnez, and Van Damme (2015) investigated whether the attentional prioritization of a specific location due to the anticipation of pain is modality specific or multisensory. They used a temporal order judgment task in which participants judged the order of either two tactile or two visual stimuli, one presented on each hand. Additionally, participants either expected the occurrence of a painful stimulus on one hand or the absence of any pain. Results showed that participants' judgments were biased to the advantage of the stimuli, tactile or visual, presented at the location where pain was expected. The authors concluded that the anticipation of pain leads to a multisensory prioritization of information presented at the threatened spatial location. Here, we would like to question their conclusion in terms of a genuine attentional modulation of multisensory nature, based on methodological and theoretical grounds.
Psychophysical and electrophysiological assessments of nociception using laser stimulation reveal... more Psychophysical and electrophysiological assessments of nociception using laser stimulation reveal a marked dysfunction of thermo-nociceptive pathways in the affected limb of patients with chronic CRPS.
For a long time, pain research has focused on understanding the mechanisms underlying the unpleas... more For a long time, pain research has focused on understanding the mechanisms underlying the unpleasant experience generated by a nociceptive stimulus. Cognitive theories emphasize the functional aspects of nociception by defining it as a warning process. Nociceptive inputs are processed in a multisensory processing system that prioritizes stimuli that are meaningful for the integrity of the body and integrates them into multi-frame representations of the body and the proximal space. The ultimate purpose of this multisensory system would be to guide defensive behaviors. Recent experimental evidence supports the role that cognitive functions such as selective attention, spatial perception and motor preparation play in nociceptive processing. In addition, the cognitive approach of pain offers new clinical perspectives by providing a framework for the treatment of chronic pain based on neuropsychological rehabilitation.
Several studies have used neuroimaging techniques in an attempt to characterize brain correlates ... more Several studies have used neuroimaging techniques in an attempt to characterize brain correlates of the attentional modulation of pain. Although these studies have advanced the knowledge in the field, important confounding factors such as imprecise theoretical definitions of attention, incomplete operationalization of the construct under exam, and limitations of techniques relying on measuring regional changes in cerebral blood flow have hampered the potential relevance of the conclusions. Here, we first provide an overview of the major theories of attention and of attention in the study of pain to bridge theory and experimental results. We conclude that load and motivational/affective theories are particularly relevant to study the attentional modulation of pain and should be carefully integrated in functional neuroimaging studies. Then, we summarize previous findings and discuss the possible neural correlates of the attentional modulation of pain. We discuss whether classical functional neuroimaging techniques are suitable to measure the effect of a fluctuating process like attention, and in which circumstances functional neuroimaging can be reliably used to measure the attentional modulation of pain. Finally, we argue that the analysis of brain networks and spontaneous oscillations may be a crucial future development in the study of attentional modulation of pain, and why the interplay between attention and pain, as examined so far, may rely on neural mechanisms shared with other sensory modalities.
Studies have suggested that, alongside sensory, motor and vegetative symptoms, patients with CRPS... more Studies have suggested that, alongside sensory, motor and vegetative symptoms, patients with CRPS also present unilateral cognitive deficits leading to impaired perception and utilization of the affected limb. This has led some authors to propose that CRPS patients present a neglect-like symptomatology similar to the left hemineglect that is classically observed in patients suffering from a lesion of the right hemisphere. In this presentation, we will review the data supporting the existence of neglect-like symptoms in CRPS. We will show that, even though it is clear that CRPS-related changes in cortical function do not only affect sensorimotor processes but also higher-order multisensory processing of spatial information, there is still no agreement as to whether patients with CRPS really present neglect symptoms and, if they do, what it is that they really neglect. Furthermore, we will discuss whether these neglect-like symptoms are specific for CRPS, or whether they can also be observed in other types of lateralized pain syndrome
Continuous theta burst stimulation (cTBS) applied over the primary motor cortex (M1) can alleviat... more Continuous theta burst stimulation (cTBS) applied over the primary motor cortex (M1) can alleviate pain although the neural basis of this effect remains largely unknown. Besides, the primary somatosensory cortex (S1) is thought to play a pivotal role in the sensori-discriminative aspects of pain perception but the analgesic effect of cTBS applied over S1 remains controversial. To investigate cTBS-induced analgesia we characterized, in two separate experiments, the effect of cTBS applied either over M1 or S1 on the event-related brain potentials (ERPs) and perception elicited by nociceptive (CO2 laser stimulation) and non-nociceptive (transcutaneous electrical stimulation) somatosensory stimuli. All stimuli were delivered to the ipsilateral and contralateral hand. We found that both cTBS applied over M1 and cTBS applied over S1 significantly reduced the percept elicited by nociceptive stimuli delivered to the contralateral hand as compared to similar stimulation of the ipsilateral hand. In contrast, cTBS did not modulate the perception of non-nociceptive stimuli. Surprisingly, this side-dependent analgesic effect of cTBS was not reflected in the amplitude modulation of nociceptive ERPs. Indeed, both nociceptive (N160, N240 and P360 waves) and late-latency non-nociceptive (N140 and P200 waves) ERPs elicited by stimulation of the contralateral and ipsilateral hands were similarly reduced after cTBS, suggesting an unspecific effect, possibly due to habituation or reduced alertness. In conclusion, cTBS applied over M1 and S1 reduces similarly the perception of nociceptive inputs originating from the contralateral hand, but this analgesic effect is not reflected in the magnitude of nociceptive ERPs.
High frequency electrical conditioning stimulation (HFS) is an experimental method to induce incr... more High frequency electrical conditioning stimulation (HFS) is an experimental method to induce increased mechanical pinprick sensitivity in the unconditioned surrounding skin (secondary hyperalgesia). Secondary hyperalgesia is thought to be the result of central sensitization, i.e. increased responsiveness of nociceptive neurons in the central nervous system. Vibrotactile and visual stimuli presented in the area of secondary hyperalgesia also elicit enhanced brain responses, a finding that cannot be explained by central sensitization as it is currently defined. HFS may recruit attentional processes, which in turn affect the processing of all stimuli. In this study we have investigated whether HFS induces perceptual biases towards stimuli presented onto the sensitized arm by using Temporal Order Judgment (TOJ) tasks. In TOJ tasks, stimuli are presented in rapid succession on either arm, and participants have to indicate their perceived order. In case of a perceptual bias, the stimuli presented on the attended side are systematically reported as occurring first. Participants performed a tactile and a visual TOJ task before and after HFS. Analyses of participants' performance did not reveal any prioritization of the visual and tactile stimuli presented onto the sensitized arm. Our results provide therefore no evidence for a perceptual bias towards tactile and visual stimuli presented onto the sensitized arm. Cutaneous tissue injury induces increased pain sensitivity (hyperalgesia) within the injured area ("primary" hyperalgesia) and also in the surrounding non-injured skin ("secondary" hyperalgesia). Secondary hyperalgesia is thought to be the result of central sensitization, defined by the International Association for the Study of Pain (IASP) as "an increased responsiveness of nociceptive neurons in the central nervous system to their normal or subthreshold afferent input" 1. Secondary hyperalgesia can also be induced experimentally, for example, after capsaicin treatment 2 or by high frequency electrical stimulation (HFS), which consists of five 1-second trains of painful electrical stimuli delivered on the skin 3,4. By using these methods, studies have showed that secondary hyperalgesia is characterized by increased pain sensitivity to mechanical pinprick stimuli but not heat stimuli 5,6 ; and by increased pinprick evoked potentials (PEPs) 7. Interestingly, previous studies have reported an increase in brain responses measured by event related potentials (ERPs) to non-nociceptive vibrotactile and visual stimuli presented into the area of secondary hyperalgesia 8,9 20 minutes after the end of HFS. This increase cannot be explained in terms of central sensitization as it is currently defined by the IASP 1 (for a debate about the concept of central sensitization please refer to 10,11) and may be considered a corollary HFS-induced effect involving supra-spinal cognitive mechanisms 9 , possibly attentional ones. Attention allocated towards a particular stimulus or location typically leads to a perceptual bias, meaning that the processing of attended stimuli is speeded up at the detriment of unattended ones 12,13. We hypothesized that HFS would increase attentional allocation towards the sensitized arm and consequently induce a perceptual bias towards the sensitized body part leading to a prioritization of the processing of the stimuli applied onto that body part. Indeed, if the aim of sensitization is to protect the body from further injury and promote healing, one might expect that, after inducing sensitization, all sensory stimuli presented on the sensitized body part could
Central sensitization refers to the increased responsiveness of nociceptive neurons in the centra... more Central sensitization refers to the increased responsiveness of nociceptive neurons in the central nervous system after repeated or sustained peripheral nociceptor activation. It is hypothesized to play a key role in the development of chronic pain. A hallmark of central sensitization is an increased sensitivity to noxious mechanical stimuli extending beyond the injured location, known as secondary hyperalgesia. For its ability to modulate the transmission and the processing of nociceptive inputs, attention could constitute a promising target to prevent central sensitization and the development of chronic pain. It was recently shown that the experimental induction of central sensitization at both forearms of healthy volunteers using bilateral high-frequency electrocutaneous stimulation (HFS), can be modulated by encouraging participants to selectively focus their attention to one arm, to the detriment of the other arm, resulting in a greater secondary hyperalgesia on the attended ar...
Part of the multifaceted pathophysiology of Complex Regional Pain syndrome (CRPS) has been ascrib... more Part of the multifaceted pathophysiology of Complex Regional Pain syndrome (CRPS) has been ascribed to a lateralized maladaptive neuroplasticity in sensorimotor cortices, a finding that has been corroborated by behavioral studies indicating that CRPS patients indeed present difficulties in mentally representing their painful limb. Hand laterality judgment tasks (HLT) are widely used to measure such difficulties, with the laterality of hand stimuli corresponding to the affected hand judged more slowly than the one of hand stimuli corresponding to the unaffected hand. Importantly, the HLT is also regularly used in the rehabilitation of CRPS and other chronic pain disorders, with the aim to activate motor imagery and, consequently, restoring the cortical representation of the limb. The potential of these tasks to elicit motor imagery is thus critical to their use in therapy. Yet, the influence of the biomechanical constraints (BMC) on HLT reaction time, supposed to reflect the activati...
Patients with complex regional pain syndrome (CRPS) report cognitive difficulties, affecting the ... more Patients with complex regional pain syndrome (CRPS) report cognitive difficulties, affecting the ability to represent, perceive and use their affected limb. Moseley, Gallace & Spence (2009) observed that CRPS patients tend to bias the perception of tactile stimulation away from the pathological limb. Interestingly, this bias was reversed when CRPS patients were asked to cross their arms, implying that this bias is embedded in a complex representation of the body that takes into account the position of body-parts. Other studies have failed to replicate this finding (Filbrich et al., 2017) or have even found a bias in the opposite direction (Sumitani et al., 2007). Moreover, perceptual biases in CRPS patients have not often been compared to these of other chronic pain patients. Chronic pain patients are often characterized by an excessive focus of attention for bodily sensations. We might therefore expect that non-CRPS pain patients would show a bias towards instead of away from their...
How we perceive our body is shaped by sensory experiences with our surrounding environment, as wi... more How we perceive our body is shaped by sensory experiences with our surrounding environment, as witnessed by poor performance in tasks during which participants judge with their hands crossed the temporal order between two somatosensory stimuli, one applied on each hand. This suggests that somatosensory stimuli are not only processed according to a somatotopic representation but also a spatiotopic representation of the body. We investigated whether the perception of stimuli occurring in external space, such as visual stimuli, can also be influenced by the body posture and somatosensory stimuli. Participants performed temporal order judgements on pairs of visual stimuli, one in each side of space, with their hands uncrossed or crossed. In Experiment 1, participants’ hands were placed either near or far from the visual stimuli. In Experiment 2, the visual stimuli were preceded, either by 60 ms or 360 ms, by tactile stimuli applied on the hands placed near the visual stimuli. Manipulati...
Simultaneous execution of cognitive and sensorimotor tasks is critical in daily life. Here, we ex... more Simultaneous execution of cognitive and sensorimotor tasks is critical in daily life. Here, we examined whether dexterous manipulation, a highly habitual and seemingly automatic behavior, involves high order cognitive functions. Specifically, we explored the impact of reducing available cognitive resources on the performance of a precision grip-lift task in healthy participants of three age groups (18-30, 30-60 and 60-75 years). Participants performed a motor task in isolation (M), in combination with a low-load cognitive task (M + L), and in combination with a high-load cognitive task (M + H). The motor task consisted in grasping, lifting and holding an apparatus instrumented with force sensors to monitor motor task performance. In the cognitive task, a list of letters was shown briefly before the motor task. After completing the motor task, one letter of the list was shown, and participants reported the following letter of the list. In M + L, letters in the list followed the alpha...
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