Mental rotation of body parts and non-corporeal objects in patients with idiopathic cervical dystonia

Impact of chronic low back pain on implicit motor imagery assessed by a new laterality judgment task

It is clear that implicit motor imagery (IMI) is impaired by chronic pain in peripheral regions (hand, feet), but unclear in axial regions (neck, shoulder, back). Previous IMI tasks displayed small-amplitude movements of axial regions, which limits person-centered IMI processes mobilization. This study aimed to assess the impact of chronic low back pain (CLBP) on IMI processes with a new task displaying large-amplitude whole-body movements mobilizing the lumbar spine. Twenty patients with CLBP and twenty age-matched controls performed a laterality judgment task on four distinct whole-body movements (trunk flexion, trunk rotation, capoeira, kickboxing). Participants viewed images from four different body viewpoints (back, left, right and front), randomly presented. Mixed ANOVAs were used to compare judgment accuracy and response times between groups and conditions. In participants with CLBP, response times were longer than in controls. The response times of participants with CLBP were also associated with DN4 scores, a self-reported questionnaire assessing neuropathic pain. We validated the use of a person-centered IMI because, for all participants, the accuracy decreased and the response times increased for images presented in the front viewpoint, i.e. when a 180° turn in IMI was required, compared to other viewpoints. The laterality judgment task proposed here confirmed that CLBP impacts IMI processes, and that the nature of pain (neuropathic or mechanical) needs to be considered because it seems to modulate IMI processes. PERSPECTIVES: A laterality judgment task with large-amplitude lumbar movements is key to show that CLBP alters processing speed of sensorimotor information originating from the painful region. This task could become an objective tool, transferable in clinical settings, for assessing the impact and the progression of CLBP on motor control processes.

Anatomical predictors of mental rotation with bodily and non-bodily stimuli: A lesion-symptom study

Mental rotation (MR) is widely regarded as a quintessential example of an embodied cognitive process. This viewpoint stems from the functional parallels between MR and the physical rotation of tangible objects, as well as participants' inclination to employ motor-based strategies when tackling MR tasks involving bodily stimuli. These commonalities imply that MR may depend on brain regions crucial for the planning and execution of motor programs. However, there is disagreement regarding the anatomy of MR between findings from functional imaging and lesion studies involving brain-injured patients. The former indicate the involvement of the right-hemispheric parietal cortex, while the latter underscore the significance of posterior areas in the left hemisphere. In this study, we aimed to discern the neural underpinnings of MR using lesion-symptom mapping (LSM) for both bodily (hands) and non-bodily (letters) stimuli. Behavioral results from the two MR tasks revealed impaired MR of bodily stimuli in patients with left hemisphere damage. LSM results pinpointed the left primary motor and somatosensory cortices, along with the superior parietal lobule, as the anatomical substrates of MR for both bodily and non-bodily stimuli. Furthermore, damage to the left angular gyrus, supramarginal gyrus, supplementary motor area, and retrosplenial cortex was associated with MR of non-bodily stimuli. These findings support the causal involvement of the left hemisphere in MR and underscore the existence of a common anatomical substrate in brain regions pertinent to motor planning and execution.

Imaging the Spin: Disentangling the Core Processes Underlying Mental Rotation by Network Mapping of Data From Meta-analysis

Research on the mental rotation task has sparked debate regarding the specific processes that underly the capability of humans to mentally rotate objects. The spread of reported brain activations suggests that mental rotation is subserved by a neural network circle. However, no common network has yet been found that uncovers the crucial processes underlying this ability. We aimed to identify the common network crucial for mental rotation by coordinate-based network mapping of previous neuroimaging findings in mental rotation. A meta-analysis revealed 710 peak activation coordinates from 42 fMRI studies in mental rotation, which include a total 844 participants. The coordinates were mapped to a normative functional connectome (n = 1000) to identify a network of connected regions. To account for experimental factors, we examined this network against two control tasks, action imitation and symbolic number processing. A common and crucial network for mental rotation, centring on dorsal premotor, superior parietal and inferior temporal lobes was revealed. This network, separated from other experimental aspects, suggests that the crucial processes underlying mental rotation are motor rotation, visuospatial processing, and higher order visual object recognition.

Topological differences and confounders of mental rotation in cervical dystonia and blepharospasm

Mental rotation (mR) bases on imagination of actual movements. It remains unclear whether there is a specific pattern of mR impairment in focal dystonia. We aimed to investigate mR in patients with cervical dystonia (CD) and blepharospasm (BS) and to assess potential confounders. 23 CD patients and 23 healthy controls (HC) as well as 21 BS and 19 hemifacial spasm (HS) patients were matched for sex, age, and education level. Handedness, finger dexterity, general reaction time, and cognitive status were assessed. Disease severity was evaluated by clinical scales. During mR, photographs of body parts (head, hand, or foot) and a non-corporal object (car) were displayed at different angles rotated within their plane. Subjects were asked to judge laterality of the presented image by keystroke. Both speed and correctness were evaluated. Compared to HC, CD and HS patients performed worse in mR of hands, whereas BS group showed comparable performance. There was a significant association of prolonged mR reaction time (RT) with reduced MoCA scores and with increased RT in an unspecific reaction speed task. After exclusion of cognitively impaired patients, increased RT in the mR of hands was confined to CD group, but not HS. While the question of whether specific patterns of mR impairment reliably define a dystonic endophenotype remains elusive, our findings point to mR as a useful tool, when used carefully with control measures and tasks, which may be capable of identifying specific deficits that distinguish between subtypes of dystonia.

Event-related potentials during mental rotation of body-related stimuli in spinal cord injury population

Mental rotations of body-related stimuli are known to engage the motor system and activate body schema. Sensorimotor deficits following spinal cord injury (SCI) alter the representation of the body with a negative impact on the performance during motor-related tasks, such as mental rotation of body parts. Here we investigated the relationship between event-related potentials in SCI participants and the difficulty in mentally rotating a body-part. Participants with SCI and healthy control subjects performed a laterality judgment task, in which left or right images of hands, feet or animals (as a control stimulus) were presented in two different orientation angles (75° and 150°), and participants reported the laterality of the stimulus. We found that reaction times of participants with SCI were slower for the rotation of body-related stimuli compared to non-body-related stimuli and healthy controls. At the brain level, we found that relative to healthy controls SCI participants show: 1) reduced amplitudes of the posterior P100 and anterior N100 and larger amplitudes of the anterior P200 for overall stimuli; 2) an absence of the modulation of the rotation related negativity by stimulus type and rotation angles. Our results show that body representation changes after SCI affecting both components of early stimulus processing and late components that process high-order cognitive aspects of body-representation and task complexity.

Imagined paralysis reduces motor cortex excitability

Mental imagery is a powerful capability that engages similar neurophysiological processes that underlie real sensory and motor experiences. Previous studies show that motor cortical excitability can increase during mental imagery of actions. In this study, we focused on possible inhibitory effects of mental imagery on motor functions. We assessed whether imagined arm paralysis modulates motor cortical excitability in healthy participants, as measured by motor evoked potentials (MEPs) of the hand induced by near-threshold transcranial magnetic stimulation (TMS) over the primary motor cortex hand area. We found lower MEP amplitudes during imagined arm paralysis when compared to imagined leg paralysis or baseline stimulation without paralysis imagery. These results show that purely imagined bodily constraints can selectively inhibit basic motor corticospinal functions. The results are discussed in the context of motoric embodiment/disembodiment.

Using crutches during walking possibly reduces gait imagery accuracy among healthy young and older adults

[Purpose] Although crutches are widely used in the field of rehabilitation to improve gait performance, patients usually have difficulties using them, and this may increase their risks for falls. This study aimed to define the accuracy of gait imagery during walking with and without crutches, in healthy young and older adults, using the mental chronometry method. [Participants and Methods] Overall, 99 healthy young (mean age, 20.2 ± 1.0 years) and 39 healthy older adults (mean age, 71.3 ± 2.9 years) performed the imagery and execution tasks, which involved walking through a distance of 10 meters both with and without crutches. Using the mental chronometry method, the accuracy of the motor imagery was defined as the difference between the imagery time and the actual execution time. Two-way analysis of variance and one-sample t-tests were performed to evaluate the accuracy of the gait imagery. [Results] Both the young and older adults significantly overestimated their gait speeds when using crutches; the overestimation was larger among the older adults. [Conclusion] The overestimations indicate that participants estimated their gait speeds with crutches to be faster than their actual speeds. Therefore, using crutches decreased the accuracy of gait imagery and might therefore increase an individual’s risk of falling during walking.

Maladaptive reorganization following SCI: The role of body representation and multisensory integration

In this review we focus on maladaptive brain reorganization after spinal cord injury (SCI), including the development of neuropathic pain, and its relationship with impairments in body representation and multisensory integration. We will discuss the implications of altered sensorimotor interactions after SCI with and without neuropathic pain and possible deficits in multisensory integration and body representation. Within this framework we will examine published research findings focused on the use of bodily illusions to manipulate multisensory body representation to induce analgesic effects in heterogeneous chronic pain populations and in SCI-related neuropathic pain. We propose that the development and intensification of neuropathic pain after SCI is partly dependent on brain reorganization associated with dysfunctional multisensory integration processes and distorted body representation. We conclude this review by suggesting future research avenues that may lead to a better understanding of the complex mechanisms underlying the sense of the body after SCI, with a focus on cortical changes.

The effect of handedness on mental rotation of hands: a systematic review and meta-analysis

Body-specific mental rotation is thought to rely upon internal representations of motor actions. Handedness is a source of distinctly different motor experience that shapes the development of such internal representations. Yet, the influence of handedness upon hand mental rotation has never been systematically evaluated. Five databases were searched for studies evaluating hand left/right judgement tasks in adults. Two independent reviewers performed screening, data extraction, and critical appraisal. Eighty-seven datasets were included, with 72 datasets pooled; all had unclear/high risk of bias. Meta-analyses showed that right-handers were faster, but not more accurate, than left-handers at hand mental rotation. A unique effect of handedness was found on performance facilitation for images corresponding to the dominant hand. Meta-analyses showed that right-handers were quicker at identifying images of right hands than left hands-a dominance advantage not evident in left-handers. Differing hand representations (more lateralised hand dominance in right-handers) likely underpin these findings. Given potential differences between hand preference and motor performance, future research exploring their distinct contributions to mental rotation is warranted.

Spatial and egocentric mental rotation in patients with cervical dystonia

Mental rotation has attracted the interest of cognitive research on dystonia, but at the moment, contrasting data are available on whether this complex cognitive ability is impaired in the disorder. Here, we assessed spatial and egocentric mental rotation in patients with cervical dystonia (CD). Patients with CD and healthy controls were required to perform a letter rotation task (spatial mental rotation) and to judge laterality of front-facing and back-facing human images (egocentric mental rotation). CD patients were selectively impaired on letter rotation, whereas they did not differ from controls when judging laterality of both front-facing and back-facing bodies. These findings support the view according to which neural circuits involved in spatial processing are dysfunctional in CD.

Mental rotation of feet in individuals with Body Integrity Identity Disorder, lower-limb amputees, and normally-limbed controls

Body Integrity Identity Disorder (BIID) is a non-psychotic condition wherein individuals desire amputation or paralysis of one or more healthy, fully-functioning limbs (predominantly the legs). Individuals with BIID have been suggested to have a mismatch between the perceived mental representation of the body and its actual physical structure, such that their desired identity matches that of a lower-limb amputee. Accordingly, studies have reported an altered central network involving body representation of the legs in BIID, but its relationship to behavior remains unclear. In the present study, we investigated the integrity of body representation in individuals with BIID, acquired lower-limb amputees, and normally-limbed controls using an online mental rotation task. Participants judged the laterality of left and right foot images presented from different views, orientations, and of different types. We expected BIID participants to be slower for mentally rotating images that corresponded to their affected legs than lower-limb amputees and normally-limbed participants. We found that the groups did not significantly differ in their performance. All participants were slower at judging feet presented in awkward postures than natural postures, replicating previous studies and validating our online paradigm. The results are discussed in terms of the robust nature of visual and sensorimotor lower-limb representations, whether related to the self or as prototype, in the context of disturbed lower-limb integrity.

Sensorimotor Control in Dystonia

This is an overview of the sensorimotor impairments in dystonia, a syndrome characterized by sustained or intermittent aberrant movement patterns leading to abnormal movements and/or postures with or without a tremulous component. Dystonia can affect the entire body or specific body regions and results from a plethora of etiologies, including subtle changes in gray and white matter in several brain regions. Research over the last 25 years addressing topics of sensorimotor control has shown functional sensorimotor impairments related to sensorimotor integration, timing, oculomotor and head control, as well as upper and lower limb control. In the context of efforts to update the classification of dystonia, sensorimotor research is highly relevant for a better understanding of the underlying pathology, and potential mechanisms contributing to global and regional dysfunction within the central nervous system. This overview of relevant research regarding sensorimotor control in humans with idiopathic dystonia attempts to frame the dysfunction with respect to what is known regarding motor control in patients and healthy individuals. We also highlight promising avenues for the future study of neuromotor control that may help to further elucidate dystonia etiology, pathology, and functional characteristics.

Comparison of brain activity between motor imagery and mental rotation of the hand tasks: a functional magnetic resonance imaging study

Motor imagery (MI) has been considered effective in learning and practicing movements in many fields. However, when evaluating the effectiveness of this technique, the examiner has no way of assessing the participant’s motor imagery process. As an alternative, we have been exploring a mental body-part rotation task, in which the examiner can estimate the participant’s motivation and ability to sustain attention through the scored results. In this study, we aimed to investigate the possible application of a mental rotation (MRot) task and used fMRI to compare the brain activity during the MRot task with that during an MI task in healthy volunteers. Increased blood oxygenation level-dependent signals were observed bilaterally in the premotor areas and supplementary motor area during performance of both MI and MRot tasks. Our findings suggest that MRot could be an alternative to MI.

Reliability and validity of a mobile tablet for assessing left/right judgements

BACKGROUND

Left/right judgement (LRJ) of body parts is commonly used to assess the ability to perform implicit motor imagery and the integrity of brain-grounded maps of the body. Clinically, LRJ are often undertaken using a mobile tablet, but the concurrent validity and reliability of this approach has not yet been established.

OBJECTIVES

To evaluate the concurrent validity and test-retest reliability of a mobile tablet for assessing LRJ.

METHOD

Participants completed LRJ for 50 hand images (Experiment 1), and 40 back, foot, or neck images (Experiment 2) using a mobile tablet and desktop computer in random order. Participants in Experiment 2 performed a repeat test the following day to assess test-retest reliability. Accuracy and response time (RT) were recorded.

RESULTS

Twenty participants aged 55.3 (±6.7) years in Experiment 1, and 37 participants aged 38.2 (±12.3) years in Experiment 2, were recruited. Concurrent validity of the mobile tablet was good to excellent for hand judgements (ICC_3,1 = 0.836 for RT; ICC = 0.909 for accuracy), and was good for back, foot, and neck judgements (ICC = 0.781 for accuracy; ICC = 0.880 for RT). Test-retest reliability of the mobile tablet was good to excellent (ICC = 0.824 for accuracy; ICC = 0.903 for RT).

CONCLUSIONS

The mobile tablet demonstrated good to excellent concurrent validity with the desktop computer in two separate samples. The mobile tablet also demonstrated good to excellent test-retest reliability. The mobile tablet for LRJ is a valid alternative to the original desktop version.

Differential influence of habitual third-person vision of a body part on mental rotation of images of hands and feet

Left/right judgement (LRJ) tasks involve determining the laterality of presented hand or feet images. Allocentric images (third-person perspective; 3PP) take longer to identify than egocentric images (first-person perspective; 1PP), supporting that implicit motor imagery (IMI)-mentally manoeuvring one's body to match the shown posture-is used. While numerous cognitive processes are involved during LRJs, it remains unclear whether features of the individual (e.g., visual exposure, experience, task-dependent use) influence the type of recognition strategy used during LRJs (IMI versus non-IMI). To investigate whether an individual's routine visual exposure to hands/feet in 3PP disrupts the typical perspective-reaction time (RT) relationship in LRJs, hand therapists, podiatrists, and healthy controls completed online LRJ tasks of hand and feet images. A group-specific reduction in RT for only allocentric images would represent a switch to non-IMI strategies. The results show that routine visual exposure to feet in 3PP (podiatrists) results in quicker RTs only for allocentric images of feet, suggesting a switch from IMI to non-IMI (e.g., visual object-based recognition) strategies. In contrast, routine visual exposure to hands in 3PP (hand therapists) does not alter RT for allocentric images, suggesting maintenance of IMI. However, hand therapists have quicker RTs (vs other groups) for egocentric hand images, supporting enhanced sensorimotor processing for the hand, consistent with task-dependent use (precise hand use). Higher accuracy in health professionals (vs control) on both tasks supports enhanced body schema. Combined, this suggests that 3PP visual exposure to body parts and task-dependent use contribute to LRJ performance/recognition strategy.

Effect of acute experimental hand pain on left-right discrimination response latency for hand recognition

Background: Recent work has indicated that acute experimental pain affects left-right discrimination latency. This phenomenon highlights an effect of pain on the cortex that may have significant clinical importance in the form of pain state assessment. However, to date only limited study has further qualified this effect. A more thorough understanding of the magnitude and characteristics of this phenomenon is needed to determine its potential clinical utility. Objective: This study aimed to closely replicate previous studies investigating response latency changes for left-right discrimination judgements as a result of acute experimental pain. Methods: Twenty-two right-handed participants (n = 11 female, n = 11 male) free from pain, analgesia use, pain-related conditions, upper limb trauma/conditions, visual impairment, and dyslexia took part in this study. Participants completed a hand left-right discrimination judgement task before, during, and after an experimental pain stimulus was delivered to each hand separately. Experimental pain was achieved using an intramuscular injection of hypertonic (5%) saline into the thenar eminence of the left and right hands. Mean response times for the left-right discrimination task were determined and compared for pain location (right, left), pain condition (before, during, after), and image laterality (right, left). Pain intensity was rated at 20 s intervals during each left-right discrimination task. Results: A main effect of pain condition (p = 0.028) confirmed that pain intensity was significantly higher in the "during pain" condition compared to the "before pain" and "after pain" conditions. A main effect of image laterality (p = 0.002) further showed that response latency for right-hand pain was significantly shorter compared to left-hand pain. No significant interaction between the factors pain location and image laterality (p = 0.086) was found. For right-hand pain, response latencies for the unaffected hand were, however, descriptively greater compared to the affected hand, and this was not the case for left-hand pain. Furthermore, no main effect of pain stimulus or of pain location on response times was found (p = 1.00 and p = 0.202, respectively). Conclusion: Our results were not consistent with previous hand left-right discrimination response latency results and may cast doubt on the attentional bias hypothesis that is currently considered to underpin response latency changes during acute experimental hand pain. Individual responses to pain, subsets of participants, and differing mental rotation strategies during the left-right discrimination task may have influenced the results.

Laterality judgment performance between people with chronic pain and pain-free individuals. A systematic review and meta-analysis

Background: Treatment of chronic pain is challenging and there is often failure of recovery, with the need to look at different approaches in its management. Central mechanisms may contribute to chronicity (i.e. disturbance in body schema). Laterality judgment is dependent on body schema and can determine affected central mechanisms. Objective: This review aimed to determine whether there are laterality judgment differences between chronic pain and pain-free individuals. Methods: A search was done of various databases, using combinations of keywords, and reference lists of full-text articles. Articles were considered from inception until February 2018. Eighteen studies were included. Methodological quality was assessed by two reviewers using the JBI Critical Appraisal Checklist. Studies were analyzed broadly then divided into subgroups. A meta-analysis or narrative review was done. Results: There was high heterogeneity for broad outcome measures, complex regional pain syndrome (CRPS1), and upper limb pain. Analysis for accuracy in lower limb conditions showed a medium significant effect size (0.59) and significant 95%CI (0.11-1.07). Low back and cervical pain results could not be pooled into meta-analysis (due to different methods of reporting). Conclusions: Laterality judgment impairment was shown in CPRS1, upper limb pain, hand and wrist pain, carpal-tunnel syndrome, facial pain, knee osteoarthritis, and leg pain. No conclusions could be drawn in low back pain, due to the low-quality evidence and differing results. There was no impairment in whiplash-associated disorders and nonspecific cervical pain showed conflicting evidence.

Difference in Response to a Motor Imagery Task: A Comparison between Individuals with and without Painful Temporomandibular Disorders

The aim of the study was to investigate the difference in response to a motor imagery task between individuals with and without painful temporomandibular disorders (TMDs). The participants were 24 adults with and without TMD (TMD and control group, resp.). A set of photographic images of the profile view of a person's head and neck and a hand and a foot were presented in a random order. The set consisted of six different orientations with rotations of each image at 0, 60, 120, 180, 240, and 300 degrees and included left and right representations. The participants were required to view the image and make a decision as to whether it was a left or a right side presented, that is, mental rotation (MR) task. Data were collected on 48 tasks (including left and right) at each orientation for each body part. Reaction times (RTs) for correct answers and accuracy in making the left or right judgements were recorded. The RT was slower in the TMD group than in the control group. The RT for the profile image was slower than those for the hand and foot images. For images that were 180 degrees, the RT was slower and the accuracy was lower than those for five of the other image orientations. The judgements made about the 180-degree rotated image were more inaccurate compared to images of all other orientations among all types of stimuli.

The development of a shoulder specific left/right judgement task: Validity & reliability

BACKGROUND

Disruption of cortically-held working body schema has been associated with a variety of pain conditions. A motor imagery technique - the left right judgement task (LRJT) - has been used as an indirect assessment of the integrity of the working body schema. To date there is no LRJT specifically designed to investigate the body schema of persons with shoulder pain.

OBJECTIVES

To develop a shoulder specific LRJT and assess its validity and reliability.

DESIGN

Cross-sectional repeated measures.

METHODS

Shoulder images were developed representing the shoulder in a variety of postures of graded complexity/awkwardness and degree of rotation. These images were digitally mirrored to represent both left and right shoulders. Participants viewed the images on a computer and determined whether images were of a left or right shoulder.

RESULTS

1413 participants were recruited worldwide and performed the shoulder LRJT (laterality judgement). Mean response time (SD) for the task was 1738(741) ms. Mean accuracy (SD) was 93.5(9.2)%. Chronbach's Alpha for shoulder image response times was 0.95. Participants were fastest responding to images of simple postures and slowest to images corresponding to the more awkward postures (mean difference 520 ms, 95%CI 469-570 ms). Participants were fastest responding to the least rotated images and slowest responding to inverted images, (mean difference 981 ms, 95%CI 919-1043 ms).

CONCLUSIONS

The shoulder specific LRJT proved to be highly reliable. Response times increased with complexity and rotation of images, implying a motor imagery strategy was used to complete the task, validating the task as a measure of shoulder joint implicit motor imagery. Abnormal performance cut-offs for age were reported. This result will enable further research examining the relationship between shoulder pain and body schema.

Mental rotation and working memory in musicians' dystonia

BACKGROUND

Mental rotation of body parts engages cortical-subcortical areas that are actually involved in the execution of a movement. Musicians' dystonia is a type of focal hand dystonia that is grouped together with writer's cramp under the rubric of "occupational dystonia", but it is unclear to which extent these two disorders share common pathophysiological mechanisms. Previous research has demonstrated patients with writer's cramp to have deficits in mental rotation of body parts. It is unknown whether patients with musicians' dystonia would display similar deficits, reinforcing the concept of shared pathophysiology.

METHODS

Eight patients with musicians' dystonia and eight healthy musicians matched for age, gender and musical education, performed a number of tasks assessing mental rotation of body parts and objects as well as verbal and spatial working memories abilities.

RESULTS

There were no differences between patients and healthy musicians as to accuracy and reaction times in any of the tasks.

CONCLUSIONS

Patients with musicians' dystonia have intact abilities in mentally rotating body parts, suggesting that this disorder relies on a highly selective disruption of movement planning and execution that manifests only upon playing a specific instrument. We further demonstrated that mental rotation of body parts and objects engages, at least partially, different cognitive networks.

Explicit Agency in Patients with Cervical Dystonia: Altered Recognition of Temporal Discrepancies between Motor Actions and Their Feedback

BACKGROUND

Abnormalities in the cognitive processing of movement have been demonstrated in patients with dystonia. The sense of agency, which is the experience of initiating and controlling one's own actions, has never before been studied in these patients.

OBJECTIVES

We investigated whether the sense of agency is altered in patients with cervical dystonia.

METHODS

We used an explicit metacognitive agency task in which participants had to catch targets with a cursor by moving a computer's mouse. The task included several conditions in which the control over the cursor could be disrupted by adding a spatial or a temporal discrepancy between the mouse and the cursor's movements. Participants had to acknowledge these discrepancies and reflect them in metacognitive judgements of agency.

RESULTS

Twenty cervical dystonia patients and 20 matched controls were included in the study. Despite performing equally well as the matched controls, cervical dystonia patients did not fully recognize alterations of agency when a temporal lag was added between their movement and the visual feedback. Moreover, they relied predominantly on their perceived performance to provide judgements of agency and less on their objective degree of controls. There was no correlation between agency scores and clinical severity of dystonia measured by the Toronto Western Spasmodic Torticollis Rating Scale.

CONCLUSION

We demonstrated an abnormal processing of agency in cervical dystonia patients, even for motor actions not affected by dystonia. The exact contribution of abnormal agency to dystonia pathophysiology remains to be clarified.

Laterality judgments in people with low back pain--A cross-sectional observational and test-retest reliability study

BACKGROUND

Disruption of cortical representation, or body schema, has been indicated as a factor in the persistence and recurrence of low back pain (LBP). This has been observed through impaired laterality judgment ability and it has been suggested that this ability is affected in a spatial rather than anatomical manner.

OBJECTIVES

We compared laterality judgment performance of foot and trunk movements between people with LBP with or without leg pain and healthy controls, and investigated associations between test performance and pain. We also assessed the test-retest reliability of the Recognise Online™ software when used in a clinical and a home setting.

DESIGN

Cross-sectional observational and test-retest study.

METHODS

Thirty individuals with LBP and 30 healthy controls performed judgment tests of foot and trunk laterality once supervised in a clinic and twice at home.

RESULTS

No statistically significant group differences were found. LBP intensity was negatively related to trunk laterality accuracy (p = 0.019). Intraclass correlation values ranged from 0.51 to 0.91. Reaction time improved significantly between test occasions while accuracy did not.

CONCLUSIONS

Laterality judgments were not impaired in subjects with LBP compared to controls. Further research may clarify the relationship between pain mechanisms in LBP and laterality judgment ability. Reliability values were mostly acceptable, with wide and low confidence intervals, suggesting test-retest reliability for Recognise Online™ could be questioned in this trial. A significant learning effect was observed which should be considered in clinical and research application of the test.

Sensory-motor integration in focal dystonia

Traditional definitions of focal dystonia point to its motor component, mainly affecting planning and execution of voluntary movements. However, focal dystonia is tightly linked also to sensory dysfunction. Accurate motor control requires an optimal processing of afferent inputs from different sensory systems, in particular visual and somatosensory (e.g., touch and proprioception). Several experimental studies indicate that sensory-motor integration - the process through which sensory information is used to plan, execute, and monitor movements - is impaired in focal dystonia. The neural degenerations associated with these alterations affect not only the basal ganglia-thalamic-frontal cortex loop, but also the parietal cortex and cerebellum. The present review outlines the experimental studies describing impaired sensory-motor integration in focal dystonia, establishes their relationship with changes in specific neural mechanisms, and provides new insight towards the implementation of novel intervention protocols. Based on the reviewed state-of-the-art evidence, the theoretical framework summarized in the present article will not only result in a better understanding of the pathophysiology of dystonia, but it will also lead to the development of new rehabilitation strategies.

Dynamic cortical gray matter volume changes after botulinum toxin in cervical dystonia

Previous electrophysiological and functional imaging studies in focal dystonia have reported on cerebral reorganization after botulinum toxin (BoNT) injections. With the exception of microstructural changes, alterations in gray matter volume after BoNT have not been explored. In this study, we sought to determine whether BoNT influences gray matter volume in a group of cervical dystonia (CD) patients. We analyzed whole brain gray matter volume in a sample of CD patients with VBM analysis. In patients, scans were repeated immediately before and some weeks after BoNT injections; controls were only scanned once. We analyzed 1) BoNT-related gray matter volume changes within patients; 2) gray matter volume differences between patients and controls; and 3) correlations between gray matter volume and disease duration and disease severity. The pre- and post-BoNT treatment analysis revealed an increase of gray matter volume within the right precentral sulcus, at the lateral border of the premotor cortex. In comparison to healthy controls, CD patients had reduced gray matter volume in area 45 functionally corresponding to the left ventral premotor cortex. No gray matter volume increase was found for CD patients in comparison to controls. Gray matter volume of the left supramarginal gyrus and left premotor cortex correlated positively with disease duration, and that of the right inferior parietal lobule correlated negatively with disease severity. We have identified structural, yet dynamic gray matter volume changes in CD. There were specific gray matter volume changes related to BoNT injections, illustrating indirect central consequences of modified peripheral sensory input. As differences were exclusively seen in higher order motor areas relevant to motor planning and spatial cognition, these observations support the hypothesis that deficits in these cognitive processes are crucial in the pathophysiology of CD.

Focal dystonia and the Sensory-Motor Integrative Loop for Enacting (SMILE)

Performing accurate movements requires preparation, execution, and monitoring mechanisms. The first two are coded by the motor system, the latter by the sensory system. To provide an adaptive neural basis to overt behaviors, motor and sensory information has to be properly integrated in a reciprocal feedback loop. Abnormalities in this sensory-motor loop are involved in movement disorders such as focal dystonia, a hyperkinetic alteration affecting only a specific body part and characterized by sensory and motor deficits in the absence of basic motor impairments. Despite the fundamental impact of sensory-motor integration mechanisms on daily life, the general principles of healthy and pathological anatomic–functional organization of sensory-motor integration remain to be clarified. Based on the available data from experimental psychology, neurophysiology, and neuroimaging, we propose a bio-computational model of sensory-motor integration: the Sensory-Motor Integrative Loop for Enacting (SMILE). Aiming at direct therapeutic implementations and with the final target of implementing novel intervention protocols for motor rehabilitation, our main goal is to provide the information necessary for further validating the SMILE model. By translating neuroscientific hypotheses into empirical investigations and clinically relevant questions, the prediction based on the SMILE model can be further extended to other pathological conditions characterized by impaired sensory-motor integration.

Reliabilities of mental rotation tasks: limits to the assessment of individual differences

Mental rotation tasks with objects and body parts as targets are widely used in cognitive neuropsychology. Even though these tasks are well established to study between-groups differences, the reliability on an individual level is largely unknown. We present a systematic study on the internal consistency and test-retest reliability of individual differences in mental rotation tasks comparing different target types and orders of presentations. In total n = 99 participants (n = 63 for the retest) completed the mental rotation tasks with hands, feet, faces, and cars as targets. Different target types were presented in either randomly mixed blocks or blocks of homogeneous targets. Across all target types, the consistency (split-half reliability) and stability (test-retest reliabilities) were good or acceptable both for intercepts and slopes. At the level of individual targets, only intercepts showed acceptable reliabilities. Blocked presentations resulted in significantly faster and numerically more consistent and stable responses. Mental rotation tasks—especially in blocked variants—can be used to reliably assess individual differences in global processing speed. However, the assessment of the theoretically important slope parameter for individual targets requires further adaptations to mental rotation tests.

Continuous theta burst stimulation (cTBS) on left cerebellar hemisphere affects mental rotation tasks during music listening

Converging evidence suggests an association between spatial and music domains. A cerebellar role in music-related information processing as well as in spatial-temporal tasks has been documented. Here, we investigated the cerebellar role in the association between spatial and musical domains, by testing performances in embodied (EMR) or abstract (AMR) mental rotation tasks of subjects listening Mozart Sonata K.448, which is reported to improve spatial-temporal reasoning, in the presence or in the absence of continuous theta burst stimulation (cTBS) of the left cerebellar hemisphere. In the absence of cerebellar cTBS, music listening did not influence either MR task, thus not revealing a "Mozart Effect". Cerebellar cTBS applied before musical listening made subjects faster (P = 0.005) and less accurate (P = 0.005) in performing the EMR but not the AMR task. Thus, cerebellar inhibition by TBS unmasked the effect of musical listening on motor imagery. These data support a coupling between music listening and sensory-motor integration in cerebellar networks for embodied representations.

Task-free functional MRI in cervical dystonia reveals multi-network changes that partially normalize with botulinum toxin

Cervical dystonia is characterized by involuntary, abnormal movements and postures of the head and neck. Current views on its pathophysiology, such as faulty sensorimotor integration and impaired motor planning, are largely based on studies of focal hand dystonia. Using resting state fMRI, we explored whether cervical dystonia patients have altered functional brain connectivity compared to healthy controls, by investigating 10 resting state networks. Scans were repeated immediately before and some weeks after botulinum toxin injections to see whether connectivity abnormalities were restored. We here show that cervical dystonia patients have reduced connectivity in selected regions of the prefrontal cortex, premotor cortex and superior parietal lobule within a distributed network that comprises the premotor cortex, supplementary motor area, primary sensorimotor cortex, and secondary somatosensory cortex (sensorimotor network). With regard to a network originating from the occipital cortex (primary visual network), selected regions in the prefrontal and premotor cortex, superior parietal lobule, and middle temporal gyrus areas have reduced connectivity. In selected regions of the prefrontal, premotor, primary motor and early visual cortex increased connectivity was found within a network that comprises the prefrontal cortex including the anterior cingulate cortex and parietal cortex (executive control network). Botulinum toxin treatment resulted in a partial restoration of connectivity abnormalities in the sensorimotor and primary visual network. These findings demonstrate the involvement of multiple neural networks in cervical dystonia. The reduced connectivity within the sensorimotor and primary visual networks may provide the neural substrate to expect defective motor planning and disturbed spatial cognition. Increased connectivity within the executive control network suggests excessive attentional control and while this may be a primary trait, perhaps contributing to abnormal motor control, this may alternatively serve a compensatory function in order to reduce the consequences of the motor planning defect inflicted by the other network abnormalities.

Mental rotation: effects of gender, training and sleep consolidation

A wide range of experimental studies have provided evidence that a night of sleep contributes to memory consolidation. Mental rotation (MR) skill is characterized by fundamental aspect of both cognitive and motor abilities which can be improved within practice sessions, but little is known about the effect of consolidation after MR practice. In the present study, we investigated the effect of MR training and the following corresponding day- and sleep-related time consolidations in taking into account the well-established gender difference in MR. Forty participants (20 women) practiced a computerized version of the Vandenberg and Kuse MR task. Performance was evaluated before MR training, as well as prior to, and after a night of sleep or a similar daytime interval. Data showed that while men outperformed women during the pre-training test, brief MR practice was sufficient for women to achieve equivalent performance. Only participants subjected to a night of sleep were found to enhance MR performance during the retest, independently of gender. These results provide first evidence that a night of sleep facilitates MR performance compared with spending a similar daytime interval, regardless gender of the participants. Since MR is known to involve motor processes, the present data might contribute to schedule relevant mental practice interventions for fruitful applications in rehabilitation and motor learning processes.

Non-invasive cerebellar stimulation in dystonia

Primary isolated dystonia is a hyperkinetic movement disorder whereby involuntary muscle contractions cause twisted and abnormal postures. Dystonia of the cervical spine and upper limb may present as sustained muscle contractions or task-specific activity when using the hand or upper limb. There is little understanding of the pathophysiology underlying dystonia and this presents a challenge for clinicians and researchers alike. Emerging evidence that the cerebellum is involved in the pathophysiology of dystonia using network models presents the intriguing concept that the cerebellum could provide a novel target for non-invasive brain stimulation. Non-invasive stimulation to increase cerebellar excitability improved aspects of handwriting and circle drawing in a small cohort of people with focal hand and cervical dystonia. Mechanisms underlying the improvement in function are unknown, but putative pathways may involve the red nucleus and/or the cervical propriospinal system. Furthermore, recent understanding that the cerebellum has both motor and cognitive functions suggests that non-invasive cerebellar stimulation may improve both motor and non-motor aspects of dystonia. We propose a combination of motor and non-motor tasks that challenge cerebellar function may be combined with cerebellar non-invasive brain stimulation in the treatment of focal dystonia. Better understanding of how the cerebellum contributes to dystonia may be gained by using network models such as our putative circuits involving red nucleus and/or the cervical propriospinal system. Finally, novel treatment interventions encompassing both motor and non-motor functions of the cerebellum may prove effective for neurological disorders that exhibit cerebellar dysfunction.

Functional (psychogenic) movement disorders

PURPOSE OF REVIEW

This review provides an overview of recent developments in diagnosis, pathophysiology, neuroimaging and management of functional (psychogenic) movement disorders (FMD).

RECENT FINDINGS

There has been increasing interest to study the underlying pathophysiology of FMD, which has resulted in a broadened disease model, taking neurobiologic and psychosocial factors equally into account. In this context, the term 'psychogenic' has been replaced by 'functional' movement disorders by many authors in the field to express the changing focus toward a multifactorial disease model. The need for establishing a positive diagnosis of FMD as opposed to providing a diagnosis of exclusion is increasingly recognized and reflected by the introduction of 'laboratory-supported' diagnostic criteria of FMD. Important advances have been made through behavioral, electrophysiological and neuroimaging studies, although the fundamental cause of FMD remains poorly understood. Of particular interest have been several reports on abnormal sensorimotor features and cortical inhibition in both organic and functional dystonia, highlighting possible shared traits of both conditions. In terms of treatment, recent studies have reported benefit from both psychiatric and physical therapy-based interventions.

SUMMARY

Increasing efforts have been made toward better understanding of FMD, and the disease model has been broadened to include neurobiologic and psychosocial factors. Laboratory-based diagnostic criteria have been established for many FMD to support the clinical diagnosis. To determine the most effective management strategies for FMD, a closer collaboration between neurologists and psychiatrists and intensified research efforts with prospective treatment trials are needed.

Nociception affects motor output: a review on sensory-motor interaction with focus on clinical implications

OBJECTIVES

Research has provided us with an increased understanding of nociception-motor interaction. Nociception-motor interaction is most often processed without conscious thoughts. Hence, in many cases neither patients nor clinicians are aware of the interaction. It is aimed at reviewing the scientific literature on nociception-motor interaction, with emphasis on clinical implications.

METHODS

Narrative review.

RESULTS

Chronic nociceptive stimuli result in cortical relay of the motor output in humans, and a reduced activity of the painful muscle. Nociception-induced motor inhibition might prevent effective motor retraining. In addition, the sympathetic nervous system responds to chronic nociception with enhanced sympathetic activation. Not only motor and sympathetic output pathways are affected by nociceptive input, afferent pathways (proprioception, somatosensory processing) are influenced by tonic muscle nociception as well.

DISCUSSION

The clinical consequence of the shift in thinking is to stop trying to restore normal motor control in case of chronic nociception. Activation of central nociceptive inhibitory mechanisms, by decreasing nociceptive input, might address nociception-motor interactions.

Disentangling motor execution from motor imagery with the phantom limb

Amputees can move their phantom limb at will. These 'movements without movements' have generally been considered as motor imagery rather than motor execution, but amputees can in fact perform both executed and imagined movements with their phantom and they report distinct perceptions during each task. Behavioural evidence for this dual ability comes from the fact that executed movements are associated with stump muscle contractions whereas imagined movements are not, and that phantom executed movements are slower than intact hand executed movements whereas the speed of imagined movements is identical for both hands. Since neither execution nor imagination produces any visible movement, we hypothesized that the perceptual difference between these two motor tasks relies on the activation of distinct cerebral networks. Using functional magnetic resonance imaging and changes in functional connectivity (dynamic causal modelling), we examined the activity associated with imagined and executed movements of the intact and phantom hands of 14 upper-limb amputees. Distinct but partially overlapping cerebral networks were active during both executed and imagined phantom limb movements (both performed at the same speed). A region of interest analysis revealed a 'switch' between execution and imagination; during execution there was more activity in the primary somatosensory cortex, the primary motor cortex and the anterior lobe of the cerebellum, while during imagination there was more activity in the parietal and occipital lobes, and the posterior lobe of the cerebellum. In overlapping areas, task-related differences were detected in the location of activation peaks. The dynamic causal modelling analysis further confirmed the presence of a clear neurophysiological distinction between imagination and execution, as motor imagery and motor execution had opposite effects on the supplementary motor area-primary motor cortex network. This is the first imaging evidence that the neurophysiological network activated during phantom limb movements is similar to that of executed movements of intact limbs and differs from the phantom limb imagination network. The dual ability of amputees to execute and imagine movements of their phantom limb and the fact that these two tasks activate distinct cortical networks are important factors to consider when designing rehabilitation programmes for the treatment of phantom limb pain.

Body context and posture affect mental imagery of hands

Different visual stimuli have been shown to recruit different mental imagery strategies. However the role of specific visual stimuli properties related to body context and posture in mental imagery is still under debate. Aiming to dissociate the behavioural correlates of mental processing of visual stimuli characterized by different body context, in the present study we investigated whether the mental rotation of stimuli showing either hands as attached to a body (hands-on-body) or not (hands-only), would be based on different mechanisms. We further examined the effects of postural changes on the mental rotation of both stimuli. Thirty healthy volunteers verbally judged the laterality of rotated hands-only and hands-on-body stimuli presented from the dorsum- or the palm-view, while positioning their hands on their knees (front postural condition) or behind their back (back postural condition). Mental rotation of hands-only, but not of hands-on-body, was modulated by the stimulus view and orientation. Additionally, only the hands-only stimuli were mentally rotated at different speeds according to the postural conditions. This indicates that different stimulus-related mechanisms are recruited in mental rotation by changing the bodily context in which a particular body part is presented. The present data suggest that, with respect to hands-only, mental rotation of hands-on-body is less dependent on biomechanical constraints and proprioceptive input. We interpret our results as evidence for preferential processing of visual- rather than kinesthetic-based mechanisms during mental transformation of hands-on-body and hands-only, respectively.

Is access to the body structural description sensitive to a body part's significance for action and cognition? A study of the sidedness effect using feet

There is evidence suggesting that viewing hands triggers automatic access to the Body Structural Description, a visual-spatial representation of human body parts configuration. Hands, however, have a special representational status within the brain because of their significance for action and cognition. We tested whether feet, less important in gestural and object-directed action, would similarly show automatic access to the Body Structural Description. Positive evidence of that would be finding a Sidedness effect (Ottoboni et al. J Exp Psychol Hum Percept Perform 31:778-789, 2005), a Simon-like paradigm previously used to study automatic hand recognition. This effect demonstrates that processing hands generates spatial codes corresponding to the side of the body on which the hand would be located within the Body Structural Description map. Feet were shown with toes pointing upwards (Experiment 1), without any connection to the ankle and the leg (Experiment 2) and with toes pointing downwards (Experiment 3). Results revealed a Sidedness effect in both Experiments 1 and 3: spatial compatibility occurred according to the side of the body that each foot would assume within the Body Structural Description. In Experiment 2, as already found in stimuli similarly featured, no effect emerged, due to the lack of the necessary anatomical links connecting the foot to a body. Results suggest that body parts with variable degrees of significance for action and cognition can access automatically the Body Structural Description hence reinforcing the hypothesis of its pure visuo-spatial nature.

Treatment of central sensitization in patients with 'unexplained' chronic pain: what options do we have?

INTRODUCTION

Central sensitization accounts for chronic 'unexplained' pain in a wide variety of disorders, including chronic whiplash-associated disorders, temporomandibular disorders, chronic low back pain, osteoarthritis, fibromyalgia, chronic fatigue syndrome and chronic tension-type headache among others. Given the increasing evidence supporting the clinical significance of central sensitization in those with unexplained chronic pain, the awareness is growing that central sensitization should be a treatment target in these patients.

AREAS COVERED

This article provides an overview of the treatment options available for desensitizing the CNS in patients with chronic pain due to central sensitization. It focuses on those strategies that specifically target pathophysiological mechanisms known to be involved in central sensitization. In addition, pharmacological options, rehabilitation and neurotechnology options are discussed.

EXPERT OPINION

Acetaminophen, serotonin-reuptake inhibitor drugs, selective and balanced serototin and norepinephrine-reuptake inhibitor drugs, the serotonin precursor tryptophan, opioids, N-methyl-d-aspartate (NMDA)-receptor antagonists, calcium-channel alpha(2)delta (a2δ) ligands, transcranial magnetic stimulation, transcutaneous electric nerve stimulation (TENS), manual therapy and stress management each target central pain processing mechanisms in animals that - theoretically - desensitize the CNS in humans. To provide a comprehensive treatment for 'unexplained' chronic pain disorders characterized by central sensitization, it is advocated to combine the best evidence available with treatment modalities known to target central sensitization.