fMRI assessment of upper extremity related brain activation with an MRI-compatible manipulandum

Purpose: Longitudinal studies to evaluate the effect of rehabilitative therapies require an objective, reproducible and quantitative means for testing function in vivo. An fMRI assessment tool for upper extremity related brain activation using an MRI-compatible manipulandum was developed and tested for use in neurorehabilitation research. Methods: Fifteen healthy, right-handed subjects participated in two fMRI sessions, which were three to four weeks apart. A block design paradigm, composed of three conditions of subject-passive movement, subject-active movement and rest, was employed for the fMRI recordings. During the rest condition, subjects simply held the device handle without applying any force or movement. The same type of auditory and visual instructions were given in all the three conditions, guiding the subjects to perform the motor tasks interactively with the MRI-compatible arm manipulandum. The tasks were controlled across the fMRI sessions. The subjects' brain activation was recorded by fMRI, and their behavioral performance was recorded by the manipulandum. The brain network activated by the subjects' interaction with the manipulandum was identified, and the reproducibility and reliability of the obtained activation were determined. Results: All subjects completed the trial protocol. Two subjects were excluded from analysis due to head motion artifacts. All passive movements were performed well. Four out of the total 780 active movements were missed by two subjects. Brain activation was found in the contralateral sensorimotor cortex, secondary somatosensory cortex and non-primary motor cortex as well as in subcortical areas in the thalamus, basal ganglia and the cerebellum. These activations were consistent across the two fMRI sessions. Conclusion: The MRI-compatible manipulandum elicited robust and reproducible brain activations in healthy subjects during the subject-active and subject-passive upper extremity motor tasks with a block design paradigm. This system is promising for many applications in neurorehabilitation research and may be useful for longitudinal studie

Corticomuscular synchronization with small and large dynamic force output

BACKGROUND: Over the last years much research has been devoted to investigating the synchronization between cortical motor and muscular activity as measured by EEG/MEG-EMG coherence. The main focus so far has been on corticomuscular coherence (CMC) during static force condition, for which coherence in beta-range has been described. In contrast, we showed in a recent study [1] that dynamic force condition is accompanied by gamma-range CMC. The modulation of the CMC by various dynamic force amplitudes, however, remained uninvestigated. The present study addresses this question. We examined eight healthy human subjects. EEG and surface EMG were recorded simultaneously. The visuomotor task consisted in isometric compensation for 3 forces (static, small and large dynamic) generated by a manipulandum. The CMC, the cortical EEG spectral power (SP), the EMG SP and the errors in motor performance (as the difference between target and exerted force) were analyzed. RESULTS: For the static force condition we found the well-documented, significant beta-range CMC (15-30Hz) over the contralateral sensorimotor cortex. Gamma-band CMC (30-45Hz) occurred in both small and large dynamic force conditions without any significant difference between both conditions. Although in some subjects beta-range CMC was observed during both dynamic force conditions no significant difference between conditions could be detected. With respect to the motor performance, the lowest errors were obtained in the static force condition and the highest ones in the dynamic condition with large amplitude. However, when we normalized the magnitude of the errors to the amplitude of the applied force (relative errors) no significant difference between both dynamic conditions was observed. CONCLUSIONS: These findings confirm that during dynamic force output the corticomuscular network oscillates at gamma frequencies. Moreover, we show that amplitude modulation of dynamic force has no effect on the gamma CMC in the low force range investigated. We suggest that gamma CMC is rather associated with the internal state of the sensorimotor system as supported by the unchanged relative error between both dynamic conditions

Changes of non‐affected upper limb cortical representation in paraplegic patients as assessed by fMRI

Peripheral and central nervous system lesions can induce reorganization within central somatosensory and motor body representations. We report changes in brain activation patterns during movements of non‐affected body parts in paraplegic patients with spinal cord injury (SCI). Nine SCI patients and 12 healthy controls underwent blood oxygen level dependent signal functional MRI during sequential finger‐to‐thumb opposition, flexion and extension of wrist and of elbow, and horizontal movements of the tongue. Single subject and group analyses were performed, and the activation volumes, maximum t values and centres of gravity were calculated. The somatotopical upper limb and tongue representations in the contralateral primary motor cortex (M1) in the SCI patients were preserved without any shift of activation towards the deefferented and deafferented M1 foot area. During finger movements, however, the SCI patients showed an increased volume in M1 activation. Increased activation was also found in non‐primary motor and parietal areas, as well as in the cerebellum during movements of the fingers, wrist and elbow, whereas no changes were present during tongue movements. These results document that, in paraplegic patients, the representation of the non‐impaired upper limb muscles is modified, though without any topographical reorganization in M1. The extensive changes in primary and non‐primary motor areas, and in subcortical regions demonstrate that even distant neuronal damage has impact upon the activation of the whole sensorimotor syste

What Disconnection Tells about Motor Imagery: Evidence from Paraplegic Patients

Brain activation during motor imagery has been the subject of a large number of studies in healthy subjects, leading to divergent interpretations with respect to the role of descending pathways and kinesthetic feedback on the mental rehearsal of movements. We investigated patients with complete spinal cord injury (SCI) to find out how the complete disruption of motor efferents and sensory afferents influences brain activation during motor imagery of the disconnected feet. Eight SCI patients underwent behavioral assessment and functional magnetic resonance imaging. When compared to a healthy population, stronger activity was detected in primary and all non-primary motor cortical areas and subcortical regions. In paraplegic patients the primary motor cortex was consistently activated, even to the same degree as during movement execution in the controls. Motor imagery in SCI patients activated in parallel both the motor execution and motor imagery networks of healthy subjects. In paraplegics the extent of activation in the primary motor cortex and in mesial non-primary motor areas was significantly correlated with the vividness of movement imagery, as assessed by an interview. The present findings provide new insights on the neuroanatomy of motor imagery and the possible role of kinesthetic feedback in the suppression of cortical motor output required during covert movement

Impact of a Weekly Dance Class on the Functional Mobility and on the Quality of Life of Individuals with Parkinson’s Disease

Individuals with Parkinson’s disease (PD) mainly suffer from motor impairments which increase the risk of falls and lead to a decline of quality of life. Several studies investigated the long-term effect of dance for people with PD. The aims of the present study were to investigate (i) the short-term effects of dance (i.e., the effect immediately after the dance class) on motor control in individuals with PD and (ii) the long-term effects of 8 months of participation in the weekly dance class on the quality of life of the PD patients and their caregivers. The dance lessons took place in a ballet studio and were led by a professional dancer. Eleven people with moderate to severe PD (58–85 years old) were subjected to a motor and quality of life assessments. With respect to the motor assessments the unified Parkinson disease rating scale III (UPDRS III), the timed up and go test (TUG), and the Semitandem test (SeTa) before and after the dance class were used. With respect to the quality of life and well-being we applied quality of life scale (QOLS) as well as the Westheimer questionnaire. Additionally, we asked the caregivers to fill out the Questionnaire for caregivers. We found a significant beneficial short-term effect for the total score of the UPDRS motor score. The strongest improvements were in rigidity scores followed by significant improvements in hand movements, finger taps, and facial expression. No significant changes were found for TUG and for SeTa. The results of the questionnaires showed positive effects of the dance class on social life, health, body-feeling and mobility, and on everyday life competences of the PD patients. Beneficial effect was also found for the caregivers. The findings demonstrate that dance has beneficial effect on the functional mobility of individuals with PD. Further, dance improves the quality of life of the patients and their caregivers. Dance may lead to better therapeutic strategies as it is engaging and enjoyable

Corticospinal interaction during isometric compensation for modulated forces with different frequencies

<p>Abstract</p> <p>Background</p> <p>During isometric compensation of modulated low-level forces corticomuscular coherence (CMC) has been shown to occur in high-beta or gamma-range. The influence of the frequency of force modulation on CMC has up to now remained unexplored. We addressed this question by investigating CMC, motor performance, and cortical spectral power during a visuomotor task in which subjects had to compensate a modulated force of 8% of the maximum voluntary contraction exerted on their right index finger. The effect of three frequencies of force modulation (0.6, 1.0 and 1.6 Hz) was tested. EEG, EMG from first dorsal interosseus, hand flexor and extensor muscles, and finger position were recorded in eight right-handed women.</p> <p>Results</p> <p>Five subjects showed CMC in gamma- (28-45 Hz) and three in beta-range (15-30 Hz). Beta- and gamma-range CMC and cortical motor spectral power were not modulated by the various frequencies. However, a sharp bilateral CMC peak at 1.6 Hz was observed, but only in the five gamma-range CMC subjects. The performance error increased linearly with the frequency.</p> <p>Conclusions</p> <p>Our findings suggest that the frequency of force modulation has no effect on the beta- and gamma-range CMC during isometric compensation for modulated forces at 8% MVC. The beta- and gamma-range CMC may be related to interindividual differences and possibly to strategy differences.</p

A Reliability Study on Brain Activation During Active and Passive Arm Movements Supported by an MRI-Compatible Robot

In neurorehabilitation, longitudinal assessment of arm movement related brain function in patients with motor disability is challenging due to variability in task performance. MRI-compatible robots monitor and control task performance, yielding more reliable evaluation of brain function over time. The main goals of the present study were first to define the brain network activated while performing active and passive elbow movements with an MRI-compatible arm robot (MaRIA) in healthy subjects, and second to test the reproducibility of this activation over time. For the fMRI analysis two models were compared. In model 1 movement onset and duration were included, whereas in model 2 force and range of motion were added to the analysis. Reliability of brain activation was tested with several statistical approaches applied on individual and group activation maps and on summary statistics. The activated network included mainly the primary motor cortex, primary and secondary somatosensory cortex, superior and inferior parietal cortex, medial and lateral premotor regions, and subcortical structures. Reliability analyses revealed robust activation for active movements with both fMRI models and all the statistical methods used. Imposed passive movements also elicited mainly robust brain activation for individual and group activation maps, and reliability was improved by including additional force and range of motion using model 2. These findings demonstrate that the use of robotic devices, such as MaRIA, can be useful to reliably assess arm movement related brain activation in longitudinal studies and may contribute in studies evaluating therapies and brain plasticity following injury in the nervous system

Observing Virtual Arms that You Imagine Are Yours Increases the Galvanic Skin Response to an Unexpected Threat

Multi-modal visuo-tactile stimulation of the type performed in the rubber hand illusion can induce the brain to temporarily incorporate external objects into the body image. In this study we show that audio-visual stimulation combined with mental imagery more rapidly elicits an elevated physiological response (skin conductance) after an unexpected threat to a virtual limb, compared to audio-visual stimulation alone. Two groups of subjects seated in front of a monitor watched a first-person perspective view of slow movements of two virtual arms intercepting virtual balls rolling towards the viewer. One group was instructed to simply observe the movements of the two virtual arms, while the other group was instructed to observe the virtual arms and imagine that the arms were their own. After 84 seconds the right virtual arm was unexpectedly “stabbed” by a knife and began “bleeding”. This aversive stimulus caused both groups to show a significant increase in skin conductance. In addition, the observation-with-imagery group showed a significantly higher skin conductance (p<0.05) than the observation-only group over a 2-second period shortly after the aversive stimulus onset. No corresponding change was found in subjects' heart rates. Our results suggest that simple visual input combined with mental imagery may induce the brain to measurably temporarily incorporate external objects into its body image

Body representation and motor imagery : effects of adaptability

We are occupants of a body that receives diverse sensory input via our visual and somatosensory system. Furthermore, as we are the agent of our own body, the brain must also deal with both the afferent and efferent signals that occur with movement, namely the motor system. How do we perceive our stationary or moving body as well as the world around us as a coherent whole? Mental representations are assumed to support and modify our perception, as well as the resulting behaviour, the action. In this thesis, representational processes in the perception of the body and its movements are discussed in relation to the particular systems: vision, somatosensory, and motor. In chapter 1, the general introduction, the terms „representation‟ and „images‟, as well as „body representation‟ and „movement representation‟ are described along the lines of previous research and defined for their appropriate use within this thesis. Specific background literature and concepts with respect to the experiments are discussed in the introductory sections within each individual chapter. Chapters 2 and 3 explore representations of the stationary body by the sensory modalities vision, proprioception, and touch, whilst chapter 4 deals with mental representation in movement. Overall, the results of these investigations exemplify the adaptability of representational processes based on different sensory systems in the stationary and the moving body (see chapter 5). The three experiments combined in chapter 2 investigated body representations based on the visual sensory system. The question was, to what extent does the form of what we visually perceive influence our mental transformation processes? All three experiments gave evidence that different 3 forms of body representations in response to vision are behaviourally not as disparate as suggested by previous investigations. For example, participants needed more time to mentally transform visually presented stimuli with increasing angular disparity between them. This was the case for abstract objects as well as for bodies when no rotation in depth was necessary (Experiment 1). The response pattern for identifying the outstretched arm in a body figure was thus comparable to that when identifying abstract objects. Hence without depth rotation, egocentric body transformation is akin to mental object rotation. In contrast to the hypothesis on effects of expertise, however, no effect could be observed between subjects: The reaction times between dancers, who are experienced in mentally transforming bodies, and novices did not differ significantly (Experiment 2). Surprisingly, when body postures were presented in the abstract dance notation of Laban (Experiment 3), no mental rotation costs were measured. These three experiments showed that mental transformations were available in different prospects, of which one is perspective-independent. Consequently, in certain conditions the mental presentations seem to switch quickly from a perspective dependent to an independent form. Accordingly, mental representations are not singularly dependent on the presentation form. Cognitive processing of either visually perceived abstract objects, body drawings, or body-related symbols were comparable, whereas the spatial frame of reference, the orientation between the observer and the perceived orientation of the stimuli, was of primary relevance. The type of visual presentation only defines the form of mental representation used for the transformation when a mental rotation in depth is needed. 4 The experiments in chapter 3 looked at how we sense the body in egocentric space based on somatosensory perception. In particular, the first of these psychophysical investigations was concerned with the perception of body limbs in space, that is, proprioceptive sensory mode (Experiment 4). The second was an experiment on tactile perception on the body surface, that is, tactile sensory mode (Experiment 5). Proprioception is the sense which is thought to give us the experience of our own body posture. The tactile sensory mode consists of two distinct perceptual processes: the tactile experience itself (tactile recognition) and the localisation on our body surface (tactile localisation). Both proprioception and tactile localisation revealed effects of adaptability on body reference points. The experiment on proprioception showed that actively pointing to a location in egocentric space is biased by two reference centres of the body located at each shoulder in all but the visual condition. Dancers showed a smaller bias of the two reference centres; but interestingly, they also showed it in the visual task. Therefore, the perception of the self in egocentric space referred to different functional body references according to both the sensory modality used and the individual‟s motor expertise. Moreover, the modality can be substituted with simulation, such as simulated proprioception in the dancers‟ group. The experiment on tactile localisation showed that the point of sensations of touch was located closer to the body centre than the original stimulation. This was the case in both sensory modes that were available to localise a point of touch: vision (by visual estimation) and motor (by pointing). Thus, the body centre acts as a reference point independent of the response mode. Interestingly, additional tactile information from the tip of the finger caused a switch in the direction of the mislocalisation from the body centre to the periphery. Consequently, 5 representations of the egocentric space are adaptable in both the short- and long-term, and this adaptability is dependent on both sensory input and expertise, respectively. Further, tactile perception is immediately integrated in the perception of the body space and has a dramatic effect on spatial localisation on the body surface. Chapter 4 discusses how movement representations can evolve by motor imagery training compared to common execution training. Mentally rehearsing the abduction of the big toe, a movement without established motor command, caused a reduction in the time taken to move whereas exertion force was most increased by execution training (Experiment 6). This finding shows conceptually different training effects between imagery and execution. It goes beyond previous behavioural studies that have shown differences between imagery training and execution training in the level of performance increase alone. In addition, a representation of the movement goal (anticipation) surprisingly improved participants‟ movement abilities, as could be observed by a performance increase in the movement range of the abduction. Thus along with representations of the stationary body, mental representations can be consciously instrumentalised in the moving body, such as motor imagery or anticipation; they can also show short- and long-term performance adaptations, respectively. Chapter 5 is a general discussion of the experimental results. The data from this thesis supports the existence of a nonmodular adaptable body representation that can accommodate long-term changes (through experience) as well as rapid switches (from different sensory feedback information). Representations are hypothesised to be the effect of adaptability processes. In addition, the importance of differential observation is highlighted. Der Körper ist unser Instrument, mit dem wir uns in der Welt zurechtfinden. Űber die verschiedenen Sinnessysteme des Körpers können wir unsere Umwelt sowie die ‚Körperinnenwelt‟ erfahren. Das visuelle System ermöglicht ein Abbild der Aussenwelt. Das somatosensorische System, bestehend aus der Propriozeption und der Berührungsempfindung ist wichtig, um die Position unseres Körpers im Raum sowie die Gestalt unseres Körpers wahrzunehmen. Nebst diesen im passiven Körper vorhandenen Sinneseindrücken haben wir aber auch Bewegungsempfindung: Wir sind nicht nur Empfänger von Sinneseindrücken, wir agieren aktiv mit unserem Körper in der Umwelt. Im Gehirn findet ein Zusammenspiel sowohl von solchen afferenten als auch efferenten Signalen statt. Wie aber ist es möglich, dass wir trotz der Information von verschiedenen Sinnessystemen unseren passiv oder aktiv (bewegten) Körper sowie die Welt um uns herum als eine zusammenhängende kohärente Entität wahrnehmen? Mentale Repräsentationen sind ein zentrales Element in diesem Integrationsprozess: Sie spielen eine wichtige Rolle in dem Zusammenspiel von Wahrnehmung und resultierendem Verhalten (die Handlung). In dieser Arbeit werden mentale Repräsentationen der Wahrnehmung des Körpers und seiner Bewegungen in Bezug auf die besonderen Sinnessysteme besprochen: visuelle, somatosensorische und motorische Sinneswahrnehmung. Das erste Kapitel gibt eine Einführung in die Begriffe Repräsentation und mentale Bilder, sowie Körperrepräsentation und Bewegungsrepräsentationen. Insbesondere wird der spezifische Gebrauch der Begriffe innerhalb dieser Arbeit 7 definiert. Weitergehende Einführungen sind in den Einleitungen der jeweiligen experimentellen Kapitel zwei bis vier zu finden. Die mentale Körpertransformation basierend auf dem visuellen System wird in Kapitel zwei besprochen. In Experiment 1 wurden die Prozesse in der mentalen Rotation von Objekten und Körpern untersucht. Dabeit hat sich gezeigt, dass insbesondere die Rotation in der Tiefe das Verhalten der Versuchspersonen beeinflusst. Versuchspersonen benötigen für die Diskriminierung zweier abstrakter Objekte in der Regel länger, je grösser die Diskrepanz in der Ausrichtung der zu beurteilenden Objekte ist. Dieser Rotationseffekt konnte auch bei der Identifizierung von Körperstimuli nachgewiesen werden, jedoch nur wenn die Ausrichtung der Stimuli mit der egozentrischen Perspektive der Versuchsperson übereinstimmte, das heisst, wenn keine Rotation in der Tiefe notwendig war. In Experiment 2 wurde der Einfluss der generellen Bewegungsexpertise von Tänzern auf die mentale Transformation von Körpern untersucht. Die Daten der beiden bis auf die Probandengruppe identischen Experimente 1 und 2 zeigten keinen Unterschied zwischen Tänzern und nicht- Tänzern in Bezug auf die mentale Körperrotation. In Experiment 3 wurde schliesslich untersucht, welchen Einfluss die Form des visuell präsentierten Körpers auf die mentale Repräsentation und Transformation hat. Dazu wurde in der Hälfte der Bedingungen der Körper in der Labanotation, einer etablierten Tanzschrift dargestellt. In der Labanotation werden arbiträre Symbole für die Darstellung der verschiedenen Körperglieder verwendet. In der Diskriminierung zweier Körperpositionen in unterschiedlicher Orientierung haben sich erhöhte Reaktionszeiten nur bei Stimuli in Form von Fotos einer Tänzerin, nicht aber in Form von abstrakter Labanotation gezeigt. Das heisst, die mentale 8 Repräsentation von Körpern und/oder deren Prozesse sind perspektiven- unabhängig, wenn die Repräsentation von arbiträren visuellen Körperstimuli generiert wurden. Die drei Experimente im ersten Kapitel zeigten, dass die Repräsentation von Körpern und Objekten sowie deren mentalen Transformation von der Form der visuellen Stimuli und insbesondere auch von deren Orientierung abhängig ist. Die Prozesse der Repräsentationen zeigten sich teilweise bei identischer primärer visueller Darstellung unabhängig und teilweise abhängig von Perspektivenwechsel. Dieser Effekt lässt eine hohe Adaptabilität der Repräsentation von Körpern basierend auf visueller Wahrnehmung vermuten. In Kapitel drei wird die Verarbeitung und Wahrnehmung des Körpers im egozentrischen Raum basierend auf somatosensorischer Empfindung untersucht und dargestellt. Im vorhergehenden Kapitel hat sich gezeigt, dass die Perspektivenabhängigkeit, und somit der egozentrische Referenzpunkt der Körperrepräsentation von den visuellen Stimuli beeinflusst ist. Die Experimente 4 und 5 untersuchten die Referenzpunkte innerhalb der Wahrnehmung des eigenen Körpers in der motorischen Interaktion im egozentrischen Raum. Mittels Experiment 4 konnte gezeigt werden, dass die beiden Schultern als Referenzpunkte wirken, wenn Probanden Punkte im Raum lokalisieren mussten. Die Bewegungserfahrung von Tänzern jedoch führte erstens zu geringeren Schätzungsfehlern basierend auf einem Referenzpunkt im Körperzentrum. Zweitens zeigten Tänzer dieselben Abweichungen in der Lokalisierung bei visuellem wie bei propriozeptivem Feedback. Möglicherweise haben die Tänzer in der visuellen Bedingung ein ‚virtuelles‟ propriozeptives Feedback generiert. In Experiment 5 mussten die Probanden taktile Berührungspunkte auf dem Arm lokalisieren. Die Punkte wurden konsistent zu nah am Körper geschätzt. Wenn 9 die Probanden jedoch zusätzlich taktile Stimulation am Finger erhielten, kehrte sich die Unterschätzung der Distanz vom Körperzentrum zum Berührungspunkt in eine Überschätzung um. Eine kurzfristige Integration zusätzlicher Berührungspunkte wurde vermuted. Beide Experimente zeigten unterschiedliche anpassungsfähige Körperreferenzpunkte, kurzfristig in bezug auf die vorhandene sensorische Information sowie langfristig basierend auf Erfahrung. Schliesslich wird in Kapitel vier der Einfluss der motorischen Vorstellung auf die Bewegungsrepräsentation untersucht. Es hat sich gezeigt, dass mentales Training und physisches Bewegungstraining sich nicht nur in der Intensität unterscheiden, sondern vermutlich zwei verschiedene Prozesse sind. Mentales Training führte zu einer rascheren Ausführung der erlernten Bewegung während Bewegungstraining die Kraft erhöhte. Die Bewegungsrepräsentation ist daher unterschiedlich adaptiv, abhängig davon, wie sie angesprochen wird. Die Befunde der Experimente 1 bis 6 werden in Kapitel fünf diskutiert. Mentale Repräsentationen zeigten sich in dieser Arbeit über verschiedene Sinnessysteme hinweg anpassungsfähig. Die Resultate lassen vermuten, dass die effiziente Interaktion mit der Umwelt durch einen adaptiven Mechanismus mentaler Repräsentationen ermöglicht wird. Repräsentationen in dem Sinne können als Effekte der Adaptabilität verstanden werden. Unter dieser Annahme wird das aktuelle Forschungsvorgehen diskutiert. Jeder Körper, jeder Geist sowie deren assoziierten Repräsentationen haben sich adaptiv an die Umwelt angepasst und tun dies kontinuierlich in einem individuellen Sinne. Um adaptive Prozesse in der Kognition zu entdecken, scheint es entgegen dem gebräuchlichen methodischen Vorgehen angebracht, das Augenmerk auf individuelle Ausprägungen zu richten. 1