Direction of Movement Is Encoded in the Human Primary Motor Cortex

The present study investigated how direction of hand movement, which is a well-described parameter in cerebral organization of motor control, is incorporated in the somatotopic representation of the manual effector system in the human primary motor cortex (M1). Using functional magnetic resonance imaging (fMRI) and a manual step-tracking task we found that activation patterns related to movement in different directions were spatially disjoint within the representation area of the hand on M1. Foci of activation related to specific movement directions were segregated within the M1 hand area; activation related to direction 0° (right) was located most laterally/superficially, whereas directions 180° (left) and 270° (down) elicited activation more medially within the hand area. Activation related to direction 90° was located between the other directions. Moreover, by investigating differences between activations related to movement along the horizontal (0°+180°) and vertical (90°+270°) axis, we found that activation related to the horizontal axis was located more anterolaterally/dorsally in M1 than for the vertical axis, supporting that activations related to individual movement directions are direction- and not muscle related. Our results of spatially segregated direction-related activations in M1 are in accordance with findings of recent fMRI studies on neural encoding of direction in human M1. Our results thus provide further evidence for a direct link between direction as an organizational principle in sensorimotor transformation and movement execution coded by effector representations in M1

Best practice for motor imagery: a systematic literature review on motor imagery training elements in five different disciplines

<p>Abstract</p> <p>Background</p> <p>The literature suggests a beneficial effect of motor imagery (MI) if combined with physical practice, but detailed descriptions of MI training session (MITS) elements and temporal parameters are lacking. The aim of this review was to identify the characteristics of a successful MITS and compare these for different disciplines, MI session types, task focus, age, gender and MI modification during intervention.</p> <p>Methods</p> <p>An extended systematic literature search using 24 databases was performed for five disciplines: Education, Medicine, Music, Psychology and Sports. References that described an MI intervention that focused on motor skills, performance or strength improvement were included. Information describing 17 MITS elements was extracted based on the PETTLEP (physical, environment, timing, task, learning, emotion, perspective) approach. Seven elements describing the MITS temporal parameters were calculated: study duration, intervention duration, MITS duration, total MITS count, MITS per week, MI trials per MITS and total MI training time.</p> <p>Results</p> <p>Both independent reviewers found 96% congruity, which was tested on a random sample of 20% of all references. After selection, 133 studies reporting 141 MI interventions were included. The locations of the MITS and position of the participants during MI were task-specific. Participants received acoustic detailed MI instructions, which were mostly standardised and live. During MI practice, participants kept their eyes closed. MI training was performed from an internal perspective with a kinaesthetic mode. Changes in MI content, duration and dosage were reported in 31 MI interventions. Familiarisation sessions before the start of the MI intervention were mentioned in 17 reports. MI interventions focused with decreasing relevance on motor-, cognitive- and strength-focused tasks. Average study intervention lasted 34 days, with participants practicing MI on average three times per week for 17 minutes, with 34 MI trials. Average total MI time was 178 minutes including 13 MITS. Reporting rate varied between 25.5% and 95.5%.</p> <p>Conclusions</p> <p>MITS elements of successful interventions were individual, supervised and non-directed sessions, added after physical practice. Successful design characteristics were dominant in the Psychology literature, in interventions focusing on motor and strength-related tasks, in interventions with participants aged 20 to 29 years old, and in MI interventions including participants of both genders. Systematic searching of the MI literature was constrained by the lack of a defined MeSH term.</p

In vivo three-dimensional reconstruction of human median nerves by diffusion tensor imaging

The in vivo assessment of axonal projections of the peripheral nervous system has been severely limited by the lack of noninvasive techniques. We examined whether MR diffusion tensor imaging with fiber tracking of the human median nerve is feasible. The median nerve was examined with a 3-T MRI scanner in wrists of three healthy volunteers and the wrist of a patient after median nerve repair. In vivo three-dimensional (3D) reconstruction of axonal projections of the median nerve Could be achieved in healthy volunteers with intact median nerves and a patient with a transected median nerve using diffusion tensor imaging combined with fiber tracking. The median nerve could be Visualized and correlated well to the expected location on T1-weighted images in the patient and all volunteers. The transected median nerve in the patient could be detected Lip to the site of repair one month postoperatively, whereas the nerve Could not be detected more distally immediately after repair. Two months postoperatively, it could clearly be tracked more distally, indicating nerve regeneration. Diffusion tensor imaging can detect the median nerve in healthy individuals as well as LIP to the lesion site in a patient with a complete transection of the median nerve. (C) 2005 Elsevier Inc. All rights reserved

CLINICAL IMPLICATIONS OF CEREBRAL REORGANISATION AFTER PRIMARY DIGITAL FLEXOR TENDON REPAIR

After flexor tendon injury, most attention is given to the quality of the tendon repair and postoperative early passive dynamic mobilisation. Schemes for active mobilisation have been developed to prevent tendon adhesions and joint stiffness. This paper describes five patients to demonstrate the cerebral consequences of immobilisation allowing only passive movements, which implies a prolonged absence of actual motor commands. At the end of such immobilisation, PET imaging revealed reduced blood flow in specific motor areas, associated with temporary loss of efficient motor control. Effective motor control was regained after active flexion exercises which was reflected in normalised cerebral activations. This suggests that temporary, reversible cerebral dysfunction may affect the outcome of flexor tendon injuries

Cerebral reorganisation of human hand movement following dynamic immobilisation

Surgical treatment of a flexor tendon lesion of the hand is followed by a 6-week period of dynamic immobilisation. This is achieved by the elastic strings of a Kleinert splint, enabling only passive and no active flexor movements. After such immobilisation, the appearance of a temporary clumsy hand indicates decreased efficiency of cerebral motor control. Using PET we identified the recruitment of contralateral parietal and cingulate activations specifically related to the suboptimal character of these hand movements. After 6-8 weeks, normalised movement was related with contralateral putamen activation. Activations of the sensorimotor cortex and cerebellum were present during both scanning sessions. Changes in the pattern of cerebral activations reflect functional reorganisation. The shift from cortical to striatal involvement, observed in the group of four patients, generates the concept of unlearned movements being relearned. (C) 2003 Lippincott Williams Wilkins