The aim of this study was to compare the areas of brain activation between complex and simple exercises in a unimanual hand and to assess the possibility of an exercise task for paretic hands following stroke. The subjects included 11 healthy right-handed volunteers. The complex exercise was a wooden ball rotation task with the unimanual hand and the simple exercise was a hand grasp task performed during a functional MRI scan. Stronger activation of the left primary sensorimotor cortex, the left premotor area, and the ipsilateral cerebellum emerged when the complex movement was performed. Ipsilateral activity was located in the primary sensory cortex and premotor area, and contralateral activity was shown in the left cerebellum. These results suggest that a unimanual ball rotation task may be appropriate for rehabilitation of a movable paretic hand in an early stage of stroke recovery, which should provide motor and sensory input using external stimuli, while the simple motor task may appropriate in a compensatory stage, and should inhibit the ipsilateral activity due to maladaptive plasticity.
"On the other hand, transcranial direct current stimulation studies have also reported that cathodal transcranial direct current stimulation over the motor cortex has a facilitative effect on the ipsilateral hand by modulating inhibitory projections between the motor cortices of the two brain hemispheres  . Furthermore, the activity of the ipsilateral motor cortex is known to be changed by various exercise conditions    . "
[Show abstract][Hide abstract] ABSTRACT: Brain plasticity can be classified as adaptive and maladaptive. Maladaptive plasticity indicates hindered functional recovery or the development of an unwanted symptom. Although a considerable amount is known about adaptive plasticity in stroke, relatively little is known of maladaptive plasticity. In the current study, previous studies on motor function-related maladaptive plasticity in stroke are reviewed in terms of compensatory movement pattern (CMP), delayed-onset involuntary abnormal movements (IAMs), and the ipsilateral motor pathway as a motor recovery mechanism. For successful stroke rehabilitation, it is important that the characteristics of maladaptive plasticity are accurately recognized. However, there is a lack of definitive evidence regarding the recognition of motor function-related maladaptive plasticity, although it seems that each of the three above-mentioned topics are involved. As for CMP, patients with a good neurological state as much as having a normal movement pattern, should be considered to have maladaptive plasticity, and in terms of the ipsilateral motor pathway, patients with bilateral innervations can be considered to have maladaptive plasticity. On the other hand, IAMs due to delayed neuronal degeneration should be ruled out in patients with delayed-onset IAMs. Therefore, for the accurate recognition of motor function-related maladaptive plasticity in stroke, a thorough evaluation of neurological state using brain mapping techniques is necessary, and subsequently, the prevention or intensive management of maladaptive plasticity is needed.
"Second, most studies have defined representations through simple evoked movements with intracortical microstimulation (ICMS) in animals (Plautz et al. 2000; Nudo et al. 1996a; Kleim et al. 2004; Molina-Luna et al. 2008) or transcranial magnetic stimulation (TMS) in humans (Pascual- Leone et al. 1993, 1995; Tyc et al. 2005; Pearce et al. 2000). However, since complex volitional movements recruit more extensive resources (Park et al. 2008; Carey et al. 2006; Gerloff et al. 1998) and their representations are key predictors of skill (Ramanathan et al. 2006), defining volitional maps may reflect learning-based reorganization more accurately. Mapping complex skill movements in healthy subjects would also establish a model that could be applied to study mechanisms underlying skill-based rehabilitation in neurological recovery. "
[Show abstract][Hide abstract] ABSTRACT: Complex skill learning at a joint initiates competition between its representation in the primary motor cortex (M1) and that of the neighboring untrained joint. This process of representational plasticity has been mapped by cortically-evoking simple movements. We investigated, following skill learning at a joint, 1) whether comparable processes of representational plasticity are observed when mapping is based on volitionally produced complex movements and 2) the consequence on the skill of the adjacent untrained joint. Twenty-four healthy subjects were assigned to either finger- or elbow-skill training or no-training control group. At pretest and posttest, subjects performed complex skill movements at finger, elbow and ankle concurrent with functional magnetic resonance imaging (fMRI) to define learning and allow mapping of corresponding activation-based representations in M1. Skill following both finger- and elbow- training transferred to the ankle (remote joint) (p = 0.05 and 0.05); however, finger training did not transfer to the elbow and elbow training did not transfer to the finger. Following finger training, location of the trained finger representation showed a trend (p = 0.08) for medial shift towards the representation of adjacent untrained elbow joint; the change in intensity of the latter representation was associated with elbow skill (Spearman's ρ = -0.71, p = 0.07). Following elbow training, the trained elbow representation and the adjacent untrained finger representation increased their overlap (p = 0.02), which was associated with finger skill (Spearman's ρ = -0.83, p = 0.04). Thus, our pilot study reveals comparable processes of representational plasticity with fMRI mapping of complex skill movements as have been demonstrated with cortically-evoked methods. Importantly, these processes may limit the degree of transfer of skill between trained and adjacent untrained joints. These pilot findings that await confirmation in large-scale studies have significant implications for neuro-rehabilitation. For instance, techniques, such as motor cortical stimulation, that can potentially modulate processes of representational plasticity between trained and adjacent untrained representations, may optimize transfer of skill.
[Show abstract][Hide abstract] ABSTRACT: Hand motor tasks are frequently used to assess impaired motor function in neurology and neurorehabilitation. Assessments can be varied by means of hand laterality, i.e. unimanual or bimanual performance, as well as by means of task complexity, i.e. different degrees ranging from simple to complex sequence tasks. The resulting functional activation in human primary motor cortex (M1) has been studied intensively by traditional neuroimaging methods. Previous studies using functional near-infrared spectroscopy (fNIRS) investigated simple hand motor tasks. However, it is unknown whether fNIRS can also detect changes in response to increasing task complexity. Our hypothesis was to show that fNIRS could detect activation changes in relation to task complexity in uni- and bimanual tasks. Sixteen healthy right-handed subjects performed five finger-tapping tasks: unimanual left and right, simple and complex tasks as well as bimanual complex tasks. We found significant differences in oxy-hemoglobin (O(2)Hb) and deoxy-hemoglobin (HHb) concentration in the right hemisphere over M1. Largest O(2)Hb concentration changes were found during complex (0.351+/-0.051 micromol/l) and simple (0.275+/-0.054 micromol/l) right hand tasks followed by bimanual (0.249+/-0.047 micromol/l), complex (0.154+/-0.034 micromol/l) and simple (0.110+/-0.034 micromol/l) left hand tasks. Largest HHb concentration changes were found during bimanual (-0.138+/-0.006 micromol/l) tasks, followed by simple right hand (-0.12+/-0.016 micromol/l), complex left (-0.0875+/-0.007 micromol/l), complex right (-0.0863+/-0.005 micromol/l) and simple left (-0.0674+/-0.005 micromol/l) hand tasks. We report for the first time that fNIRS detects oxygenation changes in relation to task complexity during finger-tapping. The study aims to contribute to the establishment of fNIRS as a neuroimaging method to assess hand motor function in clinical settings where traditional neuroimaging methods cannot be applied.
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