Effects of motor imagery training after chronic, complete spinal cord injury.

Abnormalities in brain motor system function are present following spinal cord injury (SCI) and could reduce effectiveness of restorative interventions. Motor imagery training, which can improve motor behavior and modulate brain function, might address this concern but has not been examined in subjects with SCI. Ten subjects with SCI and complete tetra-/paraplegia plus ten healthy controls underwent assessment before and after 7 days of motor imagery training to tongue and to foot. Motor imagery training significantly improved the behavioral outcome measure, speed of movement, in non-paralyzed muscles. Training was also associated with increased fMRI activation in left putamen, an area associated with motor learning, during attempted right foot movement in both groups, despite foot movements being present in controls and absent in subjects with SCI. This fMRI change was absent in a second healthy control group serially imaged without training. In subjects with SCI, training exaggerated, rather than normalized, baseline derangement of left globus pallidus activation. The current study found that motor imagery training improves motor performance and alters brain function in subjects with complete SCI despite lack of voluntary motor control and peripheral feedback. These effects of motor imagery training on brain function have not been previously described in a neurologically impaired population, and were similar to those found in healthy controls. Motor imagery might be of value as one component of a restorative intervention

Brain Areas Associated with Force Steadiness and Intensity During Isometric Ankle Dorsiflexion in Men and Women

Although maintenance of steady contractions is required for many daily tasks, there is little understanding of brain areas that modulate lower limb force accuracy. Functional magnetic resonance imaging was used to determine brain areas associated with steadiness and force during static (isometric) lower limb target-matching contractions at low and high intensities. Fourteen young adults (6 men and 8 women; 27.1 ± 9.1 years) performed three sets of 16-s isometric contractions with the ankle dorsiflexor muscles at 10, 30, 50, and 70 % of maximal voluntary contraction (MVC). Percent signal changes (PSCs, %) of the blood oxygenation level-dependent response were extracted for each contraction using region of interest analysis. Mean PSC increased with contraction intensity in the contralateral primary motor area (M1), supplementary motor area, putamen, pallidum cingulate cortex, and ipsilateral cerebellum (p \u3c 0.05). The amplitude of force fluctuations (standard deviation, SD) increased from 10 to 70 % MVC but relative to the mean force (coefficient of variation, CV %) was greatest at 10 % MVC. The CV of force was associated with PSC in the ipsilateral parietal lobule (r = −0.28), putamen (r = −0.29), insula (r = −0.33), and contralateral superior frontal gyrus (r = −0.33, p \u3c 0.05). There were minimal sex differences in brain activation across the isometric motor tasks indicating men and women were similarly motivated and able to activate cortical motor centers during static tasks. Control of steady lower limb contractions involves cortical and subcortical motor areas in both men and women and provides insight into key areas for potential cortical plasticity with impaired or enhanced leg function

Motor symptoms in Parkinson's disease: A unified framework

Parkinson’s disease (PD) is characterized by a range of motor symptoms. Besides the cardinal symptoms (akinesia and bradykinesia, tremor and rigidity), PD patients show additional motor deficits, including: gait disturbance, impaired handwriting, grip force and speech deficits, among others. Some of these motor symptoms (e.g., deficits of gait, speech, and handwriting) have similar clinical profiles, neural substrates, and respond similarly to dopaminergic medication and deep brain stimulation (DBS). Here, we provide an extensive review of the clinical characteristics and neural substrates of each of these motor symptoms, to highlight precisely how PD and its medical and surgical treatments impact motor symptoms. In conclusion, we offer a unified framework for understanding the range of motor symptoms in PD. We argue that various motor symptoms in PD reflect dysfunction of neural structures responsible for action selection, motor sequencing, and coordination and execution of movement

Impairments in Precision Grip Force Control in Individuals with Parkinson's disease.

Purpose: The purpose of our study is to identify impairments in fine motor control in individuals with Parkinson's disease(PD) during a force-tracking task using force sensors and comparing that to the fine motor control in age-matched controls. We also observed differences in fine motor coordination across a spectrum of patients with varying severity of disease Methods: 30 subjects with Parkinson's disease and 30 age-matched controls participated. Commercially available six-axes force sensors were used to provide an interface for interaction between the subject and the force-tracking task. Subjects tracked a moving sine wave on a computer screen by controlling the amount of force exerted between their index finger and thumb. The two digits were attached to the force sensors that are capable of recording the amounts of force exerted by the subject. During a part of the task, a simultaneous mental activity was introduced and the effect of this distraction was evaluated. Performance of the task was also evaluated using a pseudorandom wave for another three minutes including the distraction components. Results: We compared results between subjects and controls using univariate analysis of variance. Association between the motor score of the Unified Parkinson's disease Rating Scale (UPDRS) and the force tracking variables as well as that between the force tracking variables and chronicity of the disease was evaluated using multiple regression analyses. Individuals with PD showed greater amounts of error, lesser coordination and greater amounts of lag compared to controls. Distraction significantly affected individuals with PD to a greater extent compared to controls. The test showed no association with chronicity of the disease and showed a moderate association to function based on the UPDRS. Clinical Relevance: Deficient hand function in activities that involve fine motor coordination is one of the chief complaints of individuals with Parkinson's disease. The ability to perform activities that involve precision grip depends on the capacity to make fine adjustments to forces in response to the demands placed by complex environments with a number of distractions. Individuals with PD performed with greater deficits on our test especially during the distraction component of the task

Force Amplitude Modulation of Tongue and Hand Movements

Rapid, precise movements of the hand and tongue are necessary to complete a wide range of tasks in everyday life. However, the understanding of normal neural control of force production is limited, particularly for the tongue. Functional neuroimaging studies of incremental hand pressure production in healthy adults revealed scaled activations in the basal ganglia, but no imaging studies of tongue force regulation have been reported. The purposes of this study were (1) to identify the neural substrates controlling tongue force for speech and nonspeech tasks, (2) to determine which activations scaled to the magnitude of force produced, and (3) to assess whether positional modifications influenced maximum pressures and accuracy of pressure target matching for hand and tongue movements. Healthy older adults compressed small plastic bulbs in the oral cavity (for speech and nonspeech tasks) and in the hand at specified fractions of maximum voluntary contraction while magnetic resonance images were acquired. Volume of interest analysis at individual and group levels outlined a network of neural substrates controlling tongue speech and nonspeech movements. Repeated measures analysis revealed differences in percentage signal change and activation volume across task and effort level in some brain regions. Actual pressures and the accuracy of pressure matching were influenced by effort level in all tasks and body position in the hand squeeze task. The current results can serve as a basis of comparison for tongue movement control in individuals with neurological disease. Group differences in motor control mechanisms may help explain differential response of limb and tongue movements to medical interventions (as occurs in Parkinson disease) and ultimately may lead to more focused intervention for dysarthria in several conditions such as PD

Cortical Involvement During Sustained Lower Limb Contractions

Despite the critical role of the lower limb during functional tasks such as walking, most studies examining the role of the cortex during muscle contractions have been conducted in upper limb muscles. Modulation of force by the cortex in the lower extremity and the influence of cortical inputs are poorly understood. The purpose of this dissertation was to investigate the role the cortex plays in modulating force control during static contractions with the lower limb and to determine the influence of manipulating cortical inputs. Aim 1 determined the cortical regions involved in force-related changes between low and high forces and those areas that modulate steadiness (force fluctuations) during sustained isometric ankle dorsiflexion contractions in young men and women. This was achieved using functional magnetic imaging (fMRI). Both motor and some typically associated non-motor brain areas were active during lower limb force production and scaled linearly as force increased. Steadiness was associated with both motor and non-motor brain areas with minimal differences in areas activated between men and women. Aim 2 examined the influence of cognitive demand (null, low-cognitive demand, high-cognitive demand) on fatigability and steadiness of low- to moderate-force isometric contractions in young and older men and women. Women demonstrated greater force fluctuations than men during both the low- and moderate-force contractions and their motor output was influenced by changes in cognitive demand. Older adults were less steady than young during low- and moderate-force contractions, had greater age-related reductions in steadiness, and greater variability in fatigability when cognitive demand was increased. This dissertation shows that cortical inputs are very important to lower limb motor control of static voluntary contractions. Cortical motor and non-motor regions that are important for control of force intensity and steadiness of lower limb contractions were identified and are key areas for potential cortical plasticity with impaired or enhanced leg function. Steadiness was altered by increasing cortical inputs (cognitive demand) especially in older adults whose motor performance was impaired and more variable than young. These results have important performance implications for cognitively demanding and low- to moderate-force tasks that are common to daily function in older adults

Bilateral Grasp Force Coordination in Young and Old Adults.

The purpose of these experiments was to examine the coordination of bilateral isometric grasp force production in young and old adults during maximum and submaximum force tasks produced either simultaneously or sequentially. Thirty-six adults (12 young, 18-28y; 12 old, 65-75y and 12 old-old, 76-85y) participated in the first experiment involving maximum isometric grasp-grasp and grasp-pinch force. In the dominant hand, a force deficit was observed in bilateral compared to unilateral tasks in young adults during both maximum isometric grasp-grasp, -12 ± 5% (p < .05), and grasp-pinch, -20 ± 4% (p < .001), tasks. The force deficit was absent in the old group in both grasp, +4 ± 12%, and grasp-pinch, +5 ± 13%, tasks, as well as in the old-old group during both grasp, -9 ± 8%, and grasp-pinch, -9 ± 8%, tasks. Data therefore suggest that the force deficit is absent in both tasks with aging. These findings are consistent with the mechanism of transcallosal inhibition and degeneration of the corpus callosum in aging. The second experiment examined sequential submaximum maintained grasp force tasks. Twenty-four adults (12 young, 18-28y, and 12 old, 75-85y) participated in this experiment. During sequential light or firm grasp tasks, maintained grasp force in young adults decreased during force rise, -2 ± 1% (p < .05), or relaxation, -13 ± 2% (p < .01), in the opposite hand. The decline in maintained force was even greater in old adults during force rise, -5 ± 1% (p < .01), and relaxation, -15 ± 1% (p < .01), in the opposite hand. Overall, the decline found in maintained grasp during relaxation of the opposite hand was greater than observed during force rise, p < .001, for both age groups. These results were independent of the hand used to maintain force and the force level exerted in either hand. Divided attention is suggested to at least partially account for the decline in maintained force, with the anterior cingulate cortex posited as the locus for the integration of bilateral force production and attention.Ph.D.KinesiologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/57687/2/gconti_1.pd

Rehabilitation Outcome Following Acute Stroke: Considering Ideomotor Apraxia

Stroke is a leading cause of death and the leading cause of adult disability in the United States affecting approximately 795,000 people yearly. Stroke sequelae often span multiple domains, including motor, cognitive, and sensory subsystems. Impairments can contribute to difficulty participating in activities of daily living (ADLs) and translate into disability - a concern for patients and occupational therapists alike. The role of ideomotor apraxia (IMA) in stroke rehabilitation is unclear. Thus, the purpose of these two studies is to investigate stroke rehabilitation outcome while considering the presence of ideomotor apraxia. Stroke causes dysfunctional movement patterns arising from an array of potential etiologies. Agreement exists that understanding the patient's functioning serves as the basis for the rehabilitation process and it is insufficient for clinicians simply to determine functional movement problems without knowing how underlying impairments contribute. Stroke-induced paresis is a prevalent impairment and frequent target of traditional rehabilitation. Stroke rehabilitation often addresses paresis narrowly with little consideration for other stroke consequences. Ideomotor apraxia is one such disorder after stroke that could conceivably limit rehabilitation benefit of otherwise efficacious treatment interventions aimed at remediating paresis. This led us to an initial study of a subject who experienced a single left, ischemic stroke with paresis of his right upper extremity and comorbid ideomotor apraxia. The subject participated in combined physical and mental practice for six consecutive weeks to improve use of his right arm. After intervention, the subject demonstrated clinically significant improvements in functional performance of his more-affected right upper extremity and reported greater self-perception of performance. The subject continued to demonstrate improvements after four weeks with no intervention and despite persistent IMA. This single case report highlights the importance of recognizing that ideomotor apraxia does present after stroke, and traditional stroke rehabilitation efforts directed at paresis can be efficacious for subjects with IMA. Traditional beliefs suggested that ideomotor apraxia does not translate to disability in everyday life and that IMA resolves spontaneously. Despite accumulating evidence of the influence of IMA on functional ability, this topic remains relatively neglected. It is unclear how ideomotor apraxia affects the rehabilitation process. The second study reports rehabilitation outcomes of a group of subjects following acute stroke. The Florida Apraxia Battery gesture-to-verbal command test was used to detect IMA in subjects. Level of independence with a set of ADLs and motor impairment of the more-affected upper extremity was documented at admission and discharge. Study subjects participated in standard of care stroke rehabilitation in the inpatient rehabilitation units. A total of fifteen subjects who sustained a left hemisphere stroke participated in this study - ten with IMA and five without IMA. After rehabilitation, subjects with IMA improved ADL independence and displayed decreased motor impairment of their right upper extremity. Subjects with and without IMA exhibited comparable improvements in ADL independence, but subjects with IMA exhibited less ADL independence upon when compared to subjects without IMA. Additional findings suggested that subjects with IMA were not different with respect to motor impairments and length of stay; however, additional studies with larger sample sizes are needed. In summary, these two studies aid to elucidate the implications of ideomotor apraxia on traditional stroke rehabilitation efforts. Study subjects with ideomotor apraxia after acute stroke still derive benefit from traditional rehabilitation. Because traditional rehabilitation interventions narrowly target motor impairment, these findings support the need for considering IMA as a factor in developing interventions tailored to patients with IMA and possibly as a specific focus for interventions. A step toward addressing this need is to assess whether IMA is present after stroke on a regular basis. This work provides a framework for researchers and clinicians to investigate further how ideomotor apraxia translates into disability. These findings are important since consideration of ideomotor apraxia could influence selection and design of rehabilitation interventions to optimize patient daily functioning after stroke