Cortical activation during finger tracking vs. ankle tracking in healthy subjects.

PURPOSE: Explore in healthy subjects whether the differences in cortical activation between ankle and finger movements observed in earlier studies with no attention to accuracy also apply to accuracy-demanding tasks. METHODS: Twenty healthy subjects performed right-finger and right-ankle tracking tasks during functional magnetic resonance imaging. Cortical activation was analyzed in the primary motor area (M1), primary somatosensory area (S1), supplementary motor area (SMA), and premotor cortex (PMC). The blood-oxygen-level-dependent signal intensity of active voxels was compared between the finger and ankle conditions. RESULTS: The results indicated that finger tracking exhibited greater intensity in contralateral (left) M1 and S1 compared to ankle tracking, and ankle tracking exhibited greater intensity in both contralateral and ipsilateral SMA compared to finger tracking. Both M1 and S1 showed more lateralized (contralaterally) organization during finger tracking compared to ankle tracking. Activation maps derived from contrasting the two tracking conditions to each other suggested that ipsilateral areas serve an important role in accuracy-demanding tasks. Regression analysis revealed signal intensity in contralateral M1 and ipsilateral S1 as significant variables in predicting tracking accuracy, but only for finger tracking. CONCLUSIONS: Differences in lateralization between finger and ankle performance found earlier (Kapreli et al., 2006) during simple movement tasks also hold for accuracy-demanding tasks, but dissimilarity in brain organization exists in that the latter show greater ipsilateral activity for both joints. These results invite further research on controlled movements in the lower limb to promote favorable brain reorganization and recovery in people with brain injury.

The influence of reduced visual acuity on age-related decline in spatial working memory: an investigation.

To investigate the relationship between visual acuity and cognitive function with aging, we compared low-vision and normally-sighted young and elderly individuals on a spatial working memory (WM) task. The task required subjects to memorise target locations on different matrices after perceiving them visually or haptically. The haptic modality was included as a control to look at the effect of aging on memory without the confounding effect of visual deficit. Overall, age and visual status did not interact to affect WM accuracy, suggesting that age does not exaggerate the effects of visual deprivation. Young participants performed better than the elderly only when the task required more operational processes (i.e., integration of information). Sighted participants outperformed the visually impaired regardless of testing modality suggesting that the effect of the visual deficit is not confined to only the most peripheral levels of information processing. These findings suggest that vision, being the primary sensory modality, tends to shape the general supramodal mechanisms of memory.

Effects of complete monocular deprivation in visuo-spatial memory.

Monocular deprivation has been associated with both specific deficits and enhancements in visual perception and processing. In this study, performance on a visuo-spatial memory task was compared in congenitally monocular individuals and sighted control individuals viewing monocularly (i.e., patched) and binocularly. The task required the individuals to view and memorize a series of target locations on two-dimensional matrices. Overall, congenitally monocular individuals performed worse than sighted individuals (with a specific deficit in simultaneously maintaining distinct spatial representations in memory), indicating that the lack of binocular visual experience affects the way visual information is represented in visuo-spatial memory. No difference was observed between the monocular and binocular viewing control groups, suggesting that early monocular deprivation affects the development of cortical mechanisms mediating visuo-spatial cognition.

Safety of 6-Hz primed low-frequency rTMS in stroke.

BACKGROUND: Suppression of activity in the contralesional motor cortex may promote recovery of function after stroke. Furthermore, the known depressant effects of low-frequency repetitive transcranial magnetic stimulation (rTMS) can be increased and prolonged by preceding it with 6-Hz priming stimulation. OBJECTIVE: The authors explored the safety of 6-Hz primed low-frequency rTMS in 10 patients with ischemic stroke. METHODS: Priming consisted of 10 minutes of 6-Hz rTMS applied to the contralesional hemisphere at 90% of resting motor threshold delivered in 2 trains/min with 5 s/train and 25-second intervals between trains. Low-frequency rTMS consisted of an additional 10 minutes of 1-Hz rTMS at 90% of resting motor threshold without interruption. Possible adverse effects were assessed with the National Institutes of Health Stroke Scale (NIHSS), the Wechsler Adult Intelligence Scale-Third Edition (WAIS-III), the Hopkins Verbal Learning Test-Revised (HVLT-R), the Beck Depression Inventory-Second Edition (BDI-II), a finger movement tracking test, and individual self-assessments. Pretest, treatment, and posttest occurred on the first day with follow-up tests on the next 5 weekdays. RESULTS: There were no seizures and no impairment of NIHSS, WAIS-III, or BDI-II scores. Transient impairment occurred on the HVLT-R. Transient tiredness was common. Occasional reports of headache, neck pain, increased sleep, reduced sleep, nausea, and anxiety occurred. CONCLUSION: Because there were no major adverse effects, the authors concluded that the treatment was safe for the individuals in this study and that further investigation is now warranted to examine efficacy and safety of serial treatments of 6-Hz primed low-frequency rTMS.

Effect of finger tracking combined with electrical stimulation on brain reorganization and hand function in subjects with stroke.

Synergism of rehabilitative interventions could maximize recovery following stroke. We examined whether the combination of peripherally initiated electrical stimulation of finger extensors and centrally operating finger tracking training could accentuate brain reorganization and its relationship to recovery, beyond the effects of either treatment alone. Twenty subjects with stroke were randomly assigned to an electrical stimulation (ES), tracking training (TR) or combination (CM) group. Each group was trained for ten 1-h sessions over 2-3 weeks. Pretest and posttest measurements consisted of the Box and Block and Jebsen Taylor tests of manual dexterity and a finger tracking test that was performed during functional magnetic resonance imaging (fMRI). fMRI variables included laterality index and BOLD signal intensity of primary motor (M1), primary sensory (S1), sensorimotor (SMC) and premotor (PMC) cortices as well as, supplementary motor area (SMA). ES and CM groups improved on dexterity, whereas the TR group did not. Improvement in the CM group was not greater than the other two groups. Subjects who had an intact M1 showed greater functional improvement than those who had direct involvement of M1. fMRI analysis did not yield significant changes from pretest to posttest. In the CM group only, functional improvement was positively correlated with laterality index change in M1, S1, SMC and PMC, indicating greater ipsilesional control and was negatively correlated with BOLD Signal Intensity change in ipsilesional S1 and SMA, indicating neurophysiological trimming of irrelevant neurons. The correlational results suggest that the combined intervention may be more influential on brain reorganization than either treatment alone but a larger sample size, longer duration of training, or a restricted inclusion of stroke location and volume may be needed to demonstrate a difference in efficacy for producing behavioral changes.

Comparison of finger tracking versus simple movement training via telerehabilitation to alter hand function and cortical reorganization after stroke.

OBJECTIVE: To compare 2 telerehabilitation training strategies, repetitive tracking movements versus repetitive simple movements, to promote brain reorganization and recovery of hand function. METHODS: Twenty subjects with chronic stroke and 10 degrees of voluntary finger extension were randomly assigned to receive 1800 telerehabilitation trials over 2 weeks of either computerized tracking training (track group) with the affected finger and wrist involving temporospatial processing to achieve accuracy or movement training (move group) with no attention to accuracy. Following movement training, the move group crossed over to receive an additional 2 weeks of tracking training. Behavioral changes were measured with the Box and Block test, Jebsen Taylor test, and finger range of motion, along with a finger-tracking activation paradigm during fMRI. RESULTS: The track group showed significant improvement in all 4 behavioral tests; the move group improved in the Box and Block and Jebsen Taylor tests. The improvement for the track group in the Box and Block and Jebsen Taylor tests did not surpass that for the move group. A consistent group pattern of brain reorganization was not evident. The move group, after crossing over, did not show further significant improvements. CONCLUSION: Telerehabilitation may be effective in improving performance in subjects with chronic stroke. Tracking training with reinforcement to enhance learning, however, did not produce a clear advantage over the same amount of practice of random movements. Two weeks of training may be insufficient to demonstrate a behavioral advantage and associated brain reorganization.

Primary motor area activation during precision-demanding versus simple finger movement.

The authors used functional magnetic resonance imaging to explore whether the primary motor area (M1) serves a processing role in a finger-movement tracking task, emphasizing attention to accuracy, beyond its execution role of simple movements, with no attention to accuracy. Twenty healthy subjects performed alternating conditions: Rest, involving no finger movement; Track, involving careful control of a cursor along a target pathway with finger extension/flexion movements; and Move, involving finger extension/flexion movements without careful control. The authors compared volume of activated voxels in the M1, blood-oxygen-level-dependent (BOLD) signal intensity of activated voxels in the M1, and BOLD signal intensity of all voxels in the M1 between the Track and Move conditions. The results showed greater volume and signal intensity in both the contralateral and ipsilateral M1 during Track than during Move. Overall, the results suggest that the M1 is engaged not only in the execution of movements but also in spatial and temporal processing to produce accurately controlled movements. These findings invite further work exploring whether precision-demanding movements, such as tracking, form a more potent stimulus for promoting helpful brain reorganization in the M1 during the recovery from stroke than simple repetitive movements.

Neuroplasticity promoted by task complexity.

One condition that appears to have a strong impact on the neuroplastic changes presumed to subserve skillful motor performance is the complexity of tasks during motor training. This paper reviews some of the morphological, physiological, and behavioral effects associated with training on difficult tasks involving in-depth information processing, compared to simpler tasks, requiring lesser processing.