Learning Redundant Motor Tasks With and Without Overlapping Dimensions: Facilitation and Interference Effects

Prior learning of a motor skill creates motor memories that can facilitate or interfere with learning of new, but related, motor skills. One hypothesis of motor learning posits that for a sensorimotor task with redundant degrees of freedom, the nervous system learns the geometric structure of the task and improves performance by selectively operating within that task space. We tested this hypothesis by examining if transfer of learning between two tasks depends on shared dimensionality between their respective task spaces. Human participants wore a data glove and learned to manipulate a computer cursor by moving their fingers. Separate groups of participants learned two tasks: a prior task that was unique to each group and a criterion task that was common to all groups. We manipulated the mapping between finger motions and cursor positions in the prior task to define task spaces that either shared or did not share the task space dimensions (x-y axes) of the criterion task. We found that if the prior task shared task dimensions with the criterion task, there was an initial facilitation in criterion task performance. However, if the prior task did not share task dimensions with the criterion task, there was prolonged interference in learning the criterion task due to participants finding inefficient task solutions. These results show that the nervous system learns the task space through practice, and that the degree of shared task space dimensionality influences the extent to which prior experience transfers to subsequent learning of related motor skills

The Effect of Movement Rate and Complexity on Functional Magnetic Resonance Signal Change During Pedaling

We used functional magnetic resonance imaging (fMRI) to record human brain activity during slow (30 RPM), fast (60 RPM), passive (30 RPM), and variable rate pedaling. Ten healthy adults participated. After identifying regions of interest, the intensity and volume of brain activation in each region was calculated and compared across conditions (p \u3c .05). Results showed that the primary sensory and motor cortices (S1, M1), supplementary motor area (SMA), and cerebellum (Cb) were active during pedaling. The intensity of activity in these areas increased with increasing pedaling rate and complexity. The Cb was the only brain region that showed significantly lower activity during passive as compared with active pedaling. We conclude that M1, S1, SMA, and Cb have a role in modifying continuous, bilateral, multijoint lower extremity movements. Much of this brain activity may be driven by sensory signals from the moving limbs

Pedaling alters the excitability and modulation of vastus medialis H-reflexes after stroke

Objective Individuals post-stroke display abnormal Group Ia reflex excitability. Pedaling has been shown to reduce Group Ia reflexes and to normalize the relationship between EMG and reflex amplitude in the paretic soleus (SO). The purpose of this study was to determine whether these changes extend to the paretic quadriceps. Methods H-reflexes were used to examine Group Ia reflex excitability of the vastus medialis (VM). H-reflexes were elicited in paretic (n = 13) and neurologically intact (n = 13) individuals at 11 positions in the pedaling cycle and during static knee extension at comparable limb positions and levels of VM EMG. Results VM H-reflexes were abnormally elevated in the paretic limb of stroke survivors. During static muscle activation, H-reflex amplitude did not change with the level of background VM activity. Pedaling reduced the amplitude of paretic VM H-reflexes and restored the normal relationship between VM EMG and H-reflex amplitude. Conclusions Pedaling-induced changes in Group Ia reflex excitability that have been reported for the paretic SO are evident in the paretic VM. Pedaling may have a generalized effect on lower extremity Group Ia reflexes post-stroke. Significance Pedaling may be therapeutic for reducing Group Ia reflexes after stroke

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Health care utilisation and out-of-pocket expenditure associated with back pain: a nationally representative survey of Australian women

Background: Back pain impacts on a significant proportion of the Australian population over the life course and has high prevalence rates among women, particularly in older age. Back pain care is characterised by multiple practitioner and selfprescribed treatment options, and the out-of-pocket costs associated with consultations and self-prescribed treatments have not been examined to date. Objective: To analyse the extent of health care practitioner consultations and self-prescribed treatment for back pain care among Australian women, and to assess the self-reported costs associated with such usage. Methods: Survey of 1,310 women (response rate 80.9%) who reported seeking help for back pain from the '1946-51 cohort' of the Australian Longitudinal Study on Women's Health. Women were asked about their use of health care practitioners and self-prescribed treatments for back pain and the costs associated with such usage. Results: In the past year 76.4% consulted a complementary and alternative practitioner, 56% an allied health practitioner and 59.2% a GP/medical specialist. Overall, women consulted with, on average, 3.0 (SD = 2.0) different health care practitioners, and had, on average, 12.2 (SD = 9.7) discrete health care practitioner consultations for back pain. Average self-reported out-of-pocket expenditure on practitioners and self-prescribed treatments for back pain care per annum was AU$873.10. Conclusions: Multiple provider usage for various but distinct purposes (i.e. pain/mobility versus anxiety/stress) points to the need for further research into patient motivations and experiences of back pain care in order to improve and enhance access to and continuity of care. Our results suggest that the cost of back pain care represents a significant burden, and may ultimately limit women's access to multiple providers. We extrapolate that for Australian working-age women, total out-of-pocket expenditure on back pain care per annum is in excess of AU$1.4billion, thus indicating the prominence of back pain as a major economic, social and health burden