Contextual interference and augmented feedback: is there an additive effect for motor learning?

Learning to perform a skilled behavior is affected by the context of the practice session and the frequency of augmented feedback. We studied the combined effect of these variables in the acquisition of a ballistic, bi-directional lever movement pattern involving four different target locations as measured by performance in practice, retention, and transfer tests. Augmented feedback was presented in either an every-trial or a faded schedule during random and blocked practice. Consistent with the contextual interference effect, the blocked practice group produced lower errors in acquisition, but the random practice group outperformed the blocked practice group in both retention and transfer. In contrast, faded feedback did not have a beneficial effect on learning and degraded learning when provided during blocked practice. While the results were consistent with previous findings of random and blocked practice, they were not consistent with previous findings of reduced feedback frequencies.

Cerebral and cerebellar sensorimotor plasticity following motor imagery-based mental practice of a sequential movement.

Motor behavior and sensorimotor activation of the cerebrum and cerebellum were measured before and after motor imagery-based mental practice (MP) and physical practice (PP) of a sequential motor task. Two-button-press sequences (A, B) were performed outside a magnetic resonance imaging scanner and at 2 Hz inside the scanner during a pretest. Participants (n = 39) completed PP, MP, or no practice (NP) of Sequence A for 1 week and were posttested. Sequence A performance improved 121%, 86%, and 4% for the PP, MP, and NP groups, respectively (p < 0.05), while Sequence B improved 56%, 40%, and 38% (p > 0.05). PP improvements were accompanied by increased striatal and decreased cerebellar activation, while MP improvements were accompanied by increased cerebellar, premotor, and striatal activation. The efficacy of MP for activating cerebral and cerebellar sensorimotor networks suggests that MP might be an effective substitute or complement to PP to activate compensatory networks for motor rehabilitation.

An fMRI investigation of hand representation in paraplegic humans.

OBJECTIVE: Cortical reorganization can occur after deaf-ferentation due to loss of a limb, but the nature of the cortical reorganization after spinal cord injury (SCI) is still in debate. METHODS: Using a 1.5T MRI, we scanned paraplegic and noninjured participants during hand movement and palm stimulation, to determine whether longterm paraplegics would show different patterns of cortical activity from the noninjured participants. RESULTS: The SCI group showed stronger activation in areas posterior, rather than superior, to the areas activated by non-SCIs. Conversely, the non-SCIs showed stronger activation in more anterior areas. The signal at each individual's maximally significant voxel had a greater modulation for the SCI group than for the non-SCIs, in response to movement. CONCLUSIONS: In this study of sensory and motor representations within the same subjects, the authors show for the first time the increase in the BOLD fMRI signal modulation in SCI. The authors do not find evidence of expansion of the hand representation into nearby cortical areas, and they corroborate previous EEG studies indicating a posterior shift for hand motor representation after SCI, while showing that the sensory representation does not undergo a posterior shift of similar magnitude. The difference between the reorganization found here and the reorganization typically found following amputations suggests a rationale for the differences in neuropathic pain symptoms following a spinal cord injury or amputation.

Comparing chronic pain from spinal cord injury to chronic pain of other origins.

Acknowledged as a serious complaint of spinal cord injured (SCI) patients, chronic pain in this population is neither well studied nor well understood. To assess the quality and intensity of pain, a group of 49 SCI patients seeking treatment for chronic pain was compared to a general group of 95 patients from the Comprehensive Pain Clinic (CPC) on selected demographic variables, the McGill Pain Questionnaire (MPQ) and the Minnesota Multiphasic Personality Inventory (MMPI). The SCI patients were categorized as functionally incomplete SCI (SCI-I) or complete SCI (SCI-C). Multivariate analyses revealed differences among groups on the MPQ for Number of Words Checked, Rank Sum, and the Affective dimension. In all cases the CPC group scored higher than the SCI-C group. The MMPI profiles were elevated and typical for the CPC and SCI-C groups and substantially less elevated for the SCI-I group. We suggest in cases where chronic pain is secondary to a chronic medical catastrophe, aspects of the MPQ and the MMPI assess the person's total medical disability and not just the meaning and impact of pain.

Treating chronic low back pain. I. Admissions to initial follow-up.

For a normative study of chronic low back pain (CLBP), 702 consecutive admissions to a large multidisciplinary CLBP treatment program were assessed at admission, discharge, and 1-month follow-up, using a variety of psychological and functional performance instruments. Both univariate and multivariate approaches to appraising success are evaluated. Psychological profiles demonstrated a substantial degree of disability at admissions, which is significantly reduced at follow-up. Both behavioral and cognitive aspects of performance, as evidenced by objective assessments of patients' physical abilities and verbalizations, improved as a direct function of length of stay in the treatment program and continued to show modest improvement through follow-up. Composite indices of improvement demonstrated favorable outcomes for no less than four in every ten, and as high as nine in every ten participants. Because of the large sample size, relationships both within and across measurement domains can be assessed statistically: the separate sets of outcome measures, with the exception of psychological profiles, are generally independent of each other.

Treating chronic low back pain. II. Long-term follow-up.

Appraisal of chronic low back pain (CLBP) treatment outcome is incomplete unless results can be shown to be stable over an extended follow-up period. This paper concentrates on methods by which the long-term trends of objective outcome assessments can be studied and predictions developed given incomplete data. Employment and litigation status, self-rating of pain, activities, medications, and hospitalizations related to pain were periodically assessed in up to 210 graduates of a CLBP treatment program, over a period of 6 months to 5 years following treatment. Favorable outcomes were achieved by many of the respondents, and a good degree of stability in outcomes was observed in several of the measures. Few indicators were found which adequately predict long-term outcomes, however. Attrition in the sample and other possible systematic sources of bias are discussed.

Signal detection and threshold measures to loud tones and radiant heat in chronic low back pain patients and cohort controls.

Eleven chronic low back pain (CLBP) and 11 age- and sex-matched control subjects were tested during two separate sessions for the perception of radiant heat and uncomfortably loud tones. Following the determination of a subject's pain threshold (PT) for radiant heat, a standard signal detection methodology was used to present 26 trials each of 4 stimulus levels. The stimuli were rated on a 9-point scale ranging from 'nothing' to 'very strong pain.' A similar procedure was used for the tone stimuli with the 9-point scale ranging from 'nothing' to 'very strongly uncomfortable.' It was found that the CLBP group had both higher heat pain and tone discomfort thresholds than the control group. For radiant heat only, the CLBP group had poorer discrimination as determined by P(I). The results are discussed within the framework of the hypervigilance and adaptation theories of pain perception.