Specific Deficit in Implicit Motor Sequence Learning following Spinal Cord Injury.

Physical and psychosocial rehabilitation following spinal cord injury (SCI) leans heavily on learning and practicing new skills. However, despite research relating motor sequence learning to spinal cord activity and clinical observations of impeded skill-learning after SCI, implicit procedural learning following spinal cord damage has not been examined.To test the hypothesis that spinal cord injury (SCI) in the absence of concomitant brain injury is associated with a specific implicit motor sequence learning deficit that cannot be explained by depression or impairments in other cognitive measures.Ten participants with SCI in T1-T11, unharmed upper limb motor and sensory functioning, and no concomitant brain injury were compared to ten matched control participants on measures derived from the serial reaction time (SRT) task, which was used to assess implicit motor sequence learning. Explicit generation of the SRT sequence, depression, and additional measures of learning, memory, and intelligence were included to explore the source and specificity of potential learning deficits.There was no between-group difference in baseline reaction time, indicating that potential differences between the learning curves of the two groups could not be attributed to an overall reduction in response speed in the SCI group. Unlike controls, the SCI group showed no decline in reaction time over the first six blocks of the SRT task and no advantage for the initially presented sequence over the novel interference sequence. Meanwhile, no group differences were found in explicit learning, depression, or any additional cognitive measures.The dissociation between impaired implicit learning and intact declarative memory represents novel empirical evidence of a specific implicit procedural learning deficit following SCI, with broad implications for rehabilitation and adjustment

Control group: Demographic information.

<p>Control group: Demographic information.</p

How many strides are required for a reliable estimation of temporal gait parameters? Implementation of a new algorithm on the phase coordination index

<div><p>Background</p><p>The Phase coordination index (PCI), a temporal gait measure that quantifies consistency and accuracy in generating the anti-phased left-right stepping pattern, assesses bilateral coordination of gait in various cohorts (e.g., Parkinson's disease, post stroke). As PCI is based on mean values calculated across a series of gait cycles, individuals are required to perform lengthy walking trials, prolonging gait assessments which cause discomfort to some of them. This study introduces an algorithm to identify the required number of strides to obtain a reliable, characteristic PCI value.</p><p>Methods</p><p>Simulated data sets, as well as physiological data (obtained from healthy elderly and young persons, from over ground and treadmill trials) were used in this research. A series of N-1 PCI values was calculated for i = 2,3,4…N gait cycles for each participant. There is a value i = k, representing certain number of cycles, for which no significant change in PCI occurs as additional cycles are added, termed point of stabilization (POS). The algorithm presented here uses a 2-stage iterative process to determine POS. Stage 1 searches for the gross location of the interval of PCI values containing the POS. In stage 2, the algorithm performs a high-resolution recursive, iterative process within this interval to find the exact point. The criterion for defining stability within a window of PCI values is a coefficient of variation (CV) of ≤ 5%.</p><p>Results</p><p>Our recursive, iterative algorithm indicates that ~23 strides on average should be captured to attain a characteristic PCI.</p><p>Conclusions</p><p>Gait trials with at least 23 strides on average should suffice to obtain a reliable estimation of PCI in healthy young adults. While this methodology may be considered generic, future studies should obtain POS values based on additional cohorts (e.g., disabled participants, fixed walking speeds).</p></div

Rey Auditory Verbal Learning Task (RAVLT) performance (mean and SEM) in the spinal cord injury and control groups.

<p>Rey Auditory Verbal Learning Task (RAVLT) performance (mean and SEM) in the spinal cord injury and control groups.</p

Spinal cord injury group: Demographic and clinical information.

<p>Spinal cord injury group: Demographic and clinical information.</p

Serial Reaction Time (SRT) task performance (mean and SEM) in the spinal cord injury and control groups.

<p>Serial Reaction Time (SRT) task performance (mean and SEM) in the spinal cord injury and control groups.</p

Schematic representation of the SRT task.

<p>In each trial, the visual cue appears and the participant responds by selecting the appropriate response on the keyboard. The cue then disappears, ending the trial and, following a fixed delay, another visual cue marks the beginning of a new trial. In the current study, there were 12 trials per sequence, 9 sequences per block, and 8 blocks, of which the first 6 used a repeating sequence, the 7^th used a random interference sequence, and the 8^th returned to the original repeating sequence (recovery).</p

Algorithm performance on real data sets.

<p>(a) The average of the last 3 PCI values was considered the ‘final PCI’. PCI data of all participants were aligned to POS. The absolute error from the i^th stride after POS was calculated for POS+i, where i = {-20,…,20} and averaged per group. Note that each of the four lines shows the average of one tested group of participants. As expected, the error significantly decreases before POS and only slightly decreases after POS. It is noted that the PCI vector was padded with the first and last PCI values at either end to obtain a larger vector in cases where there are less than 20 values before/after POS per participant in each group. (b) Distribution of the True Errors calculated from the detected POS relative to the ‘final PCI’.</p

Plots illustrating the absolute error per stride (independent of the algorithm) averaged per participant within each group.

<p>Plots illustrating the absolute error per stride (independent of the algorithm) averaged per participant within each group.</p