Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale
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The goal of this study was to investigate how voluntarily abducting one arm, 90 degrees at onset of a rotational perturbation of the support surface, influences the recovery of upright stance. Young adults were tested under four stance conditions: abducting one arm to the horizontal only (AO); perturbation of stance using a support surface rotation only (PO); combined support surface rotation and abduction of the downhill arm, ipsilateral to tilt (IPS); and fourth abduction of the uphill, contralateral arm (CON). Simultaneous auditory and visual trigger cues were used for arm raising. ⋯ We conclude that triggered arm abduction, contralateral to the direction of support surface rotation, had significant stabilization benefits for young adults and ipsilateral arm movements had destabilizing effects. The arm raises could be simultaneously executed with balance corrections. These results provide insights into the integration of balance corrections and voluntary commands into one automatic reaction that may be useful in training fall avoidance.
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Chronic low back pain (CLBP) patients achieve postural stability during challenging stance conditions by increasing sway speed. We investigated the mechanisms underlying this behavior, and whether postural strategy selection may be influenced by short-term experience of postural perturbation. Thirteen CLBP patients and thirteen age-matched controls underwent posturography tests. ⋯ Platform translation findings show that both groups aimed at optimizing their posture selection strategy based on prior testing experience. CLBP patients make use of a different postural motor strategy to maintain quiet stance. This is probably the consequence of an imprecise internal estimate of body sway, due to reduced accuracy in the sensory integration process.
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Fitts' Law is commonly found to apply to motor tasks involving precise aiming movements. Children with cerebral palsy (CP) have severe difficulties in such tasks and it is unknown whether they obey Fitts' Law despite their motor difficulties. If Fitts' Law still does apply to these children, this would indicate that this law is extremely robust and that even performance of children with damaged central nervous systems can adhere to it. ⋯ The intercept 'a', corresponding to the time required to realize a tapping movement, was higher in the affected hand of the children in the CSH group. Although, the slope b (which reflects the sensitivity of the motor system to a change in difficulty of the task) and the reciprocal of slope (that represents the cognitive information processing capacity, expressed in bits/s) were similar in both groups. In conclusion, children with CSH obey Fitts' Law despite very obvious limitations in fine motor control.
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Hippocampal functions appear to be segregated along the dorso-ventral axis of the structure. Differences at the cellular and local neuronal network level may be involved in this functional segregation. In this study the characteristics of CA1 recurrent inhibition (RI) were measured and compared between dorsal (DH, n = 95) and ventral (VH, n = 60) hippocampal slices, using recordings of suprathreshold field potentials. ⋯ Specifically, in VH compared to DH, the PS suppression at 20 ms was 34.4 +/- 4.5% versus 69.9 +/- 6.5% (P < 0.001), the time constant of RI decay was 29 +/- 2.4 versus 87.5 +/- 13.6 ms (P < 0.01) and the duration was 50 versus 125 ms (P < 0.001). Thus, GABAA-mediated RI may control the CA1 excitatory output less effectively in VH compared to DH. The observed dorso-ventral differences in RI contribute to the longitudinal diversification of the structure and may underlie to some extent the region-specificity of hippocampal functions.
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The interaction between cold sensitivity and inflammation in mammals is not entirely understood. We have used adult rat dorsal root ganglion neurones in primary culture together with calcium microfluorimetry to assess the effects of selected inflammatory mediators on cold responses of cold- and menthol-sensitive (most likely TRPM8-expressing) neurones. ⋯ In both cases the effects were mainly restricted to the subgroups of cold- and menthol-sensitive cells which had responded to the application of the inflammatory agents at basal temperature. This desensitization of cold-sensitive neurones may enhance inflammatory pain by removing the analgesic effects of gentle cooling.