Combining frequency and time domain approaches to systems with multiple spike train input and output

A frequency domain approach and a time domain approach have been combined in an investigation of the behaviour of the primary and secondary endings of an isolated muscle spindle in response to the activity of two static fusimotor axons when the parent muscle is held at a fixed length and when it is subjected to random length changes. The frequency domain analysis has an associated error process which provides a measure of how well the input processes can be used to predict the output processes and is also used to specify how the interactions between the recorded processes contribute to this error. Without assuming stationarity of the input, the time domain approach uses a sequence of probability models of increasing complexity in which the number of input processes to the model is progressively increased. This feature of the time domain approach was used to identify a preferred direction of interaction between the processes underlying the generation of the activity of the primary and secondary endings. In the presence of fusimotor activity and dynamic length changes imposed on the muscle, it was shown that the activity of the primary and secondary endings carried different information about the effects of the inputs imposed on the muscle spindle. The results presented in this work emphasise that the analysis of the behaviour of complex systems benefits from a combination of frequency and time domain methods

Effects of massage on the mechanical behaviour of muscles in adolescents with spastic diplegia: a pilot study

Calf muscles of five adolescents aged 12 to 15 years (three males, two females) with spastic diplegia were massaged for 14 minutes twice a week for 5 weeks in a controlled sequence, stretching the muscles transversely rather than longitudinally, without eliciting pain. Slow, passive test stretches were applied before and after massage. After massage, the range of movement was not consistently increased but, on average, greater force was needed to stretch the muscle than before massage. However, after massage the resting ankle angle sometimes changed so that the calf muscles were either shorter or longer. We suggest that these phenomena could be explained if massage resets sarcomere lengths which corrects for thixotropic effects (i.e. previous use modifies a muscle's mechanical behaviour). A redistribution on sarcomere lengths within muscles could also have reset proprioceptive feedback. The incidence of abnormal stretch reflexes during test stretches fell from 40 to 22%, comparing the first five sessions with the last five sessions. The amplitude of voluntary alternating ankle rotation increased in three participants. Motor skills were assessed with the Gross Motor Function Measure-66 (GMFM-66) 1 week before the test period, during the 5th week, and 12 weeks later. Our participants in Gross Motor Function Classification System (GMFCS) Levels I and II made sustained improvements in GMFM-66 scores (6.4% at 5 weeks falling to 5.5% at 17 weeks), one increase being significant. One participant in GMFCS Level III improved significantly only after massage of all leg muscles for 30 weeks. © 2007 Blackwell Publishing Ltd