ASD is conceived as a cognitive-social disorder, yet we have systematically found atypical signatures of movement variability in people with idiopathic ASD. We have also found it in individuals with problems in the conduction of afferent information (e.g. in Ian Waterman who has no sense of touch, pressure or body movements, and in children with SHANK3 syndrome due to a deletion/mutation in chromosome 22q which impedes postsynaptic scaffolding). Since motor variability at the output can also be conceived as re-afferent input, it is possible that in ASD there are problems both at the motor output and at the motor re-afferent input, and that these underly problems with social interactions.
Article Atypical signatures of motor variability found in an individ...
Hi Elizabeth,
Are you sure that the probability distribution is exponential? Maybe it is a power - law distribution (P=x^y). These two may give similar fitting slopes and variances explained. Check how they behave for extreme values region of the distribution. For these values the power-law would decay more slowly than the exponential one.
Exponential distribution means that there is a characteristic value of the variability and power - law that there is no characteristic value of the variability.
Best,
Robert
Thanks Robert. This is very useful information. We do find a power-law scaling with age that seems to be speaking of a maturation process in the signatures of motor variability of typical people across ages (paper still in the typesetting process but will definitely send it to you in a few days to hear your feedback) The trouble with the participants with ASD was that invariably the frequency histograms (of the peak velocity of their trajectories) was well fit by the Exponential distribution. When we used the Gamma family of prob distr and estimated the parameters from the experimental data of the ASD people, these parameters remained stuck in the exponential ranges of shape parameter (near 1) and the scale parameter had high values indicative of higher dispersion than typical controls. Their signatures were closer to those found in 3 year old typical developing infants (as if their motor patterns never evolved). We were very surprised by this because besides 3-12 year old kids with ASD, we were also assessing teenagers and even young adults 25 yo. So we are very intrigued and puzzled by the unanimous (100%) finding across this heterogeneous sample that we examined. Will send you the papers soon and look forward to your input. Thanks!
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