A number of studies have reported that the digit ratio 2D:4D (length of the second finger divided by length of the fourth finger) is smaller (longer fourth digit) in autism spectrum disorder (ASD) than in typically developed (TD) controls. Because form and function are closely related in biological systems, we hypothesized that the 4D dominance occurs in not only finger morphology but also physical performance in ASD. Individuals with ASD and TD controls participated in a multi-digit force-producing task. Individuals with ASD showed a significant 4D dependence compared to TD controls in the task. We found a significant correlation between 4D dependence and scores of the standard diagnostic instrument across individuals with ASD. Our analysis of functional connectivity in resting-state functional MRI suggests that connectivity between the visual cortex and the cerebellum contributes to the 4D dependence. Collectively, these results extend the 2D:4D ratio beyond being a morphological marker to being involved in motor functions in the form of 4D dependence in a multi-digit force task.
Fundamental frequency (F0) of our vocalization is regulated by auditory feedback. Manipulation of F0 in the auditory feedback invokes compensatory F0 response in vocalization, whose amplitude is known to depend on the task (singing or speaking; instruction to follow/ignore the heard pitch change) and the averaged F0. In order to exclude the voluntary factor and to test if the vocal register affected the response amplitude, we used a parametric modulation of F0 according to the maximal sequence [TAF, Kawahara (1992)] and recovered an impulse response with deconvolution during vowel phonation at various averaged F0 (low, at speech fundamental frequency, high) and in two vocal registers (modal and falsetto). The normalized response amplitude increased with F0, which replicates the previous finding, while the vocal register change did not affect the response. Our findings clarify some of the characteristics of tasks dependency of the pitch control.
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