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Abstract:
The neurocognitive bases of autism remain elusive, but
learning impairment is a likely component of the disorder. We
previously presented fMRI evidence for abnormal cortical motor
organization in autism (Müller et al. Biol Psychiatry, in
press). In the present study, 6 right-handed autistic men (aged
15-39 years) and 5 age-matched normal controls acquired an 8-digit
finger tapping sequence in an explicit learning task during fMRI.
The sequence was visually presented 48 times across two consecutive
5-minute runs, in blocks alternating with a control task
(repetitive tapping with the index finger). In groupwise regression
to a hemodynamic model, both groups showed activation in bilateral
frontal premotor and parietal regions. Control subjects showed
overall stronger activation during "initial learning" (trials 1-24)
than during "subsequent learning" (trials 25-48). This
learning-related reduction was not seen in autistic patients,
consistent with more limited improvement in performance accuracy.
The control group further activated the bilateral caudate nuclei
significantly more than the autism group, especially during
subsequent learning. In contrast, autistic patients showed
abnormally strong activation in right (i.e., ipsilateral) premotor
and parietal regions during both initial and subsequent learning
stages. Our results suggest abnormal neurofunctional organization
for motor learning in autism, which may be related to known
impairments in learning and motor dexterity.
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