The hemodynamic response in children with Simplex Autism

ABSTRACTBackgroundNumerous functional magnetic resonance imaging (fMRI) studies of the brain-bases of autism have demonstrated altered cortical responses in subjects with autism, relative to typical subjects, during a variety of tasks. These differences may reflect altered neuronal responses or altered hemodynamic response. This study searches for evidence of hemodynamic response differences by using a simple visual stimulus and elementary motor actions, which should elicit similar neuronal responses in patients and controls.MethodsWe acquired fMRI data from two groups of 16 children, a typical group and a group with Simplex Autism, during a simple visuomotor paradigm previously used to assess this question in other cross-group comparisons. A general linear model estimated the blood-oxygen-level-dependent (BOLD) signal time course, and repeated-measures analysis of variance tested for potential cross-group differences in the BOLD signal.ResultsThe hemodynamic response in Simplex Autism is similar to that found in typical children. Although the sample size was small for a secondary analysis, medication appeared to have no effect on the hemodynamic response within the Simplex Autism group.ConclusionsWhen fMRI studies show BOLD response differences between autistic and typical subjects, these results likely reflect between-group differences in neural activity and not an altered hemodynamic response.

▸ Many fMRI/fcMRI studies report differences between autistic and typical children. ▸ Differences may relate to differential neurovascular coupling. ▸ We compare visuomotor task-evoked BOLD signal in Simplex Autism to typical children. ▸ Hemodynamic response in Simplex Autism children is comparable to typical children. ▸ Results in autism studies likely reflect differences in neural activity not coupling.