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The present study used functional magnetic resonance imaging (fMRI) to compare the neural activation patterns of children diagnosed with autistic disorder (AD), attention defi cit hyperactivity disorder (ADHD), and typically developing controls (TCs) in response to a task involving evaluation of facial expressions. Substantially greater functional activity was noted in TCs compared to both subjects diagnosed with AD and ADHD. Consistent with previous studies, differences in functional activation of the amygdala, fusiform gyrus, cerebellum, mesolimbic, and temporal lobe cortical regions of the brain during a task evaluating facial expressions were noted in AD compared to TCs. Differences in the neural activity in these brain regions were also observed in children diagnosed with AD compared to those diagnosed with ADHD. Overall decreased neural activity was observed during the faces task performance in the AD group compared to the other two groups, a fi nding consistent with studies using adults. Both TC and ADHD control groups showed increased inferior frontal cortex activity compared to the AD group. Signifi cant activity was present in both TC and ADHD control groups in the insula which was absent in the AD group; this is consistent with other studies showing dysfunction of the mesolimbic system in children with AD. Although frontostriatal and mesolimbic systems appear to be affected in AD, these defi cits were not in the same attentional networks which are dysfunctional in children diagnosed with ADHD.

Seventy children aged 2 to 7 years were exposed to the MRI environment through a series of steps typical of a research study. Their willingness to proceed through the process was used to estimate the prevalence of fear. Thirty-seven children (53%; 95% confidence interval [41%, 65%]) completed the approach sequence. Although the correlation of child age in months (Mean (M) 5 60.1, standard deviation 5 16.5, N 5 70) and highest successful step (M 5 5.8, standard deviation 5 2.6, 95% confidence interval [5.2, 6.4 MRI environments present psychological risks to those being imaged (1). Risks include transitory fear and panic (2) that sometimes result in prematurely terminated scans (3). Long-term effects have also been reported, including both increases and decreases in claustrophobic feelings in MRI settings (4) and in other enclosed spaces (5). A number of studies have reported proportions of people who show strong fear and refuse to receive an MRI scan unless sedated (1). These data are inadequate for estimating the prevalence of fear in children or their willingness to participate in MRI research studies.The available data on psychological risks of MRI come mainly from adult patients in clinical settings, where the MRI is often being used to diagnose a potentially serious medical condition. These situations present additional stresses to patients and may exacerbate fearful reactions to the MRI environment. The difference, if any, between fear prevalence under these conditions versus prevalence in MRI research contexts is unknown. Furthermore, the risks for children are less well studied (with the exception of Dewey et al. (6)) but may differ from those for adults due to limited understanding of the environment and reduced ability to communicate with those administering the scan.Researchers and ethics boards require data regarding the probability and severity of all of these effects in order to make accurate judgments of the risk/benefit ratio for prospective participants and to help estimate the numbers of participants who must be recruited in order to have a final sample of desired size. The lack of data on the reactions of children to MRI in research settings increases the likelihood that children will be excluded from research and the benefits it may provide. The present study addressed this need. We estimated the population proportion of children aged 2 through 7 (n ¼ 70) who demonstrated willingness to enter an MRI scanner in a nonclinical research situation. MATERIALS AND METHODS ParticipantsSeventy children (41 male, 29 female) between the ages of 2 and 7 years participated. Parents were recruited through advertisements in the local papers and information sheets and posters. Standard MRI exclusion criteria were in place; children were excluded if parents indicated that the child may have any metal in the body (with the exception of amalgam fillings; however, none of the children had these fillings) and diagnosis of claustrophobia or fear of tight or enclosed spaces. A parent provided informed consent and w...

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