1. Kenet T, Orekhova EV, Bharadwaj H, Shetty NR, Israeli E, Lee AK, Agam Y, Elam M, Joseph RM, Hamalainen MS, Manoach DS. {{Disconnectivity of the cortical ocular motor control network in autism spectrum disorders}}. {Neuroimage};2012 (Jul 16);61(4):1226-1234.
Response inhibition, or the suppression of prepotent but contextually inappropriate behaviors, is essential to adaptive, flexible responding. Individuals with autism spectrum disorders (ASD) consistently show deficient response inhibition during antisaccades. In our prior functional MRI study, impaired antisaccade performance was accompanied by reduced functional connectivity between the frontal eye field (FEF) and dorsal anterior cingulate cortex (dACC), regions critical to volitional ocular motor control. Here we employed magnetoencephalography (MEG) to examine the spectral characteristics of this reduced connectivity. We focused on coherence between FEF and dACC during the preparatory period of antisaccade and prosaccade trials, which occurs after the presentation of the task cue and before the imperative stimulus. We found significant group differences in alpha band mediated coherence. Specifically, neurotypical participants showed significant alpha band coherence between the right inferior FEF and right dACC and between the left superior FEF and bilateral dACC across antisaccade, prosaccade, and fixation conditions. Relative to the neurotypical group, ASD participants showed reduced coherence between these regions in all three conditions. Moreover, while neurotypical participants showed increased coherence between the right inferior FEF and the right dACC in preparation for an antisaccade compared to a prosaccade or fixation, ASD participants failed to show a similar increase in preparation for the more demanding antisaccade. These findings demonstrate reduced long-range functional connectivity in ASD, specifically in the alpha band. The failure in the ASD group to increase alpha band coherence with increasing task demand may reflect deficient top-down recruitment of additional neural resources in preparation to perform a difficult task.
Lien vers le texte intégral (Open Access ou abonnement)
2. Ohta H, Yamada T, Watanabe H, Kanai C, Tanaka E, Ohno T, Takayama Y, Iwanami A, Kato N, Hashimoto R. {{An fMRI study of reduced perceptual load-dependent modulation of task-irrelevant activity in adults with autism spectrum conditions}}. {Neuroimage};2012 (Jul 16);61(4):1176-1187.
Recent studies on selective attention have demonstrated that the perceptual load of a task determines the processing stage at which irrelevant sensory stimuli are filtered out. Although individuals with autism spectrum conditions (ASC) have been repeatedly reported to display several kinds of abnormal behavior related to attention deficits, the neural mechanisms underlying these deficits have not been well investigated within the framework of the load dependency of selective attention. The present study used functional magnetic resonance imaging (fMRI) to examine the brain responses of adults with high-functioning ASC to irrelevant visual distractors while performing a visual target detection task under high or low perceptual load. We observed that the increased perceptual load activated regions of the fronto-parietal attention network of controls and ASC comparably. On the other hand, the visual cortex activity evoked by visual distractors was less modulated by the increased perceptual load in ASC than in controls. Simple regression analyses showed that the degree of the modulation was significantly correlated with the severity of the autistic symptoms. We also observed reduced load-dependent modulation of the functional connectivity between the intraparietal and visual regions in the ASC group. These results revealed neural correlates for abnormal perceptual load-dependent engagement of visual attention in ASC, which may underlie aspects of cognitive and behavioral characteristics of these disorders.
