Decreased Interhemispheric Functional Connectivity in Autism

The cortical underconnectivity theory asserts that reduced long-range functional connectivity might contribute to a neural mechanism for autism. We examined resting-state blood oxygen level–dependent interhemispheric correlation in 53 males with high-functioning autism and 39 typically developing males from late childhood through early adulthood. By constructing spatial maps of correlation between homologous voxels in each hemisphere, we found significantly reduced interhemispheric correlation specific to regions with functional relevance to autism: sensorimotor cortex, anterior insula, fusiform gyrus, superior temporal gyrus, and superior parietal lobule. Observed interhemispheric connectivity differences were better explained by diagnosis of autism than by potentially confounding neuropsychological metrics of language, IQ, or handedness. Although both corpus callosal volume and gray matter interhemispheric connectivity were significantly reduced in autism, no direct relationship was observed between them, suggesting that structural and functional metrics measure different aspects of interhemispheric connectivity. In the control but not the autism sample, there was decreasing interhemispheric correlation with subject age. Greater differences in interhemispheric correlation were seen for more lateral regions in the brain. These findings suggest that long-range connectivity abnormalities in autism are spatially heterogeneous and that transcallosal connectivity is decreased most in regions with functions associated with behavioral abnormalities in autism. Autism subjects continue to show developmental differences in interhemispheric connectivity into early adulthood

Behavioural characterisation of rats exposed neonatally to bisphenol-A: responses to a novel environment and to methylphenidate challenge in a putative model of attention-deficit hyperactivity disorder.

Contains fulltext : 70090.pdf (publisher's version ) (Closed access)Neonatal exposure of rats to bisphenol-A, an endocrine disruptor, has recently been proposed as a possible animal model of attention-deficit hyperactivity disorder (ADHD), because such rats exhibit motor hyperactivity. To strengthen the face validity of this animal model, the present study replicated the original experiments and additionally analysed both changes in habituation to a novel environment and behavioural responses to methylphenidate, the two phenomena known to be altered in ADHD. Single intracisternal administration of bisphenol-A (20 and 40 microg) into 5-day-old male Wistar rats impaired habituation to a novel environment in the light, but not the dark, phase at 4 weeks of age. Thus, habituation as assessed by time-dependent decrease of locomotor activity, rearing, sniffing and grooming was significantly reduced in bisphenol-A-pretreated rats. Methylphenidate (1 and 3 mg/kg, i.p.) dose-dependently enhanced locomotor activity in both vehicle-pretreated and bisphenol-A-pretreated rats during both the dark and the light phases. Thus, the effects of methylphenidate did not differ between bisphenol-A-pretreated and vehicle-pretreated rats. Apart from a slight methylphenidate-induced increase in rearing and sniffing in bisphenol-A (20 microg)-pretreated rats, the overall effects of methylphenidate on rearing, sniffing and grooming were similar in both vehicle- and bisphenol-A-pretreated rats. It is concluded that neonatal exposure of rats to bisphenol-A is an animal model with limited face validity for ADHD, because the motor hyperactivity and reduced habituation to a novel environment are not accompanied by altered responses to methylphenidate

Autism is associated with reduced ability to interpret grasping actions of others

We investigated the ability of children with ASD to discriminate a small cylinder from a large cube by observing a point-light movie of an actor grasping the object, either from an allocentric or egocentric viewpoint (observing action of others or self). Compared with typically developing controls, high functioning autistic children showed a strong selective impairment in this task, but only with the allocentric viewpoint, where thresholds were twice as high: egocentric thresholds were similar to age- and ability-matched controls. The magnitude of the impairment correlated strongly with the degree of symptomology (R2= 0.5). The results suggest that children with ASD might be impaired in their ability to predict and infer the consequences of others' movements, which could be related to the social-communicative deficits often reported in autism