Contextual probability evaluation in autistic, receptive developmental language disorder, and control children: event-related brain potential evidence

Effects of ORG-2766 on brain event-related potentials of autistic children

A double-blind, placebo-controlled study examined the effects of 6 weeks of treatment with the adrenocorticotropin4-9 analogue ORG-2766 (40 mg/day) on brain event-related potentials (ERPs) of autistic children. In visual and auditory oddball paradigms (with task and nontask conditions), standard (80%), target (10%), and unexpected novel stimuli (10%) were presented. ORG-2766 (a) increased the occipital P3 component of the ERP to visual targets, (b) decreased the occipital P3 component of the ERP to auditory targets, (c) did not affect visual and auditory parietal target P3 components, and (d) also did not affect the A/Pcz/300 to auditory novel stimuli. In addition, ORG-2766 treatment increased the N1 component of the ERP to task-irrelevant auditory stimuli.

Sensory modulation of auditory stimuli in children with autism and receptive developmental language disorder: event-related brain potential evidence

Three groups of age- and PIQ-matched children (Autism, Receptive Developmental Language Disorder, and normal controls) participated in two event-related brain potential (ERP) experiments. Each of these experiments was aimed at evaluating whether either of the two clinical groups of children demonstrated abnormalities in two auditory ERP components, N1 and P2, which are known to be dependent on stimulus characteristics (frequency, intensity, and probability), and believed to be generated within primary and secondary cortex. Results of Experiment 1 provide partial support for the idea that both clinical groups failed to fully process changes in stimulus intensity as indexed by the N1 component. Results are discussed in reference to potential abnormalities in serotonergic regulation of auditory cortex.

Auditory event-related brain potentials in autistic children and three different control groups

ERPs to auditory stimuli, generated during an oddball task, were obtained in a group of autistic children and three control groups (normal, ADDH, and dyslectic children, respectively). The task included the presentation of standards, deviants, and novels and had a (between-group) passive vs. active (counting) condition. It was examined whether 1) it was possible to replicate several earlier findings, 2) autistics manifest an abnormal lateralization pattern of ERPs, 3) autistics have an abnormal mismatch negativity (MMN), and 4) differences between autistics and normals are really specific to the autistic group. The only finding that could be replicated was that autistics have a smaller A/Pcz/300. There was no evidence for abnormal lateralization or abnormal MMN; however, there was an unexpected effect of the task manipulation on the amplitude of the P3: in autistics, the occipital P3 to deviant stimuli was significantly larger in the active than in the passive condition, a finding, like the replication of the smaller A/Pcz/300, specific to the autistic group. It was suggested that the auditory occipital task effect is related to understimulation of the occipital lobe by visual stimuli in autistic children.

Abnormal classical eye-blink conditioning in autism

Cerebellar and limbic system pathologies have been reported in persons with autism. Because these brain areas are involved centrally in the acquisition and performance in classical eye-blink conditioning, this study evaluated conditioning in 11 persons with autism. Compared to matched controls, persons with autism learned the task faster but performed short-latency, high-amplitude conditioned responses. In addition, differences in learning the extinction rates systematically varied with age thus suggesting a developmental conditioning abnormality in autism. The observed pattern of eye-blink conditioning may indicate that persons with autism have the ability to rapidly associate paired stimuli but, depending on processing of certain contextual information, have impairments in modulating the timing and topography of the learned responses. This abnormality may relate to deviant cerebellar-hippocampal interactions. The classical eye-blink conditioning paradigm may provide a useful model for understanding the biological and behavioral bases of autism.

Childhood autism: An appeal for an integrative and psychobiological approach

The difficulty that a person with autism has in establishing relationships, maintaining them (communicating and responding appropriately) is a common experience of those close to them., That impaired perceptual and cognitive processing can underlie this difficulty and the interactions of people with autism with the material environment has been established in the laboratory. The consequences at a psychological level of analysis may converge in the inadequacy of second-order representations of the world. An attenuation of such endogenous monitoring processes could also indirectly account for features of withdrawal and the stereotypies often observed. At another level of analysis there are delays in neurotransmission, in the CNS and a lack of flexibility of physiological response shown by evoked potential recordings. Tomographic studies of blood flow and metabolism illustrate a lack of correlation between information processing centres in the brain that may sometimes arise from diffuse gray matter atrophy. A "stop-go" form of modulation of central processing is mediated by anomalous ascending serotonergic and dopaminergic function (transmitters with inhibitory and switching functions). On these bases it is no wonder that representations are not formed and inappropriate and repetitive behaviors follow, although the link remains somewhat speculative. Both levels of analysis are useful for an explanation. As behavioral and pharmacotherapy, though helpful, are severely limited in their efficacy, more effort is required to synthesize the different levels of analysis into a psycho-biological approach, to remedial programs and new forms of therapy.