Atypical connectivity in autistic spectrum disorders

Atypical connectivity in autistic spectrum disorders

204 Symposium abstracts / International Journal of Psychophysiology 69 (2008) 139–205 spectral power (SP), SP interhemispheric asymmetry, inter-regi...

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204

Symposium abstracts / International Journal of Psychophysiology 69 (2008) 139–205

spectral power (SP), SP interhemispheric asymmetry, inter-regional coherence within delta, theta, alpha, beta and gamma bands and stimulus-induced EEG alpha oscillatory response were analyzed. A numerical minority group (4 subjects) within children with autism exhibited extremely high spectral power within theta or alpha frequency bands. As excessive EEG theta is typical for such genetic disorder as Rett and ‘fragile X’ syndromes; autistic subjects with the “excessive theta endophenotype” may comprise genetically distinct sub-group of autism. The common features of ongoing EEG in BWA of Moscow and Gothenburg samples were the abnormal excess of high frequency activity (beta and gamma) and atypical hemispheric asymmetry of slower (delta, theta and alpha) EEG oscillations. The increased amount of fast brain oscillations in EEG of BWA correlated with the degree of developmental delay and may reflect abnormally high excitation/inhibition ratio of cortical networks in the autistic brain. During visual attention condition typical leftward asymmetry of central sensorimotor rhythm (mu rhythm) was absent in autism. At the same time, BWA demonstrated atypical leftward broadband SP EEG asymmetry over mid-temporal regions. This atypical asymmetry was associated with reduced theta coherence between mid-temporal region of the right hemisphere and frontal regions. During presentation of novel visual stimuli BWA demonstrated right hemispheric reduction of pre-stimulus alpha power and of stimulus-related alpha blocking response. The findings point to a decreased capacity of the right hemispheric neural circuits to generate EEG rhythms and may indicate altered regional specialization as well as altered information processing in autism. The concurrent lack of normal leftward asymmetry of mu rhythm suggests that abnormalities in EEG lateralization in autism are regionally/functionally specific. These findings support previous imaging and behavioral data highlighting the aberrant brain lateralization in autism spectrum disorders.

doi:10.1016/j.ijpsycho.2008.05.556 Anomalies of information processing in schizophrenia in convergence with clinical, molecular–genetic and immunological data I.S. Lebedeva, V.E. Golimbet, T.P. Klushnik, V.G. Kaleda, L.I. Abramova, A.N. Barkhatova National Mental Health Research Centre, Laboratory of neurophysiology, Moscow, Russia The event-related potentials (ERP) in selective attention paradigm are often used as an informative tool for the assessment of information processing anomalies in patients with schizophrenia. In this study, the ERP analysis (auditory oddball paradigm: 60 dB, 80% non-targets (1000 Hz), 20% targets (2000 Hz) tones) was combined with the multidiscipline studies in order to discriminate the processes which are the closest to the pathogenesis of schizophrenia. Examination was done in the groups of 140 patients with schizophrenia including 44 first-episode patients, 120 unaffected first-degree relatives, 80 mentally healthy subjects without family loading by mental diseases. The characteristics of all ERP waves were analyzed in respect to the illness progression (endophenotypes — first episode — illness duration more than 3 years since manifestation). Also, the clinical (PANSS scores), immunological (activity of leukocyte elastase, the level of autoantibodies to nerve growth factor) and molecular–genetic (Val158Met polymorphism of catechol-Omethyltransferase (COMT) gene, Val66Met polymorphism of brain-derived neurotrophic factor (BDNF) gene, 5-HTTLPR serotonin transporter gene polymorphism) data were taken in consideration. Main findings comprised the significant reduction of P300 and N100 to non-targets in the unaffected parents of patients with schizophrenia, marked P300 reduction and prolongation and less pronounced deviations of N100 to non-targets and targets and N200 in the first-episode patients as compared to controls. The significant correlations between P300 amplitude increase and decrease of PANSS summarized positive scores, between P300 amplitude reduction and high activity of leukocyte elastase, between the reduction of N100s to targets and non-targets and high level of autoantibodies to nerve growth factor were found. In patients, the subjects with 5-HTTLPR ss genotype had higher amplitudes of N100 to non-targets. The data assume two domains in which the pathological processes are developing in schizophrenia. The first is connected with the ability of neuronal substrate to support the processing of prolonged and/or often repeated stimuli, it is associated mostly with the functional or/and

morphological state of the temporal cortex The other domain comprises the processes of updating of currently stored information.

doi:10.1016/j.ijpsycho.2008.05.576 Atypical connectivity in autistic spectrum disorders G. Rippon Aston University, Birmingham, United Kingdom Autism is a developmental disorder that is currently defined in terms of a triad of impairments in social interaction, communication, and behavioural flexibility. Psychological models have focussed on deficits in high level social and cognitive processes, such as ‘weak central coherence’ and deficits in ‘theory of mind’. Converging evidence from different fields of neuroscience research indicates that the underlying neural dysfunction is associated with atypical patterns of cortical connectivity (Rippon et al., 2007). This arises very early in development and results in sensory, perceptual and cognitive deficits at a much earlier and more fundamental level than previously suggested, but with cascading effects on higher level psychological and social processes. Earlier research in this sphere has focussed mainly on patterns of underconnectivity in distributed cortical networks underpinning process such as language and executive function. (Just et al., 2007). Such research mainly utilises imaging techniques with high spatial resolution. This paper focuses on evidence associated with local over-connectivity, evident in more low level and transitory processes and hence more easily measurable with techniques with high temporal resolution, such as MEG and EEG. Results are described which provide evidence of such local over-connectivity, characterised by atypical results in the gamma frequency range (Brown et al., 2005) together with discussions about the future directions of such research and its implications for remediation.

doi:10.1016/j.ijpsycho.2008.05.577 SYMPOSIUM 43: New Perspectives on ADHD: Evaluation and Treatment Symposium Chair: Giuseppe Chiarenza (Italy); Co-Chair: E. Roy John (USA) EEG power and coherence in AD/HD and its common comorbidities R.J. Barry, A.R. Clarke, L.M. Mason University of Wollongong, Brain & Behaviour Research Institute and School of Psychology, Wollongong, Australia Data on EEG activity in the traditional delta, theta, alpha and beta bands through childhood, with some extensions into adolescence and adults, will be presented. Both eyes-closed and eyes-open data will be illustrated. Reflections on these indices of normal development can provide a framework for the recognition and understanding of EEG anomalies in AD/HD, and its DSM-IV subtypes, throughout the lifespan. Additional effects in the EEG of children with AD/HD comorbid with reading disabilities, conduct disorders, or anxiety/ depression, will also be illustrated. Our recent work has identified EEG effects that are distinct in the various comorbid presentations of AD/HD, and differ from those in the separate disorders. That is, the comorbid groups have EEG profiles, involving both global and focal EEG effects, which indicate anomalies similar to those apparent in the separate disorders but with different degrees of aberrance (both less and more aberrant), as well as anomalies different from those in the separate disorders. These findings are interpreted as indicating that comorbidity differs from the simple addition of the anomalies from the separate disorders. These data will be discussed in relation to the new perspectives they offer on the evaluation and treatment of children, adolescents, and adults with AD/HD, with and without a range of comorbid disabilities.

doi:10.1016/j.ijpsycho.2008.05.578 Neuropsychological profiles of children with ADHD G. Chiarenza, P. Olgiati, M.G. Lo Torto, L. Montaldi, E. Tomassini Child and Adolescent Neuropsychiatry Department, Azienda “G. Salvini” Garbagnate Milanese, Rho Hospital, Rho, Milan, Italy