Schizotypy, a schizophrenia spectrum disorder, is of interest because schizotypes share traits with schizophrenics, albeit milder, without potential confounds such as chronic neuroleptic treatment and/or hospitalization. Thus, schizotypy may be particularly useful in exploring biological correlates of an underlying schizophrenic predisposition. The P3 event-related potential, which is aberrant in schizophrenia, was measured in 11 male, right-handed, DSM-III-R-defined schizotypes and 11 matched controls while subjects covertly counted 1.5 kHz target tones (15%) in trains of 1 kHz standard tones. Like schizophrenics, schizotypes displayed an asymmetrical P3, with smaller amplitudes over the left temporal lobe. Unlike schizophrenics, schizotypes were not significantly smaller in P3 amplitude over the sagittal midline of the head, although there was a trend towards reduced amplitudes at central and posterior midline sites. Asymmetry of P3 amplitude, with left-sided deficit, may be associated with the schizophrenia diathesis, but overall P3 reductions may be more associated with chronic effects.
"The most prominent event-related-potential (ERP) component of this paradigm, the P300, has been linked to the amount of attentional resources allocated to the task (Donchin & Coles, 1988). P300 amplitude was found to be diminished in schizophrenia (Ford et al., 1992; Salisbury et al., 1996) and can show further deterioration over the course of the illness (Mathalon et al., 2000; van der Stelt et al., 2004). "
[Show abstract][Hide abstract] ABSTRACT: Electrophysiological indices are sensitive to cognitive dysfunction in schizophrenia but have rarely been used to assess benefits of cognitive remediation. Our aim was to evaluate the effect of specific cognitive training approaches on event-related potentials.
Forty-six patients with schizophrenia underwent either auditory (AUD) or visuo-spatial (VIS) cognitive training or treatment-as-usual (TAU). Cognitive training was computer-assisted and administered for 10 sessions within two weeks. Event-related potentials during an active odd-ball paradigm together with clinical and neuropsychological variables were assessed before and after training and again at a two-month follow-up.
Compared to the TAU group both the AUD and VIS training group showed decreased P2 latency following training. At follow-up, the P2-latency reduction was stable in the VIS group but the AUD group experienced a relapse. Training resulted in improved digit-span backward among neuropsychological variables. Increased P2 amplitude was related to more positive symptoms and lower social-occupational functioning and longer P2 latency was associated with greater severity of stereotyped thinking.
The more general visuo-spatial training appears to have a longer-lasting effect on P2 latency than the specific auditory training. Alternatively, there may be specific auditory discrimination deficits in schizophrenia requiring more extensive training for a stable change.
"La région corticale la plus spécifiquement retrouvée implique notamment les zones postérieures temporales gauches (gyrus temporal supérieur ou STG gauche), chez des patients schizophrènes en phase aiguë ou chronique  . Cette même asymétrie est aussi retrouvée chez des patients sans traitement médicamenteux , chez des patients schizotypiques , où lors d'un premier épisode schizophrénique  "
[Show abstract][Hide abstract] ABSTRACT: Studies on early stages of schizophrenia imply the observation of stable markers of vulnerability. Among other research fields, these early and objective markers, or potential endophenotypes, can be described in event-related potential (ERP) paradigms.
The P300 component, elicited during the allocation of attentional resources, is the most studied ERP among people with schizophrenia. In this review, we first develop the notion of endophenotypes in schizophrenia, notably in terms of stability, heritability and specificity. We also give a short account of the P300 component, its typical description, the classical paradigms which elicit it, and several interpretations of its significance.
After reviewing the main features of the schizophrenic alterations of P300 (their topography, amplitude and latency), we discuss the relevance of P300 when described as a potential schizophrenic endophenotype. In spite of an important number of studies, results remain controversial and incomplete. First, P300 in schizophrenia shows complex patterns of temporal evolution, and thus can be described as either a stable trait or a state marker. Second, its heritability is still discussed among high-risk participants with genetic, schizotypal or clinical vulnerability. Third, the issue of its specificity is the less studied criteria. In line with the debate of its specificity, only little is known about specific alterations of P300 among unipolar or bipolar disorders. In the discussion, we describe a few possible origins of such controversial results in both empirical and conceptual perspectives, and we provide several experimental propositions in order to develop a more systematic exploration of P300 alterations.
L Encéphale 10/2011; 37(5):353-60. DOI:10.1016/j.encep.2011.02.004 · 0.70 Impact Factor
"However, individuals with SPD seldom suffer the severe psychosocial impairment, hospitalization and long term anti-psychotic medication exposure that accompany schizophrenia. ERP studies of SPD have shown moderate (Mannan et al., 2001), mild (Niznikiewicz et al., 2000) or trend level reduction of auditory P300 amplitude (Salisbury et al., 1996; Trestman et al., 1996). "
[Show abstract][Hide abstract] ABSTRACT: Previous studies suggest that deficits in neural synchronization and temporal integration are characteristic of schizophrenia. These phenomena have been rarely studied in SPD, which shares phenomenological and genetic similarities with schizophrenia. Event-related potentials (ERPs) were obtained using an auditory oddball task from 21 patients with schizophrenia, 19 subjects with SPD and 19 healthy control subjects. Inter-trial coherence (ITC) and event-related spectral perturbation (ERSP) were measured across trials to target tones using time-frequency analysis. ITC measures phase locking or consistency, while ERSP measures changes in power relative to baseline activity. P300 latency and amplitude were also measured from the averaged ERP to target tones. In the time-frequency analysis, subjects with SPD showed intact power but a deficit in the ITC in delta and theta frequencies compared to control subjects. Patients with schizophrenia showed deficits for both ERSP and ITC in the delta and theta frequencies. While patients with schizophrenia showed reduced P300 amplitude and delayed latency for averaged ERPs, subjects with SPD did not differ from either group. Synchronization or timing abnormalities may represent a biomarker for schizophrenia spectrum disorders, and contribute to aberrant perceptual and cognitive integration.
Schizophrenia Research 12/2010; 124(1-3):110-8. DOI:10.1016/j.schres.2010.08.008 · 3.92 Impact Factor
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