Selective attention and mismatch negativity in antipsychotic-naïve, first-episode schizophrenia patients before and after 6 months of antipsychotic monotherapy

BackgroundAttention deficits have been frequently reported in schizophrenia. It has been suggested that treatment with second-generation antipsychotics can ameliorate these deficits. In this study, the influence of 6 months treatment with quetiapine, a compound with less affinity for dopamine D2 receptors than for serotonergic 5-HT2A receptors, on electrophysiological parameters of attention was investigated in a group of antipsychotic-naïve, first-episode schizophrenia patients compared with a group of age- and gender-matched healthy controls.MethodA total of 34 first-episode, antipsychotic-naïve patients with schizophrenia and an equal number of healthy controls were tested in a selective attention and a typical mismatch negativity (MMN) paradigm at baseline and after 6 months. The patients were treated with quetiapine according to their clinical needs during the period between baseline and follow-up, whereas controls received no treatment.ResultsPatients showed lower MMN and P200 amplitude than healthy controls in the selective attention paradigm at baseline, while this was not the case for MMN of the typical MMN paradigm. Interestingly, after 6 months treatment, this MMN deficit was only ameliorated in patients treated with above median dosages of quetiapine. Patients had lower P3B amplitude, yet showed similar levels of processing negativity and N100 amplitude compared with healthy controls, both at baseline and follow-up.ConclusionsThe results indicate that deficits in MMN, P200 and P3B amplitude are present at early stages of schizophrenia, although depending on the paradigm used. Furthermore, the results indicate that 6 months quetiapine treatment ameliorates MMN but not P3B deficits, and only in those subjects on higher dosages.</jats:sec

The influence of impaired processing speed on cognition in first-episode antipsychotic-naïve schizophrenic patients

AbstractBackground:Impaired cognition is a prominent feature of schizophrenia. To what extent the heterogeneous cognitive impairments can be accounted for by considering only a single underlying impairment or a small number of core impairments remains elusive. This study examined whether cognitive impairments in antipsychotic-naïve, first-episode schizophrenia patients may be determined by a relative slower speed of information processing.Method:Forty-eight antipsychotic-naïve patients with first-episode schizophrenia and 48 matched healthy controls were administered a comprehensive battery of neuropsychological tests to assess domains of cognitive impairments in schizophrenia. Composite scores were calculated, grouping tests into cognitive domains.Results:There were significant differences between patients and healthy controls on global cognition and all cognitive domains, including verbal intelligence, processing speed, sustained attention, working memory, reasoning and problem solving, verbal learning and memory, visual learning and memory, and reaction time. All these significant differences, except for verbal intelligence and global cognition, disappeared when processing speed was included as a covariate.Conclusion:At the first stage of illness, antipsychotic-naïve patients with schizophrenia display moderate/severe impairments in all the cognitive domains assessed. The results support the contention of a global cognitive dysfunction in schizophrenia that to some extent may be determined by impaired processing speed.</jats:sec