Schizophrenia & information processing : a comparison of the prepulse inhibition, latent inhibition, P-50 gating, and mismatch negativity paradigms, with schizophrenia, bipolar and well control samples

Shockley, Natalie. (2003). Schizophrenia & information processing : a comparison of the prepulse inhibition, latent inhibition, P-50 gating, and mismatch negativity paradigms, with schizophrenia, bipolar and well control samples PhD Thesis, School of Psychology, The University of Queensland.

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Author Shockley, Natalie.
Thesis Title Schizophrenia & information processing : a comparison of the prepulse inhibition, latent inhibition, P-50 gating, and mismatch negativity paradigms, with schizophrenia, bipolar and well control samples
School, Centre or Institute School of Psychology
Institution The University of Queensland
Publication date 2003
Thesis type PhD Thesis
Supervisor Lipp, Ottmar
McGrath, John
Total pages 267
Collection year 2003
Language eng
Subjects L
380103 Biological Psychology (Neuropsychology, Psychopharmacology, Physiological Psychology)
730104 Nervous system and disorders
Formatted abstract
Information processing research is a promising area for further developments in understanding the aetiology of schizophrenia. There have already been some influential models of schizophrenia based on information processing research (e.g. Gray et al., 1991; Gray, 1995). In addition, several information processing paradigms (e.g. P50 gating) have been suggested as useful vulnerability markers for the illness. However most of the information processing research reporting performance deficits in schizophrenia samples has used single paradigms and usually only a healthy comparison group. Few researchers have examined whether the various information processing deficits are specific to schizophrenia, an important issue for discussion of vulnerability markers, and whether a given sample of people with a diagnosis of schizophrenia would display multiple information processing deficits. The demonstration of multiple deficits within a single sample would provide greater validity to integrative models of schizophrenia. In addition, a greater understanding of potential inter-relationships between the information processing measures would also enhance our knowledge of the cognitive deficits present in schizophrenia.

Study design: Three population samples were tested on several information processing paradigms to explore whether the same sample of people with schizophrenia would show deficits on all the information processing tasks; whether people with schizophrenia would perform differently to a comparison group of people with bipolar disorder across the different tasks; and how the different information processing measures related to each other. The current study utilised a multiparadigm design with a heterogenous sample of schizophrenia (n=35) and two comparison groups - a clinical control group consisting of people with bipolar disorder (n=13), and a healthy control group (n=25). Four information processing paradigms were selected based on previously demonstrated deficits in schizophrenia populations, similar deficits in populations "at-risk' for schizophrenia, ease of administration within clinical populations and availability of animal models. Participants completed the following: a Pavlovian conditioning latent inhibition (LI) task, an operant conditioning LI task, prepulse inhibition (PPI) and prepulse facilitation (PPF), P50-gating, and a mismatch negativity (MMN) task with simultaneous recording of P300 difference waveforms. Participants also completed five neuropsychological measures, selected to provide a comparison to more 'traditional' measures of attention: the Stroop Test, the Trail Making Test, Digit Span (forwards and backwards); Letter Cancellation, and the Wisconsin Card Sorting Test. Participant groups were matched for age and gender, smoking was monitored and analysed as a potential covariate, and the Positive and Negative Symptoms of Schizophrenia scale (PANSS; Kay, Opler & Lindenmayer, 1988) was also completed.

Results: The schizophrenia sample showed significant performance deficits on the prepulse facilitation, mismatch negativity, P300 and the neuropsychological tests. The remaining paradigms - prepulse inhibition, latent inhibition, and P50 gating, did not result in performance deficits in the schizophrenia sample. On most of the tasks used, people with bipolar disorder performed very similarly to people with schizophrenia, suggesting that the information processing difficulties may not be specific to diagnosis but perhaps more closely linked to other factors that these people have in common - for example, shared symptomatology and/or shared underlying neurological/biochemical functioning. Few significant correlations were observed between the different information processing measures when selected responses from each paradigm were subjected to exploratory correlations across the combined samples. This, and the different performances across the tasks with some tasks revealing information processing deficits and others finding normal performance in the patient samples, indicates that each of the paradigms can serve as a useful tool in the study of information processing in clinical populations.

Discussion & conclusions: The people with schizophrenia who participated in this study displayed normal information processing on several of the tasks that measured early automatic, preattentive processing, but deficits on tasks that required mismatch detection (MMN), and more controlled processing resources - startle facilitation and P300 - and the neuropsychological tasks. However other studies have demonstrated deficits in people with schizophrenia on tasks that access early automatic processing resources, including P50 and PPI tasks similar to those used in this study. It is unclear why deficits were observed on only some of the information processing paradigms used in the current study. The results highlight the need for future integrative work using multiple clinical samples and/or multiple information processing paradigms, in order to determine which subgroups of people with schizophrenia show which information processing deficits and why. Limitations of the current study, implications for clinicians and directions for future research are also discussed.
Keyword Schizophrenia

Document type: Thesis
Collection: UQ Theses (RHD) - UQ staff and students only
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Created: Fri, 24 Aug 2007, 18:13:43 EST