Schizophrenia Research Trends

138A. Orosz, K. Cattapan-Ludewig, G. Gal and J. FeldonIn the following chapter the advantages of LI and LIrr, respectively, in schizophreniaresearch are discussed. Moreover, the differences between the currently applied LI paradigmswill be presented as well as the LI modulations in healthy controls, first-episode and chronicschizophrenia patients.INTRODUCTIONThe Core Symptoms of SchizophreniaSchizophrenia is a very heterogeneous disorder encompassing a variety of differentsymptoms. These are usually clustered in positive and negative symptoms as well as severalcognitive dysfunctions. Cognitive deficits are core symptoms of schizophrenia and serve asspecific markers of that disorder. There are various cognitive functions, such as memory,learning, planning and attention, an impairment of which results in the reduced ability to copewith everyday life. The cognitive deficits thought to be the most central to schizophrenia areinformation processing and attention abnormalities (1-4).Information Processing and Attentional DeficitsDisturbances in attention and pre-attentive information processing are considered to bekey features of schizophrenia (1) and are hypothesized to be strongly associated with itsclinical and functional impairments (5-7). Because of these deficits, schizophrenics cannotadequately process sequentially presented stimuli (8) and are therefore vulnerable to beoverloaded by external and internal stimuli (9). As a result they suffer from cognitivefragmentation and thought disorder (6;10-12).The phenomenon of latent inhibition (LI) is based on a form of selective attention whichenables normal individuals not to attend to and to filter out irrelevant stimuli (13-15) in orderto protect themselves from stimulus overload. Therefore, experiments measuring LI areappropriate to quantify information processing deficits in schizophrenia.Latent InhibitionLI refers to the retardation of associative learning, for example classical conditioning –the formation of an association between a conditioned stimulus (CS) and an unconditionedstimulus (US) (Fig. 1) - that normally occurs if the CS is previously preexposed withoutreinforcement (16;17). Schizophrenic patients fail to show LI. Because of this, disrupted LIhas become an important tool to model cognitive and attentional deficits in schizophrenia andmight even be treated as a state marker of it (18). Disrupted or reduced LI means that peoplewith schizophrenia learn a CS-US association faster than healthy controls and perform betteron the various tasks involved in LI paradigms (19;20). Thus, factors such as general deficitsin intellectual ability, medication side effects or lack of motivation of schizophrenia patients