Schizophrenia Research Trends

Latent Inhibition and Learned Irrelevance Paradigms … 155CONCLUSIONLIrr paradigms are appropriate to assess information processing deficits inschizophreniaLatent inhibition has become an important concept in schizophrenia research in animalsas well as in humans. To date, several human LI studies have been carried out, but haveyielded conflicting results and have been afflicted with various methodological problems.The new LIrr paradigm introduced in this chapter seems to offer a useful tool to assessassociative and attentional learning deficits in humans. It offers many advantages andachievements compared to the commonly used LI paradigms: the task is short, simple andcontinuous and the paradigm is within-subject. Moreover, no masking task is required and itis possible to test the same subject repeatedly. Last but not least, there is also a variation ofthe test paradigm which is suitable for fMRI (97).As LIrr is very closely related to LI, it has been expected that the same results areobtained by this LIrr paradigm as by previous LI experiments. Indeed, studies applying theLIrr paradigm produced the same results with healthy controls and acute and first-episodeschizophrenia patients as a predominant number of former LI studies. But there areinconsistencies concerning the findings in chronic schizophrenia, indicating the necessity offurther investigation. Possible confounding factors are differences in medication, illnessduration and symptomatology. Furthermore, it must be taken into consideration thatschizophrenia patients might not understand or might be incapable of following theinstructions which are necessary to obtain a LIrr effect.Although the necessity of the instructions is a limitation, the LIrr paradigm providesmany results which are similar to those obtained by LI paradigms, indicating that LIrr can beequally used in schizophrenia research.REFERENCES[1] Nuechterlein KH, Dawson ME. Information processing and attentional functioning inthe developmental course of schizophrenic disorders. Schizophr Bull 1984; 10(2):160-203.[2] Braff DL, Swerdlow NR. Neuroanatomy of schizophrenia. Schizophr Bull 1997;23(3):509-512.[3] Gray JA, Feldon J, Rawlins JNP, Hemsley DR, Smith AD. The neuropsychology ofschizophrenia. Behav Brain Sci 1991; 14:1-84.[4] Perry W, Braff DL. Information-processing deficits and thought disorder inschizophrenia. Am J Psychiatry 1994; 151(3):363-367.[5] Braff DL. Psychophysiological and information processing approaches toschizophrenia. In: Charney DS, Nestler E, Bunney BS, editors. NeurobiologicalFoundation of Mental Illness. New York: Oxford University Press, 1999: 258-271.[6] McGhie A, Chapman J. Disorders of attention and perception in early schizophrenia. BrJ Med Psychol 1961; 34:103-116.