Schizophrenia Research Trends

144A. Orosz, K. Cattapan-Ludewig, G. Gal and J. Feldonconductance, vasomotor activity and heart rate. The conditioning task typically involves atone as CS and an aversive (electric shock) or non-aversive (reaction time task, noise burst)US (58). Indications of the LI effect are expressed as the differences in the autonomicresponses between the subjects of the PE and NPE group during conditioning.Instrumental learning to criterionIn an instrumental learning to criterion task, the PE group is preexposed to a visual (63)or auditory CS (13;20;23;64;65). In the conditioning stage, this CS becomes the signal for thesubjects to respond to, i.e. to perform a specific task (17). Subjects are reinforced when theyrespond in the presence of the CS. The dependent variable is the CR which is the number oftrials to reach criterion, usually constituted by a specific number of consecutive correct(reinforced) responses. LI is measured by the different performance of the PE and the NPEsubjects.Most experiments (13;20;66) using instrumental learning procedures are replications ofthe experimental setup of Ginton et al. 1975 (23). In the original procedure, the CS, a shortburst of white noise, is presented to PE subjects in the preexposure stage, whilst the subjectsof the NPE group do not hear such noise bursts. Subsequently, in the conditioning stage, allsubjects hear the noise burst which now signals the increment of a score on a counter. Allsubjects are instructed to decrease this score by pressing a button every time they anticipatethat it will rise. If they respond correctly in the presence of the CS, they are reinforced by adecrement of the score. If, however, they respond in the absence of the CS or fail to respondin the presence of the CS, the score is raised. As soon as the subject presses the button severaltimes consecutively during CS presentation, the test is terminated. PE subjects preexposed tothe CS are less likely to learn the association between the noise burst and the score incrementand need more trials to reach the criterion that indicates a LI effect.Visual LI paradigmsOne of the recently developed LI paradigms (60;67) uses a visual search procedure inwhich the subjects’ task is to search for a unique target shape embedded between a number ofhomogeneous distractor elements. They are required to indicate the presence or absence ofthe target by pressing corresponding keys (0= target absent, 1= target present). Later on, thepreexposed distractor element becomes the target, while the target serves as a new distractor.In addition to that, novel elements are introduced on occasion and serve first as target and ina later stage as distractor or vice versa.Preexposure occurs in those trials in which the subject has to look for a target which wasa distractor before and which is presented among distractors consisting of a former targetshape. NPE trials are those in which a novel target is presented with familiar distractorelements.In sum, two kinds of CS are involved, preexposed (a target that was a distractor before)and a non-preexposed (novel target) stimuli allowing preexposure and non-preexposure to