REACTION-TIME PARADIGMS IN SUBJECTS AT RISK FOR SCHIZOPHRENIA

Deviant response patterns in experimental reaction time paradigms in s chizophrenic probands are well documented. Although simple reaction ti mes are strongly influenced by the current psychopathological status o f the proband (e.g. florid psychotic patients versus remitted patients ) these influences are less clear for measures obtained from more comp lex reaction time paradigms. These include the crossover paradigm (rea ction time to stimuli presented after constant preparatory intervals i n comparison to reaction time to stimuli presented after irregular pre paratory intervals) and the modality shift paradigm (reaction time to a stimulus (light or tone) when the modality of the stimulus on the pr eceding trial was the same compared to when it was different). It is n ot clear if these peculiarities of reponse patterns occur as a consequ ence of the disease or if they represent vulnerability markers for sch izophrenia. Both crossover reaction time and modality shift reaction t ime paradigms were applied to 56 drug free schizophrenics, 45 healthy siblings of these patients and 68 healthy controls. The results indica te that retarded reaction times and the occurance of the crossover eff ect as well as of the modality shift effect distinguish schizophrenics and controls. Healthy siblings of schizophrenics differed from health y controls with regard to the crossover effect but not with regard to the modality shift effect. Therefore only the crossover effect represe nts a vulnerability marker for schizophrenia. Correlations between the modality shift and the crossover effect revealed strong correlations in the schizophrenic group only.