Beat‐by‐Beat Cardiac Responses in Normals and Schizophrenics to Events Varying in Conditional Probability

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Abstract
Anticipatory cardiac deceleration and poststimulus acceleration were studied in schizopbrenic inpatient,s and controls during performance of a counting task. Reduced cardiac responding has been reported for schizophrenic patients for paradiRms usinR relatively lonR intertrial intervals. DurinR a relatively fast rate of stimulus presentation (3-s interstimulus interval), changes in cardiac interbeat interval were measured in 20 inpatient male cbronic schizophrenics and 18 control volunteers. Subjects counted an infrequent tone whicb was always followed by at least one frequent tone. Control subjects showed significant anticipatory cardiac deceleration precedinR the unpredictable tones, wbereas patient,s did not sbow a differential cardiac deceleration. Control subjects sbowed poststim- ulus acceleration tbat was inversely proportional to tbe conditional probability of events, wbereas patients exhibited Rreatly reduced poststimulus acceleration: patterns for botb Rroups resembled findings previously observed for event-related potential and pupillary dilation data. .Analysis of cardiac cycle time indicated siRnificant variation in primary bradycardia associated witb the delay between stimuli and immediately preceding R-waves in controls (replicatins l^cey & Ijicey, 1980), wilb only an immediate bradycardia at stimulus reception for patients rcRardless of cardiac cycle time. The data reinforce tbe notion thai tbe manner in wbicb information is used by scbizopbrenies, as reflected by cardiac responsivity, differs botb quantitatively and qualitatively from that of controls. DESCRIPTORS: Heart rate. Cardiac cycle time, Schizopbrenia, Information processing. Pri- mary bradycardia.