Hemispheric preference of paranoid and nonparanoid schizophrenics.

Recent evidence indicates that paranoid and nonparanoid schizophrenics exhibit differential hemispheric deficits in specific types of processing tasks which may reflect a preference of one hemisphere over another. To test this hypothesis, face and letter-recognition tasks were tachistoscopically presented, both bilaterally and unilaterally, to paranoid and nonparanoid schizophrenics, nonschizophrenic psychiatric controls, and normal controls. In the unilateral presentation of letters, all groups exhibited right visual field superiority, producing no group differences. In the unilateral presentation of faces, paranoids were found to recognize fewer faces when presented to the left visual field as compared to the control groups. With bilateral presentation of both a face and a letter no group differences were found; all groups exhibited a right visual field superiority in processing both types of stimuli. The bilateral presentation of two faces produced a right visual field superiority in all groups. In the bilateral presentation of two letters, nonparanoids were found to recognize fewer letters when presented to the right visual field as compared to control groups. Thus, paranoids and nonparanoids were found to exhibit differential hemisphere deficits. The paranoid deficit is in processing faces when presented to the left visual field-right hemisphere while the nonparanoid deficit is in processing letters presented to the right visual field-left hemisphere. These results are discussed in terms of information-processing styles and strategies as differentially employed by the paranoid and nonparanoid schizophrenic.

Information processing and lateralization in schizophrenia.

This experiment investigated two current approaches in the study of schizophrenic thought, information processing and hemispheric specialization. Ten paranoid and ten nonparanoid schizophrenics, ten nonschizophrenic psychiatric controls, and ten normal controls were presented three tasks tachistoscopically. The tasks, letter-naming and dot enumeration of unstructured and structured arrays, were designed to elicit left and right hemisphere functioning through automatic and controlled information-processing strategies. Hemisphere effects were significant in the letter task with the left hemisphere superior to the right for all groups. Position effects were also significant, suggesting that reading habits determine this function and the ability was shared by all psychiatric groups. The normal control group identified a significantly greater number of letters than all other groups which may suggest that the lower performance of the psychiatric groups was due to a general level of psychiatric pathology. The two dot enumeration tasks indicated that, unlike the other three groups, the nonparanoid group processed the dots using an automatic strategy but only in the left hemisphere. Right hemisphere processing was essentially the same for all groups. The left hemisphere performance of the nonparanoid replicates that of a previous study and leads us to consider the left hemisphere dysfunction as specifically related to nonparanoid schizophrenics and the dysfunction as the inability to process information in a serial manner.