Multivariate structure of eye movement dysfunction distinguishing schizophrenia

Abstract

The study examined processes associated with eye-movement dysfunction (EMD) maximally discriminating paranoid and nonparanoid schizophrenic subjects from psychiatric and normal controls. Measures included the linear slope of saccade number over velocities of a ramp visual target (a measure shown effectively to distinguish schizophrenia-related EMD), along with several other measures of perceptual/cognitive processes potentially contributing to oculomotor tracking. The first significant dimension, of a multiple discriminant function analysis, was one of 'EMD as related to spatial memory'. Measures of the latter reflected efficiency in encoding properties of a visual stimulus array into a task-facilitative format. The paranoid schizophrenic subgroup had the highest scores on this dimension, normals, the lowest, and depressed psychiatric controls and nonparanoid schizophrenic patients, intermediate. A second significant dimension was one of 'manual motor speed in following a ramp visual target'. Depressives were slowest, and nonparanoid schizophrenic patients fastest. Speed of the nonparanoid patients was ascribed to extrapyramidal effects, especially tremor and akathisia. The results were discussed with respect to information processing involved in oculomotor tracking, and the effects of meditation, or dyskinesia, on manual motor tracking.