Saccadic Tracking in Schizophrenia
Schizophrenic patients and their relatives exhibit a genetically increased probability of impaired smooth pursuit eye movements (Levy et al. 1993). It is less clear whether also saccadic eye movements are affected. Abnormalities such as hypometric tracking of target steps or saccadic intrusions during fixation have been reported by some groups (e.g., Cegalis et al. 1982; Mather and Putchat 1983) and denied by others (e.g., Yee et al. 1987). A number of studies considering both patients and their first degree relatives, which were carried out by our group either in a hospital environment or at the patients’ or their relatives’ homes, demonstrated an increased rate of hypometric saccades (gain < 0.75) of up to 35% as compared to about half that rate (18%) in controls (Schreiber et al. 1995, 1997). However, a hypometria incidence of 18% in controls is much higher than what is observed in a standard laboratory environment (complete darkness except visual targets), and a recent examination of juveniles at risk of schizophrenia conducted by our group under such laboratory conditions revealed no significant increase of hypometria. We therefore asked whether differences in background structure or target step timing could be responsible for these discrepancies. We argued that there might be particular experimental sets in which the saccadic tracking system is challenged to a degree where it would operate at the limits of its capability in normal subjects and would disclose otherwise unnoticeable impairments in patients.
KeywordsTarget Amplitude Target Step Visual Background Saccadic Intrusion Intrusive Saccade
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- Schreiber H, Rothmeier J, Becker W, Jürgens R, Born J, Stolz-Born, G, Westphal KP and Kornhuber HH (1995) Comparative assessment of saccadic eye movements, psychomotor and cognitive performance in schizophrenics, their first-degree relatives and control Ss. Acta Psychiatr Scand 91: 195–201PubMedCrossRefGoogle Scholar