Visual search, EEG, and psychopathology in schizophrenic patients

Abstract

Twenty acutely admitted schizophrenic inpatients diagnosed according to RDC and 8 normal controls were instructed to search for a randomly located target letter (Z) in ten lists of 284 distractor letters of either rounded or angular shape projected on a screen (23 degrees x 15 degrees). Eye movements were recorded using infrared corneal reflection-pupil centre measurement. Search performance was defined as the search time in seconds from onset of the display until localization of the target. The EEG was recorded simultaneously in schizophrenics, in whom assessment took place shortly after admission and before discharge. The psychopathological status was assessed at the same time with the Brief Psychiatric Rating Scale and the Scale for the Assessment of Negative Symptoms. Search performance was not significantly different in schizophrenics and normal controls, but was heavily affected by target/distractor similarity in both groups. Moreover, search performance in schizophrenics was not significantly affected by illness severity. However, search performance was differently related to negative and positive symptoms. Schizophrenics and normal controls differed with respect to the relationship between search performance and visuomotor microbehaviour. Additionally, two relatively time-stable eye movement patterns in schizophrenics could be distinguished, which were differently related to psychopathology, performance measures and EEG.

Display visual angle and attentional scanpaths on the span of apprehension task in schizophrenia.

“…These variables can be obtained by directly monitoring eye movements during visual search tasks using corneal reflection-pupil center instruments. Gaebel (1989) used this eye monitoring methodology and found that individuals with schizophrenia and nonpsychiatric controls did not differ significantly with regard to the number and path of directly monitored overt scan moves. Although the nature of the relationship between covert scanning of iconic images and overt scanning of visual displays is currently controversial (e.g., Klein, 1980), Gaebel’s (1989) results are consistent with the present finding that schizophrenic and nonpsychiatric individuals used a similar number and path of scan moves to search visual letter arrays.…”

Störungen der Augenbewegungen bei Schizophrenen - kritische Übersicht und zukünftige Perspektiven

“…Diese Schwierigkeit kann umgangen werden, wenn von den Pupillenrändern auf die Pupillen elektronisch hochgerechnet wird. Dieses äußerst präzise und artefaktarme Verfahren (KaI:: et al, 1987) hat jedoch in der Untersuchung von schizophrenlm Patienten bisher, aufgrund des vergleichsweise hohen technischen Aufwandes, nur in jüngster Zeit experimentelle Anwendung gefunden (Gaebel et al, 1986(Gaebel et al, . 1989Mosel' ct al., 1990;Amlt et al, 1993a, b).…”