ASYMMETRIES IN THE COVERT ORIENTING OF VISUAL-SPATIAL ATTENTION IN SCHIZOPHRENIA

The presence of attentional asymmetries in patients with schizophrenia was investigated with particular emphasis on the effects of stage of disease, medication status and clinical symptom severity. A modified v ersion of Posner's covert orienting of visual attention task (COVAT) w hich included both spatial and non-spatial cues was administered to si x volunteer samples of subjects which consisted of (i) 15 unmedicated and acutely psychotic male subjects with schizophrenia, (ii) 15 male s ubjects with schizophrenia who had been receiving medication for 14-21 days, (iii) 10 chronic male schizophrenic subjects who had been recei ving medication for at least two years, (iv) 10 acutely psychotic male subjects with non-schizophrenic psychoses, (v) 15 subjects with unila teral brain frontal lobe (n = 6) or parietal lobe (n = 9) lesions, (vi ) and 15 male control subjects. Measures of saccadic and pursuit eye m ovements were also obtained from unmedicated and recently medicated su bjects with schizophrenia. COVAT attentional asymmetries were present in unmedicated subjects with schizophrenia for the 150 msec stimulus o nset asynchrony (SOA). These asymmetries arose because reaction times (RTs) to right visual held targets were significantly slower than RTs to left visual field targets when targets followed invalid spatial or non-spatial cues. These asymmetries were qualitatively similar to thos e found in the patients with unilateral parietal lobe lesions. Attenti onal asymmetries partially resolved with brief periods of medication a nd completely resolved with long periods of medication. No asymmetries were found in controls nor in unmedicated subjects without schizophre nia. No asymmetries of ocular motor function were found. In schizophre nia, attentional asymmetries may reflect a deficit in the disengagemen t of visual attention from the right visual held and appear to be a st age marker for the disease. However this attentional deficit is dynami c and may reflect disruption to the neurocognitive network controlling attention at the level of the anterior cingulate cortex.