Transient versus sustained visual channels in the visual backward masking deficits of schizophrenia patients

Schizophrenia patients have information-processing deficits that can be quantified using visual backward masking. The visual information processing system is divided functionally and structually into transient and sustained visual channels. When visual stimuli are presented to a subject, the transient pathway detects the presence and location of the stimulus while the sustained pathway is involved in fine discrimination and identification of the stimulus. While independent subcortically, the transient and sustained visual channels converge cortically into the dorsal and ventral processing streams that assess spatial relationships and object recognition respectively. Methods: To better understand the underlying mechanisms of the visual backward masking deficits, 16 schizophrenia patients and 17 comparison subjects were tested on two different visual backward masking paradigms that required either locating or identifying a target letter. Results: Schizophrenia patients had visual backward masking deficits in a task that involved locating a target letter while there were no deficits in the task that involved identification of a target letter. Conclusions: The visual backward masking deficits of schizophrenia patients suggest impairment in the processing of spatial information. These deficits are discussed in the context of our current knowledge of visual information processing and the neuropathophysiology of schizophrenia.