Backward and forward visual masking in schizophrenia and its relation to global motion and global form perception

Whilst visual backward masking deficits in schizophrenia have been reliably reported and may reveal magnocellular dysfunction, forward masking, which may rely more heavily on the parvocellular system, has been under investigated. In a group of 64 schizophrenia patients and 65 matched controls we undertook a visual masking paradigm containing both conditions, together with tests of 'global motion' and 'global form' perception, two 'down-stream' visual tasks reflecting later processing linked to magnocellular and parvocellular function respectively. In the patient group, a significant but small deficit on the masking task, equivalent across forward and backward conditions was seen. Correlations between the masking and motion/form tasks supported the predominant theoretical framework describing the neural processes involved in masking. Performance on the motion and form tasks was differentiated by a trend-level motion processing deficit but near-normal form processing. The results suggest an 'early visual' processing deficit in both magno- and parvocellular systems but one which is only transferred to 'down-stream' processing areas with predominantly magnocellular input.