Integration and Interruption as Separate Facets of Backward Masking in Schizophrenia

Abstract

Vulnerability to visual backward masking is thought to predate the onset of symptoms of schizophrenia. That makes this attention and information-processing phenomenon a promising candidate as a gene-determined trait that helps portend schizophrenia. Two proposed mechanisms of masking include integration and interruption. Prior studies of backward masking in schizophrenia have been hampered by the use of stimuli that are meaningless except under specific conditions. Because of this, it has been difficult to differentiate integration from interruption. The study reported in this article sought to apply criteria of meaningfulness and independence to the backward-masking task. The computerized masking program created for this study, DMASK 1.0, used visual stimuli that enabled the measurement of four discrete response options, thus differentiating between integration and interruption. Selected for the study and administered DMASK 1.0 were 14 people with nonparanoid schizophrenia, 15 people with nonpsychotic major depression, and 20 people with no mental illness (controls). As expected, the people with schizophrenia were more vulnerable to masking than either the control group or the people with depression. Also, as predicted, integration responses were present but did not differ among groups. Finally, as predicted, the people with nonpsychotic depression did not differ from the controls on most key masking variables.