Dot Enumeration Perceptual Organization Task (DEPOT): evidence for a short-term visual memory deficit in schizophrenia

The Dot Enumeration Perceptual Organization Task (DEPOT) evaluates the validity of 2 specific competing cognitive models of early input dysfunction in schizophrenic individuals: a primary Stage 1, sensory store, perceptual organization deficit vs. a Stage 2, short-term visual memory (STVM) deficit. DEPOT was also designed to assess the hypothesis that schizophrenic individuals tend to perform poorly on all cognitive tasks. In DEPOT both number and form judgments are made about the same dot patterns. A response delay manipulation assesses the persistence and operation of STVM. The study included 41 psychotic inpatients (8 with acute and 16 with chronic schizophrenia and 7 with bipolar and 10 with nonbipolar affective disorder) and 38 controls (22 college students and 16 hospital personnel). Although the pattern of results was consistent with neither the Stage 1 deficit nor the general deficit hypotheses, a Stage 2, STVM deficit hypothesis could account parsimoniously for the data.