Dissociation of explicit and implicit responses during a change blindness task in schizophrenia

Background: Patients with schizophrenia are abnormally disturbed by information onsets, which may result in a disadvantage in filtering relevant information. The paradigm of change blindness offers the interesting possibility of studying sensitivity to the sudden irruption of visual information with ecological stimuli in schizophrenia. An increased attentional capture by the irruption of visual information would suggest better performance in patients than in healthy controls. This approach has the advantage of circumventing a non-specific general attentional deficit in schizophrenia.

Methods: Sixteen patients with schizophrenia and 16 healthy controls were asked to detect changes in 99 scenes with 0, 1 or 3 changes. We measured the participants' speed and accuracy in explicitly reporting the changes via motor responses and their capacity to implicitly detect changes via eye movements.

Results: Although the controls were faster and more efficient in explicitly reporting changes, the patients' eyes shifted more quickly toward the changes. Regardless of the group, increasing the magnitude of change improved the performance.

Conclusions: The better capacity of the patients to shift their eyes toward changes confirmed the capture by the sudden irruption of visual information in schizophrenia while avoiding the effects of general attentional deficits. However, the striking dissociation between this implicit response and the capacity to explicitly report changes could be interpreted as a deficit in access to conscious perception.