Nonconscious processing and a novel target for schizophrenia research.

Analysis of the pattern of altered cognition observed in schizophrenia provides better insight into neurocognitive deficits. It reveals a potential novel target for schizophrenia research. To understand this target we reviewed the findings of neuroimaging studies on implicit [nonconscious] memory. These studies have consistently reported attenuated activity in the area V3A of the extrastriate cortex during retrieval of studied items. It was suggested that the attenuation limits the pool of information available for further cognitive processing. Therefore, if V3A is functionally damaged, individuals will have access to a larger pool of information for cognitive processing. Since cognitive tasks that are not dependent on attention [attention independent] process a larger pool of information more efficiently, performance in these tasks is likely to improve after V3A is damaged. Conversely, tasks that are dependent on attentional resources are more efficient in processing smaller pool of information. Performance in these tasks therefore is expected to deteriorate if a large pool of information is made available following V3A damage. A review of cognitive performance in schizophrenia suggests that patients perform at above normal level in attention independent priming tasks and perform at subnormal level in attention dependent episodic and working memory tasks. These findings indicate possible impairment of V3A activity. It could therefore be a potentially important unstudied target for schizophrenia research, particularly because a number of investigators have reported that the activity in this area is altered in schizophrenia.