Memory deficits are commonly encountered in patients with schizophrenia, affecting everyday functioning and hindering rehabilitation efforts. To date, research has focused mainly on patients' ability to recall past information, or retrospective memory, but has neglected an important memory process known as prospective memory, or the ability to remember to perform actions in the future. Given its behavioural orientation, prospective memory is considered different from and more complex than the traditional construct of retrospective memory. Clinical experience has indicated that patients with schizophrenia experience some kind of prospective memory impairment but systematic research in this area is still lacking. Prospective memory is relevant to the management and rehabilitation of schizophrenia because prospective memory is essential for maintaining an organised daily routine and coping with social demands. For both theoretical and practical reasons, systematic investigation of the nature and extent of prospective memory impairment of patients with schizophrenia is clearly warranted. Research in this area will provide useful information for improving the assessment, management, and rehabilitation of prospective memory problems in schizophrenia. Furthermore, such research will advance our understanding of prospective memory processes and their relationship with frontal lobe functions.
Key words: Schizophrenia, Cognitive function, Prospective memory, Rehabilitation
In recent years, memory impairment has been recognised as a significant problem for patients with schizophrenia. (1-3) Systematic studies using tests of specific memory processes (short-term, long-term, verbal, and visual memory) have found that patients with acute and chronic schizophrenia performed significantly worse than matched controls. (4-7) These findings are hypothetically explained by the subtle damage to the medial temporal/hippocampal area frequently found in patients with schizophrenia. (8,9)
All studies in this area have concentrated on a type of memory that involves the ability to recall and recognise past information, that is retrospective memory. In recent years, however, the importance of another type of memory, the ability to remember to perform an action in the future or prospective memory, has been acknowledged. (10) This paper aims to review the significance of this new type of memory, discuss how this construct can enhance our understanding of memory problems in schizophrenia, and provide suggestions for practice and research in this area.
SIGNIFICANCE OF PROSPECTIVE MEMORY
Kvavilashvili and Ellis defined prospective memory as "... remembering to do something at a particular moment in the future or the timely execution of a previously formed intention." (11) Remembering to turn up for a doctor's appointment, remembering to turn off an electrical appliance, or remembering to pay a bill before the due date are examples of activities that require the proper working of prospective memory. This type of memory is regarded as more important for everyday functioning and independent living than retrospective memory because many everyday activities require more than just recalling or recognising past information but also the carrying out of an intended action at the right time or in the right context. (12)
In addition, forgetting to perform some future actions forgetting to take medication at the right time, forgetting to lock the door) can lead to undesirable consequences or life-threatening hazards. Indeed, most recent studies of prospective memory grew out of concern for the functioning of older individuals and patients with brain injury living in the community. (13-16)
Prospective memory is considered to be more complex than retrospective memory. According to Glisky, it involves at least 4 components: (17)
* forming and organising an intention
* remembering the intention over a period of time
* monitoring when and how to execute the action
* performing the action and remembering having done it. …