Human Cognitive Neuroscience Unit, Division of Psychology, University of Northumbria, Newcastle upon Tyne NE1 8ST and
1 Psychology Section, University of Teesside, Middlesborough TS1 3BA, UK
Received 30 July 2001; in revised form 28 September 2001; accepted 20 November 2001
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ABSTRACT |
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INTRODUCTION |
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One important aspect of day-to-day memory function is prospective memory (PM), which refers to the process of remembering to do things at some future point in time (Brandimonte et al., 1996). For example, remembering to attend a particular function such as a party, or to carry out a particular task, such as remembering to pay a bill on time. PM has only recently been subject to systematic empirical research (e.g. Brandimonte et al., 1996
; Ellis et al., 1999
). The Prospective Memory Questionnaire (PMQ), developed by Hannon et al. (1995) is a self-rating scale that requires participants to record the number of times their prospective memory has failed them within a period of time. Three sub-scales provide self-reported measures of short-term habitual, long-term episodic, and internally-cued prospective memory. In addition, the PMQ gauges the number of strategies used to aid remembering via the Techniques to Remember Scale. The scale has proved to be a useful tool in estimating the effectiveness of PM in a number of settings, including assessing the impact of personality differences (Heffernan and Ling, 2001
), age-related differences (Heffernan and Elmirghani, 2000
), as a neuropsychological instrument in the study of brain damaged patients (Hannon et al., 1995
), and has been used to explore self-rated prospective memory impairments in regular ecstasy users (Heffernan et al., 2001
).
There is some evidence to suggest that chronic heavy alcohol users show detriments in remembering within an everyday context (Knight and Godfrey, 1985). Given this and the evidence that retrospective memory is impaired in this group, one might expect that they would report more impairments in prospective memory when compared to a sample of low-dose/non-alcohol users. The present study aimed to extend our knowledge on potential memory deficits resulting from heavy alcohol use, focusing here on self-rated errors of prospective memory. If chronic heavy alcohol consumption does have an adverse effect on prospective memory, then one would expect this group to report significantly greater errors in their prospective memory functioning when compared to a low dose/alcohol-free group
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SUBJECTS AND METHODS |
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Prospective memory (PM) was assessed using the Prospective Memory Questionnaire (PMQ), which is a valid and reliable self-report measure (Hannon et al., 1995). The PMQ provides measures of three aspects of PM on a series of nine-point scales. Fourteen questions measure short-term habitual PM, e.g. I forgot to turn my alarm clock off when I got up this morning). Fourteen items measure long-term episodic PM, e.g. I forgot to pass on a message to someone. Ten questions measure internally cued PM, e.g. I forgot what I wanted to say in the middle of a sentence. The PMQ provides a measure of self-reported errors in the previous week, or month or year, depending upon the specific questionnaire item. The scale ranges from 1 (where least forgetting is evident) to 9 (where there is a great deal of forgetting); the greater the score, the more faulty one's prospective memory. Additionally, 14 questions make up the techniques to remember scale, providing a measure of the number of strategies used to aid remembering. The Techniques to Remember Scale ranges from 1 (few strategies used) to 9 (a high number of strategies used). On this latter scale, the greater the score, the more memory aids used. Completion of the PMQ preceded the drug-use questionnaire.
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RESULTS |
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DISCUSSION |
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The mechanisms underlying the range of cognitive impairments associated with chronic heavy alcohol use are not fully understood at present. It is known that alcohol causes brain shrinkage, particularly in alcohol-dependent people, where the damage induced may be permanent (Kril and Halliday, 1998). Alcohol has been found to reduce the number of cholinergic neurons in the basal forebrain leading to reduced hippocampal function a structure heavily implicated in memory consolidation (Garcia-Moreno et al., 2001
). Alcohol also appears to inhibit prefrontal lobe functioning (Wendt and Risberg, 2001
). Prospective memory may also be under the influence of pre-frontal and frontal cortical control (Okuda et al., 1998
; McDaniel et al., 1999
), and prospective memory performance is strongly correlated with frontal lobe executive processes (Shapiro et al., 1998
). It seems possible, therefore, that damage in the pre-frontal and frontal regions of the brain may be responsible for the self-reported deficits observed in the present study. Although this is feasible, alternative explanations cannot be ruled out, such as the role of the hippocampus in prospective memory and/or the putative depletion of specific neurotransmitter substances known to impact upon mnemonic processes, such as serotonin (Spoont, 1992
; Hunter, 2000
). It seems quite possible that a complex interaction exists between the effects of excessive alcohol use, regional brain functioning and neurotransmitter depletion.
Although the use of other drugs did not statistically affect heavy alcohol-related prospective memory impairments, one cannot rule out the possibility that biological interactions between alcohol and other drugs may contribute to the effects seen here. One way to address this issue would be to include a heavy alcohol-only group who were otherwise drug free, in addition to a matched control group. It is also necessary to consider the use of self-report measures in studies of this kind. The reliance on self-reports of remembered errors in a group where memorial deficits are already known raises the possibility of a memory paradox, in which heavy alcohol users may forget their memory lapses. But, given the direction and strength of the group differences found in the present study it could be argued that, if anything, this possibility adds strength to the present findings. It is likely that alcohol users may well have underestimated their memory deficits.
These findings have implications on the potentially harmful effects of chronic heavy alcohol use. Future research may wish to employ more objective methods for assessing prospective memory, such as laboratory based prospective memory tasks, or perhaps, video simulations which assess prospective remembering (Titov and Knight, 2001). It is clear that further research is needed to clarify the relationship between chronic heavy alcohol use, impairments in prospective memory and the neuropsychological basis for such impairments, such as the cortical and sub-cortical regions involved in these processes.
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FOOTNOTES |
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