This article was downloaded by: ["Queen's University Libraries, Kingston"] On: 03 February 2015, At: 00:31 Publisher: Routledge Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Journal of Clinical and Experimental Neuropsychology Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/ncen19
Dual-task performance in demented and nondemented elderly a
Ellen Grober & Martin J. Sliwinski
a b
a
Saul Korey Dept. of Neurology , Albert Einstein College of Medicine , b
City University of New York , Queens College Published online: 04 Jan 2008.
To cite this article: Ellen Grober & Martin J. Sliwinski (1991) Dual-task performance in demented and nondemented elderly, Journal of Clinical and Experimental Neuropsychology, 13:5, 667-676, DOI: 10.1080/01688639108401081 To link to this article: http://dx.doi.org/10.1080/01688639108401081
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sublicensing, systematic supply, or distribution in any form to anyone is expressly
Downloaded by ["Queen's University Libraries, Kingston"] at 00:31 03 February 2015
forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
Journal of Clinical and Experimental Neuropsychology 1991, Vol. 13, NO. 5, pp. f67-676
0 168-8634P1/1305-0667$3.O0 0 Swets & Zeitlinger
Downloaded by ["Queen's University Libraries, Kingston"] at 00:31 03 February 2015
Dual-task Performance in Demented and Nondemented Elderly* Ellen Grober' & Martin J. Sliwinski1s2 Saul Korey Dept. of Neurology, Albert Einstein College of Medicine City University of New York, Queens College
ABSTRACT The present study examined the ability of demented and nondemented elderly subjects to divide their attention between recalling digits and judging the similarity of pairs of letters. Both groups showed substantial decrements in digit recall following distraction by letter matching. To identify the nature of the interference effect, digit recall was scored according to a strict criterion where preservation of the serial order of the digits was required (order-based recall), and a lenient criterion where preservation of digit order was not required (order-free recall). While both groups showed a comparable decrement in order-based recall due to the interfering task, order-free recall virtually eliminated the decrement for the nondemented group whereas substantial interference was still observed in the demented group. These results suggest that letter matching interferes with digit recall in nondemented elderly primarily by disrupting order information. In the case of demented elderly, letter matching disrupts the preservation of item information as well.
Several studies support the notion that impairments in memory functioning observed in normal and demented elderly can best be understood within the framework of working m e m o r y (Baddeley, 1986; Baddeley, Logie, Bressi, Della Sala, & Spinnler, 1986; Becker, 1988; Gick, Craik, & Morris, 1988; Morris & Baddeley, 1988; Morris, Gick, & Craik, 1988). Central to the working memory model i s the concept of the Central Executive System which refers to mental processes that initiate and control cognitive operations involved in the maintenance of information and its ongoing processing (Baddeley, 1976; 1986). T h e paradigm m o s t often used t o study working memory relies on tasks which require subjects t o divide their attention between short-term storage and
* The authors thank the residents, staff, and administration of Momingside House Nursing Home and Hebrew Home for the Aged at Riverdale for making this study possible and Shereen Bang for evaluating patients, and Paula Stryjewski for preparing the manuscript. This research was supported by U. S . Public Health Service Grant AGO-3949. Address correspondence to: Ellen Grober, Ph.D., Saul Korey Dept. of Neurology, Albert Einstein College of Medicine, Van Etten, Room 317. 1300 Morris Park Ave. Bronx NY 10461, USA. Accepted for publication: November 13, 1990
Downloaded by ["Queen's University Libraries, Kingston"] at 00:31 03 February 2015
668
ELLEN GROBER AND MARTIN J. SLIWINSKI
ongoing information processing. In an early study by Hitch and Baddeley (1976). subjects were presented with a list of digits to hold in memory while performing a sentence verification task. Neither speed nor accuracy of sentence verification was affected by a two-digit preload whereas a preload of six digits significantly increased verification latencies, especially for the more complex sentences. Hitch and Baddeley argued that a small number of digits (2 or 3) could be maintained in the Articulatory Loop (see Baddeley, Lewis, & Vallar, 1984), thus making relatively few demands on the Central Executive. But as the load on this system is increased to six items, executive control processes must become involved with the task of maintaining the digits in memory, reducing the resources available to coordinate the secondary sentence verification task. While normal aging is usually associated with decreased performance on working memory tasks (Light & Anderson, 1985; Salthouse, Rogan, & Prill, 1984; Spilich, 1983; Welford, 1958; Wright, 1981) not all tasks produce agerelated deficits (Gick et al., 1988; Morris et al., 1988). For example, older subjects are slower to verify sentences than younger subjects when sentences are made more complex (i.e., were negative) but not when concurrent memory load is increased from zero to four words (Monis et al., 1988). Such age-related interactions are inconsistent with a decline in a general pool of processing resources or in the passive storage capacity of working memory and suggest, instead, that aging may affect the efficiency of task-specific resources concerned with ongoing information processing and decision-making (Craik, Morris, & Gick, 1990). A more general impairment of working memory is thought to be responsible for the memory deficits associated with early dementia (Baddeley, 1986; Baddeley et al; 1986; Becker, 1988; Moms, & Baddeley, 1988). In support of their position, Morris and Baddeley reviewed the study by Baddeley et al. (1986) which compared the performance of demented and nondemented elderly on a series of dual-task experiments. Pursuit tracking of a light square moving across a computer monitor was used as a primary task in combination with three different secondary tasks which included concurrent articulation (counting from 1 to 5). simple reaction time to tones, and a digit span task. Concurrent articulation, which is relatively automatic and requiles little effort to perform, had a similar effect on both groups whereas marked group differences emerged in the tracking-digit span combination. Not only did the demented group show a significantly greater decrement in tracking performance during the dual-task condition than the nondemented elderly, they also performed worse on the digit span task. Baddeley et al. (1986) concluded that the decrement in performance observed in the demented group was due to a dysfunction in the Central Executive system which disrupted the ability to coordinate and schedule two concurrent tasks (see also Morris, 1986; Moms & Baddeley, 1988). These studies demonstrate that under certain circumstances the coordination of two tasks can produce decrements in performance on one or both of the tasks, and that this decrement is exaggerated in demented as compared to nondemented elderly subjects. Since memory is usually assessed by serial order recall, impaired
Downloaded by ["Queen's University Libraries, Kingston"] at 00:31 03 February 2015
DUAL TASK PERFORMANCE IN DEMENTIA
669
recall performance produced by a secondary task could be due to at least two factors: (1) a loss of the items from short-term storage, and (2) a disruption in the maintenance of the serial order of the items. The present study examined this issue using a dual-task design, comprised of letter-matching and digit-recall tasks (Wright, 1981) with the dependent measure of primary concern being the number of digits recalled. Both order-based and order-free recall were examined. Order-based recall is identical to serial order recall and requires the retrieval of the digits in their proper sequence. Order-free recall only requires the retrieval of the digits, without regard to their serial order. The rationale behind using these two types of measurements is as follows. Since maintenance rehearsal is involved in the retention of order information for more than three items (Baddeley & Hitch, 1974), having to coordinate and perform two tasks simultaneously might exceed available processing resources even when storage capacity is intact. Under these conditions, the secondary letter matching task would not interfere with the ability to remember which digits had been on the list, but would hinder the ability to recall the order in which the digits had appeared. For subjects who suffer from reduced storage capacity, poor performance under divided-attention conditions would be due to a loss of item information as shown by decreased order-free recall. If normal aging is not associated with a generalized decrease in the storage capacity of working memory (Gick et al., 1988), then any disruptive effect of the letter matching task on digit recall should be eliminated or greatly reduced when order does not matter in scoring digit recall. In contrast, if demented elderly have diminished storage capacity, the letter matching task would disrupt not only their ability to retain order information but also their ability to retain the digits in any order.
METHODS Subjects All subjects were recruited from the Albert Einstein College of Medicine (AECOM) Teaching Nursing Home Study (AG 03949) and gave informed consent as specified by the Committee on Clinical Investigations. Subjects were thoroughly evaluated to determine presence or absence of dementia. The evaluation included history, medical and neurological examinations, comprehensive neuropsychological assessment, functional and depression inventories, chemical screen and blood count, thyroid profile, serum B12 and folate levels, and serological test for syphilis. A computerized tomographic scan was performed in most cases. No subject had a history of psychosis, alcoholism, or evidence of severe depression. The data were reviewed by a neurologist who classified each subject as demented or not demented. Those subjects who satisfied DSM III criteria (American Psychiatric Association, 1980) were assigned to the demented group. The nondemented group consisted of subjects who were considered cognitively normal. There were 26 subjects in each group. Information about each group is shown in Table 1. The nondemented and demented groups were similar in age (82.3vs. 83 years, respectively) but the nondemented group had more years of education (11.7 vs. 9.6). Nondemented subjects performed significantly better than demented subjects on an abbreviated version of the Information, Similarities, and Vocabulary subtests of the WAIS (prorated VIQ =
670
ELLEN GROBER AND MARTIN I. SLIWINSKI
Table 1, Descriptive statistics on the sample of 26 Nondemented and Demented elderly subjects. Standard deviations are in parentheses. Nondemented
Demented
(n=26)
(n=26)
82.3 (5.5)
83 (6.8)
61% females
80% females
Education
11.7 (3.9)
9.6 (3.6)
.01
WAIS
121.2 (11.9)
98.4 (14.9)
Journal of Clinical and Experimental Neuropsychology Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/ncen19
Dual-task performance in demented and nondemented elderly a
Ellen Grober & Martin J. Sliwinski
a b
a
Saul Korey Dept. of Neurology , Albert Einstein College of Medicine , b
City University of New York , Queens College Published online: 04 Jan 2008.
To cite this article: Ellen Grober & Martin J. Sliwinski (1991) Dual-task performance in demented and nondemented elderly, Journal of Clinical and Experimental Neuropsychology, 13:5, 667-676, DOI: 10.1080/01688639108401081 To link to this article: http://dx.doi.org/10.1080/01688639108401081
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sublicensing, systematic supply, or distribution in any form to anyone is expressly
Downloaded by ["Queen's University Libraries, Kingston"] at 00:31 03 February 2015
forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
Journal of Clinical and Experimental Neuropsychology 1991, Vol. 13, NO. 5, pp. f67-676
0 168-8634P1/1305-0667$3.O0 0 Swets & Zeitlinger
Downloaded by ["Queen's University Libraries, Kingston"] at 00:31 03 February 2015
Dual-task Performance in Demented and Nondemented Elderly* Ellen Grober' & Martin J. Sliwinski1s2 Saul Korey Dept. of Neurology, Albert Einstein College of Medicine City University of New York, Queens College
ABSTRACT The present study examined the ability of demented and nondemented elderly subjects to divide their attention between recalling digits and judging the similarity of pairs of letters. Both groups showed substantial decrements in digit recall following distraction by letter matching. To identify the nature of the interference effect, digit recall was scored according to a strict criterion where preservation of the serial order of the digits was required (order-based recall), and a lenient criterion where preservation of digit order was not required (order-free recall). While both groups showed a comparable decrement in order-based recall due to the interfering task, order-free recall virtually eliminated the decrement for the nondemented group whereas substantial interference was still observed in the demented group. These results suggest that letter matching interferes with digit recall in nondemented elderly primarily by disrupting order information. In the case of demented elderly, letter matching disrupts the preservation of item information as well.
Several studies support the notion that impairments in memory functioning observed in normal and demented elderly can best be understood within the framework of working m e m o r y (Baddeley, 1986; Baddeley, Logie, Bressi, Della Sala, & Spinnler, 1986; Becker, 1988; Gick, Craik, & Morris, 1988; Morris & Baddeley, 1988; Morris, Gick, & Craik, 1988). Central to the working memory model i s the concept of the Central Executive System which refers to mental processes that initiate and control cognitive operations involved in the maintenance of information and its ongoing processing (Baddeley, 1976; 1986). T h e paradigm m o s t often used t o study working memory relies on tasks which require subjects t o divide their attention between short-term storage and
* The authors thank the residents, staff, and administration of Momingside House Nursing Home and Hebrew Home for the Aged at Riverdale for making this study possible and Shereen Bang for evaluating patients, and Paula Stryjewski for preparing the manuscript. This research was supported by U. S . Public Health Service Grant AGO-3949. Address correspondence to: Ellen Grober, Ph.D., Saul Korey Dept. of Neurology, Albert Einstein College of Medicine, Van Etten, Room 317. 1300 Morris Park Ave. Bronx NY 10461, USA. Accepted for publication: November 13, 1990
Downloaded by ["Queen's University Libraries, Kingston"] at 00:31 03 February 2015
668
ELLEN GROBER AND MARTIN J. SLIWINSKI
ongoing information processing. In an early study by Hitch and Baddeley (1976). subjects were presented with a list of digits to hold in memory while performing a sentence verification task. Neither speed nor accuracy of sentence verification was affected by a two-digit preload whereas a preload of six digits significantly increased verification latencies, especially for the more complex sentences. Hitch and Baddeley argued that a small number of digits (2 or 3) could be maintained in the Articulatory Loop (see Baddeley, Lewis, & Vallar, 1984), thus making relatively few demands on the Central Executive. But as the load on this system is increased to six items, executive control processes must become involved with the task of maintaining the digits in memory, reducing the resources available to coordinate the secondary sentence verification task. While normal aging is usually associated with decreased performance on working memory tasks (Light & Anderson, 1985; Salthouse, Rogan, & Prill, 1984; Spilich, 1983; Welford, 1958; Wright, 1981) not all tasks produce agerelated deficits (Gick et al., 1988; Morris et al., 1988). For example, older subjects are slower to verify sentences than younger subjects when sentences are made more complex (i.e., were negative) but not when concurrent memory load is increased from zero to four words (Monis et al., 1988). Such age-related interactions are inconsistent with a decline in a general pool of processing resources or in the passive storage capacity of working memory and suggest, instead, that aging may affect the efficiency of task-specific resources concerned with ongoing information processing and decision-making (Craik, Morris, & Gick, 1990). A more general impairment of working memory is thought to be responsible for the memory deficits associated with early dementia (Baddeley, 1986; Baddeley et al; 1986; Becker, 1988; Moms, & Baddeley, 1988). In support of their position, Morris and Baddeley reviewed the study by Baddeley et al. (1986) which compared the performance of demented and nondemented elderly on a series of dual-task experiments. Pursuit tracking of a light square moving across a computer monitor was used as a primary task in combination with three different secondary tasks which included concurrent articulation (counting from 1 to 5). simple reaction time to tones, and a digit span task. Concurrent articulation, which is relatively automatic and requiles little effort to perform, had a similar effect on both groups whereas marked group differences emerged in the tracking-digit span combination. Not only did the demented group show a significantly greater decrement in tracking performance during the dual-task condition than the nondemented elderly, they also performed worse on the digit span task. Baddeley et al. (1986) concluded that the decrement in performance observed in the demented group was due to a dysfunction in the Central Executive system which disrupted the ability to coordinate and schedule two concurrent tasks (see also Morris, 1986; Moms & Baddeley, 1988). These studies demonstrate that under certain circumstances the coordination of two tasks can produce decrements in performance on one or both of the tasks, and that this decrement is exaggerated in demented as compared to nondemented elderly subjects. Since memory is usually assessed by serial order recall, impaired
Downloaded by ["Queen's University Libraries, Kingston"] at 00:31 03 February 2015
DUAL TASK PERFORMANCE IN DEMENTIA
669
recall performance produced by a secondary task could be due to at least two factors: (1) a loss of the items from short-term storage, and (2) a disruption in the maintenance of the serial order of the items. The present study examined this issue using a dual-task design, comprised of letter-matching and digit-recall tasks (Wright, 1981) with the dependent measure of primary concern being the number of digits recalled. Both order-based and order-free recall were examined. Order-based recall is identical to serial order recall and requires the retrieval of the digits in their proper sequence. Order-free recall only requires the retrieval of the digits, without regard to their serial order. The rationale behind using these two types of measurements is as follows. Since maintenance rehearsal is involved in the retention of order information for more than three items (Baddeley & Hitch, 1974), having to coordinate and perform two tasks simultaneously might exceed available processing resources even when storage capacity is intact. Under these conditions, the secondary letter matching task would not interfere with the ability to remember which digits had been on the list, but would hinder the ability to recall the order in which the digits had appeared. For subjects who suffer from reduced storage capacity, poor performance under divided-attention conditions would be due to a loss of item information as shown by decreased order-free recall. If normal aging is not associated with a generalized decrease in the storage capacity of working memory (Gick et al., 1988), then any disruptive effect of the letter matching task on digit recall should be eliminated or greatly reduced when order does not matter in scoring digit recall. In contrast, if demented elderly have diminished storage capacity, the letter matching task would disrupt not only their ability to retain order information but also their ability to retain the digits in any order.
METHODS Subjects All subjects were recruited from the Albert Einstein College of Medicine (AECOM) Teaching Nursing Home Study (AG 03949) and gave informed consent as specified by the Committee on Clinical Investigations. Subjects were thoroughly evaluated to determine presence or absence of dementia. The evaluation included history, medical and neurological examinations, comprehensive neuropsychological assessment, functional and depression inventories, chemical screen and blood count, thyroid profile, serum B12 and folate levels, and serological test for syphilis. A computerized tomographic scan was performed in most cases. No subject had a history of psychosis, alcoholism, or evidence of severe depression. The data were reviewed by a neurologist who classified each subject as demented or not demented. Those subjects who satisfied DSM III criteria (American Psychiatric Association, 1980) were assigned to the demented group. The nondemented group consisted of subjects who were considered cognitively normal. There were 26 subjects in each group. Information about each group is shown in Table 1. The nondemented and demented groups were similar in age (82.3vs. 83 years, respectively) but the nondemented group had more years of education (11.7 vs. 9.6). Nondemented subjects performed significantly better than demented subjects on an abbreviated version of the Information, Similarities, and Vocabulary subtests of the WAIS (prorated VIQ =
670
ELLEN GROBER AND MARTIN I. SLIWINSKI
Table 1, Descriptive statistics on the sample of 26 Nondemented and Demented elderly subjects. Standard deviations are in parentheses. Nondemented
Demented
(n=26)
(n=26)
82.3 (5.5)
83 (6.8)
61% females
80% females
Education
11.7 (3.9)
9.6 (3.6)
.01
WAIS
121.2 (11.9)
98.4 (14.9)
