The Journals of Gerontology Series B: Psychological Sciences and Social Sciences 62:P187-P190 (2007)
© 2007 The Gerontological Society of America
Executive Functions in Normal Aging: An Examination of Script Sequencing, Script Sorting, and Script Monitoring
Philippe Allain,
Gilles Berrut,
Frédérique Etcharry-Bouyx,
Jean Barré,
Frédéric Dubas and
Didier Le Gall
1 Laboratory of Psychology, University of Angers, France.
2 Clinical and Research Center for Memory Disorders and Degenerative Diseases, 3 Department of Neurology, and 4 Unit of Clinical Gerontology, University Hospital of Angers, France.
Address correspondence to Philippe Allain, Unité de Neuropsychologie, Département de Neurologie, Centre Hospitalier Universitaire, 4 rue Larrey, 49033 Angers Cedex 01, France. E-mail: PhAllain{at}chu-angers.fr
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Abstract
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We explored the effect of age on executive functions by using script-sequencing and script-sorting tasks. Older participants (n = 39), relative to young subjects (n = 40), committed more errors in script sequencing. However, there was no difference in performance between elderly and young subjects in excluding irrelevant items. These results suggest that aging generates impairment in the ability to produce temporally coherent sequences without deficit in the ability to eliminate distractors in the action domain. We proposed that the sequencing difficulties in elderly participants could be due to working-memory and shifting deficits mediated by changes in the dorsolateral prefrontal cortex.
PREFRONTAL cortical areas are the first cerebral regions to be affected in normal aging (Tisserand & Jolles, 2003
). Consequently, many neuropsychological models propose that this prefrontal deterioration plays a key role in many age-related cognitive changes (Dempster, 1992; West, 2000).
Planning a sequence of actions is considered to be one of the main functions of the frontal lobes (Shallice, 1988). In the theory developed by Grafman (1989), planning depends on the activation of scripts, which are thought of as knowledge structures used for the representation of familiar activities such as "going to a restaurant" (Schank & Abelson, 1977). According to Grafman, scripts are activated in the frontal lobe, which is very important in the maintenance of the sequential order of events and fixed boundaries. Therefore, Grafman proposed that lesions to the prefrontal cortex caused defects in the ability to provide a coherent sequence of actions and to discriminate between relevant and irrelevant intrusions.
In agreement with Grafman's model, several script-generation (Godbout & Doyon, 1995; Sirigu, Zalla, Pillon, Grafman, Agid, & Dubois, 1995) and script-execution (Chevignard et al., 2000; Schwartz, Montgomery, Fitzpatrick-Desalme, Ochipa, Coslett, & Mayer, 1995) studies have confirmed the presence of sequencing and monitoring impairments in frontal lobe pathology. A reconstitution procedure requires participants to sort script activities into their proper sequence. Le Gall, Aubin, Allain, and Emile (1993) and Sirigu Zalla, Pillon, Grafman, Agid, and Dubois (1996) found that frontal lobe pathology leads to reconstitution-sequencing deficits. We replicated these results; moreover, we showed that the dorsolateral regions play a major role in script sequencing and the orbital region plays a role in irrelevant action discrimination (Allain, Le Gall, Etcharry-Bouyx, Aubin & Emile, 1999; Allain, Le Gall, Etcharry-Bouyx, Forgeau, Mercier, & Emile, 2001).
Surprisingly, little is known about the ability of normal elderly individuals to manipulate script knowledge. Godbout, Doucet, and Fiola (2000) asked elderly and young subjects to enumerate a list of actions describing what people do when they go "shopping for groceries." These researchers showed that errors rates were very low in both groups, but that sequencing impairments were more marked in older people. Partially consistent with this finding, Helmes, Bush, Pike, and Drake (in press), using a script-reconstitution task involving the "cake," "shopping," and "tire" scripts, showed that sequencing errors were sensitive measures of age-related change. However, aging effects observed in the Helmes study were specific to female participants. One complication of both studies was that only a few scripts were included, which is insufficient for reasonable sensitivity in our experience (see Allain et al., in press).
To our knowledge, there is no other evidence that normal aging affects elderly individuals in their ability to manipulate script information. Our main goal was thus to further examine script representation in aging by using several script tasks that have been found to be sensitive to frontal lobe damage. Consistent with the frontal model of cognitive decline, Grafman's (1989) framework, and previous empirical data, we predicted that elderly subjects would show significant script-sequencing and script-sorting impairments.
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METHODS
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Participants
We tested 39 elderly adults (19 women and 20 men). Their mean age was 71.6 years (SD = 2.6, range = 65–77) and their mean total years of education was 9.1 years (SD = 2.1, range = 6–13). None of them presented signs of cognitive deterioration (Mini-Mental State Examination score, M = 28.2, SD = 0.9, range = 26–30). Forty young adults (21 men and 19 women) served as controls. Their mean age was 28.6 years (SD = 6.3, range = 19–40). Their mean total years of education was 9.5 years (SD = 1.4, range 7–13). All subjects were free of known serious medical illness. The groups did not differ with regard to educational level, F(1, 77) = 1.60, p =.20.
Materials
The tests we used to probe script knowledge in both groups were the same as the ones we developed for our previous studies (Allain et al., 1999, 2001). We used the normative data proposed by Bower, Black, and Turner (1979), Galambos (1983), and Corson (1990) to construct scripts that were at about the same level of description and sequencing difficulty. For this, we controlled the ranks of centrality, distinctiveness, and sequence of the actions included in each script. Mean ranks for all these characteristics were approximately identical in all scripts. The basic script-based task was identical in the four different conditions (Table 1). An experimenter gave the participants actions written on cards and requested that they sort the cards according to the scripts to which they belong or according to their order of execution. The experimenter presented all cards face up on the table so that the participants could see them all. Each script title was written on a separate card and was displayed in front of the participants throughout the actions. Participants picked cards up in order and could change their minds and check over their arrangements. There was no time limit. We designed the conditions to assess action sequencing or sorting and monitoring of irrelevant items (six actions and a header).
Two independent judges, one of whom was blind to which participant's script was being judged, scored the sequencing errors when action order was reversed within a script. Given that there are different ways in which the same script could be carried out without affecting the end result (Sirigu et al., 1995), and that experience may influence the perception of content and sequence of scripts (Hess & Tate, 1992), sequence deviations were not classed from an order set by us. We had only physically impossible and illogical errors scored (Sirigu et al.). We had all coherent sequences for the scripts accepted. There was 98% agreement between raters (when there was not complete agreement, a consensus was obtained). One of us (P. Allain) scored the sorting errors. We scored these errors were scored when a single action normally belonging to one script was incorporated in another script.
All young and elderly participants also underwent a baseline neuropsychological assessment including four tasks with presumed sensitivity to frontal lobe dysfunction: the Modified Card Sorting Test (MCST; Nelson, 1976), the Tower of London Test (ToL Test; Shallice, 1982), the Stroop Test (Stroop, 1935), and the Trail Making Test (TMT; Reitan, 1958). For test descriptions, see the sources cited.
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RESULTS
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Executive Tests
Elderly participants performed significantly more poorly than younger participants did on all executive tasks (Table 2). For Part B of the TMT, elderly participants needed more time, F(1, 77) = 33.77, p <.0001, 
2 =.43, and made more perseverative errors, F(1, 77) = 5.6, p =.02, 2 =.07, than did the younger participants On the MCST (the test was performed until all 48 cards were used), they completed fewer categories, F(1, 77) = 25.72, p <.0001, 2 =.33, and made more errors, F(1, 77) = 21.71, p <.0001, 2 =.28, and perseverative errors, F(1, 77) = 19.01, p <.0001, 2 =.24, than did the younger participants. For the ToL Test, elderly participants had a lower number of correct solutions, F(1, 77) = 10.71, p =.001, 2 =.13, and made more moves, F(1, 77) = 13.89, p =.0004, 2 =.18, than did the younger participants. For the Stroop Test, they were slower, F(1, 77) = 25.60, p <.0001, 2 =.33, and had a higher number of errors, F(1, 77) = 6.5, p =.01, 2 =.08, in the interference condition than did the younger participants.
Script Tasks
For script tasks (see Table 3), following the research of Helmes and colleagues (in press), we included sex as a factor in all script analyses. However, we obtained no significant effects, so we dropped it from further consideration.
Sequencing errors
We carried out a two-way 2 (group) x 4 (task) analysis of variance on the mean proportion of sequencing errors. There was a main effect of group, F(1, 77) = 269.78, p <.0001, 2 =.87, showing that elderly adults made significantly more sequencing errors (mean proportion for all tasks, 9.1) than did young adults (mean proportion for all tasks, 2.3). There was no significant effect of task, F(3, 231) = 2.05, p =.10, 2 =.01, or Group x Task interaction, F(3, 231) = 2.32, p =.08, 2 =.02, suggesting that sequencing condition has no effect on the likelihood of committing sequencing errors and that both groups have similar patterns of performance. The proportion of individuals making sequencing errors was higher in the elderly group (39 of 39 for all scripts) than in the young group (32 of 40): 
2 = 8.67, df = 1, p <.003. Participants respected the main sections of scripts (extreme actions steps) more than finer temporal structure (intermediate actions steps). Sequencing errors mainly concerned actions with low degree of centrality (93% and 89% of the sequencing errors for elderly and young adults, respectively).
Sorting errors
We carried out a two-way 2 (group) x 2 (task) analysis of variance on the mean proportion of sorting errors. There was no significant effect of group, F(1, 77) = 0.12, p =.72, 2 =.007; task, F(1, 77) = 0.82, p =.36, 2 =.005; or Group x Task interaction, F(1, 77) = 0.36, p =.54, 2 =.002. Sorting errors were rare in both groups, suggesting that aging and sorting conditions had no effect on the probability to produce sorting errors. Sorting errors mainly concerned actions with low degree of centrality (91% and 88% of the sorting errors for elderly and young adults, respectively).
Irrelevant actions accepted
There was no significant difference in performance between groups in inhibiting irrelevant actions, F(1, 77) = 0.20, p =.64, 2 =.002. Consistent with this finding, there was no significant difference between the proportions of elderly participants (24 of 39) and young participants (20 of 40) who made use of irrelevant actions (2 = 1.06, df = 1, p =.30).
Number of actions linked to the irrelevant title
There was no significant difference between groups in the number of actions linked to the irrelevant title, F(1, 77) = 0.38, p =.53, 2 =.004. Differences between the proportions of elderly adults (5 of 39) and young adults (6 of 40) who made use of the irrelevant title were minimal (2 = 0.07, df = 1, p =.77).
Correlation
Our analyses of the relationships between sequencing and executive performance in elderly adults revealed that the total number of sequencing errors computed for each subject was significantly correlated with the number of categories achieved (r = –.58, p <.0001) and the number of errors (r =.56, p <.0001) on the MCST, the number of correct solutions (r = –.47, p =.001) on the ToL Test, and with time measures on the Stroop Test (r =.63, p <.0001) and the TMT (r =.49, p <.001).
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DISCUSSION
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Our aim in this study was to examine the effect of age on action planning by using script-reconstitution tasks. The results mainly showed that elderly participants exhibit impairment in their ability to produce temporally coherent sequences of actions without defect in their ability to sort script actions and to eliminate irrelevant propositions.
The finding that elderly adults committed significantly more sequencing errors in our script-arrangement tasks supports the findings described by Godbout and colleagues (2000) with a script-generation task. However, in their research, Godbout and colleagues showed that sequencing-error rates were very low in both groups, suggesting that sequencing was relatively preserved. In contrast, in our script-sequencing tasks, and consistent with the findings by Helmes and associates (in press), errors appear more frequent in elderly participants; this suggests that normal aging is responsible for cognitive changes in script-information sequencing.
This finding is also consistent with previous reports showing an impairment in memory for temporal order in elderly participants using tests that require learning a specific set of temporal relationships such as recency judgment for verbal or pictorial stimuli (Fabiani & Friedman, 1997) or in tests that require retrieving information about when words occurred within a list (Cabeza, Anderson, Houle, Mangels, & Nyberg, 2000). However, in this study, the temporal information assessed through our script-based tasks is more semantic in nature.
The sequencing impairment observed in elderly adults could not be attributed to impairment of the semantic dimension of script, because we have shown that elderly participants were able to correctly categorize script actions in our third and fourth tasks. Our proposition to explain it is that ordering a preestablished sequence of actions makes extensive demands on executive functions. First, it requires the subjects to retrieve their script-memory representations and to simulate mentally the whole temporal structure of the actions in working memory. Second, the subjects must create a correspondence between each action written on the card and the internal abstract representations used as references. Third, during the sequencing stage, subjects must shift their attention back and forth throughout the task from the individual elements of the scripts to the general display dictated by the internal abstract script representations. Hence, the sequence errors committed by elderly adults might reflect a difficulty in maintaining abstract representations in working memory or a diminished shifting ability. The fact that elderly participants performed poorly on the executive tasks that engaged working memory (the MCST and ToL Test) and shifting ability (the MCST and the TMT) is consistent with this proposition. This explanation is also in accordance with the significant correlations we found between sequencing and executive scores and argues for a "frontal" model of cognitive decline (for an alternative explanation, see Guimond, Braun, Rouleau, Belanger, & Godbout, 2006).
In conclusion, elderly participants were selectively impaired in their ability to organize a coherent sequence of actions. Errors could be due to working-memory or shifting deficits. In regard to our lesions analysis in frontal patients (Allain et al., 1999, 2001), as dorsolateral lesions are associated with script-sequencing deficits, this selective impairment suggests that cognitive aging could be better interpreted in terms of changes in the dorsolateral frontal cortex rather than in all-encompassing frontal deterioration.
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Acknowledgments
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We are grateful to Dr. Alaa Ghali for improving the language of the manuscript.
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Footnotes
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Decision Editor: Thomas M. Hess, PhD
Received for publication June 27, 2006.
Accepted for publication November 21, 2006.
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References
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- Allain, P., Le Gall, D., Etcharry-Bouyx, F., Aubin, G., Emile, J. (1999). Mental representation of knowledge following frontal-lobe lesion: Dissociations on tasks using scripts. Journal of Clinical and Experimental Neuropsychology, 21,643-665.[Medline]
- Allain, P., Le Gall, D., Etcharry-Bouyx, F., Forgeau, M., Mercier, P., Emile, J. (2001). Influence of the centrality and distinctiveness of actions on script sorting and ordering in patients with frontal lobe lesions. Journal of Clinical and Experimental Neuropsychology, 23,465-483.[Medline]
- Allain, P., Le Gall, D., Foucher, C., Etcharry-Bouyx, F., Barré, J., Dubas, F., et al in press Script representation in patients with Alzheimer's disease. Cortex..
- Bower, G. H., Black, J. B., Turner, T. J. (1979). Scripts in memory for texts. Poetics, 11,177-220.
- Cabeza, R., Anderson, N. D., Houle, S., Mangels, J. A., Nyberg, L. (2000). Age-related differences in neural activity during item and temporal-order memory retrieval: A positron emission tomography study. Journal of Cognitive Neuroscience, 12,197-206.[Medline]
- Chevignard, M., Pillon, B., Pradat-Diehl, P., Taillefer, C., Rousseau, S., Le Bras, C., et al. (2000). An ecological approach to planning dysfunction: Script execution. Cortex, 36,649-669.[Medline]
- Corson, Y. (1990). The structure of scripts and their constituent elements. Cahiers de Psychologie Cognitive, 10,157-183.
- Dempster, F. N. (1992). The rise and fall of the inhibitory mechanism: Toward a unified theory of cognitive development and aging. Developmental Review, 12,45-75.
- Fabiani, M., Friedman, D. (1997). Dissociation between memory for temporal order and recognition memory in aging. Neuropsychologia, 35,129-141.[Medline]
- Galambos, J. A. (1983). Normative studies of six characteristics of our knowledge of common activities. Behavioral Research, Methods and Instrumentation, 15,327-340.
- Godbout, L., Doucet, C., Fiola, M. J. (2000). The scripting of activities of daily living in normal aging: Anticipation and shifting deficits with preservation of sequencing. Brain and Cognition, 43,220-224.[Medline]
- Godbout, L., Doyon, J. (1995). Mental representation of knowledge following frontal-lobe or postrolandic lesions. Neuropsychologia, 33,1671-1696.[Medline]
- Grafman, J. (1989). Plans, actions and mental sets: Managerial knowledge units in the frontal lobes. In E. Perecman (Ed.), Integrating theory and practice in clinical neuropsychology (pp. 93–138). Hillsdale, NJ: Erlbaum.
- Guimond, A., Braun, C. M., Rouleau, I., Belanger, F., Godbout, L. (2006). Remembering the past and foreseeing the future while dealing with the present: A comparison of young adult and elderly cohorts on a multitask simulation of occupational activities. Experimental Aging Research, 32,363-380.[Medline]
- Hess, T. M., Tate, C. S. (1992). Direct and indirect assessments of memory for script-based narratives in young and older adults. Cognitive Development, 7,467-484.
- Helmes, E., Bush, J. D., Pike, D. L., Drake, D. G., in press Gender differences in performance of script analysis by older adults. Brain and Cognition..
- Le Gall, D., Aubin, G., Allain, P., Emile, J. (1993). Script et syndrome frontal: A propos de deux observations [Scripts and the frontal lobe syndrome: Two observations]. Revue de Neuropsychologie, 3,87-110.
- Nelson, H. E. (1976). A modified card sorting test sensitive to frontal lobe defect. Cortex, 12,313-324.[Medline]
- Reitan, R. M. (1958). Validity of the Trail Making Test as an indication of brain damage. Perceptual and Motor Skills, 8,271-276.[Medline]
- Schank, R. C., Abelson, R. P. (1977). Scripts, plans, goals and understanding. Hillsdale, NJ: Erlbaum.
- Schwartz, M. F., Montgomery, M. W., Fitzpatrick-Desalme, E., Ochipa, C., Coslett, H. B., Mayer, N. H. (1995). Analysis of a disorder of everyday action. Cognitive Neuropsychology, 12,863-892.
- Shallice, T. (1982). Specific impairments of planning. Philosophical Transactions of the Royal Society of London Series B, 298,199-209.[Medline]
- Shallice, T. (1988). From neuropsychology to mental structure. Cambridge, England: Cambridge University Press.
- Sirigu, A., Zalla, T., Pillon, B., Grafman, J., Agid, Y., Dubois, B. (1995). Selective impairments in managerial knowledge following pre-frontal cortex damage. Cortex, 31,301-316.[Medline]
- Sirigu, A., Zalla, T., Pillon, B., Grafman, J., Agid, Y., Dubois, B. (1996). Encoding of sequence and boundaries of scripts following prefrontal lesions. Cortex, 32,297-310.[Medline]
- Stroop, J. R. (1935). Studies of interferences in serial verbal reactions. Journal of Experimental Neurology, 18,643-662.
- Tisserand, D. J., Jolles, J. (2003). On the involvement of prefrontal networks in cognitive aging. Cortex, 39,1107-1128.[Medline]
- West, R. L. (2000). In defense of the frontal lobe hypothesis of cognitive aging. Journal of the International Neuropsychological Society, 6,727-729.[Medline]
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Abstract
Methods
