Motor imagery: The relation between age and imagery capacity

Human Movement Science 26 (2007) 203–211 www.elsevier.com/locate/humov

Motor imagery: The relation between age and imagery capacity 夽 Th. Mulder a

a,¤

, J.B.H. Hochstenbach a,b, M.J.G. van Heuvelen a, A.R. den Otter a

Center for Human Movement Sciences, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands b Ministry of Justice, Department of Forensic AVairs (DJI), The Hague, The Netherlands Available online 6 March 2007

Abstract The imagination of motor actions forms not only a theoretical challenge for cognitive neuroscience but may also be seen as a novel therapeutic tool in neurological rehabilitation, in that it can be used for relearning motor control after damage to the motor system. However, since the majority of rehabilitation patients consist of older individuals it is relevant to know whether the capacity of mental imaging is compromised by age. Scores on the vividness of movement imagery questionnaire were obtained for 333 participants, divided in three age groups. Results showed that elderly participants were slightly worse in motor imagery capacity than younger participants, particularly in relation to motor imagery from an internal (Wrst person) perspective. Furthermore, a possible relation between the level of physical activities and motor imagery capacity is discussed. © 2007 Elsevier B.V. All rights reserved. PsycINFO classiWcation: 2330; 2340 Keywords: Mental practice; Motor imagery; Age; Rehabilitation

夽

This study has been supported by a grant from ZonMW. Corresponding author. Address: Center for Human Movement Sciences, University Medical Center Groningen, University of Groningen, P.O. Box 196, 9700 AD, Groningen, The Netherlands and Royal Netherlands Academy of Arts and Sciences (KNAW), Amsterdam. E-mail address: [email protected] (Th. Mulder). *

0167-9457/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.humov.2007.01.001

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1. Introduction Human beings have the ability to mentally imagine events that are not there or no longer there. Mental imagery refers to a process by which sensations can be relived without the appropriate stimuli being present. It may be performed in diVerent modalities such as kinaesthetic, olfactory, tactile, visual, auditory and gustatory perception. In this paper we focus on a speciWc subcategory of mental imagery, namely motor imagery. Motor imagery can be described as an active cognitive process in which movements are mentally rehearsed without any overt body movements. Brain imaging studies using positron emission tomography (PET) and magnetic resonance imaging (fMRI) revealed that motor imagery and motor performance have, at least partly, a shared neural basis (Decety, 1996, Decety, Philippon, & Ingvar, 1988; Hanakawa et al., 2003; LaXeur et al., 2002; Malouin, Richards, Jackson, Dumas, & Doyon, 2003; Porro et al., 1996, Porro, Cettolo, Francescato, & Baraldi, 2000; Rao et al., 1993; Ross, Tkach, Ruggieri, Lieber, & Lapresto, 2003). A number of studies have shown that motor imagery can be eVective in optimizing the execution of movements in athletes. Furthermore, it may help novice learners in the acquisition of new skills (Mulder, Zijlstra, Zijlstra, & Hochstenbach, 2004). Many of these studies have been reviewed by Feltz and Landers (1983) and more recently by Driskell, Copper, and Moran (1994) and by Martin, Moritz, and Hall (1999). They showed that participants who mentally trained for a speciWc task usually displayed less improvement than those who trained physically. However, compared to control participants who did not practice at all, it was shown that motor imagery, indeed, facilitated performance. Based on these eVects, some investigators have proposed the use of motor imagery in neurological rehabilitation, as it may be a novel and cost-eYcient treatment tool (Page, Levine, Sisto, & Johnston, 2001). It is, for example, an intriguing question whether motor imagery may be used as a rehabilitation method for patients who are immobilized for a longer period after an accident or surgery and have to relearn motor control. Indeed, it is known that such an immobilization period may distort the neural representation of the aVected limbs which may compromise later rehabilitation (see Mulder & Hochstenbach, 2001). In a recent PET-study of our group it was shown that a 6-week period of relative immobilization (dynamic splint therapy) after surgical tendon repair led to signiWcant cortical reorganization (De Jong et al., 2003). It has been argued that motor imagery could be a simple tool for Wghting the consequences of such a representational decay. It has even been suggested that motor imagery could play a role in stroke rehabilitation (Jackson, LaXeur, Malouin, Richards, & Doyon, 2001). Against this background it is remarkable that almost no information is available about the question whether the capacity to imagine movements is compromised by age. Indeed, when this capacity declines with age, the above mentioned therapeutic optimism becomes more problematic, particularly in relation to the Weld of neurological or orthopaedic rehabilitation where the majority of the patients belongs to the age-category of 60 yr or older. At this moment we do not really know whether motor imagery would be a viable therapeutic tool for all age groups. There are some indications that the ability to generate and manipulate mental images shows a decline in elderly participants (Craik & Dirkx, 1992; Dror & Kosslyn, 1994; for a review see also Salthouse, 1992). Dror and Kosslyn (1994) compared two groups of young

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and old participants in four visual mental imagery tasks, in each of which a diVerent imagery process was involved: image generation, image maintenance, image inspection, and image transformation. Older participants failed in image activation and image rotation, and also performed poorly in image maintenance. Also Craik and Dirkx (1992) found signiWcant age-related diVerences in tests requiring mental images to be generated and manipulated. It is, however, not known whether such a decline also exists for motor imagery. In this article it is attempted to shed some light on the following questions. First, it is asked whether the capacity to imagine movements is compromised by age. Furthermore, since two forms of imagery have been distinguished viz. imagery from an internal perspective and imagery from an external perspective, both forms of imagery will be taken into account. Imagery from an internal perspective refers to the ability to imagine that one is performing the movement him- or herself, together with the kinaesthetic sensations. Imagery from an external perspective refers to the ability to imagine that someone else is performing the movement. It is not known whether a diVerentiation takes place between these two imagery modes when participants become older. The latter is important since some evidence exists that imagery from an internal perspective plays a more important role in learning than imagination from the external perspective (Jackson et al., 2001). A third question that has to be answered is whether the level of the capacity to imagine movements at older age is related to the level of physical activity and to the perceived Wtness of a participant. 2. Methods 2.1. Participants Three groups of healthy participants participated in the study: 143 young participants (<30 yr, 71 females), 71 intermediately aged participants (30–64 yr, 38 females), and 119 elderly participants (>64 yr, 61 females). Mean age for the young group was 23.99 yr (SD D 3.01; range 19–29), for the intermediately aged group the mean age was 44.07 yr (SD D 10.00; range 30–62), whereas for the oldest group the mean age was 74.20 yr (SD D 5.38; range 67–93). The study has been approved by the local Medical Ethics Committee of the University Medical Center Groningen. 2.2. Procedure All participants Wlled out the vividness of movement imagery questionnaire (VMIQ) The VMIQ consists of 24 items speciWc to movement. It refers to the visual imagery of the movement and to the imagery of movement kinaesthetic sensations (see Isaac, Marks, & Russell, 1986). The VMIQ has the interesting feature that each item refers to two imagery perspectives; the ‘internal’ or Wrst person perspective and the ‘external’ or third person perspective. Respondents were required to imagine each item both with respect to themselves (Wrst person, internal perspective) and with respect to someone else (third person, external perspective). For each item, participants were asked to indicate the vividness of an imagined movement on a 5-point scale: 1 (excellent imagination of the movement performance as lively as actual performance), 2 (a good capacity to imagine movement performance), 3 (moderate capacity to imagine the performance of a movement), 4 (a vague or unclear image) or 5 (no image at all).

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Three scores were obtained: a score for the external perspective (VMIQ-Other; range 24–120), a score for the internal perspective (VMIQ-Self, range 24–120), and a total score where the two ratings are combined (VMIQ-Total, range 24–240). The lower the score, the more vivid the imagery. In order to determine whether a relation would exist between motor imagery capacities and the actual physical status of the participants and with the perceived Wtness, each participant had to perform a number of simple motor tasks that assessed in a very global manner the level of physical activity and Wtness. The following tests were performed: walking endurance test, balance test, manual dexterity test, and a simple RT test. Furthermore, the physical self-eYcacy has been determined. Walking endurance. Participants walked on a rectangular course, divided into three 16.7 m intervals. Walking speed was increased by 1 km/h every 3 min, starting at a speed of 4 km/h and ending at a speed of 7 km/h. Participants had to keep up the eVort as long as possible. The score was the number of completed intervals. A higher score indicated a better performance. Balance. The participant stood on a platform that could tilt sideways. For 30 s, the participant had to try to keep the platform in balance, the platform should not touch the Xoor. The total time (in 0.3 s), during this time-interval, that the platform was in balance was recorded. The Wnal score was the best of three trials. A higher score indicated a better performance. Manual dexterity. The participant had to replace 40 blocks from a full board to an empty board in a prescribed way as quickly as possible with the preferred hand. The time taken to complete the task was recorded. A lower score indicated a better performance. Simple reaction time. The participant had to react to a visual signal by pushing a button as quickly as possible. The time between signal and reaction was recorded. The score was the median of 15 trials. A lower score indicated a better performance. Validity and reliability of these tests are described elsewhere (Lemmink, 1996; Van Heuvelen, Kempen, Ormel, & Rispens, 1998). Physical self-eYcacy was measured with a Dutch version of the perceived physical ability subscale of Ryckmans physical self-eYcacy scale (Bosscher & Smit, 1998). This scale has a minimum of 10 (low level of self-eYcacy) and a maximum of 50 (high level of self-eYcacy). 2.3. Statistical analysis DiVerences in VMIQ-Other (O) and VMIQ-Self (S) scores between the three age groups were tested using univariate analysis of variance (ANOVA). When applicable, post hoc analysis with Bonferroni corrected alpha values to test the diVerences between speciWc pairs of groups was used. To establish whether age is associated with a changed preference for imagining from an internal or an external perspective, the diVerence between VMIQ-S and VMIQ-O scores was calculated for each participant. Subsequently, the association of these scores with the age of the participants was calculated using Pearson’s correlation coeYcient. For the group of elderly (n D 119), Pearson’s correlation coeYcient was calculated to establish the association between VMIQ-Self scores and manual dexterity, simple reaction time, the balance test, physical self eYcacy, and the walking test. Backward stepwise regression analysis was used to identify the variables that best predict VMIQ-Self scores in the group of elderly.

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3. Results VMIQ-O, VMIQ-S, and VMIQ-T scores were obtained from 333 participants (see Table 1). Univariate analysis of variance (ANOVA) revealed a statistically signiWcant diVerence between the three age groups on the VMIQ-S subscale, F(330, 2) D 6.859, p D .001, but not on the VMIQ-O subscale, F(330,2) D 0.094 ns. Post hoc analysis of VMIQ-S scores revealed a statistically signiWcant diVerence between the elderly group and the young group (mean diVerence D 8.79; (SD D 2.51); (p < .05) as well as between the elderly and the intermediate group (mean diVerence D 8.09; SD D 3.04); p < .05). A weak but statistically signiWcant correlation existed between age and the VMIQ-O and VMIQ-S diVerence scores (r D .31, p < .001) indicating that participants experienced relatively more vivid movement imagery from an external standpoint when age increases (see Fig. 1). The mean scores (+SD’s) for the manual dexterity, simple reaction time, the balance test, physical self-eYcacy, and the walking test are shown in Table 2. Table 1 Mean (+95% conWdence interval) for the VMIQ-Other, the VMIQ-Self, and the VMIQ-Total scores of the three age group

Mean (+95% c.i.) VMIQ-Other Mean (+95% c.i.) VMIQ-Self Mean (+95% c.i.) VMIQ-Total

Age > 64 yr

Age 30–64 yr

Age < 30 yr

50.72 (46.64–54.81) 54.61 (50.40–58.82) 105.25 (97.49–113.01)

51.54 (45.84–57.23) 46.52 (41.74–51.30) 98.04 (88.25–107.84)

51.81 (49.05–54.57) 45.83 (42.94–48.71) 97.71 (92.71–102.99)

Fig. 1. DiVerences between VMIQ-Other and VMIQ-Self, as a function of age. The higher the score, the more vivid the external perspective; the lower the score, the more vivid the internal perspective.

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Table 2 Mean scores (+standard deviations) for elderly participants on manual dexterity, simple reaction time, balance skills, walking test, and physical self-eYcacy Manual dexterity (s) Simple reaction time (ms) Balance skills (in units of 0.3 s) Walking test (no. of trajectories) Physical self-eYcacy

51.64 (6.68) 245.13 (44.00) 68.08 (11.42) 28.73 (17.15) 29.62 (6.36)

Table 3 Results of the stepwise backward regression analysis

Constant Simple reaction time Physical self-eYcacy ¤ ¤¤

B

SE B



¡11.93 0.14 ¡0.75

1.791 0.05 0.33

0.27¤¤ ¡0.21¤

p < .05. p < .001.

Weak but statistically signiWcant correlations with VMIQ-S scores were found for manual dexterity (r D .19, p < .05), simple reaction time (r D .32, p < .001), the walking test (r D ¡.24, p < .01), physical self eYcacy (r D ¡.27, p < .005), but not for the balance test (r D ¡.18, p > .05). However, after backward stepwise regression the only two variables that were retained as signiWcant predictors of VMIQ-S scores were simple reaction time and physical selfeYcacy (see Table 3). 4. Discussion The present study was primarily aimed at answering the question whether the ability to imagine movements was inXuenced by age. The results showed that a general decline did not take place across the years but that a weak but signiWcant shift from motor imagery from an internal perspective to motor imagery from an external perspective could be observed. In the oldest group the participants showed better imagery scores when they had to imagine movements from an external perspective compared to the imagery scores obtained from the internal perspective. Only 15% of the elderly proved to be good on motor imagery from the internal perspective, compared to 31% and 32.9% in the younger age groups. The latter is important as some evidence exists that the internal perspective is more eVective for learning than the external perspective (Jackson et al., 2001). Note, however, that the Wnding that only 15% of the participants older than 64 yr had a good to excellent ability to imagine movements from the internal perspective does not mean that 85% of the participants in this age group were totally unable to imagine movements. This Wnding is nevertheless intriguing since why is it that such a shift from an internal to an external perspective occurs with increasing age? May be that the decrease in physical activity that takes place during the process of aging has a negative inXuence, not only on physical Wtness but also on the ability to imagine the performance of movements, particularly in relation to self-movement. In other words, it could be that the lowered kinaesthetic input compromises not only the physical condition (Wtness) but also the movement imag-

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ery capacity. This is not an irrelevant remark since ample and convincing evidence exists that a decrease in sensory input as a result of (relative) immobilization results in reorganization of cortical areas, involved in the control of movements (see for example Brasil-Neto et al., 1993; Classen, Liepert, Wise, Hallett, & Cohen, 1998; De Jong et al., 2003; Rossini et al., 1994). Furthermore, if the imagination of a movement activates more or less the same brain areas as the actual performance of that movement and if motor imagery can be seen as part of the process of motor preparation (Jeannerod, 1994), then it seems plausible that motor imagery ‘obeys’ to the same control rules as actual movement. There is abundant research showing that with increasing age, physical activities decline (Hogan, 2005; Schutzer & Graves, 2004; Stewart, 2005; Van Gelder, Tijhuis, Kalmijn, Giampaoli, & Nissinen, 2004; Van Heuvelen et al., 2005; Westerterp, 2000; Wilson & Tanaka, 2000), so instead of moving around actively elderly may spend more time watching others moving around. Perhaps this change in ‘viewpoint’ may explain the Wnding that an increasing percentage of the oldest participants were better in using the external perspective than in using the internal perspective. If this would be true a relationship could be expected between the decreased capacity to imagine movements from an internal perspective and lower scores on the physical measures. The results are not fully in accordance with this argument. A signiWcant relationship existed between the vividness of the imagery from an internal perspective (VMIQ-S) and the scores on the simple reaction time test and the perceived Wtness scale, but not with scores on the walking and balance test and the manual dexterity test. Hence, there were some correlations indicating in the direction of the above mentioned relationship between physical self-activity and the imagination of self-performed movements, but this relationship is not very strong. The obtained signiWcant correlation between the ability to imagine movements from the internal perspective and the perceived Wtness (perceived physical ability), however, is not irrelevant. Indeed, the employed measures for assessing the physical status of the participants were very simple and global and may have lacked speciWcity. Therefore, a selfevaluation of some ones physical capacities may be still an important indication of the quality of his/her motor abilities. Some support for the relationship between motor imagery and physical activity can be found in the literature. In a classical study Colvin and Myers (1909) questioned 3000 children regarding their imagery ability. They claimed that motor imagery was only vivid in those children who where constantly involved in movement experiences. Isaac and Marks (1994) found that particularly females in the 50 plus age group reported signiWcantly less vivid movement imagery than the other adult groups between 20 and 50 yr They argued that this may reXect the fact that this age group is not as physically active as the younger groups (and the male group). This was also reXected in their Wndings that male physical education students show more vivid motor imagery than male physics students and that in general athletes experienced more vivid motor imagery than non-athletic matched controls. In the present study the VMIQ was used as a measure of imagery capacity. Some word of caution is necessary, since we are well aware of the fact that self-reports based on introspective ability may not oVer the most objective reXection of the quality the cognitive process under study. Indeed, Lequerica, Rapport, Axelrod, Telmet, and Whitman (2002) indicated that the relationship between subjective measures of imagery with objective measures of visuospatial manipulation was not very strong.

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Nevertheless, the obtained results may give some indication of the changes that take place in imagery capacity across age. The present study is one of the few attempts to get more insight into the relationship between the cognitive ability to imagine movements and increasing age. As was indicated in the introduction there are some indications that the ability to generate and manipulate mental images show a decline in elderly participants. This, however, was true for visual images. It was not known whether this decline would be true also for motor imagery. The present data show that with increasing age the capacity to imagine movements is not stable but shows a subtle change, in that elderly (>64 yr) showed some decline in the ability to imagine movements from an internal perspective. This Wnding does not mean that motor imagery as a learning procedure is senseless in elderly participants, but the results indicate that it is, indeed, important to assess whether participants selected for a mental practice program are, indeed, able to imagine selfmovement. This is particularly important in speciWc groups such as stroke patients. References Bosscher, R. J., & Smit, J. H. (1998). ConWrmatory factor analysis of the general self-eYcacy scale. Behavior Research and Therapy, 36, 339–343. Brasil-Neto, J. P., Valls-Solé, J., Pascual-Leone, A., Cammorota, A., Amassian, V. E., Cracco, R., et al. (1993). Rapid modulation of human motor outputs following ischemic nerve block. Brain, 116, 511–525. Classen, J., Liepert, J., Wise, S. P., Hallett, M., & Cohen, L. G. (1998). Rapid plasticity of human movement representation induced by practice. Journal of Neurophysiology, 79, 1117–1123. Colvin, S. S., & Myers, E. J. (1909). The development of imagination in school children and the relation between ideational types and the retentivity of material appealing to various sense departments. Review Monographs, 11, 85–125. Craik, F. I. M., & Dirkx, E. (1992). Age-related diVerences in three tests of visual imagery. Psychology and Aging, 7, 661–665. Decety, J. (1996). The neurophysiological basis of motor imagery. Behavioural Brain Research, 77, 45–52. Decety, J., Philippon, B., & Ingvar, D. (1988). rCBF landscapes during motor performance and motor ideation of a graphic gesture. European Archives of Psychiatry and Neurological Sciences, 238, 33–38. De Jong, B. M., Coert, J. H., Stenekes, M. W., Leenders, K. L., Paans, A. M., & Nicolai, J. P. (2003). Cerebral reorganisation of human hand movement following dynamic immobilisation. Neuroreport, 14, 1693–1696. Driskell, J. E., Copper, C., & Moran, A. (1994). Does mental practice enhance performance? Journal of Applied Psychology, 79, 481–492. Dror, I. E., & Kosslyn, S. M. (1994). Mental imagery and aging. Psychology and Aging, 9, 90–102. Feltz, D. L., & Landers, D. M. (1983). The eVects of mental practice on motor skill learning and performance: A meta-analysis. Journal of Sport Psychology, 5, 25–57. Hanakawa, T., Immisch, I., Toma, K., Dimyan, M., Van Gelderen, P., & Hallett, M. (2003). Functional properties of brain areas associated with motor execution and imagery. Journal of Neurophysiology, 89, 989–1002. Hogan, M. (2005). Physical and cognitive activity and exercise for older adults: A review. International Journal of Aging and Human Development, 60, 95–126. Isaac, A. R., & Marks, D. F. (1994). Individual diVerences in imagery experience: Developmental changes and specialization. British Journal of Psychology, 85, 479–500. Isaac, A. R., Marks, D. F., & Russell, D. (1986). An instrument for assessing imagery of movement: The vividness of mental imagery questionnaire (VMIQ). Journal of Mental Imagery, 10, 23–30. Jackson, P. L., LaXeur, M. F., Malouin, F., Richards, C., & Doyon, J. (2001). Potential role of mental practice using motor imagery in neurologic rehabilitation. Archives of Physical Medicine and Rehabilitation, 82, 1133–1141. Jeannerod, M. (1994). The representing brain: Neural correlates of motor intention and imagery. Behavior and Brain Sciences, 17, 187–245. LaXeur, M. F., Jackson, P. L., Malouin, F., Richards, C. L., Evans, A. C., & Doyon, J. (2002). Motor learning produces parallel dynamic functional changes during the execution and imagination of sequential foot movements. NeuroImage, 16, 142–157.

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Lequerica, A., Rapport, L., Axelrod, B. N., Telmet, K., & Whitman, R. D. (2002). Subjective and objective assessment methods of mental imagery control: Construct validations of self-report measures. Journal of Clinical and Experimental Neuropsychology, 24, 1103–1116. Lemmink, K. A. P. M. (1996). De Groninger Wtheidstest voor ouderen, ontwikkeling van een meetinstrument (The Groningen Wtnesstest for the elderly, development of a measurement instrument). Ph.D. thesis, Groningen: Center for Human Movement Sciences, University of Groningen. Malouin, F., Richards, C. L., Jackson, P. L., Dumas, F., & Doyon, J. (2003). Brain activations during motor imagery of locomotor-related tasks: A PET study. Human Brain Mapping, 19, 47–62. Martin, K. A., Moritz, S. E., & Hall, C. R. (1999). Imagery use in sport: A literature review and applied model. The Sport Psychologist, 13, 245–268. Mulder, Th., & Hochstenbach, J. (2001). Adaptability and Xexibility of the human motor system: Implications for neurological rehabilitation. Neural Plasticity, 8, 131–140. Mulder, T., Zijlstra, S., Zijlstra, W., & Hochstenbach, J. (2004). The role of motor imagery in learning a totally novel movement. Experimental Brain Research, 154, 211–217. Page, S. J., Levine, P., Sisto, S. A., & Johnston, M. V. (2001). Mental practice combined with physical practice for upper-limb motor deWcit in subacute stroke. Physical Therapy, 81, 1455–1462. Porro, C. A., Francescato, M. P., Cettolo, V., Diamond, M. E., Baraldi, P., Zuiani, C., et al. (1996). Primary motor and sensory cortex activation during motor performance and motor imagery: A functional magnetic resonance imaging study. The Journal of Neuroscience, 16, 7688–7698. Porro, C. A., Cettolo, V., Francescato, M. P., & Baraldi, P. (2000). Ipsilateral involvement of primary motor cortex during motor imagery. European Journal of Neuroscience, 12, 3059–3063. Rao, S. M., Binder, J. R., Bandettini, P. A., Hammeke, T. A., Yetkin, F. Z., Jesmanowicz, A., et al. (1993). Functional magnetic resonance imaging of complex human movements. Neurology, 43, 2311–2318. Ross, J. S., Tkach, J., Ruggieri, P. M., Lieber, M., & Lapresto, E. (2003). The mind’s eye: Functional MR imaging evaluation of golf motor imagery. American Journal of Neuroradiology, 24, 1036–1044. Rossini, P. M., Martino, G., Narici, L., Pasquarelli, A., Peresson, M., Pizella, V., et al. (1994). Short-term brain “plasticity” in humans: Transient Wnger representation changes in sensory cortex somatotopy following iscemic anesthesia. Brain Research, 642, 169–177. Salthouse, T. A. (1992). Reasoning and spatial abilities. In F. I. M. Craik & T. A. Salthouse (Eds.), The handbook of aging and cognition (pp. 167–211). Hillsdale, NJ: Erlbaum. Schutzer, K. A., & Graves, B. S. (2004). Barriers and motivations to exercise in older adults. Preventive Medicine, 39, 1056–1061. Stewart, K. J. (2005). Physical activity and aging. Annals of the New York Academy of Sciences, 1055, 193–206. Van Gelder, B. M., Tijhuis, M. A., Kalmijn, S., Giampaoli, S., Nissinen, A., et al. (2004). Physical activity in relation to cognitive decline in elderly men: The FINE Study. Neurology, 63, 2316–2321. Van Heuvelen, M. J. G., Kempen, G. I. J. M., Ormel, J., & Rispens, P. (1998). Physical Wtness related to age and physical activity in older persons. Medicine and Science in Sports and Exercise, 30, 434–441. Van Heuvelen, M. J. G., Hochstenbach, J., Brouwer, W. H., De Greef, M. H. G., Zijlstra, G. A. R., Van Jaarsveld, E., et al. (2005). DiVerences between participants and non participants in an RCT on physical activity and psychological interventions for older persons. Aging Clinical and Experimental Research, 17, 236–245. Westerterp, K. R. (2000). Daily physical activity and ageing. Current Opinion in Clinical Nutrition and Metabolic Care, 3, 485–488. Wilson, T. M., & Tanaka, H. (2000). Meta-analysis of the age-associated decline in maximal aerobic capacity in men: Relation to training status. American Journal Physiology Heart and Circulatory Physiology, 278, 829– 834.