Neuroplastizität und Lernen im Alter
Abstract
Trotz des Zitates „was Hänschen nicht lernt, lernt Hans nimmermehr“, ist man niemals zu alt um Neues zu lernen und diese Lernprozesse bewirken bis ins hohe Alter sowohl strukturelle, als auch funktionelle Veränderungen des Gehirns. Neuronale Plastizität beschreibt Veränderungen der Gehirnstruktur und/oder Funktion in Abhängigkeit von Veränderungen im Verhalten, in der Umwelt und in neuronalen Prozessen. Solche Veränderungen können adaptiv (z. B. durch Lernen) oder „restorativ“ (z. B. nach einem Schlaganfall) auftreten und finden ein Leben lang statt.
Das erwachsene Gehirn ist bemerkenswert formbar, aber im Vergleich zu Kindern scheint es für Erwachsene oft schwieriger Neues zu erlernen. Aber auch im Alter ist das Erlernen neuer Fähigkeiten bzw. eine körperliche oder kognitive Leistungssteigerung möglich. Insbesondere zugrundeliegende Veränderungen auf struktureller (Hippocampusvolumen) und funktioneller Ebene (Steigerung der Effizienz) dieser Lernprozesse werden in dieser Übersichtsarbeit exemplarisch dargestellt.
Der folgende Beitrag liefert einen selektiven Überblick über die Veränderungen im Gehirn während wir altern und stellt Möglichkeiten dar, wie erfolgreiches (Gehirn-) Altern gefördert werden kann. Sowohl eine erhöhte physische, als auch geistige Aktivität ermöglicht Leistungssteigerungen in spezifischen, geübten Bereichen und scheint förderlich für gesundes Gehirnaltern. Allerdings scheitert häufig der Transfer dieser Leistungsverbesserungen auf den Alltag. Die Förderung kreativer Denkprozesse, also der Fähigkeit konventionelle Muster des Denkens zu verlassen und Neues/Originelles zu generieren könnte eine Option bieten Transfereffekte zu erleichtern. Allerdings fehlen aktuell systematische, empirische Untersuchungen im Bereich der Kreativitätsförderung im höheren Alter.
Background: Aging refers to a progressive, multidimensional process, associated with biological, physiological, psychological and social changes. In view of the increased life expectancy of our population our society is challenged to adapt, in order to maximize the health and functional capacity of older people as well as their social participation and security. Particularly in the context of aging, many individuals strive to find ways to remain physically and mentally healthy. One possibility to promote physical and mental health during aging is to become or stay active and learn new things. Despite the former notion that “you can't teach an old dog new tricks”, an individual is never too old to learn new things and to modify his or her brain. Neuronal plasticity refers to changes in brain structure and/or function in response to changes in behavior, environment and neural processes. Such changes can be adaptive (e. g., during learning) or restorative (e. g., after a stroke) and occur throughout the entire lifespan.
The adult human brain is remarkably malleable, but compared to children it frequently seems more challenging for adults to learn new things. In this article an overview about age-related changes in our brains and possibilities to promote successful (brain) aging is provided. Even if the aging brain displays characteristic structural (e. g., atrophy, white matter hyperintensities – WMH, microbleeds) and functional (e. g., reduced functional connectivity, altered activation pattern) changes, learning of new skills and improvement of physical and cognitive performance is possible, up to old age.
Two concepts are often mentioned in the context of successful brain aging. First, it seems that a higher number of neurons or an increased brain volume respectively may attenuate the detrimental effects of brain aging on physical or cognitive function (Brain Reserve; Valenzuela, 2008). Second, recent studies found that also each individual may actively contribute to successful brain aging by promoting the Cognitive Reserve (e. g., higher educational or occupational attainment, cognitively demanding leisure activities; Stern, 2012). One approach to promote enriching experiences during aging is learning new skills, either physical or cognitive.
Methods: Exemplary studies reporting underlying structural (e. g., hippocampal volume; Erickson et al., 2011) and functional changes (e. g., increase of efficiency; Brehmer et al., 2011) of learning and training in advanced age are presented in this paper.
Results: The positive effects of physical activity are manifold (e. g., risk of cerebrovascular disease is reduced; life quality enhanced, motivation and independency are promoted). As the positive physical and psychological effects of exercise have been known for a long time, we focus on the benefit of physical exercise on cognition and brain function.
Some studies showed that through physical exercise (e. g., aerobic training, dancing) the reduction of brain volume could be reduced, neuronal connections may be strengthened, less WMH seem to appear and cognitive performance could be enhanced (Colcombe et al., 2006; Gomez-Pinilla & Hillman, 2013; Gow et al., 2012; Kraft, 2012). Physical exercise also seems to have a beneficial effect on brain function. Increased activation of the attention network in the brain (e. g., anterior cingulate, prefrontal cortex, parietal cortex) has been observed in physically fit and trained subjects (Colcombe et al., 2004).
Especially physically and mentally demanding activities (e. g., juggling) seem to have a positive effect on brain structure. This has been observed not only in adults, but in the elderly as well (Boyke et al., 2008).
Further studies showed that also through cognitive training, performance can be improved in old age, and that changes in brain structure (e. g., reduction of age-related hippocampal volume loss after four months of spatial navigation training; Lövdén et al., 2012) and function (e. g., improvement of neuronal efficiency related to enhanced working memory performance after a 5-weeks working memory training; Brehmer et al., 2011) occur even in elderly subjects.
Unfortunately, it is often seen that a training of specific cognitive domains (e. g., working memory, processing speed, and executive function) shows no improvements in other cognitive domains (lack of transfer). Therefore, studies were also particularly interested to study potential brain mechanisms underlying any transfer effects. In this context studies revealed an improvement of working memory performance after five weeks of memory training, related to an increase of activation in striatal regions. These results indicate that transfer of cognitive skills may occur, if changes in brain regions are observed that are involved in multiple cognitive domains (i. e., in the trained and in the transfer task). However, age-related restrictions of the transfer effect in older subjects were observed, suggesting that aged individuals might need increased training to accomplish transfer (Dahlin et al., 2008). The promotion of flexible thinking could improve transfer of cognitive skills to other domains. Unfortunately, currently there is a lack of systematic, empirical studies investigating the potential of creativity trainings to improve transfer in older subjects.
Discussion: In general, aging should be seen as a life-long and active process, with the major aim to prevent disease and disability. Recent (neuro-)scientific findings indicate that learning and training of new skills bear great potential to promote successful brain aging. Increased physically and mentally demanding activities have been related to training-specific improvement in old age and seem to have beneficial effects on brain aging (e. g., reduction of age-related hippocampal volume loss or increased functional efficiency). However, transfer of training-specific improvement of performance to everyday life mostly fails. One possibility to facilitate transfer effects of learned skills to everyday life might be the promotion of creativity-related skills (i. e., „thinking outside the box“, producing novelty and originality). Though studies which investigated creativity interventions specifically in samples of older adults are rare, there is no reason to assume that such type of interventions do not work in the elderly as well. „Creativity is not a timebound act nor a function of chronological age“ (Hickson & Housley, 1997, p. 539) and it „… does not have to disappear in the later years when perhaps many need it most“ (ibid., p. 545). Thus, in a continuously aging society we are all – practitioner and scientists – challenged to carefully attend to the question in which way the cognitive capacities of people can be best maintained until old age.
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