Ziel

Abstract (2015-2018):
While there is ample evidence that performance in a variety of cognitive and motor tasks can significantly be improved by specific single-task training, it is not yet clear how these improvements transfer to motor-cognitive multi-task (MCDT) situations. Of particular interest is whether motor-cognitive dual-task training (MCDTT) or motor-cognitive multi-task training (MCMTT ) is specifically helpful to improve either single¬ or multi-task performance. Some empirical and theoretical work has already been done, showing that dual-task-training (DTT) or multi-task training (MTT) might potentially have advantages compared to single-task training (STT) with respect to its long-term benefits (Wollesen & Voelcker-Rehage, 2014). The underlying explanatory concepts are based on specific assumptions on how processing is organized during practice and specific predictions are derived to which extend the improvements transfer to other unpracticed situations. However, the specific question of how central cognitive processing load is shared, or more precisely, attributed to competing requirements of concurrent motor and cognitive tasks during practice and how this determines the long-term effects of MCDTT has received limited attention yet (for an exception see Beurskens & Bock 2012).
We performed two pilot studies to screen different combinations cognitive (Calculation, auditory and visual n-back) of motor tasks (Balance, Walking, Running, Force Tracking, Ball Paddling, Nine Hole Pegboard) with respect to their interaction under dual-task conditions. We looked at performance measures of the cognitive and motor tasks and monitored processing load by a one-channel NIRS system (PortaLite®, Artinis, Elst) measuring oxygenated (HbO2) and deoxygenated (HHb) hemoglobin) concentration in prefrontal brain regions (see also Beurskens, Helmich, Rein & Bock, 2014). Our pilot study showed characteristic differences in the interference profile observed under DT conditions. The most suprising result was, that, when calculation was performed while running, overall processing activity dropped compared to ST Calculation. Particularly remarkable in our case was that subjects did not show any performance decrease. There was even a tendency (p=0.11) to complete more calculations while running compared to standing still.
In the main experiments of the project we will systematically test different explanatory concepts regarding their assumptions on the processing during practice and the expected long-term effects in the practiced tasks but also to new unpracticed tasks since these are most crucial to discriminate between concepts. Subjects practice significant combinations of a motor (e.g. walking, running, force tracking) and a cognitive tasks (calculation, n-back tasks) under STT and DTT conditions for 12 weeks. Performance will be measured in pre- and post-tests. Cognitive Load will again be monitored by the NIRS system. We will include a battery of unpracticed cognitive and motor tasks in the pre- and post-tests in order to determine the amount of transfer. We will test whether the observed effects depend on a rhythmic integration of the processing streams of the motor and the cognitive task. We will also check whether the instruction “not to move” induces processing load (movement inhibition, Huestegge & Koch 2014) as a potential explanation why cognitive tasks might benefit from a secondary motor task where subjects are allowed to move.

Abstract (2018-2021):
Multi-tasking capacity of humans is limited. Nonetheless, there is ample evidence that performance in a variety of cognitive and motor tasks can significantly be improved (plasticity perspective of the SPP) by specific single-task training that might also transfer to multi-task situations. Moreover, studies have demonstrated that multi-task training, compared to single-task training, may even lead to larger performance increments in the practiced tasks as well as in transfer to unpracticed tasks. Three possible training-induced transformations of the processing structure in dual tasks are conceivable: a) Reduction of processing demands of at least one of the tasks involved, b) smart integration of separate information processing streams, and c) increased quantity of processing resources. We will study these questions with a focus on motor-cognitive dual-task training, that is, situations in which a sufficiently complex continuous motor task is involved, like walking or other postural tasks. This type of training is widely applied in in the context of fall prevention in elderly and has been subject to specific investigations. It has also received some attention with respect to possible beneficial effects on cognitive performance. However, the mechanisms underlying these training effects have not been identified conclusively. A crucial factor for any resulting training effect is how processing streams of the different tasks interfere and recruit resources during practice. In the first funding period, we observed different effects for an “automatized” walking task compared to a more challenging force-tracking task at the level of the resulting performances in practiced and transfer tasks, and the training-induced alterations of the processing structure. In the second funding period, we will investigate the processing structure induced by these tasks in more depth. We will use a probe-reaction time technique to reveal, to which extent subjects are engaged in processing of each of the tasks at different moments in time. We combine this work with further training studies where subjects practice selected motor-cognitive dual-task combinations for several weeks. Based on the data collected in these studies, we will review existing explanatory concepts, which can be categorized as either assuming fixed-limit or flexible-limit processing during multitasking. According to the first, improvements can only be explained by more effective processing of at least one of the tasks, or by a smart integration of the processing streams. Accordingly, long-term training effects should be restricted to situations where at least one of the practiced tasks is involved. Flexible-limit concepts allow stronger recruitment of processing resources in certain contexts and, thus, see the possibility of long-term increases. This plasticity should then be observable in performance benefits in a broader range of transfer situations.

Zusammenfassung

Menschen verfügen über begrenzte Kapazitäten zur Bewältigung von Doppelaufgaben. Wie aber bereits häufig gezeigt wurde, kann die Leistung durch spezifisches Training unter Einzelaufgabenbedingungen verbessert werden (Plastizitätsaspekt des Projektes). Des Weiteren weisen empirische Studien teilweise noch größere Leistungssteigerungen in geübten und ungeübten Aufgaben nach Mehfachaufgaben-Training nach. Im Wesentlichen sind drei prinzipiell unterschiedliche Wirkungen eines solchen Trainings auf die Verarbeitungsstruktur und damit auch auf die Leistung in solchen Aufgaben denkbar: a) eine Reduktion des Prozessierungsaufwandes mindestens einer der beteiligten Aufgaben, b) eine verstärkte Integration der beiden Verarbeitungsstränge, c) eine Erhöhung der zur Verfügung gestellten Verarbeitungsressourcen. Wir untersuchen diese Art von Fragen mit einem Schwerpunkt auf kognitiv-motorische Doppelaufgaben, welche Aufgabenkombinationen sind, bei denen mindestens eine hinreichend komplexe kontinuierliche Bewegungsaufgabe beteiligt ist, wie z.B. Gehen oder andere Gleichgewichtsaufgaben. Ein solches Training wird vielfach in der Sturzprävention von älteren Menschen eingesetzt. Es ist daher auch bereits häufig untersucht worden, wobei auch die Frage möglicher Verbesserungen der kognitiven Leistung betrachtet wurde. Allerdings konnten die Wirkfaktoren eines solchen Trainings noch nicht abschließend identifiziert werden.
Ein entscheidender Faktor ist auf jeden Fall die Art und Weise, wie die Verarbeitungsstränge der beteiligten Aufgaben interferieren, bzw. sich die vorhandenen Kapazitäten teilen. In der ersten Projektphase konnten wir unterschiedliche Trainingseffekte im Vergleich einer als „automatisiert“ angesehenen Aufgabe (Gehen) und einer kraftbezogenen Verfolgungsaufgabe finden. Unterschiede zeigten sich sowohl in Leistung als auch in den jeweils bewirkten Veränderungen in den Verarbeitungsstrukturen. In der zweiten Projektphase wollen wir diese Unterschiede in der Verarbeitung genauer analysieren. Dazu setzen wir eine Probe-Reaktions-Technik ein, um zu testen, zu welchem Zeitpunkt die Probanden in welchem Umfang mit welcher der geforderten Aufgaben beschäftigt sind. Wir werden diese Untersuchungen mit weiteren Trainingsstudien verbinden, in denen die Probanden über mehrere Wochen unter Doppeltätigkeitsbedingungen trainieren. Auf der Basis der dabei entstehenden Ergebnisse werden wir grundlegende Annahmen aktueller Erklärungskonzepte hinterfragen. Diese gehen nämlich entweder davon aus, dass die zur Verfügung stehende Menge an Verarbeitungsressourcen prinzipiell begrenzt ist oder halten es für möglich, dass diese auch durch Training verändert werden kann. Aus diesen unterschiedlichen Annahmen ergeben sich jeweils spezifische Vorhersagen hinsichtlich des Umfangs und des Profils von trainingsbedingtem Transfer, die mit den von uns gewonnenen Daten in Beziehung gesetzt werden.
(DFG-Projektnummer 275317215)

Zusammenfassung

Multi-tasking capacity of humans is limited. Nonetheless, there is ample evidence that perfor-mance in a variety of cognitive and motor tasks can significantly be improved (plasticity perspective of the SPP) by specific single-task training that might also transfer to multi-task situations. Moreo-ver, studies have demonstrated that multi-task training, compared to single-task training, may even lead to larger performance increments in the practiced tasks as well as in transfer to unpracticed tasks. Three possible training-induced transformations of the processing structure in dual tasks are conceivable: a) Reduction of processing demands of at least one of the tasks involved, b) smart integration of separate information processing streams, and c) increased quantity of processing resources.We will study these questions with a focus on motor-cognitive dual-task training, that is, situations in which a sufficiently complex continuous motor task is involved, like walking or other postural tasks. This type of training is widely applied in in the context of fall prevention in elderly and has been subject to specific investigations. It has also received some attention with respect to possible beneficial effects on cognitive performance. However, the mechanisms underlying these training effects have not been identified conclusively.A crucial factor for any resulting training effect is how processing streams of the different tasks in-terfere and recruit resources during practice. In the first funding period, we observed different effects for an "automatized" walking task compared to a more challenging force-tracking task at the level of the resulting performances in practiced and transfer tasks, and the training-induced altera-tions of the processing structure. In the second funding period, we will investigate the processing structure induced by these tasks in more depth. We will use a probe-reaction time technique to reveal, to which extent subjects are engaged in processing of each of the tasks at different moments in time. We combine this work with further training studies where subjects practice selected motor-cognitive dual-task combinations for several weeks. Based on the data collected in these studies, we will review existing explanatory concepts, which can be categorized as either assuming fixed-limit or flexible-limit processing during multitasking. According to the first, improvements can only be explained by more effective processing of at least one of the tasks, or by a smart integration of the processing streams. Accordingly, long-term training effects should be restricted to situations where at least one of the practiced tasks is involved. Flexible-limit concepts allow stronger recruitment of processing resources in certain contexts and, thus, see the possibility of long-term increases. This plasticity should then be observable in performance benefits in a broader range of transfer situations.
(DFG-Project number 275317215)