Dokument: Two types of learning in healthy and pathological aging exemplified by Parkinson’s disease
|Titel:||Two types of learning in healthy and pathological aging exemplified by Parkinson’s disease|
|URL für Lesezeichen:||https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=44691|
|Dokumententyp:||Wissenschaftliche Abschlussarbeiten » Dissertation|
|Autor:|| Meissner, Sarah [Autor]|
|Beitragende:||Prof. Dr. phil. Pollok, Bettina [Gutachter]|
Prof. Dr. Bellebaum, Christian [Gutachter]
|Dewey Dezimal-Klassifikation:||600 Technik, Medizin, angewandte Wissenschaften » 610 Medizin und Gesundheit|
|Beschreibung:||Learning is a driving force for successful adjustment to our environment. The present thesis concentrated on implicit motor sequence and feedback learning, both essential for proper functioning in daily life.
The acquisition of motor sequences occurs online during practice and is followed by motor consolidation describing stabilization of skills (i.e., reduced susceptibility to interference) as well as offline improvement (i.e., skill enhancement without further practice). Furthermore, working memory might contribute to this type of learning. At the neural level, motor sequence learning relies on distributed brain networks including cortico-basal ganglia circuits. In young adults, motor cortical beta oscillations are assumed to be of functional significance for this type of learning. In the light of an aging population, a better understanding of age-related changes takes on increasing relevance to ensure a self-determined life up until old age. Knowledge about changes across the adult life span is necessary to derive concepts for early detection and prevention of possible declines in old age. In the context of aging and its associated diseases, another line of research on motor sequence learning investigated patients with Parkinson’s disease (PD), a neurodegenerative disorder associated with loss of dopaminergic neurons and pathological alterations in cortico-basal ganglia circuits including altered synchronization of beta oscillations. Considering this, it might not be surprising that motor sequence learning has been found to be diminished in patients with PD. But, whether pathological beta oscillations are indeed associated with impaired motor sequence learning in PD is yet to be determined. Similar to motor sequence learning, areas of cortico-basal ganglia circuits and the dopaminergic system in particular play a crucial role in feedback learning. This type of learning occurs by linking either own (active) or observed actions (observational) to accompanying outcomes (e.g., positive or negative feedback). Previous studies in PD patients suggest that whereas performance patterns in observational feedback learning may be similar to those in healthy older adults – at least in early stages of PD – active learning from feedback is altered and may vary with the dopaminergic state. Besides dopamine substitution, deep brain stimulation (DBS) of the subthalamic nucleus (STN) is an effective treatment option in advanced PD. Regarding active feedback learning, there is first evidence that this type of learning might be enhanced by STN-DBS. Whether STN-DBS also promotes observational feedback learning remains to be investigated. Disentangling influences of treatment methods such as DBS on
cognitive functions including feedback learning are of high relevance for both the improvement of therapy and the prognosis of therapeutic effects. As DBS is also considered as a treatment option for younger, working PD patients, alterations in cognitive functions due to STN-DBS might have considerable consequences for gainful employment and thereby quality of life.
The present thesis comprises three studies to contribute to the understanding of implicit motor sequence and feedback learning in healthy and pathological aging using PD as a prominent example. The investigation of motor sequence learning across the adult life span at the behavioral level (study 1) was complemented by the investigation of its underlying brain oscillations in healthy and pathological aging (study 2). Study 3 examined the effect of STN-DBS on feedback learning in PD patients. Healthy older adults served as control group.
Study 1 examined motor sequence acquisition and consolidation across the adult life span and explored whether working memory is associated with these processes. It revealed that young and older but not middle-aged adults showed acquisition of a motor sequence. Since the data suggest that older adults may adopt explicit learning strategies, one might argue that the decline in middle-aged adults reflects that implicit learning may become less effective while a compensatory strategy has not been successfully implemented yet. Immediately after acquisition, young and older adults were susceptible to interference. However, after an offline period of 1 hour, both showed stabilization of the newly acquired skill indicating consolidation. Additional offline improvement, which was not specific for sequence trials but rather represented general reaction time improvement, was only observed in young and middle-aged adults. These results give rise to the hypothesis that different forms of consolidation may be distinctly affected by aging. Working memory was not linked to motor sequence acquisition or consolidation, independent of age.
Study 2 investigated motor sequence learning in PD – representing a prominent example of pathological aging – as compared to healthy aging. Neuromagnetic activity was recorded using magnetoencephalography (MEG) to investigate the functional role of brain oscillations with a special emphasis on beta oscillations. PD patients exhibited diminished but basically preserved motor sequence acquisition as well as higher susceptibility to interference immediately after acquisition when compared to healthy adults. These differences were accompanied by less beta power suppression in motor cortical areas in PD patients supporting its significance in motor sequence learning. Interestingly, while reduced susceptibility to interference may rely on successful acquisition in healthy adults, these two processes were found to be distinct in PD. Indirectly supporting this assumption, beta power suppression was found to promote reduced susceptibility to interference but was not beneficial for sequence acquisition in PD. Beyond beta activity, the study provided first evidence that motor cortical theta oscillations might be associated with susceptibility to interference, at least in an aging but healthy motor system.
Study 3 concentrated on active and observational feedback learning in PD patients and healthy older adults. The investigation of STN-DBS effects on feedback learning was the main focus of the study. Healthy older adults served as control group. The data revealed that STN-DBS facilitates active feedback learning which requires to link own actions to accompanying outcomes and that PD patients OFF but not ON STN-DBS showed worse active learning than healthy adults. Interestingly, when it came to the application of what had been learned during feedback trials, only more severely impaired patients benefited from STN-DBS. In addition to active feedback learning, the study provided first evidence that STN-DBS might also be beneficial for observational feedback learning when outcomes are required to be linked to actions of another person.
This thesis contributes to the understanding of implicit motor sequence and feedback learning in healthy aging as well as in PD representing a prominent example of pathological aging. The three studies revealed (i) preserved initial learning of a motor sequence probably due to compensatory explicit strategies as well as stabilization of the newly acquired sequence indicating consolidation in healthy older adults, (ii) diminished motor sequence learning in pathological aging such as PD associated with alterations in the modulation of beta and theta oscillations, and (iii) a beneficial effect of STN-DBS on feedback learning in PD patients which enhanced learning to a level similar to that in healthy older adults. Such knowledge about physiological and pathological changes as well as treatment effects is indispensable for the preservation of functionality in healthy aging as well as for a precise prognosis and optimization of treatment outcome in PD.
|Fachbereich / Einrichtung:||Medizinische Fakultät » Institute » Institut für Medizinische Psychologie|
|Dokument erstellt am:||25.01.2018|
|Dateien geändert am:||25.01.2018|
|Datum der Promotion:||19.12.2017|