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Beeinflussung der kognitiven Leistung durch so-tDCS während des Nachtschlafs bei älteren gesunden Probanden: Explorative post hoc Analyse verschiedener Faktoren bezüglich der Ansprechbarkeit auf die elektrische Stimulation

  • Die der Konsolidierung hippocampus-abhängiger, deklarativer Gedächtnisinhalte zugrundeliegenden neurophysiologischen Prozesse im Schlaf (z.B. langsame Oszillationen, engl. Slow Oscillations und Spindeln) unterliegen im Laufe des Lebens altersbedingten Veränderungen. Einige Studien konnten eine Leistungsverbesserung bei jungen Probanden aufzeigen, die während des nächtlichen, frühen nonREM Schlafs (non-rapid eye movement) eine Stimulation mit schwachem, transkraniell verabreichtem Gleichstrom (so-tDCS) erhielten. Ob eine nächtliche Anwendung von so-tDCS mit einem ähnlichen Studienprotokoll die schlafabhängige Gedächtniskonsolidierung bei einer älteren Probandenpopulation in gleicher Weise moduliert, war eine grundlegende Überlegung der vorliegenden Studie. Da bisherige Studien zu so-tDCS allerdings ein divergentes Bild in den kognitiven Leistungen zeigten, sollten anhand von posthoc Analysen verschiedene Faktoren (Aufgabencharakteristika, interinidviduelle Unterschiede), die die Ansprechbarkeit modulieren können, exploriert werden.
  • Introduction: Some studies in young subjects have shown an improvement of memory consolidation during early, nocturnal nonREM sleep after applying slow-oscillatory transcranial direct current stimulation (so-tDCS). Consolidation of declarative memories during sleep depends on neurophysiological events which are observed to undergo a change while aging. In this study we focused on the posthoc analysis that as a central question explored inter-individual differences in responsiveness to so-tDCSdue to the large variability demonstrated in previous studies. Methods: Ina randomized, single-blind crossover study so-tDCS (0.75 Hz) versus sham stimulation was applied over the frontal cortex of 22 healthy subjects in the age of 50 –80. Posthoc SO were used to devide subject group in Responder (increase of power in frontal SO following so-tDCS) and Nonresponder (no increase or decrease of power in frontal SO following so-tDCS) to explore inter-individual factors of responsiveness to stimulation correlating cognitive and anatomic parameters as well as sleep characteristic andsleep behavior. Therefore five stimulation blocks (five minutes each) followed by an 1-min stimulation-free intervals were applied and the impact of stimulation on performance of declarative, hippocampal-dependent memory task was assessed. Electroencephalographic activity was recorded throughout the night and effects of stimulation on brain activity such as spectral power within three frequency bands (slow oscillatory activity, slow spindle and fast spindle activity) were evaluated. Results: Explorationof inter-individual responsiveness between Responder and Nonresponder may have shown no differences in cognitive and anatomic analysis. In sleep characteristic though we observed a difference between Responder and Nonresponder during stimulation night different from a night without so-tDCS. Responder spent more time in bed than Nonresponder, had better sleep efficiency, spent more time in NonREM 1 and more total cycling time. Nonresponder had a higher power in prefrontal and frontal SO 60 min post stimulation. so-tDCS, as compared to sham, increased power in slow oscillations and spindle activity following stimulation whereas verbal memory performance remained unaffected. Conclusion: In the posthoc analysis some differences between Responder and Nonresponder such as sleep characteristic and total cycling time were detected. Even though so-tDCS increased SO and spindle activity in older adults, it failed to improve consolidation of declarative memories as shown previously in young adults. To identify additional differences in inter-individual responsiveness to so-tDCS further studies with larger subject group and even more numerous baseline characteristics (nutrition, metabolism and inflammation, endocrinolgic changes) are needed.

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Metadaten
Author: Lena Alexa Reich
URN:urn:nbn:de:gbv:9-opus-39519
Title Additional (German):Beeinflussung der kognitiven Leistung durch so-tDCS während des Nachtschlafs bei älteren gesunden Probanden: Explorative post hoc Analyse verschiedener Faktoren bezüglich der Ansprechbarkeit auf die elektrische Stimulation
Referee:Prof. Dr. med. Martin Lotze, Prof. Dr. med. Björn Rasch
Advisor:Prof. Dr. med. Martin Lotze
Document Type:Doctoral Thesis
Language:German
Year of Completion:2020
Date of first Publication:2020/09/15
Granting Institution:Universität Greifswald, Universitätsmedizin
Date of final exam:2020/08/24
Release Date:2020/09/15
Tag:so-tDCS
GND Keyword:Nachtschlaf, so-tDCS
Pagenumber:92
Faculties:Universitätsmedizin / Institut für Diagnostische Radiologie
DDC class:600 Technik, Medizin, angewandte Wissenschaften / 610 Medizin und Gesundheit