P 139 Effects on memory consolidation of non-invasive brain stimulation combined with cognitive training – Which factors modulates responsiveness?

Abstract

Background Object-location memory (OLM) is known to decline with normal aging, a process accelerated in pathological conditions like mild cognitive impairment (MCI) ( Iachini et al., 2009 ). In order to delay the transition from healthy to pathological conditions, novel strategies are being explored. For example, non-invasive brain stimulation, e. g., anodal transcranial direct current stimulation atDCS, may be a promising tool to enhance the effect of cognitive training. However, results are inconsistent so far, possibly due to inter-individual differences ( Li et al., 2015 ). Within this context trait (motivational need for cognition) and state (affect) variables, which might influence corticalexcitability, may be important, but have not been explored in detail until now. Research question Is responsiveness to combined intervention of atDCS and 3-day cognitive training modulated by trait and state variables?. Methods 33 healthy older subjects (mean 69 years, 22 females) participated in a 3-day visual-spatial training task (LOCATO) together with right-temporal brain (anodal, 20 min, 1 mA) or sham (30 s, 1 mA) stimulation (cross-over: randomized, counterbalanced, 3 month in between). Training consisted of learning of 30 building-location-associations on a street map. Memory consolidation (off-line effects) were assessed as follows: memory performance day n + 1 - day n . In addition, delayed memory after 1 month was measured. As co-variates affective state (multidimensional scaling) and subjective sleep quality were assessed before each training as well as need for cognition (NFC, one-time) as motivational trait. Results Linear Mixed Model analysis (Factors: day, condition) revealed a significant day × condition interaction but only if the following co-variates were taken into account ( F = 4,14, p = .02): Consolidation performance was improved after the first training day with atDCS compared to sham in subjects with higher scores in self-rated performance-related arousal ( p p = .02) and higher number of educational years ( p = .07). All other effects did not even show a trend (all p ’s > .1). Self-assessed quality of sleep did not modulate the atDCS effect on memory, but was significant associated with delayed memory performance ( p = .03). Discussion In line with other studies ( Pena-Gomez et al., 2011 , Krause et al., 2014 ) we demonstrated high inter-individual variability of atDCs effects on cognitive functions, here memory consolidation. Moreover, we were able to identify several factors that modulate responsiveness to atDCS in healthy older adults. More detailed delineation of such factors is important for development of individualized protocols with the ultimate goal to use atDCs as effective adjuvant therapy and to develop preventive strategies to counteract age-associated cognitive decline.