Cargando…

No Effect of Anodal tDCS on Verbal Episodic Memory Performance and Neurotransmitter Levels in Young and Elderly Participants

Healthy ageing is accompanied by cognitive decline that affects episodic memory processes in particular. Studies showed that anodal transcranial direct current stimulation (tDCS) to the left dorsolateral prefrontal cortex (DLPFC) may counteract this cognitive deterioration by increasing excitability...

Descripción completa

Detalles Bibliográficos
Autores principales: Habich, Annegret, Slotboom, Johannes, Peter, Jessica, Wiest, Roland, Klöppel, Stefan
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Hindawi 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7528151/
https://www.ncbi.nlm.nih.gov/pubmed/33029128
http://dx.doi.org/10.1155/2020/8896791
_version_ 1783589202643910656
author Habich, Annegret
Slotboom, Johannes
Peter, Jessica
Wiest, Roland
Klöppel, Stefan
author_facet Habich, Annegret
Slotboom, Johannes
Peter, Jessica
Wiest, Roland
Klöppel, Stefan
author_sort Habich, Annegret
collection PubMed
description Healthy ageing is accompanied by cognitive decline that affects episodic memory processes in particular. Studies showed that anodal transcranial direct current stimulation (tDCS) to the left dorsolateral prefrontal cortex (DLPFC) may counteract this cognitive deterioration by increasing excitability and inducing neuroplasticity in the targeted cortical region. While stimulation gains are more consistent in initial low performers, relying solely on behavioural measures to predict treatment benefits does not suffice for a reliable implementation of this method as a therapeutic option. Hence, an exploration of the underlying neurophysiological mechanisms regarding the differential stimulation effect is warranted. Glutamatergic metabolites (Glx) and γ-aminobutyric acid (GABA) are involved in learning and memory processes and can be influenced with tDCS; wherefore, they present themselves as potential biomarkers for tDCS-induced behavioural gains, which are affiliated with neuroplasticity processes. In the present randomized, double-blind, sham-controlled, crossover study, 33 healthy young and 22 elderly participants received anodal tDCS to their left DLPFC during the encoding phase of a verbal episodic memory task. Using MEGA-PRESS edited magnetic resonance spectroscopy (MRS), Glx and GABA levels were measured in the left DLPFC before and after the stimulation period. Further, we tested whether baseline performance and neurotransmitter levels predicted subsequent gains. No beneficial group effects of tDCS emerged in either verbal retrieval performances or neurotransmitter concentrations. Moreover, baseline performance levels did not predict stimulation-induced cognitive gains, nor did Glx or GABA levels. Nevertheless, exploratory analyses suggested a predictive value of the Glx : GABA ratio, with lower ratios at baseline indicating greater tDCS-related gains in delayed recall performance. This highlights the importance of further studies investigating neurophysiological mechanisms underlying previously observed stimulation-induced cognitive benefits and their respective interindividual heterogeneity.
format Online
Article
Text
id pubmed-7528151
institution National Center for Biotechnology Information
language English
publishDate 2020
publisher Hindawi
record_format MEDLINE/PubMed
spelling pubmed-75281512020-10-06 No Effect of Anodal tDCS on Verbal Episodic Memory Performance and Neurotransmitter Levels in Young and Elderly Participants Habich, Annegret Slotboom, Johannes Peter, Jessica Wiest, Roland Klöppel, Stefan Neural Plast Research Article Healthy ageing is accompanied by cognitive decline that affects episodic memory processes in particular. Studies showed that anodal transcranial direct current stimulation (tDCS) to the left dorsolateral prefrontal cortex (DLPFC) may counteract this cognitive deterioration by increasing excitability and inducing neuroplasticity in the targeted cortical region. While stimulation gains are more consistent in initial low performers, relying solely on behavioural measures to predict treatment benefits does not suffice for a reliable implementation of this method as a therapeutic option. Hence, an exploration of the underlying neurophysiological mechanisms regarding the differential stimulation effect is warranted. Glutamatergic metabolites (Glx) and γ-aminobutyric acid (GABA) are involved in learning and memory processes and can be influenced with tDCS; wherefore, they present themselves as potential biomarkers for tDCS-induced behavioural gains, which are affiliated with neuroplasticity processes. In the present randomized, double-blind, sham-controlled, crossover study, 33 healthy young and 22 elderly participants received anodal tDCS to their left DLPFC during the encoding phase of a verbal episodic memory task. Using MEGA-PRESS edited magnetic resonance spectroscopy (MRS), Glx and GABA levels were measured in the left DLPFC before and after the stimulation period. Further, we tested whether baseline performance and neurotransmitter levels predicted subsequent gains. No beneficial group effects of tDCS emerged in either verbal retrieval performances or neurotransmitter concentrations. Moreover, baseline performance levels did not predict stimulation-induced cognitive gains, nor did Glx or GABA levels. Nevertheless, exploratory analyses suggested a predictive value of the Glx : GABA ratio, with lower ratios at baseline indicating greater tDCS-related gains in delayed recall performance. This highlights the importance of further studies investigating neurophysiological mechanisms underlying previously observed stimulation-induced cognitive benefits and their respective interindividual heterogeneity. Hindawi 2020-09-22 /pmc/articles/PMC7528151/ /pubmed/33029128 http://dx.doi.org/10.1155/2020/8896791 Text en Copyright © 2020 Annegret Habich et al. https://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
spellingShingle Research Article
Habich, Annegret
Slotboom, Johannes
Peter, Jessica
Wiest, Roland
Klöppel, Stefan
No Effect of Anodal tDCS on Verbal Episodic Memory Performance and Neurotransmitter Levels in Young and Elderly Participants
title No Effect of Anodal tDCS on Verbal Episodic Memory Performance and Neurotransmitter Levels in Young and Elderly Participants
title_full No Effect of Anodal tDCS on Verbal Episodic Memory Performance and Neurotransmitter Levels in Young and Elderly Participants
title_fullStr No Effect of Anodal tDCS on Verbal Episodic Memory Performance and Neurotransmitter Levels in Young and Elderly Participants
title_full_unstemmed No Effect of Anodal tDCS on Verbal Episodic Memory Performance and Neurotransmitter Levels in Young and Elderly Participants
title_short No Effect of Anodal tDCS on Verbal Episodic Memory Performance and Neurotransmitter Levels in Young and Elderly Participants
title_sort no effect of anodal tdcs on verbal episodic memory performance and neurotransmitter levels in young and elderly participants
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7528151/
https://www.ncbi.nlm.nih.gov/pubmed/33029128
http://dx.doi.org/10.1155/2020/8896791
work_keys_str_mv AT habichannegret noeffectofanodaltdcsonverbalepisodicmemoryperformanceandneurotransmitterlevelsinyoungandelderlyparticipants
AT slotboomjohannes noeffectofanodaltdcsonverbalepisodicmemoryperformanceandneurotransmitterlevelsinyoungandelderlyparticipants
AT peterjessica noeffectofanodaltdcsonverbalepisodicmemoryperformanceandneurotransmitterlevelsinyoungandelderlyparticipants
AT wiestroland noeffectofanodaltdcsonverbalepisodicmemoryperformanceandneurotransmitterlevelsinyoungandelderlyparticipants
AT kloppelstefan noeffectofanodaltdcsonverbalepisodicmemoryperformanceandneurotransmitterlevelsinyoungandelderlyparticipants