Browsing by Author "Berryhill, Marian E."

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Citation - WoS: 49
Citation - Scopus: 47
Frontoparietal tDCS benefits visual working memory in older adults with Low working memory capacity
(Frontiers Media S.A. info@frontiersin.org, 2018) Hector Arciniega; Filiz Gözenman; Kevin T. Jones; Jaclyn A. Stephens; Marian E. Berryhill; Arciniega, Hector; Berryhill, Marian E.; Gözenman, Filiz; Jones, Kevin T.; Stephens, Jaclyn A.
Working memory (WM) permits maintenance of information over brief delays and is an essential executive function. Unfortunately WM is subject to age-related decline. Some evidence supports the use of transcranial direct current stimulation (tDCS) to improve visual WM. A gap in knowledge is an understanding of the mechanism characterizing these tDCS linked effects. To address this gap we compared the effects of two tDCS montages designed on visual working memory (VWM) performance. The bifrontal montage was designed to stimulate the heightened bilateral frontal activity observed in aging adults. The unilateral frontoparietal montage was designed to stimulate activation patterns observed in young adults. Participants completed three sessions (bilateral frontal right frontoparietal sham) of anodal tDCS (20 min 2 mA). During stimulation participants performed a visual long-term memory (LTM) control task and a visual WM task. There was no effect of tDCS on the LTM task. Participants receiving right unilateral tDCS showed a WM benefit. This pattern was most robust in older adults with low WM capacity. To address the concern that the key difference between the two tDCS montages could be tDCS over the posterior parietal cortex (PPC) we included new analyses from a previous study applying tDCS targeting the PPC paired with a recognition VWM task. No significant main effects were found. A subsequent experiment in young adults found no significant effect of either tDCS montage on either task. These data indicate that tDCS montage age and WM capacity should be considered when designing tDCS protocols. We interpret these findings as suggestive that protocols designed to restore more youthful patterns of brain activity are superior to those that compensate for age-related changes. © 2018 Elsevier B.V. All rights reserved.
Citation - WoS: 48
Citation - Scopus: 49
Working memory capacity differentially influences responses to tDCS and HD-tDCS in a retro-cue task
(ELSEVIER IRELAND LTD, 2016) Filiz Gozenman; Marian E. Berryhill; Gözenman, Filiz; Berryhill, Marian E.
There is growing interest in non-invasive brain stimulation techniques. A drawback is that the relationship between stimulation and cognitive outcomes for various tasks are unknown. Transcranial direct current stimulation (tDCS) provides diffuse current spread whereas high-definition tDCS (HD-tDCS) provides more targeted current. The direction of behavioral effects after tDCS can be difficult to predict in cognitive realms such as attention and working memory (WM). Previously we showed that in low and high WM capacity groups tDCS modulates performance in nearly equal and opposite directions on a change detection task with improvement for the high capacity participants alone. Here we used the retro-cue paradigm to test attentional shifting among items in WM to investigate whether WM capacity (WMC) predicted different behavioral consequences during anodal tDCS or HD-tDCS to posterior parietal cortex (PPC). In two experiments with 24 participants each we used different stimulus categories (colored circles letters) and stimulation sites (right left PPC). The results showed a significant (Experiment 1) or trending (Experiment 2) WMC x stimulation interaction. Compared to tDCS after HD-tDCS the retrocueing benefit was significantly greater for the low WMC group but numerically worse for the high WMC group. These data highlight the importance of considering group differences when using non-invasive neurostimulation techniques. (C) 2016 Elsevier Ireland Ltd. All rights reserved.