Prefrontal tDCS fails to modulate memory retrieval in younger and older adults

• Published in: Current biology Vol. 35; no. 1; pp. 50 - 58.e4
• Main Authors: Arar, Tesnim, Hirsch, Gabriella V., Chamberlain, Taylor A., Malone, Miranda, Wakeland-Hart, Cheyenne D., Snarskis, Martynas, Lauderdale, Diane S., Schumm, L. Philip, Gallo, David A.
• Format: Journal Article
• Language: English
• Published: England Elsevier Inc 06.01.2025
• Subjects: Adult; Age Factors; Aged; circadian rhythms; dorsolateral prefrontal cortex; Dorsolateral Prefrontal Cortex - physiology; Double-Blind Method; episodic memory; Female; Humans; Male; Memory, Episodic; Memory, Short-Term - physiology; Mental Recall - physiology; Middle Aged; Prefrontal Cortex - physiology; transcranial direct current stimulation; Transcranial Direct Current Stimulation - methods; working memory; Young Adult; episodic memory; circadian rhythms; working memory; dorsolateral prefrontal cortex; transcranial direct current stimulation
• ISSN: 0960-9822; 1879-0445; 1879-0445
• DOI: 10.1016/j.cub.2024.10.080

Previous research shows that a single session of anodal transcranial direct current stimulation (tDCS) to the left dorsolateral prefrontal cortex (dlPFC) can improve the accuracy of episodic memory retrieval, but stimulation effects are not always found and may be moderated by time of day. Here, we report the results from a rigorous clinical trial (NCT 03723850) designed to replicate these tDCS findings in younger adults and extend them to cognitively normal older adults. We conducted the largest double-blind, between-subjects tDCS study on memory retrieval in younger and older adults to date. 150 younger adults and 91 older adults received anodal tDCS or sham stimulation to the left dlPFC prior to episodic memory retrieval and working memory tasks. We also manipulated when tDCS was administered (time of day: morning vs. afternoon), task difficulty (easy vs. hard), and stimulus format (verbal vs. visual/pictorial) to test the extent that these variables are important for identifying tDCS effects. Contrary to our preregistered predictions, we did not find any effect of tDCS or time of day on younger or older adults' episodic or working memory performance. This outcome was not due to insensitivity of our cognitive tasks, given that we found expected effects of task difficulty and age-related effects on our memory measures. Based on these and prior tDCS results, we conclude that a single dose of tDCS using the typical and often recommended parameters does not reliably improve episodic memory retrieval in either age group. •Conducted the largest double-blind, between-subjects tDCS study on retrieval to date•dlPFC stimulation using the standard anodal montage did not improve performance•Neither younger nor older adults benefited from dlPFC stimulation•Null effects persisted even when accounting for other factors (e.g., time of day) Prior work shows that tDCS to the dlPFC can improve memory retrieval, but effects are not always found and may be moderated by aging or time of day. Arar et al. aim to replicate these findings in both younger (n = 150) and older adults (n = 91) but ultimately find that neither tDCS nor time of day has an effect on either group’s memory performance.