Stevan Nikolin1, Colleen K Loo2, Siwei Bai3, Socrates Dokos4, Donel M Martin5. 1. School of Psychiatry, University of New South Wales, Black Dog Institute, Sydney, Australia. 2. School of Psychiatry, University of New South Wales, Black Dog Institute, Sydney, Australia; St. George Hospital, Sydney, Australia. 3. Faculty of Engineering, University of New South Wales, Sydney, Australia; IMETUM, Technische Universität München, 85748 Garching, Germany. 4. Faculty of Engineering, University of New South Wales, Sydney, Australia. 5. School of Psychiatry, University of New South Wales, Black Dog Institute, Sydney, Australia. Electronic address: donel.martin@unsw.edu.au.
Abstract
BACKGROUND:Declarative verbal learning and memory are known to be lateralised to the dominant hemisphere and to be subserved by a network of structures, including those located in frontal and temporal regions. These structures support critical components of verbal memory, including working memory, encoding, and retrieval. Their relative functional importance in facilitating declarative verbal learning and memory, however, remains unclear. OBJECTIVE: To investigate the different functional roles of these structures in subserving declarative verbal learning and memory performance by applying a more focal form of transcranial direct current stimulation, "High Definition tDCS" (HD-tDCS). Additionally, we sought to examine HD-tDCS effects and electrical field intensity distributions using computer modelling. METHODS:HD-tDCS was administered to the left dorsolateral prefrontal cortex (LDLPFC), planum temporale (PT), and left medial temporal lobe (LMTL) to stimulate the hippocampus, during learning on a declarative verbal memory task. Sixteen healthy participants completed a single blind, intra-individual cross-over, sham-controlled study which used a Latin Square experimental design. Cognitive effects on working memory and sustained attention were additionally examined. RESULTS:HD-tDCS to the LDLPFC significantly improved the rate of verbal learning (p=0.03, η(2)=0.29) and speed of responding during working memory performance (p=0.02, η(2)=0.35), but not accuracy (p=0.12, η(2)=0.16). No effect of tDCS on verbal learning, retention, or retrieval was found for stimulation targeted to the LMTL or the PT. Secondary analyses revealed that LMTL stimulation resulted in increased recency (p=0.02, η(2)=0.31) and reduced mid-list learning effects (p=0.01, η(2)=0.39), suggesting an inhibitory effect on learning. CONCLUSIONS:HD-tDCS to the LDLPFC facilitates the rate of verbal learning and improved efficiency of working memory may underlie performance effects. This focal method of administrating tDCS has potential for probing and enhancing cognitive functioning.
RCT Entities:
BACKGROUND: Declarative verbal learning and memory are known to be lateralised to the dominant hemisphere and to be subserved by a network of structures, including those located in frontal and temporal regions. These structures support critical components of verbal memory, including working memory, encoding, and retrieval. Their relative functional importance in facilitating declarative verbal learning and memory, however, remains unclear. OBJECTIVE: To investigate the different functional roles of these structures in subserving declarative verbal learning and memory performance by applying a more focal form of transcranial direct current stimulation, "High Definition tDCS" (HD-tDCS). Additionally, we sought to examine HD-tDCS effects and electrical field intensity distributions using computer modelling. METHODS:HD-tDCS was administered to the left dorsolateral prefrontal cortex (LDLPFC), planum temporale (PT), and left medial temporal lobe (LMTL) to stimulate the hippocampus, during learning on a declarative verbal memory task. Sixteen healthy participants completed a single blind, intra-individual cross-over, sham-controlled study which used a Latin Square experimental design. Cognitive effects on working memory and sustained attention were additionally examined. RESULTS:HD-tDCS to the LDLPFC significantly improved the rate of verbal learning (p=0.03, η(2)=0.29) and speed of responding during working memory performance (p=0.02, η(2)=0.35), but not accuracy (p=0.12, η(2)=0.16). No effect of tDCS on verbal learning, retention, or retrieval was found for stimulation targeted to the LMTL or the PT. Secondary analyses revealed that LMTL stimulation resulted in increased recency (p=0.02, η(2)=0.31) and reduced mid-list learning effects (p=0.01, η(2)=0.39), suggesting an inhibitory effect on learning. CONCLUSIONS:HD-tDCS to the LDLPFC facilitates the rate of verbal learning and improved efficiency of working memory may underlie performance effects. This focal method of administrating tDCS has potential for probing and enhancing cognitive functioning.
Keywords:
Declarative verbal memory; High definition transcranial direct current stimulation; Left dorsolateral prefrontal cortex; Left medial temporal lobe; Planum temporale
Authors: Marom Bikson; Zeinab Esmaeilpour; Devin Adair; Greg Kronberg; William J Tyler; Andrea Antal; Abhishek Datta; Bernhard A Sabel; Michael A Nitsche; Colleen Loo; Dylan Edwards; Hamed Ekhtiari; Helena Knotkova; Adam J Woods; Benjamin M Hampstead; Bashar W Badran; Angel V Peterchev Journal: Brain Stimul Date: 2019-07-17 Impact factor: 8.955
Authors: Christopher A Turski; Alanna Kessler-Jones; Clara Chow; Bruce Hermann; David Hsu; Jana Jones; Susanne K Seeger; Rick Chappell; Melanie Boly; Chrysanthy Ikonomidou Journal: Restor Neurol Neurosci Date: 2017 Impact factor: 2.406
Authors: Zeinab Esmaeilpour; Paola Marangolo; Benjamin M Hampstead; Sven Bestmann; Elisabeth Galletta; Helena Knotkova; Marom Bikson Journal: Brain Stimul Date: 2017-12-13 Impact factor: 8.955