[p4–023]: High‐definition Transcranial Direct Current Stimulation Modulates Bold Signal During Spatial Navigation in Older Controls and Patients With Mci
Year: 2017
Type: article
Study designs: Randomized Controlled Trial, Clinical Trial
Abstract: Navigation is critical in daily life and can be accomplished using allocentric and/or egocentric systems. Allocentric navigation utilizes an external reference system and cognitive maps that are preferentially mediated by spatial processing (e.g., parietal cortex) and episodic memory (e.g., hippocampus) brain areas. Egocentric navigation uses an internal reference system and stimulus-response relationships that are preferentially mediated by the striatum (e.g., caudate nucleus). “Normal” age-related decline is evident in the allocentric, but not egocentric, processing and is exacerbated in those with mild cognitive impairment (MCI). Transcranial direct current stimulation (tDCS) may hold promise for enhancing functioning due to its neuromodulatory effects. The current study evaluated the behavioral and neurophysiological effects of high-definition tDCS in cognitively intact older adults (HOA) and patients with MCI. Using a double-blind cross-over design, 36 participants (18 MCI) each completed two sessions wherein they were randomized to active or sham HD-tDCS (2mA for 20 minutes) that targeted the right superior parietal lobule (center anode over site P2 in 10–10 system). Participants underwent functional magnetic resonance imaging (fMRI) immediately after stimulation, during which they encoded a series of allocentric and egocentric environments. Memory was evaluated after the scan session. While there were no effects of HD-tDCS on memory accuracy (likely related to task difficulty), there was a group by session interaction on reaction time where HOA were slower but MCI were faster to respond following stimulation. Preliminary fMRI analyses revealed main effects of group (greater caudate activation in HOA) and session (increased activation in the left superior parietal lobule but decreased activation in the anterior cingulate following HD-tDCS). Group by session effects were evident in a number of left hemisphere regions associated with successful encoding (e.g., hippocampus, insula, lateral prefrontal cortex) and bilateral rostral prefrontal cortices that may reflect increased top-down control. This double blind RCT revealed offline behavioral and neurophysiologic effects of HD-tDCS that differ as a function of cognitive phenotype (HOA vs. MCI). Findings add to knowledge of individual differences in tDCS response, support age- and disease-related compensatory patterns of activation, and hold promise for more extensive neurorehabilitative approaches that target this vital cognitive ability.
Source: Alzheimer s & Dementia
Institutions: University of Michigan, VA Ann Arbor Healthcare System
Language: English
Subfield: Neurology
Field: Neuroscience
Domain: Life Sciences
Open Access status: bronze
OpenAlex ID: W2765940673