Immediate memory and electrophysiologic effects of prefrontal cortex transcranial direct current stimulation on neurotypical individuals and individuals with chronic traumatic brain injury: a pilot study

Purpose/aim: Memory impairment post-TBI is common, frequently persistent, and functionally debilitating. The purposes of this pilot study were to assess and to compare immediate behavioral auditory working memory and electrophysiologic effects of three different, randomized, conditions of left dorsolateral prefrontal cortex (LDLPFC) transcranial direct current stimulation (tDCS) applied to four neurotypical adults and four adults with chronic traumatic brain injury (TBI). Materials/methods: Pre- and post-anodal, cathodal, and sham tDCS auditory memory performance, auditory event-related potentials (P300 amplitude and latency) and power of alpha and theta EEG bands were measured across individuals in each group. Results: Post-anodal tDCS only, the neurotypical and TBI groups both demonstrated significantly improved immediate auditory memory function. Also post-anodal tDCS, the TBI group demonstrated significantly increased P300 amplitude versus post-sham tDCS. The neurotypical group demonstrated no pre- post-tDCS electrophysiologic changes across conditions. Conclusions: These findings are consistent with findings of other studies of immediate tDCS effects on other types of memory in neurotypical individuals and in individuals with Parkinson's disease, Alzheimer's disease and stroke and suggest that individuals with memory impairments second to chronic TBI may benefit from LDLPFC anodal tDCS. Pairing tDCS with traditional behavioral memory interventions may facilitate TBI rehabilitation outcomes and warrants continued investigation.