Differential effects from cognitive rehabilitation and high-definition tDCS in posterior cortical atrophy: A single-case experimental design.

Posterior cortical atrophy (PCA) is a progressive neurodegenerative syndrome characterized by visual-perceptual deficits, which impact daily life. Recent research has focused on non-pharmacological techniques to ameliorate these deficits, with the most common being cognitive rehabilitation. The present study investigates the differential effects of high definition-transcranial direct current stimulation (HD-tDCS) and cognitive rehabilitation in a single-case experimental design with two separate experimental phases in a patient with PCA. Experimental Phase 1 consisted of 10 sessions of HD-tDCS targeting the pre-SMA/dACC and Phase 2 consisted of 10 sessions of cognitive rehabilitation. Normed and standardized scores from figure copy and recall tests served as the primary outcome measures for visuospatial processing. The participant showed no immediate or long-term changes in visuospatial measures following HD-tDCS intervention. However, cognitive rehabilitation showed immediate improvement in visuospatial memory (figure recall) and clinically significant improvement in visuospatial construction (figure copy). Visuospatial construction gains remained in the low average range in the 10-week follow-up while visuospatial memory returned to baseline. Results indicated differential effects between HD-tDCS and cognitive rehabilitation with cognitive rehabilitation showing clinically significant improvement in primary outcome measures with sustained improvement in the long-term follow-up measure. Additional research is warranted to confirm these effects.