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Abstract:
The executive functions underlying Tower of London (TOL) planning performance depend on the integrity of the dorsolateral prefrontal cortex (DLPFC) and can be
modified by acute transcranial direct current stimulation (tDCS) with lasting benefits to performance. Both anodal and cathodal tDCS of the left DLPFC result in phasedependent, polarity-specific benefits on TOL performance (Dockery et al., 2009). This experiment evaluated differential effects of DLPFC hemisphere stimulated by comparing TOL performance in a between-subject design with 46 randomly assigned healthy
participants (left n 5 24, right n 5 22). tDCS (real or sham) was applied over three sessions. Subjects were then grouped according to tDCS sequence, defined as either
anodal tDCS before cathodal (tDCS_AC), or the contrary (tDCS_CA). For reaction time, a significant interaction of STIMULATION CONDITION X tDCS SEQUENCE, F(2,82) 5 18.063, p 5 .000, showed that only the real tDCS groups but not sham tDCS were sensitive to phase of application. A significant interaction of HEMISPHERE X tDCS SEQUENCE, F(1,41) 5 5.144, p 5 .029 showed that left DLPFC benefited more from the tDCS_CA sequence (tDCS_AC: 8.20870.538, tDCS_CA: 6.56170.515) while right DLPFC benefited from tDCS_AC (tDCS_AC: 7.48970.538, tDCS_CA: 8.25770.538). This study elucidates how tDCS can be used to study differences in the functional anatomy of dorsolateral prefrontal cortical circuits and their role in planning. The results suggest optimal stimulation parameters to achieve the most beneficial effects of tDCS on these executive functions.
