Transcranial Alternating Current Stimulation Affects Decision Making

to the gamma band (Varela et al., 2001). This resonance-like interplay between externally applied and internally generated regional oscillatory activity may prove a powerful approach to manipulate brain activity. So far, investigations of tACS effects on cognitive performance have been limited to visual and somatosensory perception (Feurra et al., 2011b), and motor control (Pogosyan et al., 2009; Feurra et al., 2011a). There is thus an emergent need to test tACS effects on higher cognitive functions. In a recent paper in Frontiers in Decision Neuroscience, Sela et al. (2012) used tACS to investigate the effects of oscillatory prefrontal theta stimulation, a frequency involved in regulatory control during decision making processes. Subjects performed a modified version of the Balloon Analog Risk Task (BART; Lejuez et al., 2004). In this task, volunteers pump a balloon without knowing when it will explode. The more the pump button is pressed, the more points accumulate while at the same time the risk of losing points with a balloon explosion increases. Subjects are thus pressured to decide whether to adopt a risky behavior and keep pumping, or to use a more conservative strategy and stop. tACS was delivered to three groups of healthy volunteers. One group received stimulation over the left prefrontal cortex (lPFC), one over the right prefrontal cortex (rPFC), and the other received sham stimulation. tACS was delivered online during the task. Stimulation started 5 min before the task began and lasted for approximately 10 min until the BART was completed. Crucially, active tACS was only delivered at a theta frequency of 6.5 Hz. Sham stimulation involved the same parameters, but was only delivered for 30 s. Results showed a striking effect of lPFC stimulation, whereas rPFC and sham stimulations failed to produce any considerable effect on task performance. More specifically, the increase of sequential losses during tACS stimulation over lPFC suggested that volunteers lost the Transcranial alternating current stimulation affects decision making