The effects of TMS over dorsolateral prefrontal cortex on multiple visual object memory across fixation and saccades

Trans-saccadic memory, the process by which the visual system maintains the spatial position and features of objects across eye movements, is thought to be a form of visual working memory (Irwin, 1991). It has been shown that TMS over the frontal and parietal eye fields degrades trans-saccadic memory of multiple object features (Prime et al., 2008, 2010). We used a similar TMS protocol to investigate whether dorsolateral prefrontal cortex (DLPFC) is also involved in trans-saccadic memory. We predicted that performance would be disrupted similarly during either fixation or saccades. Instead, we found both task and hemisphere-dependent effects. During fixation, TMS over left DLPFC produced inconsistent effects, whereas TMS over right DLPFC reduced performance, consistent with its known role in working memory (Goldman-Rakic, 1987). In contrast, TMS over both sides of DLPFC enhanced trans-saccadic memory, suggesting a dis-inhibition of trans-saccadic processing. These results suggest that visual working memory during fixation and trans-saccadic memory may be supported by different, but interacting, neural circuits.