Consistent with the results of a previous study (van de Ven et al.,
2012), we did not find any effect of TMS on short-term memory of a single object. However, we did find an effect in situations in which one would expect the remembered object to be remapped contralaterally into the magnetically stimulated EVC/quadrant (
Figure 8a). Again, this effect was only statistically significant for leftward saccades, and was much weaker overall for rightward saccades (
Figure 6). The mathematical reason behind this can be appreciated by the summary in
Figure 8, which shows normalized TMS performance (“remapping” hemisphere to “perceiving” hemisphere), sorted first by direction (
Figure 8b,
c) and then also by saccade size. Here, very similar saccade amplitude–dependent trends are visible for both saccade directions, but performance relative to the control site is shifted upward (more positive) for the right EVC/rightward saccades (
Figure 8c). It is thus possible that the statistics for these rightward saccades might be a “false negative,” but given that the
p value for this result was more than an order of magnitude greater than the standard 0.05, we cannot make such a claim based on our current data set. Previously, we also observed hemisphere-specific effects during TMS over the parietal cortex in a similar task with multiple stimuli (Prime et al.,
2008). Not enough is known at this time about the mechanisms of action of TMS to know for certain if these asymmetries are related to these mechanisms or intrinsic brain functions. It may be that TMS suppressed feature remapping here by decreasing signal strength, by overwriting the neural representation of memory trace in the visual cortex, or (as we believe) by injecting “noise” into local cortical signals (Harris, Clifford, & Miniussi,
2008; van de Ven et al.,
2012; Vesia, Prime, Yan, Sergio, & Crawford,
2010). In any case, our finding is consistent with both the general notion that trans-saccadic memory, updating, and integration involve a complex interplay between sensory, cognitive, and motor signals and the specific notion that this involves recurrent feedback to the EVC (Cavanagh et al.,
2010; Hamker & Zirnsak,
2006; Hamker et al.,
2011; McMains & Kastner,
2011; Melcher & Colby,
2008; Prime et al.,
2006; Prime et al.,
2007; Prime et al.,
2008,
2011).