Direction-Sensitive Differences in Bilateral Event-Related Potentials (ERPs) During Map-Based Spatial Perspective Taking

Map-based spatial perspective taking (SPT) requires integration of symbolic and first-person reference frames. This brief report examines whether bilateral scalp activity distinguishes orientations with the same minimum angular disparity. Twenty-three right-handed university students completed a compass-verification task with $0^\circ$, $90^\circ$, $180^\circ$, and $270^\circ$ clockwise-coded conditions during electroencephalographic recording. The $90^\circ$ and $270^\circ$ orientations permit a comparison between geometrically opposite $90^\circ$ transformations. Behavioral analyses showed an effect of rotation condition, with no significant Bonferroni-adjusted $90^\circ$–$270^\circ$ difference in accuracy or correct-response time. Exploratory double-subtraction indices were evaluated at F5/F6, C3/C4, and P3/P4 in a 250–600 ms interval selected after waveform inspection. Each index expresses one half of the Direction $\times$ Hemisphere interaction contrast in microvolts. Holm-adjusted $p$ values were $.034$, $.034$, and $.008$, respectively, and the contrasts were positive in all nine windows examined during interval selection. The central right-minus-left difference reversed in sign across orientations, whereas the frontal and parietal patterns involved a change in the magnitude of the bilateral difference. Thus, direction sensitivity can be robustly expressed through either a sign reversal or a significant change in asymmetry magnitude. This contrast was absent on nonmatch trials, which were answered with the alternate hand, indicating the directional pattern was specific to match responses. These findings characterize direction-sensitive bilateral scalp activity during map-based compass verification. The interaction-based measure provides a common framework for examining directional processing across electrode pairs and complements the study of angular-disparity effects in SPT.