In a parity judgment task, the ERPs at parietal electrode sites become more negative as more mental rotation has to be executed. This article provides a review of the empirical evidence regarding this amplitude modulation. More specifically, experiments are reported that validate both the functional relationship between mental rotation and the amplitude modulation as well as the temporal relationship both in single- and in dual-task situations. Additionally, ERP effects are reported in the psychological refractory period (PRP) paradigm with mental rotation as the second task. Finally, unresolved issues are discussed that, I hope, might stimulate future research.

We investigated the nature of event-related potential (ERP) effects in a handedness recognition task requiring mental rotation. Thirty subjects were tested with rotated and sometimes reflected alphanumeric characters while ERPs were recorded from 18 electrodes. On each trial, a cue provided valid information about the angular displacement of the following probe. This design allowed a distinction between three processing episodes: evaluation of the difficulty of the forthcoming task, preparation for the task, and the mental rotation task itself. The three episodes were accompanied by distinct ERP effects having distinct polarities, a different rank order of amplitudes for different probe orientations, and a different topography. These data confirm previous findings showing that mental rotation is accompanied by a parietal negativity. However, they also suggest that the rotation-related negativity found after tilted stimuli in standard mental rotation tasks is most likely overlapping with another, simultaneously triggered ERP effect functionally related to an evaluation of task difficulty.