Induced EEG alpha oscillations are related to mental rotation ability: the evidence for neural efficiency and serial processing.

People with better skills in mental rotation require less time to decide about the identity of rotated images. In the present study, alphanumeric characters rotated in the frontal plane were employed to assess the relationship between rotation ability and EEG oscillatory activity. Response latency, a single valid index of performance in this task, was significantly associated with the amplitude of induced oscillations in the alpha (8-13 Hz) and the low beta band (14-20 Hz). In accordance with the neural efficiency hypothesis, less event-related desynchronization (ERD) was related to better (i.e. faster) task performance. The association between response time and ERD was observed earlier (approximately 600-400 ms before the response) over the parietal cortex and later (approximately 400-200 ms before the response) over the frontal cortex. Linear mixed-effect regression analysis confirmed that both early parietal and late frontal alpha/beta power provided significant contribution to prediction of response latency. The result indicates that two distinct serially engaged neurocognitive processes comparably contribute to mental rotation ability. In addition, we found that mental rotation-related negativity, a slow event-related potential recorded over the posterior cortex, was unrelated to the asymmetry of alpha amplitude modulation.