Abstract: PURPOSE: Intrinsic neural oscillations synchronize with external rhythmic stimuli, a process known as neural entrainment. The current study investigated the cortical entrainment to rhythmic biological motion (BM), especially regarding whether the observed effect reflects BM-specific neural processing.
METHODS: Stimuli consisted of point-light walkers (PLWs) with two orientations (upright and inverted) and two speeds (1Hz and 1.33Hz), which were presented in separated blocks. Each trial began with a white fixation followed by a PLW displayed for 6s. Among 20%-30% of the trials, the speed of the PLW changed one or two times. Observers were required to attend to the display and judge the number of changes at the end of each trial, while their brain activity was recorded via EEG. Only the non-changed trials were included in EEG data analysis.
RESULTS: Upright PLW but not inverted PLW enhanced the power of cortical oscillations at the walking cycle frequency, inducing significantly higher strength of neural entrainment in the upright than in the inverted condition, consistent with the BM inversion effect revealed by fMRI studies. Moreover, this inversion effect occurred over the centroparietal and the occipitoparietal regions and was strongly lateralized to the right hemisphere, coinciding with the right lateralization of orientation-dependent BM processing.
CONCLUSIONS: This study demonstrated the cortical tracking of BM information, which is sensitive to its orientation and lateralized to the right hemisphere, establishing the role of neural entrainment as a promising tool to investigate the oscillatory brain mechanisms underlying visual BM processing.

Key words: biological motion, neural entrainment, inversion effect, neural oscillations