The Importance of Spatiotemporal Information in Biological Motion Perception: White Noise Presented with a Step-like Motion Activates the Biological Motion Area Akiko Callan, Daniel Callan, and Hiroshi Ando Abstract ■ Humans can easily recognize the motion of living creatures using only a handful of point-lights that describe the motion of the main joints (biological motion perception). This special ability to perceive the motion of animate objects signifies the importance of the spatiotemporal information in perceiving biological motion. The posterior STS (pSTS) and posterior middle temporal gyrus (pMTG) region have been established by many functional neuroimaging studies as a locus for biolog- ical motion perception. Because listening to a walking human also activates the pSTS/pMTG region, the region has been pro- posed to be supramodal in nature. In this study, we investigated whether the spatiotemporal information from simple auditory stimuli is sufficient to activate this biological motion area. We compared spatially moving white noise, having a running-like tempo that was consistent with biological motion, with station- ary white noise. The moving-minus-stationary contrast showed significant differences in activation of the pSTS/pMTG region. Our results suggest that the spatiotemporal information of the auditory stimuli is sufficient to activate the biological motion area. ■ INTRODUCTION For animals, including humans, detecting the sound of footsteps and determining the direction and location of their movement have ecological significance for survival. Although the sound of a single footstep merely provides auditory information about the footwear contacting the walking surface, listening to consecutive footsteps in real life allows us to infer how the person is moving in a cer- tain environment. People can determine not only the direction and speed of locomotion but also the gender (Li, Logan, & Pastore, 1991), posture (Pastore, Flint, Gaston, & Solomon, 2008) and stride length (Young, Rodger, & Craig, 2013) of the walker. This phenomenon is compara- ble to visual biological motion perception. Johansson (1973) used the term “biological motion” to refer to the characteristic motion patterns of living beings during locomotion and showed that the movement of 10–12 small light bulbs attached to the main joints (known as point-light [PL] animation) could evoke biological mo- tion perception. A single frame of the PL animation may appear as a meaningless assembly of dots. However, successive frames of the PL animation depict a compelling impression of human motion, such as walking, running, or dancing. This special ability to perceive the motion of animate objects demonstrates the importance of the spatiotemporal information in perceiving biological mo- tion. Many human neuroimaging studies that have inves- tigated the brain areas responsive to biological motion perception using PL animations have reported that the posterior STS (pSTS) region is activated more by actual PL animations than by scrambled PL animations (for a review, see Blake & Shiffrar, 2007). In this article, we use the term “pSTS/posterior middle temporal gyrus (pMTG)” because biological motion perception activates pSTS as well as the adjacent pMTG (Allison, Puce, & McCarthy, 2000). Bidet-Caulet, Voisin, Bertrand, and Fonlupt (2005) investigated whether the pSTS/pMTG region was activated by the auditory stimuli and revealed that the pSTS/pMTG region was activated by detecting the direction of motion of the crossing walker while listening to the footsteps. This result indicates that auditory stimuli related to human motion also activate the pSTS/pMTG region. In our previous study, we compared realistic (external- ized) and artificial (internalized) spatial sounds and found that the activity in the posterior superior temporal gyrus (pSTG) and pMTG were greater in response to the exter- nalized stimuli than in response to internalized stimuli (Callan, Callan, & Ando, 2013). The externalized stimuli were individualized binaural recordings, and the internal- ized stimuli were stereo recordings. By recording sounds with microphones placed within the left and right pinnae, binaural recordings include the acoustic filter characteris- tics of the head and ears (head-related transfer function [HRTF]) and room reverberation. During headphone lis- tening, the HRTF is known to be responsible for percep- tual sound externalization when head motion cues are CiNet, National Institute of Information and Communication Technology, and Osaka University © 2016 Massachusetts Institute of Technology Journal of Cognitive Neuroscience 29:2, pp. 277–285 doi:10.1162/jocn_a_01046