Hanako Ikeda

Eccentric perception of biological motion is unscalably poor

Accurately perceiving the activities of other people is a crucially important social skill of obvious survival value. Human vision is equipped with highly sensitive mechanisms for recognizing activities performed by others [Johansson, G. (1973). Visual perception of biological motion and a model for its analysis. Perception and Psychophysics, 14, 201; Johansson, G. (1976). Spatio-temporal differentiation and integration in visual motion perception: An experimental and theoretical analysis of calculus-like functions in visual data processing. Psychological Research, 38, 379]. One putative functional role of biological motion perception is to register the presence of biological events anywhere within the visual field, not just within central vision. To assess the salience of biological motion throughout the visual field, we compared the detectability performances of biological motion animations imaged in central vision and in peripheral vision. To compensate for the poorer spatial resolution within the periphery, we spatially magnified the motion tokens defining biological motion. Normal and scrambled biological motion sequences were embedded in motion noise and presented in two successively viewed intervals on each trial (2AFC). Subjects indicated which of the two intervals contained normal biological motion. A staircase procedure varied the number of noise dots to produce a criterion level of discrimination performance. For both foveal and peripheral viewing, performance increased but saturated with stimulus size. Foveal and peripheral performance could not be equated by any magnitude of size scaling. Moreover, the inversion effect--superiority of upright over inverted biological motion [Sumi, S. (1984). Upside-down presentation of the Johansson moving light-spot pattern. Perception, 13, 283]--was found only when animations were viewed within the central visual field. Evidently the neural resource responsible for biological motion perception are embodied within neural mechanisms focused on central vision.

Larger right posterior parietal volume in action video game experts: a behavioral and voxel-based morphometry (VBM) study.

Recent studies suggest that action video game players exhibit superior performance in visuospatial cognitive tasks compared with non-game players. However, the neural basis underlying this visuospatial cognitive performance advantage remains largely unknown. The present human behavioral and imaging study compared gray matter volume in action video game experts and non-experts using structural magnetic resonance imaging and voxel-based morphometry analysis. The results revealed significantly larger gray matter volume in the right posterior parietal cortex in experts compared with non-experts. Furthermore, the larger gray matter volume in the right posterior parietal cortex significantly correlated with individual performance in a visual working memory task in experts. These results suggest that differences in brain structure may be linked to extensive video game play, leading to superior visuospatial cognitive performance in action video game experts.

Anger and Happiness are Linked Differently to the Explicit Detection of Biological Motion

The detection of biological motion and the detection of emotion from this motion are important visual functions with obvious survival and social values. The perception of biological motion is remarkably robust, and numerous studies have shown that the emotional states of a person can be deduced from point-light biological motion. In the present study, we investigated the extent to which the detection of emotion from biological motion is linked to the explicit detection of human gait. Subjects performed gait detection and emotion detection for the same stimulus. The stimulus consisted of one coherent interval and one scrambled biological-motion interval, each of which contained one emotionally neutral and one emotional (angry or happy) walker. Significant correlations with gait detection performance were observed for anger detection but not necessarily for happiness detection, implying that the detection of anger may be more strongly linked to explicit gait detection. This leads to a hypothesis that differential dependence may reflect the differential behavioural meaning between anger and happiness detection; it may be more crucial to localise or identify a person with anger than happiness.

Effects of explicit knowledge of workspace rotation in visuomotor sequence learning

Previous experimental and theoretical studies have suggested that two separate neural networks contribute to visuomotor learning of spatial sequences, one to the accuracy of performance and the other to the speed of performance (Nakahara et al. in J Cogn Neurosci 13:626–647, 2001). This study examined the influence of explicit knowledge of stimulus configuration (workspace) in visuomotor sequence learning. Twenty-eight right-handed subjects learned the sequences of button presses by trial and error (Hikosaka et al. in J Neurophysiol 76:617–621, 1996) in the course of two sessions. In the first session, both the number of completion failures (accuracy measure) and the performance time to complete a sequence (speed measure) decreased. In the second session, the workspace was rotated without notifying the subjects. About half the subjects remained unaware of the workspace rotation, and no transfer of learning occurred (i.e., neither accuracy nor speed of performance was preserved in the second session). The remaining subjects spontaneously noticed the rotation and they were able to use this knowledge to perform the task with less completion failures in the second session. However, the knowledge of workspace rotation did not decrease the performance time in the second session. The lack of influence of explicit knowledge on the speed of performance is consistent with the two-loop model of visuomotor sequence learning (Nakahara et al. in J Cogn Neurosci 13:626–647, 2001).

Roles of the upper and lower bodies in direction discrimination of point-light walkers.

We can easily recognize human movements from very limited visual information (biological motion perception). The present study investigated how upper and lower body areas contribute to direction discrimination of a point-light (PL) walker. Observers judged the direction that the PL walker was facing. The walker performed either normal walking or hakobi, a walking style used in traditional Japanese performing arts, in which the amount of the local motion of extremities is much smaller than that in normal walking. Either the upper, lower, or full body of the PL walker was presented. Discrimination performance was found to be better for the lower body than for the upper body. We also found that discrimination performance for the lower body was affected by walking style and/or the amount of local motion signals. Additional eye movement analyses indicated that the observers initially inspected the region corresponding to the upper body, and then the gaze shifted toward the lower body. This held true even when the upper body was absent. We conjectured that the upper body subserved to localize the PL walker and the lower body to discriminate walking direction. We concluded that the upper and lower bodies play different roles in direction discrimination of a PL walker.

Action Congruency Influences Crowding When Discriminating Biological Motion Direction.

Identification and discrimination of peripheral stimuli are often difficult when a few stimuli adjacent to the target are present (crowding). Our previous study showed that crowding occurs for walking direction discrimination of a biological motion stimulus. In the present study, we attempted to examine whether action congruency between the target and flankers would influence the crowding effect on biological motion stimuli. Each biological motion stimulus comprised one action (e.g., walking, throwing wastepaper, etc.) and was rotated in one of five directions around the vertical axis. In Experiment 1, observers discriminated between the directions of the target stimulus actions, which were surrounded by two flankers in the peripheral visual field. The crowding effect was stronger when the flankers performed the same action as the target and the directions differed. The congruency of action type enhanced the crowding effect in the direction-discrimination task. In Experiment 2, observers discriminated between action types of target stimuli. The crowding effect for the action-discrimination task was not modulated by the congruency of action direction. Thus, identical actions induced a larger crowding effect for action-direction discrimination, but congruent directions did not influence crowding for action-type discrimination. These results suggest that the processes involved in direction discrimination of biological motion are partially distinct from action discrimination processes.

Visual-motor sequence learning by competitive fighting game experts

Playing action video games has been reported to modify some cognitive functions. However, no study has investigated whether the explicit learning of arbitrary visual-motor sequences would differ between video game expert and non-expert groups. The present study compared the explicit learning of visual-motor sequences in 12 expert players of a competitive fighting video game with 20 non-expert control participants. The participants were required to determine a sequence of button presses by trial and error and elaborate the learned sequence. The results showed that the expert game players were generally faster in visual-motor responses and kept improving at the later stage of learning compared with the control group. These results suggest that competitive fighting game experts have enhanced ability in sequence learning and imply that this can be generalized to the learning of arbitrary spatiotemporal structures of visual-motor behaviors.