Neural processing of bottom up perception of biological motion under attentional load

Considering its importance for one’s survival and social significance, biological motion (BM) perception is assumed to occur automatically. Indeed, Thornton and Vuong (2004) showed that task-irrelevant BM in the periphery interfered with task performance at the fovea. However, the neural underpinnings of this bottom-up processing of BM lacks thorough examination in the field. Under selective attention, BM perception is supported by a network of regions including the occipito-temporal, parietal, and premotor cortices. A retinotopy mapping study on BM showed distinct maps for its processing under and away from selective attention (Saygin & Sereno, 2008). Based on these findings, we investigated how bottom-up perception of BM would be processed in the human brain under attentional load when it was shown away from the focus of attention as a task-irrelevant stimulus. Participants (N=31) underwent an fMRI study in which they performed an attentionally demanding visual detection task at the fovea while intact or scrambled PLDs of BM were shown at the periphery. Our results showed the main effect of attentional load in fronto-parietal regions and the main effect of peripheral stimuli in occipito-temporal cortex. Both univariate activity maps and multivariate pattern analysis results support the attentional load modulation on BM in the occipito-temporal cortex. In conclusion, BM is processed within the motion sensitive regions in the occipito-temporal cortex even when it is away from selective attention, and is modulated by the top-down factor of attentional load.