Does Implicit Biological Motion processing affect visuo-spatial attention? A behavioral study with Multiple Sclerosis patients

The perception of Biological Motion (BM) is critical for understanding social cues. A limited number of moving light dots resembling a moving individual can suggest social intention information, providing an attentional orienting. This ability to predict other's intentions from BM cues refers to social cognition, an ability impaired in several neurological diseases. As in people with Multiple Sclerosis (PwMS) an impairment in visuo-spatial attention and social cognition has been observed, we aim to investigate the possible differences in the visuo-spatial attention between MS patients and healthy individuals by using BM stimuli as cues. We tested 37PwMS and 40 healthy controls (HC), who performed a modified central cue Posner task, using BM stimuli as cues that are not always predictive of the target location. They were represented by Point Light Walker (PLW) configuration, a series of dots arranged at the human joints and walking through the left or right of the screen, presented in the global (whole body) or local (two dots, indicating the feet of the PLW) configuration. For each participant, the Inverse Efficiency Score (IES) was calculated as the ratio between mean RTs and accuracy. We tested the significance of fixed effects performing an ANOVA analysis; we also assessed the magnitude of the found effects as the Effect Size (ES) estimated by Cohen’s coefficient. Furthermore, Pearson’s correlational analysis was conducted to test the possible relationship between IES and individual or disease-related characteristics, finding no significant differences. MS patients exhibited overall slower responses compared to HC. In PwMS, a weaker advantage of valid trial over invalid ones was evident when cue had a local than global BM configuration. Also, PwMS showed a slower performance than HC in valid trials with local BM cues. The difference between groups was reduced when the cue had a global BM configuration. These findings suggest possible impairment of local BM cue processing in PwMS, possibly due to delays or deficits in interpreting feet motion as biological information, reducing the cue's predictive power.