Heart rate complexity and attentional orienting: a new look at the role of vagal tone.

This study is aimed at elucidating (a) whether heart rate (HR) complexity measures are associated with the attentional orienting function, and (b) which of these measures better predicts orienting efficiency indexes. Vagal tone, sample entropy, scaling exponents ?1 and ?2, and fractal dimension (FD) were calculated in HR time series (n=109). Vagal tone, entropy, and FD were positively associated with orienting, while this association was negative for ?2. These results show that HR scaling properties, which underlie the role of vagal tone and reflect allometric control mechanisms, are associated with orienting deficits. FD was the best predictor of attentional orienting.