Stepping in time: Alpha-mu and beta oscillations during a walking synchronization task.

Interpersonal behavioral synchrony is defined as the temporal coordination of action between two or more individuals. Humans tend to synchronize their movements during repetitive movement tasks such as walking. Mobile EEG technology now allows us to examine how this happens during gait. 18 participants equipped with foot accelerometers and mobile EEG walked with an experimenter in three conditions: With their view of the experimenter blocked, walking naturally, and trying to synchronize their steps with the experimenter. The experimenter walked following a headphone metronome to keep their steps consistent for all conditions. Step behavior and synchronization between the experimenter and participant were compared between conditions. Additionally, event-related spectral perturbations (ERSPs) were time-warped to the gait cycle in order to analyze alpha-mu (7.5-12.5 Hz) and beta (16-32 Hz) rhythms over the whole gait cycle. Step synchronization was significantly higher in the synchrony condition than in the natural condition. Likewise regarding ERSPs, right parietal channel (C4, C6, CP4, CP6) alpha-mu and central channel (C1, Cz, C2) beta power were suppressed from baseline in the walking synchrony condition compared to the natural walking condition. The natural and blocked conditions were not found to be significantly different in behavioral or spectral comparisons. Our results are compatible with the view that intentional synchronization employs systems associated with social interaction as well as the central motor system.

Characteristic Sizes of Life in the Oceans, from Bacteria to Whales.

The size of an individual organism is a key trait to characterize its physiology and feeding ecology. Size-based scaling laws may have a limited size range of validity or undergo a transition from one scaling exponent to another at some characteristic size. We collate and review data on size-based scaling laws for resource acquisition, mobility, sensory range, and progeny size for all pelagic marine life, from bacteria to whales. Further, we review and develop simple theoretical arguments for observed scaling laws and the characteristic sizes of a change or breakdown of power laws. We divide life in the ocean into seven major realms based on trophic strategy, physiology, and life history strategy. Such a categorization represents a move away from a taxonomically oriented description toward a trait-based description of life in the oceans. Finally, we discuss life forms that transgress the simple size-based rules and identify unanswered questions.