  Social behavior is a complex integrative function that entails many aspects
of the brain's sensory, cognitive, emotional and motor capacities. Neural
processes are seldom simultaneous but occur according to precise temporal and
coordinative choreographies within and between brains. Methods with good
temporal resolution such as EEG can help to identify so-called "neuromarkers"
of social function (Tognoli, et al., 2007) and aid in disentangling the
dynamical architecture of social brains. We have studied neuromarkers and their
dynamics during synchronic interactions in which pairs of subjects coordinate
behavior spontaneously and intentionally (social coordination) and during
diachronic transactions that required subjects to perceive or behave in turn
(action observation and delayed imitation). We examined commonalities and
differences in the neuromarkers that are recruited for both kinds of tasks. We
found that the neuromarker landscape was task-specific: synchronic paradigms of
social coordination revealed medial mu, alpha and the phi complex as
contributing neuromarkers. Diachronic tasks recruited alpha as well, in
addition to lateral mu rhythms and the newly discovered nu and kappa rhythms
whose functional significance is still unclear. Social coordination,
observation, and delayed imitation share commonality of context: in our
experiments, subjects exchanged information through visual perception and moved
in similar ways. Nonetheless, there was little overlap between the neuromarkers
recruited for synchronic and diachronic tasks, a result that hints strongly of
task-specific neural mechanisms for social behaviors. The only neuromarker that
transcended both synchronic and diachronic social behaviors was the ubiquitous
alpha rhythm, which appears to be a key signature of visually-mediated social
behaviors. The present paper is both an entry point and a challenge...
