Since the beginning of neuroscience as its own discipline in the early 20th century, there have been many theories about how the brain works. One of the most heated discussions was between two Nobel Prize-winners – Santiago Ramón y Cajal and Camillo Golgi – over the role of local versus global coding and processing in the brain. Ramón y Cajal was arguing for a localist perspective where the single neurons carried out most if not all of the coding, while Golgi was in favour of global, distributed processing. Initially, Ramón y Cajal seemed victorious, mostly due to his careful dissection and beautiful drawings of neurons and their synapses. This strongly biased neurophysiology research, leading to remarkable single-neuron recordings, such as those in the Nobel Prize-winning work on the visual system by David Hubel and Torsten Wiesel.

Over the past few decades, human neuroimaging has taken this localist approach to an even higher level with correlations of often indirect measures of brain activity with behaviour, establishing a highly successful and highly cited field. Yet, in contrast to this localist legacy, recent work has started to take inspiration from the dynamical systems described by physics and mathematics, such as the one put forward by the physicist Hermann Haken, and has shown how the meso- and macroscopic distributed activity of these models adds synergistically to the microscopic (localist) activity.

This new framework points to a view of the brain as a fusion of the local and the global, arranged in a hierarchical manner. In this context, some researchers including Marsel Mesulam have suggested that the human brain is in fact hierarchically organised, a view that fits well with our orchestra metaphor. Yet, given the distributed nature of the brain hierarchy, there is unlikely to be just a single ‘conductor’. Instead, in 1988 the psychologist Bernard Baars proposed the concept of a ‘global workspace’, where information is integrated in a small group of brain regions (or ‘conductors’) before being broadcast to the whole brain.

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