In neuroscience, quantum brain dynamics (QBD) is a hypothesis to explain the function of the brain within the framework of quantum field theory.
As described by Harald Atmanspacher, since quantum theory is the most fundamental theory of matter that is currently available, it is a legitimate question to ask whether quantum theory can help us to understand consciousness.
Large systems, such as those studied biologically, have less symmetry than the idealized systems or single crystals often studied in physics. Jeffrey Goldstone proved that where symmetry is broken, additional bosons, the Nambu–Goldstone bosons, will then be observed in the spectrum of possible states; one canonical example being the phonon in a crystal.
Ricciardi and Umezawa proposed in 1967 a general theory of quanta of long-range coherent waves within and between brain cells, and showed a possible mechanism of memory storage and retrieval in terms of Nambu–Goldstone bosons. This was later fleshed out into a theory encompassing all biological cells and systems in the quantum biodynamics of Del Giudice and co-authors. Mari Jibu and Kunio Yasue later popularized these results and discussed the implications towards consciousness.