  Recent proposals in quantum gravity have suggested that unknown systems can
mediate entanglement between two known quantum systems, if and only if the
mediator itself is non-classical. This approach may be applicable to the brain,
where speculations about quantum operations in consciousness and cognition have
a long history. Proton spins of bulk water, which most likely interfere with
any brain function, can act as the known quantum systems. If an unknown
mediator exists, then NMR methods based on multiple quantum coherence (MQC) can
act as entanglement witness. However, there are doubts that today's NMR signals
can contain quantum correlations in general, and specifically in the brain
environment. Here, we used a witness protocol based on zero quantum coherence
(ZQC) whereby we minimised the classical signals to circumvent the NMR
detection limits for quantum correlation. For short repetitive periods, we
found evoked signals in most parts of the brain, whereby the temporal
appearance resembled heartbeat-evoked potentials (HEPs). We found that those
signals had no correlates with any classical NMR contrast. Similar to HEPs, the
evoked signal depended on conscious awareness. Consciousness-related or
electrophysiological signals are unknown in NMR. Remarkably, these signals only
appeared if the local properties of the magnetisation were reduced. Our
findings suggest that we may have witnessed entanglement mediated by
consciousness-related brain functions. Those brain functions must then operate
non-classically, which would mean that consciousness is non-classical.
