The Default Mode Network and inner time consciousness

Abstract

The default mode network (DMN) exhibits distinct dynamic and topographic features relative to the brain’s other networks, yet their link to consciousness remains unclear. We review both neural (DMN-based topography and dynamics) and mental (experience of time speed, mental time travel, and self-non-self) findings across diverse nonordinary states of consciousness, including reduced (anesthesia, Unresponsive Wakefulness Syndrome), elevated (meditation and, to some degree, psychedelics), and abnormal (depression, mania) consciousness. Both reduced and elevated states are featured by topographic ‘flattening’ of the brain’s DMN-centric organization while they differ in their dynamics, that is, longer versus shorter timescales. A neural continuum emerges with different degrees of DMN-centric topography along its extremes: from heightened DMN-centric re-organization in depression, over flattened configurations in psychedelics and meditation, to heightened sensorimotor-centric re-organization in mania. This neural continuum parallels a mental continuum along different balances within inner time consciousness, including slow versus fast time speed, past–present–future (mental time travel) and self versus non-self/other. In conclusion, we propose novel neurophenomenological hypotheses about the intrinsic relationship (‘complex correspondence’) of the brain’s DMN-centred topography and dynamics with inner time consciousness.