awareness.
Hearing your inner voice is a matter of paying careful attention to internal physiological signals.
These subtle cues are monitored by the insula,
which is tucked behind the frontal lobes of the brain.
Attention given to any part of the body amps up the insula's sensitivity to that part. Tune in to your heartbeat, and the insula activates more neurons in that circuitry.
How well people can sense their heartbeats has,
in fact, become a standard way to measure their self-awareness