Definition
The self-symbol is Hofstadter's term for the brain's active symbol that represents the brain itself. Most symbols (kitchen, Tuesday, your mother) represent things external to the brain that contains them. The self-symbol is recursive: it represents the system it lives inside. Its activations are influenced by, and influence, almost every other symbol — because almost everything the brain represents is represented as related to "me."
On Hofstadter's view, the self-symbol is the structural home of the strange loop that constitutes the self. Consciousness is what such a loop feels like from inside.
Why it matters
How it works
The self-symbol is not a single neuron or a single cortical area. Like all active symbols on Hofstadter's account, it is a distributed pattern of activity across many regions that becomes self-sustaining when triggered and that primes neighboring symbols. What distinguishes it is its centrality: most symbol activations partially activate the self-symbol, and the self-symbol partially activates most other symbols. The connectivity is so dense that the self-symbol effectively is the high-level coherence of the brain's symbol-level activity.
This is why selective damage to the self-symbol's substrate (medial prefrontal cortex, default mode network) produces global disturbances of self-experience rather than local deficits.