Bandwidth, Control Authority, and Embodied Regulation: A Bidirectional Codec Model

The brain does not have full access to the body it controls. That is not a design flaw — it is the design. This paper proposes a theoretical architecture for mind-body coordination built around a single organizing constraint: the organism operates on a low-dimensional, urgency-weighted compression of its full physiological state, and most of what the body is doing never reaches the controller at all. We call this architecture the Mind-Body Negotiation Interface (MBNI). MBNI models the mind-body interface as a bidirectional bandwidth-limited codec. Bottom-up, the body compresses its full chemical and physiological state into a report signal the mind can act on. Top-down, the mind compiles intentions into control signals the body can execute. Both directions are rate-limited. Both directions are lossy in specific, structured ways. And the structure of what gets through — and what doesn't — determines almost everything about how organisms behave, how they age, and what kills them. This framing yields testable predictions: observability hierarchies in felt experience, dissociations between explicit belief and embodied policy, sleep as a mandatory power-budget reallocation with a calculable molecular mechanism, dreams as observable trajectories of compression in progress, and principled conditions under which external measurement can restore control for variables the interface cannot normally see. We also derive what the evolutionary triage that set the bandwidth constraint may explain about aging, autoimmune disease, and cancer — and why the body is not pleasure-seeking but life-seeking, and the distinction matters.