Can the Brain Function as a Quantum Information Transducer? An Eight-Principle Synthesis from Biological Precedents to Microtubule Coherence

180 years. Zero answers. Until now. Since 1846, anesthesia has saved millions of lives — yet no one knows how it actually turns off consciousness. The Meyer-Overton correlation (1899) proved that chemically unrelated anesthetics hit the same physical target. 127 years later, that target remains unidentified. This paper connects eight independent breakthroughs — from the 2025 Nobel Prize in Physics to room-temperature quantum superradiance in microtubules — into a single integrative pathway that delivers a candidate answer: consciousness is a quantum coherence phenomenon, and anesthesia destroys it. Two models emerge. Either the brain generates quantum information internally (production), or the brain receives and converts quantum information from external sources (transduction). For the first time, these two interpretations are explicitly separated and a discriminating experiment is proposed (Prediction 7: Faraday cage electromagnetic shielding test with full protocol outline). The analytical foundation has been independently verified across companion papers: C = Θ (Rτ/I − 1) derived with three-path convergence at 1. 004 (zero fitted parameters), projection operator P̂ = |n₀⟩⟨n₀| proved via Lindblad dynamics, and Rτ/I = 1 established as the unique globally stable fixed point via Banach contraction. Seven falsifiable predictions. Three core experiments. One 180-year mystery. Paper 5 in the Information Physics Series. The empirical gatekeeper — every formal development that follows must pass through this door first. Full simulation code included (BrainQuantumTransducerFig2. py, BrainQuantumTransducerFig3. py).