If the bridge's reading (SR-eff) is the mass of information, what does the bridge correspond to in a brain?
The most direct mapping is to the noradrenergic locus coeruleus system. LC neurons fire in response to unexpected events, modulate cortical gain, and their firing rate is proportional to the degree of surprise. The bridge opens (SR-eff rises) when the input violates the system's model. The LC fires when the brain's model is violated. Both are gain modulators. Both operate on a timescale of hundreds of milliseconds. Both amplify the significance of unexpected structure.
The 4.2× response to an accelerating gap is the computational equivalent of the mismatch negativity (MMN) — the event-related potential generated when a regular pattern is broken. MMN amplitude scales with the degree of violation. SR-eff scales with the rate of interval compression. Both are pre-conscious. Both measure the "weight" of the violation before the system knows what the violation is.
The critical gap — 8–12 steps — corresponds to the temporal window of integration in auditory cortex (≈3 seconds). Below this window, successive events are bound into a single Gestalt. Above it, they are processed as independent events. The break at Gap 8–12 maps to the boundary of the "specious present" — the duration within which the brain treats multiple events as one perceptual moment.
The three τ values — probe, tracker, anchor — correspond to the three classes of auditory nerve fibers by spontaneous rate. High-SR fibers are sensitive to small changes at low thresholds (probe). Medium-SR fibers cover the middle range (tracker). Low-SR fibers respond only to large changes at high thresholds (anchor). Three τ values are three vigilance levels, spread across the dynamic range of the auditory system.
G0 corresponds to the planum temporale — the region in the superior temporal gyrus that integrates multiple auditory streams into a coherent scene. When G0's coupling is too weak (w < 0.28), the streams remain independent — no binding. When G0 is too strong (w > 0.42), the streams collapse to identity — no separation. The optimal coupling window (w = 0.28–0.42) corresponds to the range in which PT integrates without erasing.
These correspondences do not validate the model. They indicate that the architecture's constraints — capacity, coupling, timescale — converge on the same numerical regimes that biology independently discovered. The mass of information is not a metaphor for neural activity. It is a quantity that the brain must compute, and the bridge computes it the same way.