Neural circuits operate at wildly different speeds simultaneously. Some neurons fire and reset in milliseconds; others integrate information over seconds. The standard explanation invokes molecular diversity — different ion channels, different membrane time constants, different receptor kinetics. Hardware determines the clock.

Zenari et al. show that wiring alone is sufficient. In a random recurrent network with heterogeneous degree (some neurons are hubs, some are peripheral) and partially symmetric weights, an emergent self-coupling appears whose strength scales with the neuron’s degree. Hub neurons, receiving many connections, effectively feed back to themselves more strongly. This self-coupling slows their response. Peripheral neurons, weakly self-coupled, respond fast.

The result is a timescale spectrum generated entirely from the graph structure — no molecular specialization required. They validate the theory against the MICrONS mouse cortex connectome, where measured timescales correlate with input connectivity as the model predicts.

The mechanism is specific: partial weight symmetry means each neuron’s activity feeds back through its neighbors and returns to it. If a neuron has many neighbors (high degree), this feedback loop is stronger, the effective time constant is longer. The topology doesn’t merely influence the timescale — it constitutes it. The degree IS the clock period.

This has a structural consequence the paper notes but doesn’t emphasize: the same architecture that produces slow hubs also enables multiplexed processing. Hub neurons, being slow integrators, naturally filter slow signal components from broadband input. The network doesn’t need separate fast and slow processors — it generates them from a single connectivity pattern.

The through-claim: the brain doesn’t build clocks and then wire them together. It wires neurons together and clocks appear. The temporal hierarchy is not a design feature but a topological side effect. Any network with degree heterogeneity and weight symmetry will produce it, whether it evolved to or not.