The cerebellar long-term-depression rule Ito (1970) proposed — extending Marr's (1969) cerebellar model but flipping its synaptic sign from potentiation to depression — was confirmed by Ito's own lab in 1982, a shorter, same-scientist variant of the theory-precedes-anatomy shape

David Marr (1969) and, following him, Masao Ito (1970) proposed computational models of cerebellar motor learning resting on activity-dependent plasticity at Purkinje-cell synapses. The two differed on the sign of that plasticity, however: Marr assumed synaptic potentiation, whereas the long-term-depression (LTD) rule confirmed here was specifically Ito's — the 2020 review lists "potentiation versus depression of synaptic plasticity" among the defining differences between the models. That retrospective states: "Fifty years ago, David Marr (1969), Masao Ito (1970), and James Albus (1971) proposed computational models of cerebellar learning functions, based on neural circuits of the cerebellum," and specifies Ito's rule: "Ito proposed that climbing-fiber inputs represent error signals and that parallel-fiber-to-Purkinje-cell synapses undergo long-term depression (LTD) when both parallel-fiber and climbing-fiber inputs are activated." At proposal this synaptic rule was theoretical — the predicted depression had not been recorded.

The experimental demonstration came from Ito's own laboratory twelve years later: "Ito and others experimentally demonstrated LTD (Ito et al., 1982; Ito and Kano, 1982...)." The Ito & Kano 1982 paper (Neurosci. Lett. 33(3):253–258) showed that conjunctive stimulation of parallel and climbing fibers produced lasting depression of parallel-fiber–Purkinje-cell transmission.

This is a fourth instance of the shape the vault tracks in claim-neural-circuit-theories-wait-decades-for-anatomical-confirmation, but it differs from the other three in two ways worth holding onto. The gap is much shorter — ~12 years, versus ~24 for claim-drosophila-connectome-confirmed-zhang-1996-ring-attractor, ~42 for claim-jeffress-1948-place-theory-waited-decades-for-anatomical-confirmation, and ~46 for claim-barlow-levick-1965-direction-selectivity-confirmed-briggman-2011. And the confirming experiment came from the same scientist who proposed the theory, not a later independent group. Both facts complicate any claim that the pattern runs on a fixed timescale or on independent confirmation — see claim-circuit-theory-vindication-lacks-denominator-survivorship-not-ruled-out.