The reasoning: a forward model that predicts and corrects
Circuitry: mossy fibres (pontine, spinal, vestibular, reticular) → granule cells (most numerous neurons in the brain) → parallel fibres → Purkinje cells; climbing fibres (inferior olive, contralateral) → one Purkinje cell each (complex spike — error/teaching signal). Inhibitory interneurons: basket, stellate (→ Purkinje), Golgi (→ granule). Purkinje cells (GABA) are the sole cortical output → deep nuclei (excited by mossy/climbing collaterals) → thalamus, red nucleus, vestibular and reticular nuclei. Learning: cerebellar LTD at parallel fibre–Purkinje synapses when parallel and climbing fibres are coactive (VOR gain adaptation, eyeblink conditioning).