Embedding Operant Conditioning Functions in a Four-Terminal Memristor

We present an all-in-one operant conditioning (OC) implementation in a single four-terminal memristor, requiring no external circuits or logic. Unlike conventional two-terminal devices, our multi-terminal architecture enables true co-localization of learning functions, supporting both heterosynaptic plasticity and synaptic competition. The operant training process can be scheduled via controlled dopant-ion migration, precisely modulated by a bulk-switching mechanism of our device. This process is visualized via electrochromism, enhancing the interpretability of brain-inspired computation in our device. Our work offers a compact, higher-order functional hardware platform for neuromorphic computing, paving the way toward large-scale neuromorphic systems with embedded learning functionality.