Information flow as nerve impulses in neuronal circuits is regulated at synapses. The synapse is therefore a key element for information processing in the brain. Much attention has been given to fast synaptic transmission, which predominantly regulates impulse-to-impulse transmission. Slow synaptic transmission and modu lation, however, sometimes have been neglected in considering and attempting to understand brain function. Slow synaptic potentials and modulation occur with a considerable delay in response to the accumulation of synaptic and modulatory inputs. In these contexts, they are...