Calcium dynamics encode the magnitude of a graded memory underlying sensorimotor adaptation.

The role of Ca(2+) in the induction of neural correlates of memory has frequently been described in binary terms despite the fact that many forms of memory are graded in their strength and/or persistence. We find that Ca(2+) dynamics encode the magnitude of sensorimotor adaptation of the electromotor output in a weakly electric fish. The neural correlate of this memory is a synaptically induced Ca(2+)-dependent enhancement of intrinsic excitability of neurons responsible for setting the electromotor output. Changes in Ca(2+) during induction accurately predict the magnitude of this graded memory over a wide range of stimuli. Thus despite operating over a range from seconds to tens of minutes, the encoding of graded memory can be mediated by a relatively simple cellular mechanism.