On Hebbian-like adaptation in heart muscle: a proposal for 'cardiac memory'

Studies on the effects of external pacing of heart suggest that the organ, like the nervous system, possesses the properties of 'memory' and adaptation. Changes induced in cardiac activation patterns persist long after the agent that induced those changes itself is removed. After the effects of stimulation have disappeared, response to the stimulus applied for a second time is much greater than the earlier response. Motivated by such results, this paper further explores the possibility of a 'cardiac memory'. In particular, we point out that communication via gap junctions in cardiac tissue is similar to synaptic conductance in nervous tissue and demonstrate, with the aid of a mathematical model, that cardiac tissue can exhibit memory-like behavior if gap-junctional conductances are allowed to adapt according to a Hebbian-like mechanism.