The rise and fall of memory in a model of synaptic integration.
Plasticity-inducing stimuli must typically be presented many times before synaptic plasticity is expressed, perhaps because induction signals gradually accumulate before overt strength changes occur. We consider memory dynamics in a mathematical model with synapses that integrate plasticity induction signals before expressing plasticity. We find that the memory trace initially rises before reaching a maximum and then falling. The memory signal dissociates into separate oblivescence and reminiscence components, with reminiscence initially dominating recall. In radical contrast, related but nonintegrative models exhibit only a highly problematic oblivescence. Synaptic integration mechanisms possess natural timescales, depending on the statistics of the induction signals. Together with neuromodulation, these timescales may therefore also begin to provide a natural account of the well-known spacing effect in the transition to late-phase plasticity. Finally, we propose experiments that could distinguish between integrative and nonintegrative synapses. Such experiments should further elucidate the synaptic signal processing mechanisms postulated by our model.
Department of Electronics and Computer Science, University of Southampton, Highfield, Southampton SO17 1BJ, UK. te@ecs.soton.ac.uk
Terry
T
Elliott
Konstantinos
K
Lagogiannis
D000818:Animals; D006801:Humans; D008568:Memory / Q000502:physiology*; D008959:Models, Neurological; D009473:Neuronal Plasticity; D011336:Probability; D013569:Synapses / Q000502:physiology*; D013997:Time Factors