Model Synapses with Frequency Potentiation Characteristics Can Cooperatively Enhance Hebbian Learning

Frequency potentiation, a short-term form of plasticity, is an enhancement in the amplitude of neuronal responses to each pulse in a train of stimulation pulses which occurs when the pulses are delivered within a certain frequency range. In the model, theta-frequency input from the subiculum via synapses with frequency potentiation characteristics cooperatively enhances Hebbian learning in pyriform cortex efferents to the entorhinal cortex, particularly when the inputs are phase-locked. This effect is further enhanced when inhibitory inter-neurons are added within the entorhinal layer. These simulations demonstrate a mechanism for frequency-dependent heterosynaptic modulation of Hebbian learning, and may be relevant to theta rhythm-related enhancements of plasticity in the hippocampal formation.