On the origins of aperiodicities in sensory neuron entrainment

Abstract

Aperiodic entrainment to rhythmic sensory input was obtained with either a single neuron or an excitatory network model, without addition of a stochastic or "noisy" element. The entrainment properties of primary sensory neurons were well captured by the dynamics of the Hodgkin-Huxley ordinary differential equations with a quiescent resting state or threshold for spike output. The frequency-amplitude parameter space was compressed and aperiodic regimes were small in comparison to those of periodically activated pacemaker like neurons. Transitions between phase-locked and aperiodic entrainment patterns were predictable and determined by the equation dynamics; supporting the contention that some aperiodicities observed ${in}$ ${situ}$ arise from the inherent membrane properties of neurons. When the rhythmically activated neuron was embedded in an excitatory network of Hodgkin-Huxley neurons with heterogeneous synaptic delays, aperiodic entrainment patterns were more frequently encountered and these were associated with asynchronous output from the network. Embedding the rhythmically activated neuron in a network with synaptic delays, greatly reduced the range of entrained spike frequencies. Other biological mechanisms of modifying the entrainment properties and promoting aperiodic entrainment are discussed.