Oscillatory Neural Synchronization Can Predict Intensity-Dependent Enhancement: A Bridge between Sensory Binding Theory and Multisensory Integration

Abstract

Although conceptually similar, sensory binding theory is based on oscillatory synchronization while multisensory integration is largely grounded on multisensory neurons. Many multisensory neurons show strong enhancement of response when both senses are stimulated, but the mechanism is obscure. This is a potential bridge between binding and sensory integration because oscillatory synchronization can enhance synchronized firing rates. Consider two independent excitatory neurons, each driven by a different sensory input. For synaptic coupling with a small delay, they can synchronize at a firing rate that lies well above either of their independent activities. We use this model to simulate behavior of a pair of “Enhanced Single Modality” (ESM) neurons like those in rattlesnake optic tectum, driven by stimulation in the eyes and infrared pits (Newman & Hartline, 1981). If these units both drive a common third cell, it will behave like an “Enhanced OR” neuron: it could be driven by either infrared or visible, but will fire at a higher rate when both of its inputs are present. Although the rattlesnake binds two visual modalities, the binding model behaves like superadditive multisensory units in Superior Colliculus (Stein & Meredith, 1993) and exhibits the intensity-dependent enhancement of Meredith & Stein's (1983) Principle of Inverse Effectiveness.