Talk Title: Intrinsic Traveling Waves and Visual Perception
Abstract: Perceptual sensitivity varies from moment to moment. One potential source of this variability is spontaneous fluctuations in neural sensitivity. Using newly developed techniques to characterize the moment-to-moment dynamics of noisy multi-electrode data, we find that spontaneous cortical activity is organized into traveling waves that traverse visual cortex several times per second. Recording in Area MT of the common marmoset, we find that these intrinsic traveling waves (iTWs) regulate both the gain of the stimulus-evoked spiking response and the monkey’s perceptual sensitivity. In monkeys trained to detect faint visual targets, the iTW state prior to target onset predicts the magnitude of target-evoked neural response and the likelihood that the monkey will detect the target. A large-scale spiking network model with conductance-based synapses recapitulates the properties of iTWs measured in vivo. The model shows that iTWs naturally emerge from the delays that occur as action potentials traverse unmyelinated horizontal fibers. The model predicts that iTWs are sparse, in the sense that only a small fraction of the neural population participates in any individual iTW. As a result, iTWs can occur without inducing correlated variability, which we have found, in separate experiments, can impair sensory discrimination. We thus refer to the model as the sparse-wave model of iTWs. The model also predicts that iTWs fall into feature-selective motifs whose selectivity stems from the horizontal fibers that preferentially connect similarly tuned feature domains. Consistent with this prediction, we find distinct clusters of iTW motifs. Some motifs modulate neural activity and perceptual sensitivity in a feature-selective manner. Taken together, these findings lead to the conclusion that traveling waves strongly modulate neural and perceptual sensitivity, in a feature-selective manner. These findings are consistent with studies of traveling waves in the motor system, suggesting that iTWs may represent a brain-wide computational principle.
Bio: Perception is a constructive process in which the brain integrates sensory information to build an internal representation of the external world. This occurs so quickly and effortlessly that we are unaware it has happened at all. The Reynolds lab wants to know how the brain achieves this remarkable feat. Vision is the most well-developed sensory system in humans, and arguably the most well-studied system in the brain. Since the neurons that make up its circuitry are found throughout the brain, vision acts as key to understanding the rest of the brain. Reynolds develops models of the neural mechanisms underlying vision, perception, and conscious awareness and leverages those models to derive specific hypotheses that can be tested using a variety of experimental techniques, including visual psychophysics, multi-channel neurophysiology, neuroanatomy and optogenetics.