Don’t you know about the wave? Everybody knows that the wave is the word.
We have a new paper out in Neuron called “A sensorimotor role for traveling waves in visual cortex” (Zanos et al. 2015) [pdf]. Synchronous neuronal activity often propagates parallel to the cortical surface. These traveling waves are a fascinating example of the complex dynamics exhibited by the brain during the performance of sensory, motor, and cognitive functions.
It’s striking that noisy, microscopic neurons can synchronize and exhibit complex emergent dynamics that can be picked up centimeters away from their source. There’s been a lot of interest in traveling waves, and there’s some excellent review articles on the subject, including Traveling Waves in Visual Cortex (Sato et al. 2012) and Propagating waves of activity in the neocortex: what they are, what they do (Wu et al. 2008).
Although traveling waves have been observed under many different conditions, it’s been difficult to ascribe a functional role to them. Waves could be epiphenomenal: in sensory cortex, they don’t generally encode sensory stimuli, and waves in the motor cortex don’t encode movement parameters. Because they’re a reflection of complex interactions in large ensembles of neurons which are scarcely visible at the level of single neurons, they are of great theoretical interest, but their relevance to behavior remains a matter of speculation.
Our paper shows a possible functional role for traveling waves. We report on traveling waves of local field potential (LFP) activity in the visual cortex (area V4) while subjects perform a standard eye movement task. Consistent with previous reports, we find traveling waves of LFP activity that do not seem to encode visual stimuli. However, these waves do encode eye movements.
Furthermore, neurons are strongly modulated by the phase by the local field potential. That implies that travelling waves of activity have the potential to coordinate the visually-evoked activity of a large chunk of cortex following a saccade.
As the waves sweep across the visual cortex, neurons become receptive to visual stimulation in a stereotyped sequence, from fovea to periphery, which favors the processing of stimuli that are immediately behaviorally relevant. This suggests that the function of traveling waves is to allow motor systems to control the dynamics of sensory processing, according to the behavioral demands of the animal.
I’m very happy seeing the paper published, especially after it spent 9 months in review over at Neuron. But hey, we got the cover, lovely designed by Kenneth Fitzgerald (ephemeralstates.com)!
Here’s a nice short writeup in Nature Reviews Neuroscience.
This post was mostly written by Dr. Theo Zanos. He claims no responsibility for getting Surfing Bird stuck in your head.