Sinusoidal Mapping Pattern Found in V2 of the Visual Cortex of Tree Shrews

Article: Cartography of the Visual Cortex: Charting a New Course for the Organization of Visual Space 
Source: Max Planck Florida Institute for Neuroscience
Published: October 26, 2021 

Sinusoidal transformation corresponding to the azimuth (left/right)
axis of the visual field and its mapping onto V2 of the visual cortex 

Similar to mapping the cartography of geographic space, neuroscientists who study vision map how our brain represents and makes sense of the world we see. One organizing property of the visual cortex is known as retinotopic mapping, wherein the spatial arrangement of neurons from the retina, via the optic nerve, is preserved in their spatial arrangement on the visual cortex. The prevailing theory is that the primary visual cortex (V1) follows a simple, linear pattern of roughly identical mapping of visual space represented on the cortex. However, hints of discrepancies in some studies prompted the researchers to wonder if additional patterns exist in the brain. Using a combination of single-cell functional imaging, computational modeling and connectivity studies, they uncovered such a pattern for the first time in area V2 of the tree shrew, an animal model that is amenable to research tools developed in mice (including both having a smooth brain), but is a closer relative to primates. Specifically, the researchers report that mapping of an object’s elevation, how high or low it is, followed closely with the smooth linear map found in V1, but mapping the azimuth, its horizontal position left or right of center, revealed a dramatically different sinusoidal, or oscillating pattern. One difference is that V1 is a "square" region while V2 has a thin, elongated shape. Using colored dyes to trace the connection between the two regions  confirmed that neuronal projections from V1 perfectly aligned with the sinusoidal map in V2. Furthermore, the researchers discovered that neuronal preference for certain visual features is tied directly to the retinotopic map of visual space, illustrating that the sensitivity that neurons have to particular features can vary depending on its location in visual space, that is, not only what but also where. Senior author of the study states, “Our findings open the door to a different way of thinking about how cortical circuits are organized, how they contribute to visual perception, and ultimately, behavior.”

My rating of this study: ⭐

Sedigh-Sarvestani M, Lee K, Jaepel J, et al. "A sinusoidal transformation of the visual field is the basis for periodic maps in area V2." Neuron.  109(24):4068-4079.e6. 15 December 2021. https://doi.org/10.1016/j.neuron.2021.09.053