Stripes and pinwheels, the fashion for vision
In a nutshell: Cells in the visual cortex are organised in a “pinwheel” formation that is altered by visual experience during development — including exposure to stripes.View Paper Abstract
What we see during our early life has a strong effect on the way that our brain’s visual areas are organised.
The “primary visual cortex” is a key area of the brain that receives information from the eyes. Brain cells here respond differently depending on the orientation of stripes, or edges, that we’re looking at — some respond to vertical edges, as on a light post, some to slanted edges, as on a roof, and so on. These different orientations get organised in the visual cortex forming a map that follows a pinwheel formation (indicated by the stars in the figure below).
In normal conditions approximately equal numbers of brain cells are devoted to each orientation, as in the figure above. But if brought up in a stripy world with only one orientation of stripes, say vertical, a greater number of brain cells would be devoted to that orientation (in the image above, it would result in a lot more yellow on the map, compared to other colours).
In this research by authors including Brain Function CoE chief investigator Michael Ibbotson, associate investigator Geoff Goodhill, and affiliate research fellow Shaun Cloherty, a new method was used to study changes in the pinwheel structure of primary visual cortex. This method was able to pinpoint changes in other aspects of the pinwheel map (besides the proportion of cells devoted to each orientation) resulting from seeing only one orientation in early life.
In addition to responding differently to the orientation of stripes, brain cells in primary visual cortex can be categorised depending on whether they respond mostly to input from the right or the left eye, or a combination of both. The primary visual cortex therefore also contains an “eye preference” map.
In a follow up study, the team used similar techniques to assess the effect of visual experience on both the pinwheel map (shown above) and the eye preference map. They found that changes in both maps were predictably related.
These studies reveal the extent to which brain organisation is determined by experience in early life and advance our understanding of disorders where the visual input is disrupted early in life, as occurs during misalignment of the two eyes (strabismus).
The team will study the changes in these maps as a result of seeing through bionic eyes or other novel visual environments in early life. This will inform the design of better bionic eyes in the future.
Hughes, N. J., Hunt, J. J., Cloherty, S. L., Ibbotson, M. R., Sengpiel, F., & Goodhill, G. J. (2014). Stripe-rearing changes multiple aspects of the structure of primary visual cortex. NeuroImage, 95, 305-319.
Cloherty, SL, Hughes, NJ, Hietanen, MA, Bhagavatula, P, Goodhill, GJ, Ibbotson, MR (2016). Sensory experience modifies feature map relationships in visual cortex. eLife Jun 16;5: e13911.
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