In a nutshell: The distribution of highly active cells in the brain’s visual processing area reveals similarities between humans and other primates.

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Humans process visual information in a part of the brain called the primary visual cortex, or V1. To investigate the organization of V1, researchers have studied the distribution of cytochrome c oxidase (CytOx). This metabolic enzyme marks highly active groups of cells in the brain, which are known as patches, blobs, or spots.

The distribution of CytOx patches had been studied in several primate species, and their presence in humans had also been reported. However, no one had looked closely at how these patches were distributed in the human brain.

Working with colleagues in Brazil, Brain Function CoE chief investigator Marcello Rosa mapped the CytOx patches in humans for the first time. The researchers manually unfolded brains from human organ donors, cut them into sections, and stained them so that the entire pattern of patches could be seen.

They found that CytOx patches were distributed throughout V1, with little variation in patch size or density. The patches in human brains were bigger and set more widely apart from each other than in other primate species. However, because the human brain is larger, the proportion of V1 dedicated to patches was roughly the same.

Based on these results, the researchers believe that the same developmental process gives rise to the distribution of these patches in different species.

Next steps:
The researchers are not planning any next steps, as this was a one-off study made possible by a unique opportunity to examine these brains. However, the results of the study have raised topics for others to pursue. For example, the researchers found that the size of V1 – and thus the number of patches – varied between individuals. One of the next questions worth investigating is whether this variation translates into differences in perception.

Marcondes, M. , Rosa, M. G., Fiorani, M. , Lima, B. and Gattass, R. (2018), Distribution of cytochrome oxidase‐rich patches in human primary visual cortex. J Comp Neurol. Accepted Author Manuscript. doi:10.1002/cne.24435

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