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Perception Control: How the Brain’s "Colliculum Superior" Helps to Thread a Needle

Researchers at the Hertie Institute in Tübingen attribute greater function to the area in the brainstem than previously assumed

We only see about one to two percent of our environment really sharp, which is the image section that falls into the visual pit (lat.: Fovea Centralis) of the retina. In order to perform tricky actions, such as threading a needle, we have to make very accurate tiny eye movements. This is the only way can we see the whole process in high resolution – and avoid piercing our finger. But how does our brain control these movements? Neuroscientists led by Professor Ziad M. Hafed at the Hertie Institute for Clinical Brain Research and the University of Tübingen have investigated this question. According to the results, the so-called Superior Colliculum in the brain stem plays a leading role, the researchers report in the current issue of the journal Current Biology. The findings help to better understand the visual system and its disorders.

"We knew  that this region could control precise eye movements," says Hafed, head of the study. "What was unclear was: Does this also apply to eye movements that depend on a high degree of visual acuity, such as those we need when threading a needle? In order to answer this question, Hafed and his team measured the activity of nerve cells in the Colliculum Superior of the rhesus monkey brain. The animals had to react to high-resolution images with small and precise eye movements. The scientists then compared the pattern of nerve cell activity with the anatomical structure of the Colliculum Superior.

"We observed that about a quarter to a third of all nerve cells in the Colliculum Superior are responsible for processing information from the visual pit," said Hafed. "In other words, 30 to 40 percent of the nerve cells in the Colliculum Superior process one to two percent of the visual image. This drastically increases the number of nerve cells involved in the processing of high-resolution image areas. Hafed's conclusion: "This makes the Colliculum Superior perfectly suited to direct precise eye movements." This represents a turning point for visual research: So far, it has been assumed that the Colliculum Superior is only necessary to move the eyes away from the area of sharpest vision.

The decoding of visual processing in deeper brain structures also helps brain researchers to better understand certain visual disorders. In blind vision, for example, the primary visual cerebral cortex is damaged by a stroke. These patients are blind, but can react unconsciously to some visual stimuli and, for example, catch an approaching ball or avoid it. "Parallel visual pathways, such as those running over the upper hill, lend this area its residual capacity," explains Hafed. "Knowledge about these paths can be used in the future to specifically stimulate them and thus alleviate specific visual problems.

Wissenschaftliche Ansprechpartner

Prof. Dr. Ziad M. Hafed
Universität Tübingen
Hertie-Institut für klinische Hirnforschung
Abteilung Kognitive Neurologie
Telefon +49 7071 29-88819
ziad.m.hafed[at]cin.uni-tuebingen.de


Originalpublikation

Chen et al. (2019): The Foveal Visual Representation of The Primate Superior Culliculus, Current Biology, 29, 1-11.
doi.org/10.1016/j.cub.2019.05.040


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