The superior colliculus is preserved during evolution, but differs in relative size between species. Credit: Adapted from Basso et al. 2021/Netherlands Institute for Neuroscience
Key points:
- Researchers have identified the role of the superior colliculus—an ancient visual system structure—in supporting mice’s ability to distinguish an object from the background.
- When the team turned off the superior colliculus with optogenetics, mice became worse at detecting the object.
- These findings suggest the superior colliculus is more crucial for vision than originally thought.
Humans are able to easily distinguish an object from the background, but the neural basis for this ability has yet to be characterized. Visual information travels from the retina to the visual cortex, but also to a structure called the superior colliculus. The superior colliculus is an ancient visual system common to all classes of vertebrates that has been preserved throughout evolution.
A new study, published in eLife, identifies the role of the superior colliculus in vision. Researchers trained mice to distinguish features from the background, which appeared on the left or right side of the image. The mice reported on which side the image appeared by licking either left or right.
Earlier work demonstrated that mice were able to complete the task without a functional visual cortex, meaning that there is a parallel pathway for visual object detection. Building off this foundation, the team used optogenetics to turn off the superior colliculus during the task. Without the superior colliculus, mice were worse at detecting the object.
Their analysis also revealed that information about the visual task was present in the superior colliculus. Importantly, at the moment a mouse made a mistake, the information was less present in the region suggesting that task performance was correlated with their superior colliculus measurements.
The team hopes to translate their findings into understanding superior colliculus function in humans. Humans have two parallel systems with a highly developed visual cortex, but the role of the superior colliculus is not entirely clear.
“It is known that the moment someone starts waving, the superior colliculus directs your gaze there,” explained Alexander Heimel, professor at The Netherlands Institute for Neuroscience. “It is also striking that those who are blind with a double lesion in the visual cortex do not see anything consciously but can often still navigate and avoid objects. Our research shows that the superior colliculus might be responsible for this and may therefore be doing more than we thought.”