by Recent research conducted by scientists at the Netherlands Institute for Neuroscience has revealed that the superior colliculus, an ancient brain area, plays a more significant role in vision than previously thought. When we observe something, our brain effortlessly distinguishes objects from the background. Although this may seem instinctive, the process behind it is quite complex. While it has long been understood that the visual cortex is involved in this process, there are species in which this area is less developed or nonexistent. So, how do these animals perceive their surroundings when faced with approaching prey or predators in a cluttered environment? Could there be another participant in this visual processing?
Visual information is transmitted from our retina to both the visual cortex and a brain structure known as the superior colliculus. The superior colliculus is part of the ancient visual system found in all vertebrates, ranging from fish and amphibians to reptiles, birds, and mammals. Interestingly, this structure has remained conserved over evolution, but its size varies significantly between different organisms. For instance, the superior colliculus is comparatively large in fish and birds, whereas it resembles a minute pea nestled within gray matter in humans. In order to understand the precise role of the superior colliculus, a team of researchers led by Leonie Cazemier from the groups of Alexander Heimel and Pieter Roelfsema conducted experiments on mice to determine their ability to distinguish objects from the background.
Mice were selected as an ideal model for the study due to the similarities between their brain and that of humans. Like humans, mice possess two parallel pathways in their brain – the visual cortex and the superior colliculus. During the study, the mice were trained to differentiate between figures and their background, which were presented on either the left or right side of the image. By licking either the left or right side, the mice indicated the side on which the image appeared.
Alexander Heimel explains, “Previous research has already indicated that a mouse can successfully complete this task even when its visual cortex is switched off, suggesting the existence of a parallel pathway for visual object detection. In this study, we utilized optogenetics to deactivate the superior colliculus and examine the effect it had.”
In contrast to the earlier study, the mice displayed a reduced ability to detect objects when the superior colliculus was switched off, indicating the vital role of this brain area in the process. The team’s measurements also demonstrated that the superior colliculus contains information regarding the visual task at hand, and the presence of this information decreases when the mouse makes an error. Therefore, the performance of the mice in the task aligns with the data collected.
While the exact workings of the superior colliculus in humans are not entirely understood, it is known that humans possess two parallel visual systems. However, the visual cortex in humans is significantly more developed, suggesting that the role of the superior colliculus may be less prominent. Heimel adds, “It is worth noting that when someone starts waving at you, the superior colliculus directs your gaze towards that gesture.”
Furthermore, it is intriguing to observe that individuals who are blind due to double lesions in the visual cortex often retain the ability to navigate and avoid objects unconsciously. The research indicates that the superior colliculus may be responsible for this phenomenon, suggesting that its function extends beyond that which was previously understood.
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- Source: Coherent Market Insights, Public sources, Desk research
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