According to most studies, 80 percent of what humans learn comes from vision. Of course, all that visual information goes to the brain, where it is processed, and a person does a specific action, such as picking up an object or moving from Point A to Point B. This makes the eyes the front part of the brain. How do the eyes and brain work together so that complex tasks can be done? Also, how does the brain react to visual clutter? Scientists are working to find the answers to these questions.
Research at the University of Chicago demonstrates that a brain region controlling eye movements, known as the superior colliculus, plays a role in higher cognitive functions like categorization and decision making.
The superior colliculus is a part of the brain that helps to position the movements of the head and eyes towards a visual stimuli. It was previously thought to trigger reflexive motor actions by relaying inputs from upstream brain regions. Recent studies have shown that the superior colliculus is involved in multipart tasks like picking an orientation point and paying attention to stimuli at different locations.
Researchers in this study wanted to see if the superior colliculus is also involved in abstract thinking. They trained monkeys to complete a visual decision-making task that involved viewing images on a computer screen. They received a reward for pushing a button at the right time to assign an image to the proper category.
Scientists measured the patterns of brain cell activity across regions involved in visual category decisions as the monkeys performed the task. Two of the areas of activity they measured were the superior colliculus and the lateral intraparietal area. The latter is part of the posterior parietal cortex, which involved in visual categorical decisions.
What they found was surprising. Scientists discovered that the superior colliculus was more involved in guiding category decisions than the posterior parietal cortex. They also injected a drug to numb the superior colliculus while the monkeys did the same task. This drug didn’t impair their motor and visual functions. What it did affect their ability to properly categorize the images.
This suggests that the superior colliculus helps to coordinate higher-order processes. One example of this is when someone has to weigh a decision between two choices. More often than not, the person would move his or her hands up and down like two sides of a balance scale.
Still, what happens when there is a lot visual information, i.e. clutter? For example, when you direct your gaze to someone across the table, there are other objects in the periphery, but those items aren’t what you are focusing on. How does this clutter affect visual processing? Researchers at Yale School of Medicine wanted to explore how the brain handles this phenomenon.
Previous research in this area showed that visual clutter affects the perception of a target at different levels, depending on where the clutter is located relative to the viewer’s focus. For example, if someone is asked to read the word “cat” out of the corner of their eye, the ‘t’ will have a greater effect than the ‘c’ in the person’s ability to identify the ‘a’ even though the ‘c’ and ‘t’ are equally spaced from the ‘a’. This is known as “visual crowding,” and it explains why people can’t read out of the corner of their eyes and why they struggle to identify items located among peripheral clutter.
In order to learn what happens in the brain when visual clutter is present, scientists trained macaque monkeys to fixate on the center of a screen while visual stimuli were presented both in and outside of their receptive fields. Scientists recorded the activity in the monkeys’ primary visual cortex while they performed the task. The primary visual cortex is the brain’s main entry point for visual information processing.
What they found is that the exact location of the clutter within the monkey’s visual field didn’t affect how much information passed between the neurons. It did affect how efficiently the information flowed. It is like a phone tree, where one person is asked to call another with a piece of information until each person in the group has the information. In visual perception, the clutter’s location didn’t change the phone tree’s structure but did affect how well the message was relayed.
What researchers discovered in this study is that there are subunits within the larger areas of the brain that are doing their own computations and they are relaying some of the information to the other subunits, but not all of it. Next, they will study how the clutter affects information processing between brain regions and how attention influences this system. For example, when a person is driving, they may look at the car in front while focusing their attention on a car in the next lane, trying to figure out if it is about to merge.
These two research projects show how involved the superior colliculus and the visual cortex are in processing images from the eyes. You could say there is more to visual processing than meets the eye.
Sources:
https://biologicalsciences.uchicago.edu/news/brain-superior-colliculus-spatial-thinking
https://news.yale.edu/2024/10/22/visual-clutter-alters-information-flow-brain