The superior colliculus, located in the midbrain, is commonly understood to assist animals in focusing on significant spatial cues, such as turning their eyes and head towards a sudden burst of light. However, recent findings from the University of Chicago have revealed that this brain region is also involved in intricate cognitive functions such as visual categorization and decision-making.
The superior colliculus, located in the midbrain, is commonly understood to assist animals in focusing on significant spatial cues, such as turning their eyes and head towards a sudden burst of light. However, recent findings from the University of Chicago have revealed that this brain region is also involved in intricate cognitive functions such as visual categorization and decision-making.
The recent study, published in Nature Neuroscience, assessed the information from brain cell activity patterns across numerous brain areas related to visual categorization. The scientists tracked activity in both the superior colliculus (SC) and a region of the posterior parietal cortex (PPC), which is vital for making categorical visual choices. To their astonishment, the researchers found that the SC’s activity was more closely associated with guiding the subjects’ category decisions than that of the PPC, indicating its participation in coordinating advanced cognitive functions typically attributed to the neocortex.
“It’s quite surprising to uncover cognitive signals in this region, traditionally linked to basic spatial orientation and reflexive actions,” mentioned David Freedman, PhD, Professor of Neurobiology and at the Neuroscience Institute at UChicago, and the study’s senior author. “This ancient brain structure appears to play a significant role in complex cognitive choices, even more so than the cortical areas we examined.”
An ancient brain region with surprising powers
All animals, from fish and reptiles to mammals, including primates and humans, must quickly differentiate and classify objects in their view. Is the moving object an obstacle or a danger? Is that creature rushing by a predator or prey?
The SC is an evolutionarily conserved brain area present in all vertebrates, even those lacking a more advanced neocortex. It supports the orientation of head and eye movements towards visual stimuli and was once thought to initiate reflexive motor functions by relaying inputs from higher brain regions. However, recent studies indicate its involvement in complicated tasks, such as selecting a point of orientation and focusing attention on stimuli at varying spatial locations.
Freedman and his team have long been exploring other cortical regions with strong anatomical ties to the SC. These neighboring areas are integral to flexible and demanding decision-making tasks, and the researchers aimed to determine if the SC also participated in abstract thinking. For their latest research, they trained monkeys to engage in a visual decision-making task where they viewed images on a computer screen and received fruit juice rewards for correctly categorizing these images by pressing a button at appropriate times.
As the subjects performed the task, the researchers recorded the activity of neurons in both the SC and the lateral intraparietal area (LIP), part of the PPC known to be involved in categorical decisions. The experimental setup designed their gaze to remain fixed while indicating choices through hand movements, effectively isolating the brain activity related to categorization rather than the typical eye or head movements that were previously associated with the SC’s functions.
They detected substantial activity within the SC that represented the categories of the images being viewed, showing that this activity was stronger than that seen in the PPC. They also conducted an experiment, administering a drug that temporarily numbed the SC during the task. This intervention did not impair most subjects’ motor or visual functions, yet it significantly hindered their ability to accurately categorize images until the numbness subsided.
“Our findings indicate the SC’s vital role in the task,” Freedman stated. “Even in scenarios where the animals don’t need to move their eyes or shift their attention, the superior colliculus is integral to these higher-level cognitive activities.”
That special “oomph” for problem-solving
Freedman remarked that discovering this activity in the SC is not only surprising but could also suggest why this region is recruited for complex tasks. Since it exists in all vertebrates, from primitive sharks to modern humans, it is among the earliest brain regions to evolve for processing visual inputs and facilitating related movements. However, this new research indicates it also plays a part in functions unrelated to spatial awareness. Might this imply that spatial processing imparts a unique advantage in problem-solving?
Freedman noted that the eye movements and hand gestures people make when recalling information or making decisions can be telling. For instance, when asked about last night’s dinner, one’s eyes may drift upwards, as if seeking the answer written on the ceiling. Or, when deliberating between two options, downward and upward hand movements may resemble a balance scale.
“This data may suggest that our spatial gestures and eye movements result from the spatial areas of the brain assisting in non-spatial cognitive functions,” commented first author Barbara Peysakhovich, PhD, a former graduate student in Freedman’s lab who is now a postdoctoral researcher at Harvard.
We have all experienced struggling to grasp information from a written source—like a detailed press release about a neuroscience study—only to find everything clicks when the same information is displayed visually.
“They say a picture can convey 1,000 words—even a simple spatial diagram can communicate so much more than one could articulate,” Freedman explained. “It’s as if our brains have established an intricate mental graph paper to solve both spatial and non-spatial challenges.”
The study titled, “Primate superior colliculus is causally engaged in abstract higher-order cognition,” was funded by the National Institutes of Health (grants R01EY019041, U19NS107609, 1F31MH124395, F30EY033648, F31 EY029155) and the Department of Defense Vannevar Bush Faculty Fellowship (N000141912001). Additional contributors include Barbara Peysakhovich, Ou Zhu, Stephanie M. Tetrick, Vinay Shirhatti, Alessandra A. Silva, Sihai Li, Matthew C. Rosen, and W. Jeffrey Johnston from UChicago, along with Guilhem Ibos from UChicago and Institut de Neurosciences de la Timone, Aix-Marseille Université, France.
