Ancient Brain Structures Shape Visual Processing and Attention

New research highlights the role of the superior colliculus, a primitive brain region, in processing visual information independently of the cortex. This finding, published in PLOS Biology on November 8, 2025, challenges the long-held belief that complex visual computations are solely the domain of the brain’s advanced outer layer. The study emphasizes how neural circuits, which have existed for over 500 million years, continue to influence attention and perception.

The superior colliculus functions as an essential radar system within the brain, processing direct signals from the retina before they reach the cortex. This region plays a crucial role in identifying which elements of the visual scene warrant attention. When a movement or sudden change occurs, the superior colliculus responds first, directing the eyes toward new stimuli.

To investigate this process, researchers employed advanced methodologies, including patterned optogenetics and electrophysiology. By activating specific retinal pathways and analyzing responses in brain slices of mice, they discovered that the superior colliculus can modulate visual signals. It suppresses central visual inputs when surrounding areas become active, a fundamental aspect of center-surround processing, which is vital for detecting edges and enhancing contrasts in the environment.

Andreas Kardamakis, head of the Neural Circuits in Vision for Action Laboratory at the Institute for Neurosciences (IN), a collaboration of the Spanish National Research Council (CSIC) and the Miguel Hernández University of Elche, explained, “For decades it was thought that these computations were exclusive to the visual cortex, but we have shown that the superior colliculus can also perform them autonomously.” This revelation indicates that the mechanisms for analyzing visual stimuli and determining what deserves attention are not recent developments but rather ancient features of the brain.

Insights into Visual Processing and Attention

The superior colliculus is likened to a built-in radar, quickly assessing visual information and filtering it according to its significance. This rapid processing capability allows the brain to prioritize what is most relevant in a dynamic environment. The research team’s findings indicate that attention mechanisms are deeply rooted in the brain’s ancient architecture, predating the evolution of more complex cortical areas.

Kuisong Song, co-first author of the study, stated, “We have seen that the superior colliculus not only transmits visual information but also processes and filters it actively.” This ability to select and prioritize visual information stems from circuits that have been preserved throughout vertebrate evolution. The study suggests that these fundamental computations play a critical role in survival, facilitating the detection of threats and the navigation of obstacles.

Kardamakis further noted the implications of understanding these ancient structures for modern neurological disorders. He pointed out that conditions such as attention deficit disorder or sensory hypersensitivity may arise from disruptions in the balance between cortical communication and these fundamental circuits.

Collaborative Research Efforts

The research represents a significant collaboration involving the Karolinska Institutet, KTH Royal Institute of Technology in Sweden, and the Massachusetts Institute of Technology (MIT) in the USA. This international effort also included contributions from Teresa Femenía of IN CSIC-UMH, who played a vital role in developing the experimental components of the study.

Building on these findings, Kardamakis and Giovanni Usseglio contributed a chapter to the upcoming Evolution of Nervous Systems series, edited by JH Kass. Their work compares subcortical visual systems across various species, highlighting that structures analogous to the superior colliculus are present in fish, amphibians, reptiles, birds, and mammals. These shared features underscore the evolutionary significance of these ancient brain systems in integrating sensory and motor information to guide attention and gaze.

The research received support from several organizations, including Spain’s State Research Agency, the Severo Ochoa Programme for Centres of Excellence, and the Swedish Research Council. This backing emphasizes the importance of understanding how these ancient neural circuits function, especially in an era characterized by overwhelming visual stimuli.

As researchers continue to explore the superior colliculus’s role in guiding attention and managing distractions, the insights gained will contribute to a deeper understanding of visual processing and its implications for cognitive function in contemporary life.