The visual cortex, a critical area responsible for interpreting visual information, plays a key role in shaping our world perception. Visual processing in the cortex is often considered a simple, linear process. However, recent research shows that the cortex operates as a complex network with finely tuned connections between different regions, supporting specialized visual functions across distinct brain areas.
Researchers at Neuro-Electronics Research Flanders (NERF), led by Prof. Vincent Bonin, have published two groundbreaking studies that reveal new insights into how visual information is processed and distributed across the brain. These studies challenge traditional ideas about the simplicity of visual processing, highlighting instead the complexity and flexibility of how the brain interprets sensory input.
Targeting vs. Broadcasting Visual Information
The first study sheds light on the intricate pathways governing visual signal transmission throughout the brain. Led by postdoctoral researcher Xu Han, the research team employed advanced imaging and circuit-tracing techniques in mice to map how visual information moves across interconnected brain regions. The study identified two main types of visual signal transmission: targeted and broadcasted.
Han explained that certain neurons, located in the pulvinar and specific layers of the cortex, are finely tuned to their targets, which suggests their role in constructing detailed and focused visual representations. In contrast, other neurons—particularly those in deeper brain layers—broadcast visual information more broadly, potentially coordinating activity across multiple brain regions.
“These findings challenge the conventional view of visual processing as a step-by-step flow,” Han said. “Instead, we discovered that visual information is part of a highly dynamic and adaptable network, with pathways that can switch between selective targeting and broad broadcasting.”
Quiet vs. Aroused States: The Role of the Thalamus
In a second study, Bonin and Dr. Karolina Socha (now at the University of California, LA) explored the role of the thalamus, a central relay station for sensory signals, in adjusting visual processing depending on the brain’s behavioral state. The study found that during quiet wakefulness, the thalamus amplifies responses to back-to-front motion, absent during brain anesthesia or heightened arousal.
Using imaging techniques to observe the activity of neurons in awake mice, the team discovered that the modulation of motion processing was linked to changes in pupil size, a common marker of arousal.
“When the pupils dilate, we see a stronger response to the back-to-front motion,” Bonin said. “This suggests that the thalamus doesn’t just relay sensory input but also integrates the brain’s behavioral context to prioritize specific visual stimuli.”
These findings indicate that the thalamus plays a crucial role in shaping visual perception dynamically, adjusting how the brain processes motion based on the individual’s state of alertness.
Moving Toward a Functional-Anatomical Map of Vision
Together, these studies provide a significant step toward creating a “functional-anatomical map” of the brain’s visual system. By better understanding how different regions of the brain process visual information in various contexts, researchers can begin to predict and manipulate visual perception.
“These findings open up new possibilities for understanding how the brain’s visual pathways operate and how we might intervene to modulate perception,” said Bonin.
As neuroscientists continue to map out the complexities of visual processing, these studies promise to inform future research and potentially lead to new treatments for sensory processing and perception disorders. The groundbreaking work at NERF brings us closer to understanding how the brain integrates visual input in ways that are far more sophisticated and adaptable than previously thought.
Journal Reference:
- Han X, Bonin V. Higher-order cortical and thalamic pathways shape visual processing streams in the mouse cortex. Current Biology, 2024. DOI: 10.1016/j.cub.2024.10.048
- Socha KZ, Couto J, Whiteway MR, Hosseinjany S, Butts DA, Bonin V. Behavioral modulations can alter the visual tuning of neurons in the mouse thalamocortical pathway. Cell Reports. DOI: 10.1016/j.celrep.2024.114947