Neuroscientists are unraveling the mysteries of human vision by studying the remarkable eyesight of mice. Despite the nursery rhyme's claim, mice possess surprisingly sensitive eyesight, allowing researchers to uncover unprecedented details about how individual brain cells communicate and work together to create a mental picture of the visual world. This research is crucial for understanding how the visual systems of people function.
Neuroscientists, including the author, study how brain cells drive visual perception and how these processes can fail in conditions like autism. The cerebral cortex, a large portion of the brain that processes visual information, is the focus of their "listening" to the electrical activity of neurons. Injuries to this area can lead to blindness and other visual deficits, even when the eyes are unharmed.
Understanding the activity of individual neurons and their collaboration during information processing is a long-standing goal of neuroscience. New technologies aimed at the mouse visual system have brought researchers closer to achieving this goal, and these findings will enhance our understanding of human visual systems.
The visual cortex neurons in mice, similar to those in humans, monkeys, cats, and ferrets, require specific visual features to trigger activity and are highly selective in alert and awake conditions. Researchers have discovered that mice are particularly sensitive to visual stimuli directly in front of them, despite their outward-facing eyes. This finding suggests a shared specialization in the visual system between mice and humans, highlighting the frontal visual field.
For mice, focusing on what's straight ahead may aid in detecting shadows or edges in front of them, enhancing their responsiveness to potential threats or prey. The center of view is crucial in aging and many visual diseases in people, and since mice rely heavily on this part of the visual field, they are valuable models for studying and treating visual impairment.
Advances in technology have accelerated scientific understanding of vision and the brain. Researchers can now record the activity of thousands of neurons simultaneously and pair this data with real-time video of a mouse's behavior. This method reveals how behavior interacts with brain activity, providing a more comprehensive understanding of visual processing.
For example, the author's lab found that the speed of visual signaling is highly dependent on the physical environment's possible actions. Mice's visual signals travel faster to the cortex when they can run on a disc compared to when they view the same images in a stationary tube, even when still in both conditions. This highlights the influence of environmental factors on visual processing.
To connect electrical activity to visual perception, researchers employ innovative methods. Mice can learn to indicate their visual perceptions through behavior, such as releasing a lever when a pattern brightens or tilts, rotating a Lego wheel to move a visual stimulus, or stopping on a wheel or licking a water spout when the visual scene changes. These behaviors provide valuable insights into how mice interpret and respond to visual stimuli.
Mice also use visual cues to focus their visual processing on specific parts of the visual field, allowing for quicker and more accurate responses to stimuli in those regions. However, this precision comes at a cost; if an image appears unexpectedly in a different location, mice may be slower and less likely to respond. These findings parallel studies on spatial attention in humans.
The author's lab has also discovered that inhibitory neurons strongly control the strength of visual signals. Activating certain inhibitory neurons in the visual cortex can effectively "erase" a mouse's perception of an image. This research reveals the intricate relationship between perception and action in the brain, showing that visual responses vary depending on behavioral circumstances.
To further understand how different factors shape cortical neurons' rapid responses to visual images, advancements in computational tools and technologies are needed to separate behavioral signals from visual ones and isolate the communication of specific brain cell types. The surge in research on the mouse visual system has led to a significant increase in data collection and public sharing among scientists, fostering collaboration and accelerating discoveries.
Technological advancements in data collection and sharing can enhance the efficiency and transparency of scientific discovery, aligning with the major data informatics goal of neuroscience in the future. The author believes that the mouse's leading role in understanding the human brain's mysteries is just the beginning, and further discoveries await.
