When you go for a walk, how does your brain know the difference between a parked car and a moving car? This seemingly simple distinction is challenging because eye movements, such as the ones we make when watching a car pass by, make even stationary objects move across the retina—motion that has long been thought of as visual “noise” the brain must subtract out.

Now, researchers at the have discovered that instead of being meaningless interference, the visual motion of an image caused by eye movements helps us understand the world. The specific patterns of visual motion created by eye movements are useful to the brain for figuring out how objects move and where they are located in 3D space.

“The conventional idea has been that the brain needs to somehow discount, or subtract off, the image motion that is produced by eye movements, as this motion has been thought to be a nuisance,” says , George Eastman Professor; professor in the Departments of , , and and the ; member of the ; and lead author of the new research, published in . “But we found that the visual motion produced by our eye movements is not just a nuisance variable to be subtracted off; rather, our brains analyze these global patterns of image motion and use this to infer how our eyes have moved relative to the world.”

The research team developed a new theoretical framework to predict how humans should perceive an object’s motion and depth during different types of eye movements. They tested these predictions by having participants view 3D virtual environments in which a target object moved through a scene while the participants kept their eyes focused on a single point. In one task, participants estimated the direction the target object was moving by using a dial to match its motion with a second object. In a second task that measured depth perception, participants reported whether the target object appeared nearer or farther than the fixation spot. Across both tasks, the researchers found consistent, predictable patterns of errors that closely matched the theoretical predictions.

“We show that the brain considers many pieces of information to understand the 3D structure of the world through vision, including the patterns of image motion caused by eye movements,” says DeAngelis. “Contrary to conventional ideas, the brain doesn’t ignore or suppress image motion produced by eye movement. Instead, it uses this image motion to understand a scene and accurately estimate an object’s motion and depth.”

This research has important implications for understanding visual perception, which informs how the brain interprets everyday activities like reading and recognizing faces. But it could also provide insight and new applications for visual technologies, such as virtual reality headsets.

“VR headsets don’t factor in how the eyes are moving relative to the scene when they compute the images to show to each eye. There may be a stark mismatch between the image motion that is shown to the observer in VR and what the brain is expecting to receive based on the eye movements that the observer is making,” says DeAngelis. This could be what causes some people to experience motion sickness while using a VR headset.

Additional authors include first author Zhe-Xin Xu ’25 (PhD), a former graduate student in the DeAngelis lab who is now a postdoctoral fellow at Harvard University; Jiayi Pang ’25 (BS), who is now a graduate student at Brown University; and Akiyuki Anzai, a research associate at the University of Rochester. The National Institutes of Health supported this research.

Once, twice, three times a head hit.

How many are too many? How could a traumatic brain injury be diagnosed with minimal or no outward symptoms? What’s the lasting impact of a mild traumatic brain injury or concussion?

According to the Centers for Disease Control, suffer traumatic brain injuries (TBIs) each year. While most are caused by accidents or falls, many are the direct result of sports injuries. In the last several years, how the brain responds to a concussive head hit and to repeated sub-concussive hits, particularly during a sporting event, has shifted. Researchers at the �����Թ� have been at the forefront of concussion and traumatic brain injury discoveries, resulting in updated rules and protocols in sports like soccer and football.

, a professor of emergency medicine and of neurology at Rochester, has dedicated his career to improving the detection and treatment of traumatic brain injuries—particularly those on the lower end of the severity spectrum, which are more likely to be overlooked. That work has not only benefited the scientific community, but also the people most likely to experience the effects of concussions and other head injuries.

Case in point: Nearly 10 years ago, Bazarian and , a professor of public health sciences at the University, recommended that for high school and college-aged students after a concussion. Their research findings showed that academic problems were more frequent at one week after concussions compared to the students with other types of sports injuries. Today, the CDC’s provides schools with guidelines on how to work with students after a concussion.

Bazarian continues to work with student-athletes, this time as the leader of a (DOD) to detect subtle neurologic dysfunction after repetitive head hits—many of which don’t result in obviously outward injury—and to develop treatments to mitigate this dysfunction. He is also a site investigator for , this one supported by the National Institute of Neurological Disorders and Stroke (NINDS), to study the effects of concussions on children, including how this injury impacts the developing brain of youths and adolescents.

And so, study by study, researchers like Bazarian and his colleagues at the University are bringing clarity to the big questions of how trauma and injuries—one-off and repeated—can affect the human brain and overall health and well-being across the lifespan.

The hidden dangers of repetitive head hits

Each hit to the head can compound the one before—sometimes without symptoms to warn of a growing injury. When a person’s occupation or activity exposes them to repeated head hits—like members of the military or athletes—they can experience subtle declines in neurologic function, such as balance, eye movements, and rapid decision making.

These declines in neurological function are not currently detectable by a doctor but can nonetheless impair athletic or military performance and increase the risk of sustaining other injuries. In the long run, such repeated head hits may contribute to the development of serious neurodegenerative diseases or disorders. However, unlike concussion, there is no current standard of care to track, prevent, or treat these hits.

Bazarian is at the front lines of efforts to address that gap.

This fall, he’s recruiting football players at the University of Rochester, University at Buffalo, Indiana University, and the Citadel military college. The aim? To track the subtle changes that occur because of sports-related head hits in student-athletes in order to better understand the early indicators of repetitive injuries and what the response protocol should be. The researchers hope to add female soccer players to the research project next year. This would provide critical insight into the impact these head hits have on the female brain, since previous work has only included male subjects.

“We’re trying to determine if we can detect and mitigate the acute effects of exposure to repetitive head hits on the brain,” says Bazarian. “Do these hits alter neurologic functions in a way we can pick up using objective measures suitable for use in low-resource environments like battlefields and athletic fields? If so, what can be done to return neurologic function back to baseline as quickly as possible?”

Bazarian received the aforementioned grant from the DOD’s Army Medical Research Acquisition Activity (ARMY MRAA), a congressionally directed medical research program, to better understand these repetitive hits to the head, with goals to find ways to detect, prevent injury, and treat them.

“In a sense, we are borrowing from the field of occupational medicine by applying a brain health monitoring approach to individuals exposed to an environmental factor, in this case repetitive head hits, that increases their risk for neurologic injury,” he says. “Our hope is that one day this approach will lower the long-term risk of neurodegeneration in those exposed.”

Blood tests for brain health

Recently, Bazarian joined nearly 100 clinicians and researchers from around the world to propose the first revision to how TBIs are classified since 1974, when the current diagnostic method known as the was established.

The new method of characterizing TBI replaces the standard categories of “mild,” “moderate,” and “severe,” with descriptors in four domains: Clinical, Biomarkers, Imaging, and patient Modifiers (CBI-M). This new characterization approach was recently described in and .

Decades of research in Bazarian’s lab has produced in how the blood can inform brain health. Specifically, the researchers have identified a technique that measures three brain proteins that can appear in the blood within hours of a brain-injuring head hit—glial fibrillary acidic protein (GFAP), ubiquitin carboxy-terminal hydrolase L1 (UCH-L1), and S100 calcium-binding protein B (S100B).

The levels of these proteins can provide unique insight into the magnitude of brain injury that was not previously available to clinicians. High levels can predict six-month mortality and incomplete recovery, while low levels indicate an extremely low risk of a brain bleed on CT scan, which would inform whether a CT scan is necessary.

In 2018, the Food and Drug Administration approved a blood test called the Banyan Brain Trauma Indicator. The University’s Medical Center was a site for , with Bazarian as the lead author of a related study that appeared in the journal The Lancet Neurology. That work proved influential as part of the FDA’s decision to approve the first blood-based biomarkers of traumatic brain injury in the United States.

Recruiting subjects for this research, Bazarian and his fellow researchers work with �����Թ� student-athletes and patients in the Strong Memorial Hospital Emergency Department. They also collaborate with , an associate professor of emergency medicine at Rochester, to follow these subjects through their recovery. Beyond the initial diagnosis, a person is generally monitored based on what symptoms they have–subjective markers like patient-reported symptoms such as headaches, nausea, or light sensitivity.

“Not knowing what is happening in the brain can affect an individual’s quality of life in the long term,” Merchant-Borna says. “Concussion recovery can be difficult to track, and symptoms often dissipate before the brain is fully healed.”

The �����Թ�’s concussion research is more than a series of studies—it’s a sustained effort to safeguard brain health across the lifespan. In pushing the boundaries of what medicine can know and do, Rochester is leading the way toward a future where the complex dangers of head injuries are better understood, better treated, and ultimately, better prevented.

�����Թ� researchers have demonstrated a noninvasive method using BL-OG, or bioluminescent optogenetics, that harnesses light to activate neurons in the brain. The ability to regulate brain activation could transform invasive procedures such as deep brain stimulation that are used to treat Parkinson’s disease and other neurological conditions.

The advantage of this new technique is that it can create brain activation without the use of an implanted device in the brain to deliver physical light, according to Manuel Gomez-Ramirez, an assistant professor of and with the University’s , and the senior author of the , which appears in the journal NeuroImage.

“BL-OG is an ideal method for noninvasively teasing apart neural circuits in the brain,” says Emily Murphy, the first author of the study and manager of the Haptics Lab, led by Gomez-Ramirez. “There are still so many things to learn about the structure and function of distinct brain areas and neuronal cell types that will help us understand how healthy brains function.”

How to turn on a light—without a switch

To turn on light in the brain, researchers need a few tools. The first one is optogenetics, an established research technique that uses light to activate or inactivate cells in the brain. The next tool is bioluminescence, the same chemical reaction that gives a firefly its glow, which provides the light optogenetics needs to work.

Combining these tools creates the material needed for BL-OG. But in order to work, BL-OG still needs something to “turn on” the light. The organic substance luciferin, when combined with bioluminescence, creates light that activates the optogenetics and modulates cellular response in the brain without an incision. by Gomez-Ramirez has shown that the chemical luciferin is harmless to the body.

The researchers in the Haptics Lab tested this combination. They put BL-OG into a pre-determined brain region in mice. They then injected luciferin through a vein in the animal’s tail to activate the targeted cells in the brain. They found that BL-OG effects occur rapidly in the brain, but that these effects could be controlled by scaling the dosage of the luciferin in the animal.

‘Fine-tuning’ bioluminescent optogenetics

“The advantage of this technique is we can create brain activation without a cable. There is less risk for infection and other things to go awry because it is a noninvasive method,” Gomez-Ramirez says. “If we want to standardize this technique in the lab, and potentially in the clinic, it is critical to map all the important parameters around using it. These latest findings allow us to now work on fine-tuning the desired effects of BL-OG based on need and requirements.”

Researchers were also able to track the neuromodulation effects of BL-OG through the bioluminescent activity, another potential feature of this method that could provide insight into how the brain works.