What is going on in the brain that leads to us to look for an object, such as a coffee mug, grab it, fill it with coffee, and go about our day? What are the elements of cerebral visual impairment that both parents and healthcare providers need be on the lookout for? As always, medical research, provides insights into these questions.
Researchers at Weill Cornell Medicine studied zebrafish to learn about how neurons in the fish’s brainstem guide its gaze. They wanted to know how short-term memory behaviors are created from the fish’s neural mechanisms. Zebrafish are ideal models for this kind of research since the brain region that controls their eye movements is similar to mammals—and they only have 500 neurons.
The team used advanced imaging techniques to identify the neurons involved in controlling the fish’s gaze. From there, they determined how the neurons are wired together. Researchers learned that the fish’s visual system consists of two feedback loops containing three clusters of connected cells. This allowed them to build a computational model, and they found that the network could predict the activity patterns of the fish’s neural circuit.
Next, scientists will investigate how the cells in each cluster influence the behavior of the circuit and whether the neurons in different clusters have different genetic signatures. This information could be used to target malfunctioning cells in eye movement disorders. It can also be used to learn more about the neural systems that rely on short-term memory, such as understanding visual scenes or understanding speech.
But what happens when vision doesn’t work the way it should—such as in the case of dyslexia or reduced contrast sensitivity? This is known as cerebral visual impairment (CVI). Experts at the National Institutes of Health (NIH) identified five components of brain based visual impairment that start in childhood.
The five components are:
Brain Involvement—CVI includes many visual impairments that involve a brain abnormality that affect the development of the visual pathway. This impairment interferes with how a person uses vision for everyday purposes.
Visual Disfunction Greater than An Eye Exam Suggests—Those with CVI may have a co-existing visual processing problems not detected through standard eye exams.
Types of Visual Deficits—CVI can present as lower-order deficits, such as difficulty seeing an eye chart clearly, or higher-order deficits, such as trouble recognizing faces and objects.
Overlap with Other Neurological Disorder—While not present in every case of CVI, it can exist alongside of other disorders, such as cerebral palsy.
CVI is Easily Missed—A child might not be able to clearly articulate the problem he or she is having or even know that there is a problem. That’s where screening by medical professionals becomes essential, especially when a child is at high risk for CVI, such as a baby born prematurely.
To advance research in this area, the National Eye Institute (NEI) is working on the development of a registry to collect data from persons with CVI. This database will be made available to researchers to study the signs and symptoms of CVI and develop best practices for diagnosis and treatment. To learn more, go to NIH CVI Registry webpage: https://cvi.nih.gov
Understanding how the brain processes vision leads to new ways to diagnose and treat conditions like cerebral visual impairment. As research progresses, especially by way of initiatives like NEI’s CVI Registry, healthcare providers and scientists will be better able to identify these developments early and design targeted interventions. Partnerships between neuroscience and clinical care holds the key to improving both quality of life and outcomes for children affected by vision-related disorders.