Vision scientists: Experienced and accomplished in brain activity mapping

By Denise A. Valenti, OD, FAAO

President George H. W. Bush declared the 1990s to be the “decade of the brain.” More recently President Barack Obama mentioned in his inaugural address what is expected to be a decade-long, nationwide initiative to fully map the brain. Vision scientists are already far along with such an endeavor. The “decade of the brain” saw substantial gains in our ability to map neural processing, and neuroscientists in the field of vision achieved groundbreaking results in our understanding of retinal neural circuitry.

Dr. Charles L. Zucker is one such scientist who has been mapping connections — when one considers the retina an extension of the brain — for two decades. He was awarded the Cogan Medal as a promising young scientist by ARVO in 1999. Vision clinicians and researchers have been involved in brain mapping for well over a century when one considers the structural relation of retina and functional visual field. With current and emerging technologies, we are now in position to achieve mapping retinal cells, axonal pathways and brain interface.

President Obama stated during his 2013 address: "Every dollar we invested to map the human genome returned $140 to our economy — every dollar. Today, our scientists are mapping the human brain to unlock answers to Alzheimer’s."

The project, known as the Brain Activity Map (BAM), would benefit our understanding of healthy and diseases brains. Very little is known of this project, and more information is expected to be revealed by the White House as early as March, according to an article in The New York Times. The piece reveals that the project will include federal agencies and private foundations; among them might be the National Institutes of Health, the Defense Advanced Research Projects Agency, the National Science Foundations, Howard Huges Medical Institute, Kavli Foundation and the Allen Institute for Brain Science in Seattle. The overall initiative is expected to be organized by the Office of Science and Technology Policy.

During the Sixth Kavli Futures Symposium in January 2012, previous discussions of a large-scale coordinated effort to use and develop technology to map cells and functional connectivity of the entire brain resulted in a paper in the June issue of Neuron. The publication and the authors may have been the inspiration and motivation spurring the current administration’s interest in a thorough understanding of brain connectivity and processing. Dr. Rafael Yuste, M.D., Ph.D., is the corresponding author; Neuron, June 2012. The paper discusses what is being called "connectomics." Dr. Sebastian Seung of MIT and professor of computational neuroscience describes a connectome as "a map between neurons inside a nervous system."

One of the current accomplishments of connectomics is the complete mapping of the neural connections of a piece of mouse retina. This involved imaging a section of retinal tissue with an estimated 1,000 neurons. With more than 13,000 images, it took more than two years to reconstruct the circuitry. However, technology and techniques are evolving, allowing for greater efficiency.

Technology exists to image retinal neural tissue in vivo; without harm to the tissue or host. With such tools allowing imaging of human tissue — normal and diseased &mdash we have already gained ground in achieving connectome models. When one considers the ability to see retinal tissue and structures when using state-of-the-art imaging such as Optical Coherence Tomography and Adaptive Optics and how we can now relate structure to function with complex visual field or retinal function using electrodiagnostic technology, it is not far-reaching to appreciate that the same structure function aspects can also be applied to tissue and cells up stream — in the brain. The precise retinotopic relationship follows throughout the visual system and throughout the brain. We now have ever-increasing accuracy in retinotopic mapping1, and we are able to more accurately track a cell originating in the retina to its connections in the brain.

Given how much of the brain is taken up by visual processing and activity that originates in the brain, it is essential that those studying such function and structure have an active role in the BAM Initiative. Dr. Jose-Manuel Alonso of the State University of New York College of Optometry has been actively mapping the brain visual pathways — also since the “decade of the brain” — and he and his colleagues have been productive in their contributions to the field. Using a lesion-disease model with glaucoma as the lesion in the optic nerve neural tissue, early corresponding brain loss can now be identified using structural and functional MRI techniques.2

Dr. Denise A. Valenti is a residency-trained, low-vision/blind-rehabilitation optometrist with additional education and expertise in the field of age-related neurodegenerative diseases with the emphasis on Parkinson’s disease and Alzheimer’s disease. Her research has included the study of imaging of retinal neural tissue using Optical Coherence Tomography and functional assessment of neural processing in the visual system using Frequency Doubling Technology. Dr. Valenti provided direct clinical care for more than 25 years and currently is active in research and consultation related to vision, aging, neuroprocessing and cognitive functions.

References

1. Garway-Heath, D., et al., Mapping the visual field to the optic disc in normal tension glaucoma eyes. Opthalmology, 2000. 107: p. 1809-1815.

2. Gupta, N. and Y. Yucel, Brain changes in glaucoma. European Journ of Ophthal, 2003. 13: p. S32-S35.