Stewart A. Bloomfield, PhD

Neuroscience Institute

Adjunct Professor, Department of Neuroscience and Physiology

Adjunct Professor, Department of Ophthalmology

Keywords
neuroscience, vision, ophthalmology
Summary

As part of the central nervous system, the retina has for many years been an important model for understanding cell-to-cell communication and information processing in the brain. Although the retina has been traditionally thought of as a rather simple part of the brain as there are only five main neuronal types, we now know that each is comprised of numerous subtypes so that there are in fact over sixty morphological subtypes of retinal neurons. These cells partake in a wide variety of complex synaptic circuits that function to extract and encode information about an image including parameters like contrast, color, and motion. When we consider the neural circuitry of the retina, as well the rest of brain, we usually focus on chemical synaptic pathways whereby a neuron communicates with its neighbors by releasing a neurotransmitter. However, in addition to these chemical synapses, nerve cells often maintain direct specialized contacts with each other called gap junctions. These junctions take the form of intercellular channels that are composed of transmembrane proteins called connexins. These channels provide for direct electrical communication between cells by allowing the intercellular transfer of ions. Gap junctions are thus the morphological substrate for so-called electrical synapses. One important advantage for electrical synapses over the conventional chemical types is the great speed at which information can be passed from cell to cell in either direction. Although evidence for gap junctions between retinal neurons has existed for many years, their ubiquitous nature has only recently been revealed. Results from our lab indicate that nearly all neuronal cell types in the retina maintain electrical synapses. Moreover, we find that electrical synapses are highly dynamic and are regulated by light acting through protein kinase-mediated phosphorylation of gap junction connexins. Direct electrical communication between retinal neurons thus forms a major mechanism for the transmission and integration of visual information that is constantly modified as we move from night to day. A major goal of our lab is to elucidate the different functional roles played by gap junctions in visual processing. So far, we have found that electrical synapses in the retina have a wide range of functions, including spatial integration of visual signals, dark/light adaptation, encoding of image motion, and generating correlated signals sent to the brain. A second goal of our work is to determine the role of gap junctions in retinopathies such as glaucoma and retinitis pigmentosa in which there is extensive cell death. We believe that at least a portion of the cell death is secondary in which factors from dying cells are released across gap junctions to kill coupled neighbors. Understanding this mechanism, including the factors released, will guide us toward therapies to increase neuronal survival in the retina and elsewhere in the nervous system under pathological conditions.

These focus areas and their associated publications are derived from medical subject headings from PubMed.
represents one publication
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Adjunct Professor, Department of Neuroscience and Physiology

Adjunct Professor, Department of Ophthalmology

PhD from Washington University at Saint Louis

Akopian, Abram; Atlasz, Tamas; Pan, Feng; Wong, Sze; Zhang, Yi; Volgyi, Bela; Paul, David L; Bloomfield, Stewart A

Journal of neuroscience. 2014 Aug 06; 34(32):10582-10591

Excitotoxic and ischemic conditions change the expression of gap junction connexins in the inner retina [Meeting Abstract]

Akopian, A; Atlasz, T; Bloomfield, S A

Investigative ophthalmology & visual science. IOVS. 2014 April; Conference:(2014):2390

Volgyi, Bela; Pan, Feng; Paul, David L; Wang, Jack T; Huberman, Andrew D; Bloomfield, Stewart A

PLoS one. 2013; 8(7):e69426-e69426e69426

Farajian, Reza; Pan, Feng; Akopian, Abram; Volgyi, Bela; Bloomfield, Stewart A

Journal of physiology. 2011 Sep 15; 589(Pt 18):4473-4489

Osterhout, Jessica A; Josten, Nicko; Yamada, Jena; Pan, Feng; Wu, Shaw-Wen; Nguyen, Phong L; Panagiotakos, Georgia; Inoue, Yukiko U; Egusa, Saki F; Volgyi, Bela; Inoue, Takayoshi; Bloomfield, Stewart A; Barres, Ben A; Berson, David M; Feldheim, David A; Huberman, Andrew D

Neuron. 2011 Aug 25; 71(4):632-639

Hu, Edward H; Pan, Feng; Volgyi, Bela; Bloomfield, Stewart A

Journal of physiology. 2010 Nov 01; 588(Pt 21):4145-4163

Pan, Feng; Paul, David L; Bloomfield, Stewart A; Volgyi, Bela

Journal of comparative neurology. 2010 Mar 15; 518(6):911-927

Ackert, Jessica M; Farajian, Reza; Volgyi, Bela; Bloomfield, Stewart A

Journal of physiology. 2009 Sep 15; 587(Pt 18):4481-4495