{"441311":{"#nid":"441311","#data":{"type":"news","title":"Closing the Loop with Optogenetics","body":[{"value":"\u003Cp\u003EOptogenetics provides a powerful tool for studying the brain by allowing researchers to activate neurons using simple light-based signals. But until now, these optical stimulation techniques have been \u201copen loop,\u201d meaning they lack the kind of feedback control that most biological and engineering systems use to maintain a steady operating state.\u003C\/p\u003E\u003Cp\u003EAn engineering example of closed-loop control is a simple thermostat used to maintain a steady temperature in the home. Without it, heating or air conditioning would run without reacting to changes in outside conditions, allowing inside temperatures to vary dramatically.\u003C\/p\u003E\u003Cp\u003EOptogenetics technology places genes that express light-sensitive proteins into mammalian cells that normally lack such proteins. When the proteins are illuminated with specific wavelengths of light, they change the behavior of the cells, introducing certain types of ions or pushing ions out of the cells to alter electrical activity. But without a feedback loop, scientists could only assume that the optical signals were having the effects desired \u2013 or try to confirm at the end of the experiment that this had happened.\u003C\/p\u003E\u003Cp\u003ETo address that shortcoming, researchers have created an open-source technology called the optoclamp which closes the loop in optogenetic systems. The technique uses a computer to acquire and process the neuronal response to the optical stimulus in real-time and then vary the light input to maintain a desired firing rate. By providing this feedback control, the optoclamp could facilitate research into new therapies for epilepsy, Parkinson\u2019s disease, chronic pain \u2013 and even depression.\u003C\/p\u003E\u003Cp\u003E\u201cOur work establishes a versatile test bed for creating the responsive neurotherapeutic tools of the future,\u201d said \u003Ca href=\u0022https:\/\/www.bme.gatech.edu\/bme\/faculty\/Steve-M.-Potter\u0022\u003ESteve Potter\u003C\/a\u003E, an associate professor in the \u003Ca href=\u0022http:\/\/www.bme.gatech.edu\/\u0022\u003EWallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University\u003C\/a\u003E. \u201cNeural modulation therapies of the future, whether they be targeted drug delivery, electrical stimulation or even light-plus-optogenetics through fiber optics, will all be closed loop. That means they will be responsive to the moment-to-moment needs of the nervous system.\u201d\u003C\/p\u003E\u003Cp\u003EThe research, supported by the National Institutes of Health and the National Science Foundation, was recently published in the open-access journal \u003Cem\u003EeLife\u003C\/em\u003E. Feedback control already exists for neural stimulation systems based on electrical inputs, but the optoclamp is the first system to provide similar closed-loop control for optical stimulation.\u003C\/p\u003E\u003Cp\u003EOptoclamp provides continuous, real-time adjustments of optical stimulation to lock neural spiking activity to specified targets over time scales ranging from seconds to days. By providing precise optical control of firing in neuronal populations, the technology will help scientists disentangle causally related variables of circuit activation.\u003C\/p\u003E\u003Cp\u003EResearchers in Potter\u2019s lab studied the effects of open-loop optical stimulation on neural systems, and found considerable variation in the responses of neuronal networks grown on multi-electrode arrays and in the neurons of animal models.\u003C\/p\u003E\u003Cp\u003E\u201cThe same stimulus pattern can produce highly variable levels of activity,\u201d said Jon Newman, who built the optoclamp while a Ph.D. student in Georgia Tech\u2019s Laboratory for Neuroengineering. Newman is now a postdoctoral researcher at MIT. \u201cThe amount of optical stimulation needed to achieve the same level of activity varied by orders of magnitude, depending on the population that was being controlled, or even in the same type of cells and preparation, but within different subjects.\u201d\u003C\/p\u003E\u003Cp\u003EIn a cultured cortical network, the optoclamp records activity from as many as 200 cells, using them to measure activity in the larger culture population, which can include as many as a million cells.\u003C\/p\u003E\u003Cp\u003E\u201cBecause we have all those electrodes, we can process the data in real-time and then compare the amount of activity being expressed by the culture to a target rate, then use the difference between those two signals to inform our optical stimulator to vary the intensities of different wavelengths of light,\u201d Newman explained.\u003C\/p\u003E\u003Cp\u003EThe optoclamp can be used to control cell cultures grown atop electrode arrays, as well as in living animal models in which electrodes have been implanted.\u003C\/p\u003E\u003Cp\u003EIn research conducted with colleagues at Emory University, the optoclamp\u2019s ability to maintain a steady neural firing state allowed researchers to study a key control issue in homeostatic plasticity, a phenomenon that results from a lack of neural stimulation. Scientists had believed that the effect was controlled by the firing rate of cells, but the optoclamp allowed a team of researchers from Georgia Tech and Emory University to clamp firing at normal levels during the addition of a drug that inhibits neurotransmission. This showed that neurotransmission levels, not firing activity, governed a key form of homeostatic plasticity.\u003C\/p\u003E\u003Cp\u003E\u201cEffectively, we were able to decouple two things that are normally very closely related,\u201d said Newman. \u201cThis is potentially a very big deal in terms of developing therapies for aberrant forms of synaptic plasticity.\u201d Potential applications include chronic pain, epilepsy, tinnitus, phantom limb syndrome and other nervous systems disorders where the brain has over-reacted to the loss of normal inputs.\u003C\/p\u003E\u003Cp\u003EThat work, recently published in the journal \u003Cem\u003ENature Communications\u003C\/em\u003E, was a collaboration with Emory University Professor Pete Wenner and former graduate student Ming-fai Fong, demonstrating the value of bringing biological scientists together with engineers. Newman, an engineer by training, says concepts common in engineering can be useful in the life sciences.\u003C\/p\u003E\u003Cp\u003E\u201cClosed-loop control is a concept that is woven through all engineered systems, but it\u2019s often hard to find in the biological sciences,\u201d he said. \u201cAny time you can introduce feedback control into an experiment, it almost always produces better control of the variables of interest. Feedback control is an extremely important concept for the life sciences.\u201d\u003C\/p\u003E\u003Cp\u003EScientists are already using the optoclamp in its current form, but the researchers hope to improve spatial differentiation of the optical signals, allowing experiments to focus stimulation on specific areas of the brain or brain cell cultures. The light signals now affect an entire culture or brain region.\u003C\/p\u003E\u003Cp\u003E\u201cWe want to precisely control where photons are being sent to activate different cells,\u201d Newman said. \u201cOptogenetics allows genetic specification of which cells express these proteins, and that gives you some level of spatial control. But I don\u2019t believe that\u2019s as precise as what will be required to speak the language of the brain.\u201d\u003C\/p\u003E\u003Cp\u003EIn addition to those already mentioned, the research team included Professor Garrett Stanley from the Coulter Department of Biomedical Engineering at Georgia Tech and Emory University, and graduate students Daniel C. Millard and Clarissa J. Whitmire, also from the Coulter Department.\u003C\/p\u003E\u003Cp\u003E\u003Cem\u003EThis research was supported by the National Science Foundation under Collaborative Research in Computational Neuroscience grant IOS-1131948 and Emerging Frontiers in Research and Innovation grant 1238097, and by the National Institutes of Health National Institute of Neurological Disorders and Stroke grant 2R01NS048285 and National Institute of Neurological Disorders grant 1R01NS079757-01. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Science Foundation or National Institutes of Health.\u003C\/em\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003ECITATIONS\u003C\/strong\u003E:\u003Cbr \/\u003ENewman, J. P., Fong, M-f, Millard, D. C., Whitmire, C. J., Stanley, G. B., \u0026amp; Potter, S. M., \u201cOptogenetic feedback control of neural activity,\u201d (eLife, 2015). \u003Ca href=\u0022http:\/\/dx.doi.org\/10.7554\/eLife.07192\u0022\u003Ehttp:\/\/dx.doi.org\/10.7554\/eLife.07192\u003C\/a\u003E.\u003C\/p\u003E\u003Cp\u003EMing-fai Fong, et al, \u201cUpward synaptic scaling is dependent on neurotransmission rather than spiking,\u201d (Nature Communications, 2015). \u003Ca href=\u0022http:\/\/dx.doi.org\/10.1038\/ncomms7339\u0022\u003Ehttp:\/\/dx.doi.org\/10.1038\/ncomms7339\u003C\/a\u003E.\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EResearch News\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003EGeorgia Institute of Technology\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003E177 North Avenue\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003EAtlanta, Georgia 30332-0181 USA\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EMedia Relations Contact\u003C\/strong\u003E: John Toon (\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E) (404-894-6986).\u003Cbr \/\u003E\u003Cstrong\u003EWriter\u003C\/strong\u003E: John Toon\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003EResearchers have created an open-source technology called the optoclamp which closes the loop in optogenetic systems. The technique uses a computer to acquire and process the neuronal response to the optical stimulus in real-time and then vary the light input to maintain a desired firing rate.\u0026nbsp;\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"Researchers have created a technology called the optoclamp which closes the loop in optogenetic systems."}],"uid":"27303","created_gmt":"2015-08-27 23:27:48","changed_gmt":"2016-10-08 03:19:26","author":"John Toon","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2015-08-27T00:00:00-04:00","iso_date":"2015-08-27T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"441281":{"id":"441281","type":"image","title":"Preparing culture for optoclamp","body":null,"created":"1449256190","gmt_created":"2015-12-04 19:09:50","changed":"1475895179","gmt_changed":"2016-10-08 02:52:59","alt":"Preparing culture for optoclamp","file":{"fid":"203078","name":"optoclamp-001.jpg","image_path":"\/sites\/default\/files\/images\/optoclamp-001_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/optoclamp-001_0.jpg","mime":"image\/jpeg","size":1732736,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/optoclamp-001_0.jpg?itok=Q2TP8M5Z"}},"441291":{"id":"441291","type":"image","title":"The optoclamp system","body":null,"created":"1449256190","gmt_created":"2015-12-04 19:09:50","changed":"1475895179","gmt_changed":"2016-10-08 02:52:59","alt":"The optoclamp system","file":{"fid":"203079","name":"optoclamp-006.jpg","image_path":"\/sites\/default\/files\/images\/optoclamp-006_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/optoclamp-006_0.jpg","mime":"image\/jpeg","size":1079398,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/optoclamp-006_0.jpg?itok=q6OCp6EL"}},"441301":{"id":"441301","type":"image","title":"The optoclamp system2","body":null,"created":"1449256190","gmt_created":"2015-12-04 19:09:50","changed":"1475895179","gmt_changed":"2016-10-08 02:52:59","alt":"The optoclamp system2","file":{"fid":"203080","name":"optoclamp-003.jpg","image_path":"\/sites\/default\/files\/images\/optoclamp-003_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/optoclamp-003_0.jpg","mime":"image\/jpeg","size":1622856,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/optoclamp-003_0.jpg?itok=vXBqDlC4"}}},"media_ids":["441281","441291","441301"],"groups":[{"id":"1188","name":"Research Horizons"}],"categories":[{"id":"146","name":"Life Sciences and Biology"},{"id":"135","name":"Research"}],"keywords":[{"id":"1912","name":"brain"},{"id":"139461","name":"closed-loop"},{"id":"5282","name":"feedback"},{"id":"1110","name":"gene"},{"id":"68411","name":"neurons"},{"id":"2768","name":"optics"},{"id":"139451","name":"optoclamp"},{"id":"11635","name":"optogenetics"},{"id":"168365","name":"Steve Potter"}],"core_research_areas":[{"id":"39441","name":"Bioengineering and Bioscience"}],"news_room_topics":[{"id":"71891","name":"Health and Medicine"}],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003EJohn Toon\u003C\/p\u003E\u003Cp\u003EResearch News\u003C\/p\u003E\u003Cp\u003E\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E\u003C\/p\u003E\u003Cp\u003E(404) 894-6986\u003C\/p\u003E","format":"limited_html"}],"email":["jtoon@gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}