Viviana Gradinaru, Ph.D.

Principal Investigator

Dr. Viviana Gradinaru completed her B.S. at Caltech and her Ph.D. research at Stanford University and is now an Assistant Professor of Biology and Biological Engineering at Caltech. Dr. Gradinaru’s research interests focus on developing tools and methods for neuroscience (optogenetic actuators and sensors; tissue clearing and imaging; gene delivery vehicles) as well as on investigating the mechanisms underlying deep brain stimulation (DBS). She has been awarded the NIH Director’s New Innovator Award and been honored as a World Economic Forum Young Scientist and as one of Cell’s 40 under 40. Viviana Gradinaru is also a Sloan Fellow, Pew Scholar, Human Frontier Science Program Young Investigator, and Kimmel Scholar. Most recently Dr. Gradinaru was awarded a PECASE: "Presidential Early Career Awards for Scientists and Engineers.”

During her graduate work Dr. Gradinaru played an instrumental role in the early development and applications of optogenetics. For example, although now a mature field, in the early days of optogenetics starting with 2005 there were significant challenges: many opsins, especially pumps, were not well tolerated by mammalian cells and therefore could not be used in vivo. Dr. Gradinaru worked out subcellular and transcellular trafficking strategies that resulted in potent and safe optogenetic tools used nowadays. She then used these tools to challenge the traditional perception that Deep Brain Stimulation (DBS) acts mainly by inhibiting local cell bodies at the stimulation site by showing that controlling axons in the stimulation area was sufficient to restore motor behavior in parkinsonian animals. Dr. Gradinaru also helped train scientists from all over the world in the Optogenetics Innovation Laboratory at Stanford and in summer courses at Cold Spring Harbor.

During her postdoctoral work, also at Stanford with Dr. Karl Deisseroth, Dr. Gradinaru pioneered work towards a novel method for intact tissue mapping and phenotyping (known as CLARITY). While working to bypass some of the limitations of first generation methods, the Gradinaru group at Caltech has reported the first case of whole-body clearing – transparent rodents that can be used to obtain detailed maps of both central and peripheral nerves at their target organs throughout the body.

Detailed Research Program

Jennifer Treweek, Ph.D.

Postdoctoral Fellow

Jenny received her B.S. from CALTECH in Chemistry and Economics, and her Ph.D. in Chemistry at The Scripps Research Institute. During her PhD with the Janda group, she conducted research at the interface between immunology and neuropharmacology. Major projects included developing passive vaccination strategies for treating drug abuse, investigating the in vivo relevance of methamphetamine-initiated advanced glycation endproduct formation in the pathophysiological symptoms of chronic methamphetamine addiction, and finally, studying the role of corticotropin releasing factor receptor type-1 signaling in maladaptive states. Now, as a postdoctoral fellow in the Gradinaru lab, Jenny hopes to elucidate how neurocircuits gated by another CRF receptor subtype: CRFr2, contribute to the persistence of pathological anxiety and stress-related disorders. Herein, advanced optogenetic techniques, viral tracing methods, and the combined use of tissue clearing with subcellular labeling methodologies will be used to examine CRF system plasticity in the brain.

Collin Challis, Ph.D.

NRSA Postdoctoral Fellow

Collin received his B.S. in Molecular Biology from UC San Diego and Ph.D. in Neuroscience from the University of Pennsylvania. His thesis focused on top-down control of the serotonergic dorsal raphe nucleus by the ventromedial prefrontal cortex in the context of social behaviors and depression. In the GLab Collin is exploring neural circuits that underlie behavior using optogenetics, electrophysiology and imaging techniques.

Alon Greenbaum, Ph.D.

LSRF Postdoctoral Fellow

Alon holds his BS and MS degrees in Electrical Engineering from Tel Aviv University, and his Ph.D in Electrical Engineering from University of California, Los Angeles. In his doctorate degree, Alon conducted biophotonics research under Prof. Aydogan Ozcan, focusing on high-resolution and high-throughput microscopy for biomedical applications. In Prof. Viviana Gradinaru’s lab, he is exploring innovative imaging techniques for various neuroscience applications.

Rosemary Challis, Ph.D.

AHA Postdoctoral Fellow

Rose received her B.S. in Biochemistry from UCLA and Ph.D. in Cell and Molecular Biology from the University of Pennsylvania. Her thesis work focused on the structure and function of olfactory cilia in the mouse nose. In the Gradinaru Lab, Rose is studying the neural circuitry of the mammalian cardiac nervous system using tissue clearing, viral tracing, and optogenetic techniques.

Min Jee Jang, Ph.D.

Postdoctoral Fellow

Min received her BS, MS and PhD in Bio and Brain Engineering at KAIST. Her doctoral thesis focused on developing algorithms for quantitative analysis of large-scale calcium imaging data. Before joining Caltech, she worked as a postdoctoral fellow at Korea University on developing macro-scale 3D imaging and digital reconstruction methods using tissue clearing technique. In the Gradinaru lab, Min is interested in computational approaches to reconstruct the cellular structure of cleared tissue.

Elliott Robinson, M.D., Ph.D.

CTF Postdoctoral Fellow

Elliott got his B.S. from Georgetown University and his MD/PhD from the University of North Carolina at Chapel Hill. His graduate work focused on the consequences of the OPRM1 A118G polymorphism on reward circuitry and was co-mentored by C.J. Malanga (UNC) and Markus Heilig (NIAAA). Elliott also collaborated with Bryan Roth to help validate the kappa opioid receptor DREADD (KORD) and spent the majority of his fourth year of medical school in Garret Stuber's lab learning optogenetic techniques and honing his skills as an electrophysiologist. In the Gradinaru Lab, Elliott will study dopaminergic circuits in a model of Neurofibromatosis Type 1 as part of a Children's Tumor Foundation Young Investigator Award.

Anat Kahan, Ph.D.

Caltech Divisional Postdoctoral Fellow

Anat received her BS, MS and PhD in Physical Chemistry in The Hebrew University of Jerusalem, Israel. Her doctoral thesis, under the supervision of Prof. Yehuda Haas, focused on environmental effects on ultrafast molecular photo-induced reactions in condensed phase. She worked as a postdoctoral fellow at Yoram Ben-Shaul’s lab at The Hebrew University on discrimination between socially related cues in the accessory olfactory bulb. In the Gradinaru lab, Anat is interested in the effect of behavioral stress on reproduction, using tissue clearing, viral tracing, electrophysiology and optogenetic techniques.

Nick Goeden, Ph.D.

Postdoctoral Fellow

Nick received his B.S. from Caltech in biology, and his Ph.D. in neuroscience from The University of Southern California. Nick’s graduate work focused on characterizing developmental origins of mental disorders like autism and schizophrenia. While pursuing his Ph.D., Nick aided in the development and optimization of a novel ex-vivo placental perfusion system, with which he characterized the capacity of the placenta to metabolize serotonin. He later demonstrated that disruption of placental serotonin metabolism due to maternal inflammation impacts fetal neurodevelopment, and contributes to the onset of behavioral disruptions commonly seen in autism and schizophrenia. As a postdoctoral fellow in the Gradinaru lab, Nick aims to engineer systemically delivered viral vectors that are capable of modulating activity in specific neural circuits, thereby providing a noninvasive approach for the modulation of defined neural circuits.

Nick Flytzanis, B.S.

Graduate Student

Biology and Biological Engineering

Nick received his B.S. in Biology from MIT in 2010. Before joining the Gradinaru lab at Caltech, Nick worked as a research assistant in the lab of Prof. Frank Gertler at MIT on understanding the post-transciptional splicing mechanisms that play a role in the epithelial-to-mesenchymal transition of cancer cells and its resulting effect on metastasis. Nick’s Ph.D. thesis work in the Gradinaru lab is focused around developing fluorescent sensors for monitoring neuronal activity of large populations of cells simultaneously.

Claire Bedbrook, B.S.

Graduate Student, NRSA Fellow


Claire received her BS in Chemical Engineering from the University of California, Berkeley in 2011. Before starting her PhD at Caltech, she worked in agbiotech as a research associate at DuPont Pioneer. Claire is co-advised by Viviana Gradinaru and Frances Arnold at Caltech. Claire is working to engineer new optogenetic tools using protein engineering methods.

Ken Chan, B.S.

Graduate Student

Biology and Biological Engineering

Ken received his B.S. in micro- and molecular biology from Portland State University. Before starting his Ph.D. research at Caltech, Ken was a research technician in the lab of Professor Alexei Aravin at Caltech study piRNA genesis. Ken’s Ph.D training is over tissue clearing, engineering viruses for higher efficiency via systemic delivery and producing an adeno-associated virus based toolbox for anatomical characterization.

Ryan Cho, M.S.E.

Graduate Student

Computation and Neural Systems

Ryan received his BS from the Johns Hopkins University in 2008 and MSE from the University of Pennsylvania in 2009. Before joining to Caltech for PhD, he gained experience in single neuron recording and intracranial EEG in surgical patients with epilepsy, while working as a research associate in Samsung Biomedical Research Institute. Ryan is combining his skills in neural signal processing and machine learning with optogenetics and in vivo optical imaging in the Gradinaru Lab to study diverse functional roles of dopaminergic neurons.

Sripriya Kumar, M.S.

Graduate Student

Biology and Biological Engineering

Priya received her B.Tech from Anna University, Chennai, India in 2010; and MS from University of Illinois at Chicago. Before starting her PhD at Caltech, she worked as a scientific researcher/lab manager in Dr. Gradinaru's lab for two plus years where she gained experience in developing molecular tools for neuroscience. As a graduate student, she is interested in engineering AAV capsids for broad applications.

Michael Altermatt, M.S.

Graduate Student


Michael received his B.S. and M.S. in Biotechnology from ETH Zurich. He completed his Master’s Thesis in the Bio Engineering Laboratory at ETH Zurich where he investigated the modulation of signaling in mammalian axons using a high-density MEA. In the Gradinaru Lab, Michael is applying optogenetics, in vivo optical imaging and electrical recordings to study neural circuits implicated in behavioral states.

Xiaozhe Ding, B.S.

Graduate Student


Xiaozhe received his BS from Tsinghua University, Bejing, China in 2014. Before joining Caltech, he was involved in multiple projects on structural biology and protein engineering. In the Gradinaru Lab, Xiaozhe is working on developing new molecular tools and viral vectors for neuroscience.

Elisha Mackey, B.S.

Lab Manager

Pat Anguiano

Administrative Assistant

Beckman Institute Center for CLARITY,

Optogenetics and Vector Engineering