Research

We apply neuroengineering principles to understanding the function of neural systems, and devising strategies for future biomedical applications in neuroscience. Current projects employ electrophysiological, behavioral, optogenetic and theoretical methods applied to the rodent whisker system, a highly refined tactile sensory system. Experiments combine multi-electrode recording of brain activity; high speed videography of behavior and development of automated image analysis algorithms; and optical stimulation of specific cell types (e.g., excitatory vs. inhibitory neurons) using genetically targeted expression of light sensitive ion channels. Parallel modeling uses tools from dynamical systems, control theory and decision theory. Augmenting experiments with model-driven, real-time feedback forms a basis for development of brain machine interfaces, with an emphasis on sensory neural prosthetics, in addition to providing state of the art tools to address basic questions of neural function.

Active touch strategies. Using behavioral training in freely moving mice, in combination with high-speed videography, we assess sensing strategies mice use in tactile tasks, including exploration for reward, and aperture width discrimination. For example, we have found that mice, known to coordinate head and whisker motions during tactile search, in fact exhibit sophisticated choices of whether to move whiskers in concert with or counter to their head motion, depending on immediate situation and goal. The observation of contextualized responses to contact supports high-level supervision of sensory motions, that implicates central brain regions also involved in perceptual processing.

Neural recording and closed loop stimulation in freely moving animals. To understand the active sensing loop from whisker contacts through cortex and back to whisker motions, we add an artificial loop, developing methods to record and optogenetically stimulate whisker cortex, driven in real time by the animal’s own motion. For example, we find a striking reduction in cortical responsiveness during whisker retractions, compared to during protractions or random times. This within-whisk modulation of cortex likely plays a role in both guidance of sensing motions and interpretation of whisker contacts. Combined with other neurotechnology projects, such as a lensless “needle” optrode (with Jerome Mertz, BU) for implantable all-optical interfaces, we seek to elucidate the role of specific pathways in somatosensory cortex that process active touch.

Neurocontrol theory. The above experiments expose a major engineering challenge: the underactuation of neural stimulation technologies, with local ratios of neurons to independent stimulation channels often 1000:1 or greater. With ShiNung Ching (WUSTL), building from collaboration started during his postdoc, we pursue novel adaptations of control theory to large, highly underactuated neural ensembles. While uncontrollable in a naïve sense, exploitation of neural dynamics allows construction of controls possibly suitable in practice for neuroprostheses, in addition to providing state of the art tools to address basic questions of neural function.

Publications

A. Nandi, H. M. Schattler, J. Ritt, and S. Ching, “Time-Optimal Underactuated Control of Multi-neuron Spike Patterns.” (Submitted).

C. Ba, M. Palmiere, J. Ritt, J. Mertz (2016) “Dual-modality endomicroscopy with co-registered fluorescence and phase contrast”. Biomedical Optics Express 7(9) 3403-3411.

View article through: OSA Site

D. S. Freedman, J. B. Schroeder, G. I. Telian, Z. Zhang, and J. T. Ritt (2016). “OptoZIF Drive: a 3D printed implant and assembly tool package for neural recording and optical stimulation in freely moving mice.” (Journal of Neural Engineering, In Press).

J. B. Schroeder and J. T. Ritt (2016). “Selection of Head and Whisker Coordination Strategies During Goal Oriented Active Touch”. J. of Neurophysiology (In press).

View article through: Journal of Neurophysiology early online

J. A. Nandi, J. T. Ritt and S.-N. Ching (2014). “Non-negative Inputs for Underactuated Control of Spiking in Coupled Integrate-and-Fire Neurons”. IEEE 53rd Conf. Decision and Control 2014: 3041-3046.
View article through: IEEE

S.-N. Ching and J. T. Ritt, (2013). “Control strategies for underactuated neural ensembles driven by optogenetic stimulation”. Frontiers in Neural Circuits 7:1-16.
View article through: Frontiers In Neural Circuits

J. B. Schroeder, V. J. Mariano, G. I. Telian, and J. T. Ritt (2013).  “Stimulation of Somatosensory Cortex Locked to Whisker Motions in a Mouse Model of Active Sensing”.  Conf. Proc. IEEE Eng. Med. Biol. Soc. Neural Eng. (NER) 2013: 637-640.
View article through: IEEE

J. B. Schroeder and J. T. Ritt (2013). “Extraction of Intended palpation times from facial EMGs in a mouse model of active sensing”.  Conf. Proc. IEEE Eng. Med. Biol. Soc. 2013: 2016-2019
View article through: PubMed or IEEE

M. M. Halassa, J. H. Siegle, J. T. Ritt, J. T. Ting, G. Feng and C. I. Moore, (2011). “Selective optical drive of thalamic reticular nucleus generates thalamic bursts & cortical spindles”. Nat. Neurosci. 14(9): 1118-20.
View article through: PubMed or Nature

J. H. Siegle, M. Carlen, K. Meletis, L.-H. Tsai, C. I. Moore and J. T. Ritt, (2011). “Chronically Implanted Hyperdrive for Cortical Recording and Optogenetic Control in Behaving Mice”. Conf. Proc. IEEE Eng. Med. Biol. Soc. 2011: 7529-7532.
View article through: PubMed or IEEE

J. T. Ritt and C. I. Moore, (2008) “Response to Diamond, et al.” Neuron 60:745-747.
View article through: Neuron

J. T. Ritt, M. L. Andermann, C. I. Moore, (2008) “Embodied information processing: vibrissa mechanics and texture features shape micromotions in actively sensing rats”. Neuron 57: 599-613.
View article through: PubMed or ScienceDirect

M. A. Saito, T. Goepfert, J. T. Ritt, (2008) “Some thoughts on the concept of co-limitation: Three definitions and the importance of bioavailability”. Limnology and Oceanography 53(1): 276-290.
View article through: ASLO

M. L. Andermann, J. Ritt, M. A. Neimark, C. I. Moore, (2004) “Neural correlates of vibrissa resonance: band-pass and somatotopic representation of high frequency stimuli”. Neuron, 42(3):451-63.
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J. Ritt, (2003) “Evaluation of entrainment of a nonlinear neural oscillator to white noise”, Phys. Rev. E, 68: 041915.
View article through: PubMed or Physical Review E

Y. Manor, F. Nadim, S. Epstein, J. Ritt, E. Marder and N. Kopell, (1999) “Network oscillations generated by balancing graded asymmetric reciprocal inhibition in passive neurons”. J. Neurosci., 19: 2765-2779.
View article through: PubMed or The Journal of Neuroscience

C. C. Chow, J. A. White, J. Ritt, and N. Kopell, (1998) “Frequency control in synchronous networks of inhibitory neurons.” J. Comput. Neurosci., 5: 407-420.
View article through: Springer

J. A. White, C. C. Chow, J. Ritt, C. Soto-Trevino, and N. Kopell, (1998) “Synchronization and oscillatory dynamics in heterogeneous, mutually inhibited neurons.” J. Comput. Neurosci., 5: 5-16.
View article through: PubMed or Springer