A next generation spatial light modulator for mapping of neural networks

Boulder Nonlinear Systems BNS and Prof Edward Boyden s Synthetic Neurobiology Group at the Massachusetts Institute of Technology MIT Media Lab propose to develop a new liquid crystal spatial light modulator SLM capable generating high resolution holograms to overcome the imaging gap that currently divides cellular level optogenetic techniques and whole brain techniques to improve functional mapping dissection of complex brain networks This effort builds upon the successful Phase I effort in which new modeling techniques were developed to guide this Phase II hardware development Whole brain imaging techniques such as functional magnetic resonance imaging fMRI and diffusion tensor imaging DTI are powerful tools for visualizing neural activity and connections respectively across regions of the brain however their spatial resolution is limited to the millimeter scale and therefore they cannot resolve individual neurons Meanwhile optical imaging and photostimulation provide complimentary tools that allow not only direct imaging of neurons and their action potentials but also the ability to directly stimulate action potentials all with single cell resolution over small sub millimeter volumes This disconnect between the length scales of whole brain imaging and optical techniques the so called imaging gap is one of the critical barriers to understanding how coherent states arise from the activity of neuronal ensembles In Phase I BNS and MIT worked with Zemax Inc to develop a new optical modeling capability able to simulate holographic microscopy with pixelated phase modulating SLMs Using this new modeling capability BNS identified the barriers to closing the imaging gap by holographically addressing a mm volume of tissue Specifically we identified the need for a new SLM that optimally balances the trade offs between addressable field of view resolution and switching speed and for corrective optics that undo the lateral chromatic dispersion experienced by the ultrashort laser pulses used for deep tissue microscopy In Phase II BNS will develop a next generation SLM consisting of a V pixel backplane designed to achieve or exceed ms switching speed This device will be delivered via custom corrective optics into a commercial microscope at MIT for demonstration of holographic interrogation of neuronal ensembles over a mm volume of tissue There is an optical revolution underway in neuroscience that is providing researchers with new tools to both record and control neural activity with light at the cellular level Spatial light modulators are one such tool and they enable the projection of three dimensional holograms into the brain capable of probing many hundreds of neurons at once This proposed Phase II effort aims to develop the next generation of spatial light modulator to dramatically increase the volume of brain that can be studied with this technique so that neuroscientists can better understand the larger context of neural activity