Award details

All-optical readout and manipulation of neural circuits in the intact mammalian brain

Reference	BB/N009835/1
Principal Investigator / Supervisor	Professor Michael Hausser
Co-Investigators / Co-Supervisors	Dr Adam Packer
Institution	University College London
Department	The Wolfson Inst for Biomedical Research
Funding type	Research
Value (£)	472,865
Status	Completed
Type	Research Grant
Start date	01/04/2016
End date	31/03/2019
Duration	36 months

Abstract

Neural circuits display complex spatiotemporal patterns of activity on the millisecond timescale. Understanding how these activity patterns drive behaviour is a fundamental problem in neuroscience. To address this challenge we have recently introduced a novel approach which combines simultaneous two-photon calcium imaging and two-photon targeted optogenetic photostimulation with the use of a spatial light modulator (SLM) to provide 'all-optical' readout and manipulation of the same neurons in vivo. Here we aim to develop order-of-magnitude improvements in this approach to enable flexible real-time probing of the neural code with cellular resolution. First, we will expand the volume of all-optical interrogation by combining large volume 3D imaging and photostimulation. We will probe deeper using adaptive optics in combination with novel red calcium indicators and spectrally separated opsins for photostimulation. Next, we will optimize photostimulation efficiency using faster SLMs and stronger lasers to allow activation of more neurons in shorter timeframes. These enhancements should enable targeted interrogation of >100 neurons within 3 ms in 3D, across a wide area (>1 mm) and throughout the depth of cortex (~1 mm). Next, we will develop fast real-time analysis and photostimulation pattern generation strategies by combining large-scale distributed computing and GPU-based algorithms. This will permit 'on-the-fly' all-optical interrogation, allowing flexible targeting of functionally defined neural ensembles during behaviour. Our approach will be implemented for experiments probing the neural code in mouse barrel cortex during sensory discrimination tasks. Finally, we will ensure dissemination of these advances in collaboration with a range of industrial partners. Our overall goal is to create a set of tools that will enable this 'all-optical' approach to be used to investigate the neural code of the cortex, and to be widely implemented by the neuroscience community.

Summary

Neurons in the brain store, process, and transmit information via electrical impulses. How does the spatiotemporal pattern of electrical impulses in the brain drive perception, or enable performance of an action? Such crucial questions have yet to be answered despite substantial recent progress in neuroscience. We propose to develop novel approaches to answer these fundamental questions, in order to reveal how our brains work to perform complex computational feats surpassing what human engineers can create. Such understanding may give us deep insights into the workings of the cerebral cortex, and will aid the fight against debilitating disorders of the brain. Previous research on how the electrical activity drives behaviour has taken two complementary approaches: correlating neuronal activity with what is happening in the environment, and stimulating neuronal activity while recording behavioural responses. In the first approach, many of the basic calculations performed by an animal's sensory system can be characterized by altering the environment and recording the response of neurons in the brain. Recent technical advances now enable recording of movies showing the activity of large groups of neurons at once. Such data are often highly informative, but nonetheless cannot reveal whether the recorded activity is solely responsible for one's perception, or may have just coincidentally occurred at the time of the recording. The second approach is to stimulate neuronal activity and record responses from an animal. While these experiments complement the first approach by providing more direct evidence, they show only that activating certain neurons is sufficient. For example, a neuron that is sufficient to drive an action in the lab may not necessarily be the neuron that is normally active when the animal behaves naturally. This subtle difference is crucial in understanding the neural code because the goal is to understand how the brain works under normal conditions, not how it is able to work under artificial conditions in the laboratory. The goal of this proposal is to bring these two approaches together by closing the loop between recording and manipulating neural activity and linking with behaviour. We have developed an optical approach which allows us to use light to both record and manipulate the activity of many neurons simultaneously on the level of individual electrical impulses. We will further develop this strategy for 'all-optical' readout and manipulation of entire neural circuits during behaviour. This will involve optimizing a toolkit for in vivo 'all-optical' interrogation incorporating custom optics, novel genetically engineered probes, and software built on large-scale computing platforms. This approach will allow us to perform 'real-time' readout and manipulation of functionally defined sets of neurons, allowing us to probe and interrogate the neural code 'on the fly' during behaviour. We will test this approach using experiments in the sensory cortex of a mouse performing a sensory discrimination task, in which we can manipulate neurons in precisely targeted manner and examine the influence on behaviour. The strategy outlined in this application will provide a new technology platform that is applicable to many fundamental problems in neuroscience with the potential for translation to clinical applications.

Impact Summary

This research programme will deliver a range of economic and societal impacts, as summarized below. 1. Scientific community Our investigations into the dynamics of neural circuits and the nature of the neural code will provide essential information for understanding the function of the cerebral cortex. The results will inspire further work which will build on our discoveries to apply this knowledge to understand dysfunction in animal models of disease. The "all-optical" strategy that we are developing should be widely applicable across a range of fields in neuroscience, as well as allied fields such as developmental and cell biology. 2. Industry engagement As part of the preliminary work leading up to this proposal we have engaged with a range of commercial companies, from laser manufacturers (e.g. Coherent) to microscopy companies (e.g. Bruker), which will continue within the framework of the work proposed here. Moreover, for the dissemination aspects of the proposal we will take advantage of these links to implement and widely distribute the technological and scientific advances we have developed. 3. Public awareness This work will increase our understanding of the function of neural circuits of the mammalian brain, a topic of widespread public interest. The members of the laboratory have a longstanding interest and experience in public engagement activities (e.g. presentations at the Science Museum in London; presentations at local schools; presentations at Brain Awareness Week) which will be further expanded during the course of this work help to disseminate the results of our research. 4. Contribution to the 3Rs The approach we are developing will help to address the 3Rs because it allows simultaneous readout and manipulation of activity from a large population of neurons. As a consequence, fewer animals are required to generate the same amount of data compared to conventional methods. Moreover, the experimental data we generate will help to constrain models of neural circuits which will help to optimize future experiments and reduce the number of animals necessary to obtain significant results.

Committee	Research Committee A (Animal disease, health and welfare)
Research Topics	Neuroscience and Behaviour, Technology and Methods Development
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	X – not Funded via a specific Funding Scheme

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