All-optical bidirectional neural interfacing using hybrid multiphoton holographic optogenetic stimulation

Abstract

Our understanding of neural information processing could potentially be advanced by combining flexible three-dimensional (3-D) neuroimaging and stimulation. Recent developments in optogenetics suggest that neurophotonic approaches are in principle highly suited for noncontact stimulation of network activity patterns. In particular, two-photon holographic optical neural stimulation (2P-HONS) has emerged as a leading approach for multisite 3-D excitation, and combining it with temporal focusing (TF) further enables axially confined yet spatially extended light patterns. Here, we study key steps toward bidirectional cell-targeted 3-D interfacing by introducing and testing a hybrid new 2P-TF-HONS stimulation path for accurate parallel optogenetic excitation into a recently developed hybrid multiphoton 3-D imaging system. The system is shown to allow targeted all-optical probing of in vitro cortical networks expressing channelrhodopsin-2 using a regeneratively amplified femtosecond laser source tuned to 905 nm. These developments further advance a prospective new tool for studying and achieving distributed control over 3-D neuronal circuits both in vitro and in vivo.

Wide-field three-photon excitation in biological samples

“…who focussed a single point onto a neuron to excite calcium activity in cell culture and hippocampal brain slices. Other researchers have found that, while two-photon single-point scanning can trigger an action potential in an opsin-expressing neuron29–31, two-photon wide-field excitation is more effective at triggering the action potential5,32–34. In a report using a similar laser configuration to our high-power femtosecond OPA system, a home-built three-stage OPA system was used to illuminate an entire fly brain, without spatial selectivity, to demonstrate that two-photon excitation of opsins is not limited to small numbers of neurons—potentially the entire brain of an animal can be exposed simultaneously35.…”

Fast wide-volume functional imaging of engineered in vitro brain tissues

“…Such a task will additionally require the use of cell-type-specific fluorescent markers with spectral properties complementary to those of the genetically encoded sensors. Furthermore, the causality of one network with respect to the activity of another could be further explored by combining optical monitoring of one layer with electrical 63 and/or optogenetic stimulation 64 – 66 of the other layer.…”

Precise optical probing of perceptual detection

“…We simultaneously performed 2P holographic optogenetic stimulation and 2P calcium imaging [12,19] in the olfactory bulb of awake, head-fixed mice outfitted with a cranial window. To boost excitation efficiency and temporal precision, our system used a low-repetition rate, amplified laser source (at 1028 nm) for stimulation [15,16,18,27], which was combined with a standard femtosecond oscillator at 920 nm for imaging ( Fig. 1A).…”