Tools for resolving functional activity and connectivity within intact neural circuits - PubMed (original) (raw)

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Tools for resolving functional activity and connectivity within intact neural circuits

Joshua H Jennings et al. Curr Biol. 2014.

Abstract

Mammalian neural circuits are sophisticated biological systems that choreograph behavioral processes vital for survival. While the inherent complexity of discrete neural circuits has proven difficult to decipher, many parallel methodological developments promise to help delineate the function and connectivity of molecularly defined neural circuits. Here, we review recent technological advances designed to precisely monitor and manipulate neural circuit activity. We propose a holistic, multifaceted approach for unraveling how behavioral states are manifested through the cooperative interactions between discrete neurocircuit elements.

Copyright © 2014 Elsevier Ltd. All rights reserved.

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Figures

Figure 1

Figure 1

Phototagging neuronal populations based on their genetic identity and projection targets during in vivo electrophysiological recordings. (A) Microinfusion of virally encoded ChR2-eYFP into a particular brain region isolates genetically defined neuronal subpopulations for optogenetic identification. (B) Multielectrode array is coupled to an optical fiber and implanted within the viral-targeted brain region to detect orthodromic elicited spikes. (C) Somata photostimulation via blue light delivery from an optical fiber evokes detectable orthodromic spikes at the tip of each electrode wire. (D) Virally encoded ChR2-eYFP is introduced to the presynaptic brain region, allowing the fused protein to traffic down to the axonal terminals within the postsynaptic brain region. (E) Optical fiber is inserted directly above the postsynaptic region to photoactivate the ChR2-expressing presynaptic fibers, while the multielectrode array is implanted in the presynaptic region to record the antidromic elicited spikes originating from the terminals within the postsynaptic target region. (F) Terminal photostimulation elicits a back propagating action potential (antidromic spike) that is detected near the cell bodies of the presynaptic region where the multielectrode array is located.

Figure 2

Figure 2

In vivo calcium imaging using genetically encoded indicators reveals discrete neuronal network activity. (A) Microinfusion of virally-encoded RCaMP (red) into the postsynaptic region allows two-photon imaging of somata calcium activity. In parallel, virally-encoded GCaMP (green) is targeted to the presynaptic input neurons, enabling simultaneous imaging of terminal calcium activity. (B) Schematic illustrating in vivo somata calcium imaging with a two-photon microscope in a head fixed mouse. (C) Configuration for calcium imaging in freely behaving mice using mini epi-fluorescent microscopes that are equipped with microendoscopes. (D) Illustration of microendoscopes that can detect calcium signals from GCaMP6.0-expressing cells during complex behavioral tasks.

Figure 3

Figure 3

Virally encoded neuronal tracing of genetically defined neuronal populations. (A) Schematic outlining viral targeting of ChR2-eYFP (top) and a confocal image showing ChR2-eYFP labeling of axon projections (bottom). (B) Diagrams for anterograde multisynaptic viral tracing using WGA. (C) Timeline and schematic for modified rabies virus tracing. Cre-expressing neurons (red) are first infected with TVA and RG (left) allowing subsequent monosynaptic retrograde viral spread of rabies virus to presynaptic input neurons (green; right).

Figure 4

Figure 4

Clearing tissue for imaging intact neural circuits. (A) Diagram for electrophoresis clearing of hydrogel-hybridized tissue. (B) Multiple rounds of immunostaining in cleared whole brains. (C) Configuration for high-speed light sheet imaging of intact neural circuits in cleared tissue. (D) Two-photon imaging of neuronal populations in a cleared whole brain.

Figure 5

Figure 5

In vivo optogenetic manipulations of genetically distinct neurons during behavioral measurements. (A) Somata photostimulation of genetically defined neuronal populations during a behavioral task. (B) Somata photoinhibition of genetically distinct neuronal populations during a behavioral task.

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