Optical Imaging Of Neuronal Activity Research Articles

Current Practice in Using Voltage Imaging to Record Fast Neuronal Activity: Successful Examples from Invertebrate to Mammalian Studies.

The optical imaging of neuronal activity with potentiometric probes has been credited with being able to address key questions in neuroscience via the simultaneous recording of many neurons. This technique, which was pioneered 50 years ago, has allowed researchers to study the dynamics of neural activity, from tiny subthreshold synaptic events in the axon and dendrites at the subcellular level to the fluctuation of field potentials and how they spread across large areas of the brain. Initially, synthetic voltage-sensitive dyes (VSDs) were applied directly to brain tissue via staining, but recent advances in transgenic methods now allow the expression of genetically encoded voltage indicators (GEVIs), specifically in selected neuron types. However, voltage imaging is technically difficult and limited by several methodological constraints that determine its applicability in a given type of experiment. The prevalence of this method is far from being comparable to patch clamp voltage recording or similar routine methods in neuroscience research. There are more than twice as many studies on VSDs as there are on GEVIs. As can be seen from the majority of the papers, most of them are either methodological ones or reviews. However, potentiometric imaging is able to address key questions in neuroscience by recording most or many neurons simultaneously, thus providing unique information that cannot be obtained via other methods. Different types of optical voltage indicators have their advantages and limitations, which we focus on in detail. Here, we summarize the experience of the scientific community in the application of voltage imaging and try to evaluate the contribution of this method to neuroscience research.

Light-Field Microscopy for Optical Imaging of Neuronal Activity: When Model-Based Methods Meet Data-Driven Approaches.

Understanding how networks of neurons process information is one of the key challenges in modern neuroscience. A necessary step to achieve this goal is to be able to observe the dynamics of large populations of neurons over a large area of the brain. Light-field microscopy (LFM), a type of scanless microscope, is a particularly attractive candidate for high-speed three-dimensional (3D) imaging. It captures volumetric information in a single snapshot, allowing volumetric imaging at video frame-rates. Specific features of imaging neuronal activity using LFM call for the development of novel machine learning approaches that fully exploit priors embedded in physics and optics models. Signal processing theory and wave-optics theory could play a key role in filling this gap, and contribute to novel computational methods with enhanced interpretability and generalization by integrating model-driven and data-driven approaches. This paper is devoted to a comprehensive survey to state-of-the-art of computational methods for LFM, with a focus on model-based and data-driven approaches.

A Guide to Emerging Technologies for Large-Scale and Whole-Brain Optical Imaging of Neuronal Activity.

The mammalian brain is a densely interconnected network that consists of millions to billions of neurons. Decoding how information is represented and processed by this neural circuitry requires the ability to capture and manipulate the dynamics of large populations at high speed and high resolution over a large area of the brain. Although the use of optical approaches by the neuroscience community has rapidly increased over the past two decades, most microscopy approaches are unable to record the activity of all neurons comprising a functional network across the mammalian brain at relevant temporal and spatial resolutions. In this review, we survey the recent development in optical technologies for Ca2+ imaging in this regard and provide an overview of the strengths and limitations of each modality and its potential for scalability. We provide guidance from the perspective of a biological user driven by the typical biological applications and sample conditions. We also discuss the potential for future advances and synergies that could be obtained through hybrid approaches or other modalities.

Optical imaging of neuronal activity and visualization of fine neural structures in non-desheathed nervous systems.

Locating circuit neurons and recording from them with single-cell resolution is a prerequisite for studying neural circuits. Determining neuron location can be challenging even in small nervous systems because neurons are densely packed, found in different layers, and are often covered by ganglion and nerve sheaths that impede access for recording electrodes and neuronal markers. We revisited the voltage-sensitive dye RH795 for its ability to stain and record neurons through the ganglion sheath. Bath-application of RH795 stained neuronal membranes in cricket, earthworm and crab ganglia without removing the ganglion sheath, revealing neuron cell body locations in different ganglion layers. Using the pyloric and gastric mill central pattern generating neurons in the stomatogastric ganglion (STG) of the crab, Cancer borealis, we found that RH795 permeated the ganglion without major residue in the sheath and brightly stained somatic, axonal and dendritic membranes. Visibility improved significantly in comparison to unstained ganglia, allowing the identification of somata location and number of most STG neurons. RH795 also stained axons and varicosities in non-desheathed nerves, and it revealed the location of sensory cell bodies in peripheral nerves. Importantly, the spike activity of the sensory neuron AGR, which influences the STG motor patterns, remained unaffected by RH795, while desheathing caused significant changes in AGR activity. With respect to recording neural activity, RH795 allowed us to optically record membrane potential changes of sub-sheath neuronal membranes without impairing sensory activity. The signal-to-noise ratio was comparable with that previously observed in desheathed preparations and sufficiently high to identify neurons in single-sweep recordings and synaptic events after spike-triggered averaging. In conclusion, RH795 enabled staining and optical recording of neurons through the ganglion sheath and is therefore both a good anatomical marker for living neural tissue and a promising tool for studying neural activity of an entire network with single-cell resolution.

Optical imaging of neuronal activity in rat primary motor cortex evoked by stimulation of the ventral tegmental area

Optical imaging of neuronal activity in rat primary motor cortex evoked by stimulation of the ventral tegmental area

Optical imaging of epileptiform activity in experimentally induced cortical malformations

Electrophysiological studies of human cortical dysplasia and rodent models revealed widespread hyperexcitability in the malformation itself as well as in its vicinity. We here analyzed the initiation of paroxysmal epileptiform activity using optical imaging of neuronal activity in rats with cortical malformations induced by neonatal freeze lesions. Brain slice preparations were incubated with the voltage-sensitive dye RH795 and neuronal activity was monitored using a fast-imaging photodiode array combined with standard field potential recordings. Spontaneous paroxysmal epileptiform activity emerged in all slices from animals with cortical malformations and sham-operated controls 20–40 min after omission of extracellular Mg 2+. Following electrophysiological and optical recordings, slices were histochemically processed. Using this approach, the present study demonstrated that in animals with freeze-lesion-induced focal cortical malformations, paroxysmal epileptiform activity always emerged from the dysplastic cortex and then spread to adjacent areas through superficial layers. This distribution of initiation sites was significantly different to sham-operated controls in which epileptogenic foci were located in various cytoarchitectonic areas. The present study indicates that following global changes in excitability, the dysplastic cortex itself is the main initiation site of paroxysmal epileptiform activity in animals with focal cortical malformations.

Selective Imaging of the Receptor Neuron Population in the Olfactory Bulb of Zebrafish and Mice

Convergence of the olfactory projections allows analysis of receptor repertoires in the olfactory bulb The neuronal processing of odors takes place in several types of neurons, including the sensory neurons, projection neurons and interneurons. To understand the neuronal representation of odors and eventually the encoding of those odors it is important to selectively measure the contributions of the different neuron populations to odor-induced neuronal activity. We are analyzing the odor responses of the population of olfactory receptor neurons in two experimental systems, zebrafish and mouse. Odor responses are measured in the receptor neuron terminals within the olfactory bulb. Thus, the response properties of many different odorant receptors can be visualized simultaneously by optical imaging of neuronal activity in the olfactory bulb, since olfactory receptor neurons expressing the same odorant receptor converge onto common neuropil structures in the olfactory bulb, the glomeruli (cf. Korsching, 2002). This transition from presumably stochastic expression of odorant receptor genes in scattered olfactory receptor neurons within the sensory epithelium to an ordered map in the olfactory bulb (Figure 1) allows a unique view on the size and composition of the receptor repertoires that are activated by particular odorants. Selective analysis of odor-induced presynaptic

Olfactory input to the parahippocampal region of the isolated guinea pig brain reveals weak entorhinal-to-perirhinal interactions.

The processing of olfactory inputs by the parahippocampal region has a central role in the organization of memory in mammals. The olfactory input is relayed to the hippocampus via interposed synapses located in the piriform and entorhinal cortices. Whether olfactory afferents directly or indirectly project to other areas of the parahippocampal region beside the entorhinal cortex (EC) is uncertain. We performed an electrophysiological and imaging study of the propagation pattern of the olfactory input carried by the fibres that form the lateral olfactory tract (LOT) into the parahippocampal region of the in vitro isolated guinea pig preparation. Laminar analysis was performed on field potential depth profiles recorded with 16-channel silicon probes at different sites of the insular-parahippocampal cortex. The LOT input induced a large amplitude polysynaptic response in the lateral EC. Following appropriate LOT stimulation, a late response generated by the interposed activation of the hippocampus was observed in the medial EC. LOT stimulation did not induce any local response in area 36 of the perirhinal cortex (PRC), while a small amplitude potential with a delay similar to the lateral EC response was inconsistently observed in PRC area 35. No PRC potentials were observed following the responses evoked by LOT stimulation in either the lateral or the medial EC. These findings were substantiated by current source density analysis of PRC laminar profiles. To further verify the absence of EC-to-PRC field interactions after LOT stimulation, high-resolution optical imaging of neuronal activity was performed after perfusion of the isolated brain with the voltage-sensitive dye RH-795. The optical recordings confirmed that olfactory-induced activity in the EC does not induce massive PRC activation. The present findings suggest that the olfactory input into the parahippocampal region is confined to the entorhinal cortex. The results also imply that, as demonstrated for the PRC-to-EC pathway, the propagation of neuronal activity from the EC to the PRC is hindered, possibly by a powerful inhibitory control generated within the EC.

Odorant Feature Detection: Activity Mapping of Structure Response Relationships in the Zebrafish Olfactory Bulb

The structural determinants of an odor molecule necessary and/or sufficient for interaction with the cognate olfactory receptor(s) are not known. Olfactory receptor neurons expressing the same olfactory receptor converge in the olfactory bulb. Thus, optical imaging of neuronal activity in the olfactory bulb can visualize at once the contributions by all the different olfactory receptors responsive to a particular odorant. We have used this technique to derive estimates about the structural requirements and minimal number of different zebrafish olfactory receptors that respond to a series of naturally occurring amino acids and some structurally related compounds. We report that the alpha-carboxyl group, the alpha-amino group, and l-conformation of the amino acid are all required for activation of amino acid-responsive receptors. Increasing carbon chain length recruits successively more receptors. With increasing concentrations, the activity patterns induced by a homolog series of amino acids became more similar to each other. At intermediate concentrations patterns were unique across substances and across concentrations. The introduction of a terminal amino group (charged) both recruits additional receptors and prevents binding to some of the receptors that were responsive to the unsubstituted analog. In contrast, the introduction of a beta-hydroxyl group (polar) excluded the odorants from some of the receptors that are capable of binding the unsubstituted analog. Cross-adaptation experiments independently confirmed these results. Thus, odorant detection requires several different receptors even for relatively simple odorants such as amino acids, and individual receptors require the presence of some molecular features, the absence of others, and tolerate still other molecular features.

Optical imaging of neuronal activity in tissue labeled by retrograde transport of Calcium Green Dextran

In many neurophysiological studies it is desirable to simultaneously record the activity of a large number of neurons. This is particularly true in the study of vertebrate motor systems that generate rhythmic behaviors, such as the pattern generator for locomotion in vertebrate spinal cord. Optical imaging of neurons labeled with appropriate fluorescent dyes, in which fluorescence is activity-dependent, provides a means to record the activity of many neurons at the same time, while also providing fine spatial resolution of the position and morphology of active neurons. Voltage-sensitive dyes have been explored for this purpose and have the advantage of rapid response to transmembrane voltage changes [3, 7]. However, voltage-sensitive dyes bleach readily, which results in phototoxic damage and limits the time that labeled neurons can be imaged. In addition, the signal-to-noise ratio is typically small, so that averaging of responses is usually required [3, 7, 8]. As an alternative to voltage-sensitive dyes, calcium-sensitive dyes can exhibit large changes in fluorescence [9]. Most neurons contain voltage-sensitive Ca 2+ channels, and numerous reports indicate that neuronal activity is accompanied by increased intracellular Ca 2+ concentration [14, 16, 21, 22, 24, 25]. In this protocol we describe a method to use retrograde transport of the dextran conjugate [6]of a calcium-sensitive dye (Calcium Green Dextran) to label selectively populations of brain and spinal interneurons in a primitive vertebrate (lamprey), for subsequent video-rate imaging of changes in intracellular fluorescence during neuronal activity. Although described with specific reference to lampreys, the technique has also been applied to embryonic chick spinal cord and larval zebrafish preparations and should be easily adaptable to other systems [4, 15, 16]. The most significant novel feature of the protocol is the use of retrograde axonal transport to selectively fill neurons that have known axonal trajectories. Using lampreys, we have obtained activity-sensitive labeling across longer distances and over a longer transport time (up to 14 mm and 4 days) than has been reported in other species [4, 14, 16]. In addition, retrograde transport allows filling of neurons more deeply within tissue than would be possible with bath application of calcium-sensitive dyes. Furthermore, the dyes are readily taken up by adult tissues, while bath application is usually limited to embryonic and neonatal vertebrate nervous tissues (although the reasons for this limitation are not clear). Attempts to load the AM (acetomethoxy) esters of calcium-sensitive dyes into lamprey spinal cord neurons by bath application have been unsuccessful (McPherson, unpublished observations, and [1]).

1919 Optical imaging of neuronal activity and coupled metabolic activity in rat barrel cortex

1919 Optical imaging of neuronal activity and coupled metabolic activity in rat barrel cortex

1812 Optical imaging of neuronal activity with a voltage-sensitive dye in guinea pig piriform cortex in vitro

1812 Optical imaging of neuronal activity with a voltage-sensitive dye in guinea pig piriform cortex in vitro

Optical imaging of neuronal activity of auditory cortex: Toru Hashimoto, Inst. Med. Dent. Engin., Tokyo Med. Dent. Univ., Chiyoda-ku, Tokyo 101, Japan

Optical imaging of neuronal activity of auditory cortex: Toru Hashimoto, Inst. Med. Dent. Engin., Tokyo Med. Dent. Univ., Chiyoda-ku, Tokyo 101, Japan

Optical imaging of neuronal activity.

Optical imaging of neuronal activity.

Real-time optical imaging of neuronal activity

The availability of suitable voltage-sensitive dyes and arrays of photodetectors has facilitated the optical monitoring of electrical activity simultaneously from hundreds of sites on the processes of single nerve cells, both in culture and in invertebrate ganglia. This method also provides a unique ability to detect activity in many individual neurons in an entire invertebrate ganglion controlling particular behavioral responses. The in-vitro activity of individual populations of neuronal elements (cell bodies, axons, dentrites or nerve terminals) at many neighboring loci in mammalian brain slices or isolated brain structures has been investigated. Recently dynamic patterns of electrical activity evoked in the intact vertebrate or mammalian brain by natural stimuli have also been monitored. By employing computerized optical recording and a display processor, video-displayed images of neuronal elements can be superimposed on the corresponding patterns of the optically detected electrical activity, thus allowing the spatio-temporal patterns of intracellular activity to be visualized in slow motion.