(2021) Current Opinion in Neurobiology. 68, p. 67-75 Abstract
Mammalian social interactions are orchestrated by a wide array of neural circuits. While some aspects of social behaviors are driven by subcortical circuits, and are considered to be highly conserved and hard-wired, others require dynamic and context-dependent modulation that integrates current state, past experience and goal-driven action selection. These cognitive social processes are known to be dependent on the integrity of the prefrontal cortex. However, the circuit mechanisms through which the prefrontal cortex supports complex social functions are still largely unknown, and it is unclear if and how they diverge from prefrontal control of behavior outside of the social domain. Here we review recent studies exploring the role of prefrontal circuits in mammalian social functions, and attempt to synthesize these findings to a holistic view of prefrontal control of sociability.
(2020) Handbook of Neurophotonics. Pavone F. S. & Shoham S.(eds.). p. 235-269 Abstract
Optogenetic technology uses light to control or modulate neuronal function, providing a means of interacting with neurons that is unchallenged in its temporal resolution, spatial resolution, and cell type specificity. Optogenetic experiments, particularly involving inhibitory optogenetic tools, often require prolonged illumination of neural tissue which may cause temperature changes. Numerous studies ensued, utilizing Channelrhodopsin-2 and other microbial rhodopsins in a variety of neural circuits and animal models. In neural circuits, connectivity and function are thought to be tightly linked. Neurons projecting to defined long-range targets have been shown to possess defined functional properties, and dissecting these roles has been a major application of optogenetic tools. Optogenetics is readily applicable to light-accessible preparations such as cultured neurons, brain slices, transparent organisms such as zebrafish larvae, or to the cortical surface of rodents, allowing for extensive flexibility in light delivery. Light needs to reach the target with sufficient irradiance to induce opsin activation in a sufficient number of neurons.
Anatomically and functionally distinct thalamocortical inputs to primary and secondary mouse whisker somatosensory cortices(2020) Nature Communications. 11, 1, 3342. Abstract
Subdivisions of mouse whisker somatosensory thalamus project to cortex in a region-specific and layer-specific manner. However, a clear anatomical dissection of these pathways and their functional properties during whisker sensation is lacking. Here, we use anterograde trans-synaptic viral vectors to identify three specific thalamic subpopulations based on their connectivity with brainstem. The principal trigeminal nucleus innervates ventral posterior medial thalamus, which conveys whisker-selective tactile information to layer 4 primary somatosensory cortex that is highly sensitive to self-initiated movements. The spinal trigeminal nucleus innervates a rostral part of the posterior medial (POm) thalamus, signaling whisker-selective sensory information, as well as decision-related information during a goal-directed behavior, to layer 4 secondary somatosensory cortex. A caudal part of the POm, which apparently does not receive brainstem input, innervates layer 1 and 5A, responding with little whisker selectivity, but showing decision-related modulation. Our results suggest the existence of complementary segregated information streams to somatosensory cortices.
(2020) Nature Nanotechnology. 15, 8, p. 690-697 Abstract[All authors]
Understanding the function of nitric oxide, a lipophilic messenger in physiological processes across nervous, cardiovascular and immune systems, is currently impeded by the dearth of tools to deliver this gaseous molecule in situ to specific cells. To address this need, we have developed iron sulfide nanoclusters that catalyse nitric oxide generation from benign sodium nitrite in the presence of modest electric fields. Locally generated nitric oxide activates the nitric oxide-sensitive cation channel, transient receptor potential vanilloid family member 1 (TRPV1), and the latency of TRPV1-mediated Ca(2+)responses can be controlled by varying the applied voltage. Integrating these electrocatalytic nanoclusters with multimaterial fibres allows nitric oxide-mediated neuronal interrogation in vivo. The in situ generation of nitric oxide in the ventral tegmental area with the electrocatalytic fibres evoked neuronal excitation in the targeted brain region and its excitatory projections. This nitric oxide generation platform may advance mechanistic studies of the role of nitric oxide in the nervous system and other organs.
(2020) Nature Neuroscience. 23, 5, p. 625-637 Abstract[All authors]
Decades of research support the idea that associations between a conditioned stimulus (CS) and an unconditioned stimulus (US) are encoded in the lateral amygdala (LA) during fear learning. However, direct proof for the sources of CS and US information is lacking. Definitive evidence of the LA as the primary site for cue association is also missing. Here, we show that calretinin (Calr)-expressing neurons of the lateral thalamus (Calr
+LT neurons) convey the association of fast CS (tone) and US (foot shock) signals upstream from the LA in mice. Calr
+LT input shapes a short-latency sensory-evoked activation pattern of the amygdala via both feedforward excitation and inhibition. Optogenetic silencing of Calr
+LT input to the LA prevents auditory fear conditioning. Notably, fear conditioning drives plasticity in Calr
+LT neurons, which is required for appropriate cue and contextual fear memory retrieval. Collectively, our results demonstrate that Calr
+LT neurons provide integrated CS–US representations to the LA that support the formation of aversive memories.
Wireless Optogenetic Stimulation of Oxytocin Neurons in a Semi-natural Setup Dynamically Elevates Both Pro-social and Agonistic Behaviors(2020) Neuron. 107, 4, p. 644-655 Abstract[All authors]
Complex behavioral phenotyping techniques are becoming more prevalent in the field of behavioral neuroscience, and thus methods for manipulating neuronal activity must be adapted to fit into such paradigms. Here, we present a head-mounted, magnetically activated device for wireless optogenetic manipulation that is compact, simple to construct, and suitable for use in group-living mice in an enriched semi-natural arena over several days. Using this device, we demonstrate that repeated activation of oxytocin neurons in male mice can have different effects on pro-social and agonistic behaviors, depending on the social context. Our findings support the social salience hypothesis of oxytocin and emphasize the importance of the environment in the study of social neuromodulators. Our wireless optogenetic device can be easily adapted for use in a variety of behavioral paradigms, which are normally hindered by tethered light delivery or a limited environment.
(2020) Science Advances. 6, 15, 4232. Abstract[All authors]
A defining feature of sleep is reduced responsiveness to external stimuli, but the mechanisms mediating sensory-evoked arousal remain unclear. We hypothesized that reduced locus coeruleus (LC) norepinephrine (NE) activity during sleep mediates unresponsiveness, and its action promotes sensory-evoked awakenings. We tested this using electrophysiological, behavioral, pharmacological, and optogenetic techniques alongside auditory stimulation in freely behaving rats. We found that systemic reduction in NE signaling lowered probability of sound-evoked awakenings (SEAs). The level of tonic LC activity during sleep anticipated SEAs. Optogenetic LC activation promoted arousal as evident in sleep-wake transitions, EEG desynchronization, and pupil dilation. Minimal LC excitation before sound presentation increased SEA probability. Optogenetic LC silencing using a soma-targeted anion-conducting channelrhodopsin (stGtACR2) suppressed LC spiking and constricted pupils. Brief periods of LC opto-silencing reduced the probability of SEAs. Thus, LC-NE activity determines the likelihood of sensory-evoked awakenings, and its reduction during sleep constitutes a key factor mediating behavioral unresponsiveness.
(2020) Neuron. 106, 1, p. 14-16 Abstract
Neurons in neocortical layer 1 (L1) are thought to regulate attentional processes through integration of longrange inputs and disinhibitory effects on the underlying cortex. A new study combines genetically targeted voltage imaging and optogenetics to elucidate the input-output transformations of the L1 network in the mouse somatosensory cortex, revealing unique features of sensory-evoked dynamics in L1 neurons.
(2020) Nature Neuroscience. 23, 1, p. 47-60 Abstract[All authors]
Scheggia et al. show that a specific subpopulation of cortical neurons expressing somatostatin in the prefrontal cortex has a primary role in orchestrating the ability of mice to discriminate positive and negative affective states in others.The prefrontal cortex (PFC) is implicated in processing of the affective state of others through non-verbal communication. This social cognitive function is thought to rely on an intact cortical neuronal excitatory and inhibitory balance. Here combining in vivo electrophysiology with a behavioral task for affective state discrimination in mice, we show a differential activation of medial PFC (mPFC) neurons during social exploration that depends on the affective state of the conspecific. Optogenetic manipulations revealed a double dissociation between the role of interneurons in social cognition. Specifically, inhibition of mPFC somatostatin (SOM+), but not of parvalbumin (PV+) interneurons, abolishes affective state discrimination. Accordingly, synchronized activation of mPFC SOM+ interneurons selectively induces social discrimination. As visualized by in vivo single-cell microendoscopic Ca2+ imaging, an increased synchronous activity of mPFC SOM+ interneurons, guiding inhibition of pyramidal neurons, is associated with affective state discrimination. Our findings provide new insights into the neurobiological mechanisms of affective state discrimination.
(2019) Nature Neuroscience. 22, 12, p. 2013-2022 Abstract
The prefrontal cortex (PFC) plays an important role in regulating social functions in mammals, and its dysfunction has been linked to social deficits in neurodevelopmental disorders. Yet little is known of how the PFC encodes social information and how social representations may be altered in such disorders. Here, we show that neurons in the medial PFC of freely behaving male mice preferentially respond to socially relevant olfactory cues. Population activity patterns in this region differed between social and nonsocial stimuli and underwent experience-dependent refinement. In mice lacking the autism-associated gene Cntnap2, both the categorization of sensory stimuli and the refinement of social representations were impaired. Noise levels in spontaneous population activity were higher in Cntnap2 knockouts and correlated with the degree to which social representations were disrupted. Our findings elucidate the encoding of social sensory cues in the medial PFC and provide a link between altered prefrontal dynamics and autism-associated social dysfunction.
(2019) eLife. 8, 52665. Abstract
Mouse primary somatosensory barrel cortex (wS1) processes whisker sensory information, receiving input from two distinct thalamic nuclei. The first-order ventral posterior medial (VPM) somatosensory thalamic nucleus most densely innervates layer 4 (L4) barrels, whereas the higher-order posterior thalamic nucleus (medial part, POm) most densely innervates L1 and L5A. We optogenetically stimulated VPM or POm axons, and recorded evoked excitatory postsynaptic potentials (EPSPs) in different cell-types across cortical layers in wS1. We found that excitatory neurons and parvalbumin-expressing inhibitory neurons received the largest EPSPs, dominated by VPM input to L4 and POm input to L5A. In contrast, somatostatin-expressing inhibitory neurons received very little input from either pathway in any layer. Vasoactive intestinal peptide-expressing inhibitory neurons received an intermediate level of excitatory input with less apparent layer-specificity. Our data help understand how wS1 neocortical microcircuits might process and integrate sensory and higher-order inputs.
(2019) Trends in Pharmacological Sciences. 40, 6, p. 362-364 Abstract
Chemogenetic techniques allow selective manipulation of neurons by activating engineered actuator proteins with otherwise inert effector molecules. A recent study (Magnus et al. Science 2019;364: eaav5282) describes the coevolution of highly potent actuator effector pairs based on a clinically approved antismoking drug. These tools allow selective excitation or inhibition of neurons in the living brain with high specificity and no detectable side-effects.
Human genetics and neuropathology suggest a link between miR-218 and amyotrophic lateral sclerosis pathophysiology(2019) Science Translational Medicine. 11, 523, 5264. Abstract[All authors]
Motor neuron-specific microRNA-218 (miR-218) has recently received attention because of its roles in mouse development. However, miR-218 relevance to human motor neuron disease was not yet explored. Here, we demonstrate by neuropathology that miR-218 is abundant in healthy human motor neurons. However, in amyotrophic lateral sclerosis (ALS) motor neurons, miR-218 is down-regulated and its mRNA targets are reciprocally up-regulated (derepressed). We further identify the potassium channel Kv10.1 as a new miR-218 direct target that controls neuronal activity. In addition, we screened thousands of ALS genomes and identified six rare variants in the human miR-218-2 sequence. miR-218 gene variants fail to regulate neuron activity, suggesting the importance of this small endogenous RNA for neuronal robustness. The underlying mechanisms involve inhibition of miR-218 biogenesis and reduced processing by DICER. Therefore, miR-218 activity in motor neurons may be susceptible to failure in human ALS, suggesting that miR-218 may be a potential therapeutic target in motor neuron disease.
(2018) Current Opinion in Neurobiology. 52, p. 149-155 Abstract
Animals constantly evaluate their environment in order to avoid potential threats and obtain reward in the form of food, shelter and social interactions. In order to appropriately respond to sensory cues from the environment, the brain needs to form and store multiple cue-outcome associations. These can then be used to form predictions of the valence of sounds, smells and other sensory inputs arising from the surroundings. However, these associations must be subject to constant update, as the environment can rapidly change. Failing to adapt to such change can be detrimental to survival. Several systems in the mammalian brain have evolved to perform these important behavioral functions. Among these systems, the amygdala and prefrontal cortex are prominent players. Although the amygdala has been shown to form strong cue-outcome associations, the prefrontal cortex is essential for modifying these associations through extinction and reversal learning, and synaptic plasticity occurring in the strong reciprocal connections between these structures is thought to underlie both adaptive and maladaptive learning. Here we review the synaptic organization of the amygdala-prefrontal circuit, and summarize the physiological and behavioral evidence for its involvement in appetitive and aversive learning.
Two-Photon Bidirectional Control and Imaging of Neuronal Excitability with High Spatial Resolution In Vivo(2018) Cell Reports. 22, 11, p. 3087-3098 Abstract[All authors]
Sensory information is encoded within the brain in distributed spatiotemporal patterns of neuronal activity. Understanding how these patterns influence behavior requires a method to measure and to bidirectionally perturb with high spatial resolution the activity of the multiple neuronal cell types engaged in sensory processing. Here, we combined two-photon holography to stimulate neurons expressing blue light-sensitive opsins (ChR2 and GtACR2) with two-photon imaging of the red-shifted indicator jRCaMP1a in the mouse neocortex in vivo. We demonstrate efficient control of neural excitability across cell types and layers with holo-graphic stimulation and improved spatial resolution by opsin somatic targeting. Moreover, we performed simultaneous two-photon imaging of jRCaMP1a and bidirectional two-photon manipulation of cellular activity with negligible effect of the imaging beam on opsin excitation. This all-optical approach represents a powerful tool to causally dissect how activity patterns in specified ensembles of neurons determine brain function and animal behavior.
(2018) Nature Communications. 9, 4125. Abstract
Optogenetic silencing allows time-resolved functional interrogation of defined neuronal populations. However, the limitations of inhibitory optogenetic tools impose stringent constraints on experimental paradigms. The high light power requirement of light-driven ion pumps and their effects on intracellular ion homeostasis pose unique challenges, particularly in experiments that demand inhibition of a widespread neuronal population in vivo. Guillardia theta anion-conducting channelrhodopsins (GtACRs) are promising in this regard, due to their high single-channel conductance and favorable photon-ion stoichiometry. However, GtACRs show poor membrane targeting in mammalian cells, and the activity of such channels can cause transient excitation in the axon due to an excitatory chloride reversal potential in this compartment. Here, we address these problems by enhancing membrane targeting and subcellular compartmentalization of GtACRs. The resulting soma-targeted GtACRs show improved photocurrents, reduced axonal excitation and high light sensitivity, allowing highly efficient inhibition of neuronal activity in the mammalian brain.
(2018) bioRxiv. p. 321182 Abstract
The prefrontal cortex (PFC) plays an important role in regulating social functions in mammals, and impairments in this region have been linked with social dysfunction in psychiatric disorders. Yet little is known of how the PFC encodes social information and of how social representations may be altered in such disorders. Here, we show that neurons in the medial PFC (mPFC) of freely behaving mice preferentially respond to socially-relevant sensory cues. Population activity patterns in the mPFC differed considerably between social and nonsocial stimuli and underwent experience-dependent refinement. In Cntnap2 knockout mice, a genetic model of autism, both the categorization of sensory stimuli and the refinement of social representations were impaired. Noise levels in spontaneous population activity were higher in Cntnap2 mice, and correlated strongly with the degree to which social representations were disrupted. Our findings elucidate the encoding of social sensory cues in the mPFC, and provide an important link between altered prefrontal dynamics and autism-associated social dysfunction.
Our latest preprint, in which we characterize the responses of neurons in the mouse prefrontal cortex to socially-relevant odors. We also compare the prefrontal representation of social and non-social odors in wild-type mice and in Cntnap2 knockout mice, a genetic model of autism and related neurodevelopmental disorders.
(2017) Neuron. 95, 3, p. 504-529 Abstract
Reversible silencing of neuronal activity is a powerful approach for isolating the roles of specific neuronal populations in circuit dynamics and behavior. In contrast with neuronal excitation, for which the majority of studies have used a limited number of optogenetic and chemogenetic tools, the number of genetically encoded tools used for inhibition of neuronal activity has vastly expanded. Silencing strategies vary widely in their mechanism of action and in their spatial and temporal scales. Although such manipulations are commonly applied, the design and interpretation of neuronal silencing experiments present unique challenges, both technically and conceptually. Here, we review the most commonly used tools for silencing neuronal activity and provide an in-depth analysis of their mechanism of action and utility for particular experimental applications. We further discuss the considerations that need to be given to experimental design, analysis, and interpretation of collected data. Finally, we discuss future directions for the development of new silencing approaches in neuroscience.
(2017) Proceedings of the National Academy of Sciences of the United States of America. 114, 26, p. E5167-E5176 Abstract[All authors]
Key mitochondrial functions such as ATP production, Ca2+ uptake and release, and substrate accumulation depend on the proton electrochemical gradient (Delta mu H+) across the inner membrane. Although several drugs can modulate Delta mu H+, their effects are hardly reversible, and lack cellular specificity and spatial resolution. Although channelrhodopsins are widely used to modulate the plasma membrane potential of excitable cells, mitochondria have thus far eluded optogenetic control. Here we describe a toolkit of optometabolic constructs based on selective targeting of channelrhodopsins with distinct functional properties to the inner mitochondrial membrane of intact cells. We show that our strategy enables a light-dependent control of the mitochondrial membrane potential (Delta Psi(m)) and coupled mitochondrial functions such as ATP synthesis by oxidative phosphorylation, Ca2+ dynamics, and respiratory metabolism. By directly modulating Delta Psi(m), the mitochondriatargeted opsinswere used to control complex physiological processes such as spontaneous beats in cardiac myocytes and glucose-dependent ATP increase in pancreatic beta-cells. Furthermore, our optometabolic tools allow modulation of mitochondrial functions in single cells and defined cell regions.
CRF receptor type 2 neurons in the posterior bed nucleus of the stria terminalis critically contribute to stress recovery(2017) Molecular Psychiatry. 22, 12, p. 1691-1700 Abstract[All authors]
The bed nucleus of the stria terminalis (BNST) is critical in mediating states of anxiety, and its dysfunction has been linked to stress-related mental disease. Although the anxiety-related role of distinct subregions of the anterior BNST was recently reported, little is known about the contribution of the posterior BNST (pBNST) to the behavioral and neuroendocrine responses to stress. Previously, we observed abnormal expression of corticotropin-releasing factor receptor type 2 (CRFR2) to be associated with post-traumatic stress disorder (PTSD)-like symptoms. Here, we found that CRFR2-expressing neurons within the pBNST send dense inhibitory projections to other stress-related brain regions (for example, the locus coeruleus, medial amygdala and paraventricular nucleus), implicating a prominent role of these neurons in orchestrating the neuroendocrine, autonomic and behavioral response to stressful situations. Local CRFR2 activation by urocortin 3 depolarized the cells, increased the neuronal input resistance and increased firing of action potentials, indicating an enhanced excitability. Furthermore, we showed that CRFR2-expressing neurons within the pBNST are critically involved in the modulation of the behavioral and neuroendocrine response to stress. Optogenetic activation of CRFR2 neurons in the pBNST decreased anxiety, attenuated the neuroendocrine stress response, ameliorated stress-induced anxiety and impaired the fear memory for the stressful event. Moreover, activation following trauma exposure reduced the susceptibility for PTSD-like symptoms. Optogenetic inhibition of pBNST CRFR2 neurons yielded opposite effects. These data indicate the relevance of pBNST activity for adaptive stress recovery.
The Anterior Insular Cortex -> Central Amygdala Glutamatergic Pathway Is Critical to Relapse after Contingency Management(2017) Neuron. 96, 2, p. 414-427 Abstract[All authors]
Despite decades of research on neurobiological mechanisms of psychostimulant addiction, the only effective treatment for many addicts is contingency management, a behavioral treatment that uses alternative non-drug reward to maintain abstinence. However, when contingency management is discontinued, most addicts relapse to drug use. The brain mechanisms underlying relapse after cessation of contingency management are largely unknown, and, until recently, an animal model of this human condition did not exist. Here we used a novel rat model, in which the availability of a mutually exclusive palatable food maintains prolonged voluntary abstinence from intravenous methamphetamine self-administration, to demonstrate that the activation of monosynaptic glutamatergic projections from anterior insular cortex to central amygdala is critical to relapse after the cessation of contingency management. We identified the anterior insular cortex-to-central amygdala projection as a new addiction-and motivation-related projection and a potential target for relapse prevention.
(2017) Neuromethods. Stroh A.(eds.). p. 25-42 Abstract
Optogenetic techniques allow versatile, cell type-specific light-based control of cellular activity in diverse set of cells, circuits, and brain structures. Optogenetic actuators are genetically encoded light-sensitive membrane proteins that can be selectively introduced into cellular circuits in the living brain using a variety of genetic approaches. Gene targeting approaches used in optogenetic studies vary greatly in their specificity, their spatial coverage, the level of transgene expression and their potential adverse effects on neuronal cell health. Here, we describe the major gene targeting approaches utilized in optogenetics and provide a simple set of guidelines through which these approaches can be evaluated when designing an in vitro or in vivo optogenetic study.
(2017) Current Biology. 27, 4, p. 549-555 Abstract
The ability to plan and execute appropriately timed responses to external stimuli is based on a well-orchestrated balance between movement initiation and inhibition. In impulse control disorders involving the prefrontal cortex (PFC) , this balance is disturbed, emphasizing the critical role that PFC plays in appropriately timing actions [2-4]. Here, we employed optogenetic and electro-physiological techniques to systematically analyze the functional role of five key subareas of the rat medial PFC (mPFC) and orbitofrontal cortex (OFC) in action control [5-9]. Inactivation of mPFC subareas induced drastic changes in performance, namely an increase (prelimbic cortex, PL) or decrease (infralimbic cortex, IL) of premature responses. Additionally, electrophysiology revealed a significant decrease in neuronal activity of a PL subpopulation prior to premature responses. In contrast, inhibition of OFC subareas (mainly the ventral OFC, i.e., VO) significantly impaired the ability to respond rapidly after external cues. Consistent with these findings, mPFC activity during response preparation predicted trial outcomes and reaction times significantly better than OFC activity. These data support the concept of opposing roles of IL and PL in directing proactive behavior and argue for an involvement of OFC in predominantly reactive movement control. By attributing defined roles to rodent PFC sections, this study contributes to a deeper understanding of the functional heterogeneity of this brain area and thus may guide medically relevant studies of PFC-associated impulse control disorders in this animal model for neural disorders [10-12].
(2017) Nature Neuroscience. 20, 6, p. 836-844 Abstract
Fear-related disorders are thought to reflect strong and persistent fear memories. The basolateral amygdala (BLA) and the medial prefrontal cortex (mPFC) form strong reciprocal synaptic connections that play a key role in acquisition and extinction of fear memories. While synaptic contacts of BLA cells onto mPFC neurons are likely to play a crucial role in this process, the BLA connects with several additional nuclei within the fear circuit that could relay fear-associated information to the mPFC, and the contribution of direct monosynaptic BLA–mPFC inputs is not yet clear. Here we establish an optogenetic stimulation protocol that induces synaptic depression in BLA–mPFC synapses. In behaving mice, optogenetic high-frequency stimulation of BLA inputs to mPFC interfered with retention of cued associations, attenuated previously acquired cue-associated responses in mPFC neurons and facilitated extinction. Our findings demonstrate the contribution of BLA inputs to mPFC in forming and maintaining cued fear associations.
(2017) PLoS ONE. 12, 7, 0179232. Abstract
Sodium pumping rhodopsins (NaRs) are a unique member of the microbial-type I rhodopsin family which actively transport Na+ and H+ depending on ionic condition. In this study, we surveyed 12 different NaRs from various sources of eubacteria for their electrophysiological as well as spectroscopic properties. In mammalian cells several of these NaRs exhibited a Na+ based pump photocurrent and four interesting candidates were chosen for further characterization. Voltage dependent photocurrent amplitudes revealed a membrane potential-sensitive turnover rate, indicating the presence of an electrically-charged intermediate(s) in the photocycle reaction. The NaR from Salinarimonas rosea DSM21201 exhibited a red-shifted absorption spectrum, and slower kinetics compared to the first described sodium pump, KR2. Although the ratio of Na+ to H+ ion transport varied among the NaRs we tested, the NaRs from Flagellimonas sp_DIK and Nonlabens sp_YIK_SED-11 showed significantly higher Na+ selectivity when compared to KR2. All four further investigated NaRs showed a functional expression in dissociated hippocampal neuron culture and hyperpolarizing activity upon light-stimulation. Additionally, all four NaRs allowed optical inhibition of electrically-evoked neuronal spiking. Although efficiency of silencing was 3-5 times lower than silencing with the enhanced version of the proton pump AR3 from Halorubrum sodomense, our data outlines a new approach for hyperpolarization of excitable cells without affecting the intracellular and extracellular proton environment.
(2017) Neuron. 96, 4, p. 730-735 Abstract
Science is ideally suited to connect people from different cultures and thereby foster mutual understanding. To promote international life science collaboration, we have launched "The Science Bridge'' initiative. Our current project focuses on partnership between Western and Middle Eastern neuroscience communities.[All authors]
(2016) Nature Neuroscience. 19, 11, p. 1489-1496 Abstract[All authors]
Social encounters are associated with varying degrees of emotional arousal and stress. The mechanisms underlying adequate socioemotional balance are unknown. The medial amygdala (MeA) is a brain region associated with social behavior in mice. Corticotropin-releasing factor receptor type-2 (CRF-R2) and its specific ligand urocortin-3 (Ucn3), known components of the behavioral stress response system, are highly expressed in the MeA. Here we show that mice deficient in CRF-R2 or Ucn3 exhibit abnormally low preference for novel conspecifics. MeA-specific knockdown of Crfr2 (Crhr2) in adulthood recapitulated this phenotype. In contrast, pharmacological activation of MeA CRF-R2 or optogenetic activation of MeA Ucn3 neurons increased preference for novel mice. Furthermore, chemogenetic inhibition of MeA Ucn3 neurons elicited pro-social behavior in freely behaving groups of mice without affecting their hierarchal structure. These findings collectively suggest that the MeA Ucn3 CRF-R2 system modulates the ability of mice to cope with social challenges.
(2016) Nature Neuroscience. 19, 4, p. 554-556 Abstract
We investigated the efficacy of optogenetic inhibition at presynaptic terminals using halorhodopsin, archaerhodopsin and chloride-conducting channelrhodopsins. Precisely timed activation of both archaerhodopsin and halorhodpsin at presynaptic terminals attenuated evoked release. However, sustained archaerhodopsin activation was paradoxically associated with increased spontaneous release. Activation of chloride-conducting channelrhodopsins triggered neurotransmitter release upon light onset. Thus, the biophysical properties of presynaptic terminals dictate unique boundary conditions for optogenetic manipulation.
(2016) Neuron. 92, 3, p. 564-566 Abstract
Major resources are now available to develop tools and technologies aimed at dissecting the circuitry and computations underlying behavior, unraveling the underpinnings of brain disorders, and understanding the neural substrates of cognition. Scientists from around the world shared their views around new tools and technologies to drive advances in neuroscience.
(2015) Optogenetics. Koizumi A., Kandori H. & Yawo H.(eds.). p. 331-339 Abstract
Patients with psychiatric disease are diagnosed by psychiatrists based on the information of non-quantitative objective parameters, including behavioral phenotypes. However, how any neural mechanism affects such behavioral phenotypes in patients is still unclear. Recent functional studies suggested the alteration in brain neural/network activity responds to subjected stimuli in some brain regions of psychiatric patients, indicating that excitatory/inhibitory (E/I) imbalance occurs in local neural circuits responsible for regional activities. Moreover, in human genetics, a large number of genetic variations, including single nucleotide variation (SNV) and copy number variation (CNV), have been found in psychiatric patients. Such variations must be causes of a psychiatric behavioral phenotype, while understanding of the relationship between genetic variations and neural mechanisms underlying psychiatric behavior remains poor due to the heterogeneity in genetic variations. Functional and molecular analyses with SNV and CNV suggest the mutations of synaptic genes might contribute to the abnormal neural activity due to synaptic dysfunction. To overcome the sparse knowledge of psychiatric neural phenotypes, we can choose two ways: one is to detect the abnormalities of neural function in animal models with the genetic variations found in human genetics, which means construct validity of an animal model, and another is to reproduce the behavioral phenotypes seen in psychiatric disorders by artificially controlling neural functions, referred to as face validity. Analyzing the neural activity in animal models with construct and face validities would help us understand the neural state in psychiatric patients.
(2015) Cell Reports. 11, 6, p. 859-865 Abstract[All authors]
Invivo experimental evidence indicates that acute neuronal activation increases Aβ release from presynaptic terminals, whereas long-term effects ofchronic synaptic activation on Aβ pathology remain unclear. To address this issue, we adopted optogenetics and transduced stabilized step-function opsin, a channelrhodopsin engineered to elicit a long-lasting neuronal hyperexcitability, into the hippocampal perforant pathway of APP transgenic mice. Invivo microdialysis revealed a ~24% increase in the hippocampal interstitial fluid Aβ42 levels immediately after acute light activation. Five months of chronic optogenetic stimulation increased Aβ burden specifically in the projection area of the perforant pathway (i.e., outer molecular layer of the dentate gyrus) of the stimulated side by ~2.5-fold compared with that in the contralateral side. Epileptic seizures were observed during the course of chronic stimulation, which might have partly contributed to the Aβ pathology. These findings implicate functional abnormalities of specific neuronal circuitry in Aβ pathology and Alzheimer disease.
(2015) Nature. 525, 7570, p. 519-522 26375004. Abstract
It is commonly assumed, but has rarely been demonstrated, that sex differences in behaviour arise from sexual dimorphism in the underlying neural circuits. Parental care is a complex stereotypic behaviour towards offspring that is shared by numerous species. Mice display profound sex differences in offspring-directed behaviours. At their first encounter, virgin females behave maternally towards alien pups while males will usually ignore the pups or attack them. Here we show that tyrosine hydroxylase (TH)-expressing neurons in the anteroventral periventricular nucleus (AVPV) of the mouse hypothalamus are more numerous in mothers than in virgin females and males, and govern parental behaviours in a sex-specific manner. In females, ablating the AVPV TH+ neurons impairs maternal behaviour whereas optogenetic stimulation or increased TH expression in these cells enhance maternal care. In males, however, this same neuronal cluster has no effect on parental care but rather suppresses inter-male aggression. Furthermore, optogenetic activation or increased TH expression in the AVPV TH+ neurons of female mice increases circulating oxytocin, whereas their ablation reduces oxytocin levels. Finally, we show that AVPV TH+ neurons relay a monosynaptic input to oxytocin-expressing neurons in the paraventricular nucleus. Our findings uncover a previously unknown role for this neuronal population in the control of maternal care and oxytocin secretion, and provide evidence for a causal relationship between sexual dimorphism in the adult brain and sex differences in parental behaviour. 2015 Macmillan Publishers Limited.
(2014) VIRAL VECTOR APPROACHES IN NEUROBIOLOGY AND BRAIN DISEASES. p. 289-310 (Neuromethods). Abstract
Optogenetics is a technical methodology that allows direct light-based manipulation of genetically specified cells. Optogenetic methods have provided novel insights into the role of defined neuronal populations in brain function and animal behavior. An expanding palette of single-component optogenetic tools provides powerful interventional strategies for modulating the function of targeted neurons in awake, behaving mammals and for detailed interrogation of circuit physiology in vitro. Although several genetic methods can be utilized for delivering these genes into target cell populations, the use of viral vectors for delivery of optogenetic tools has several important advantages. In recent years, techniques for viral vector-mediated delivery of optogenetic tools have improved and expanded significantly. These techniques now allow modular use of optogenetic tools in defined cell types and circuits and dovetail well with genetic mouse models and recombinase-based driver lines. Here, we review the use of viral vectors for delivering genes encoding optogenetic tools into the rodent brain and provide a detailed protocol for viral transduction of mouse cortical neurons and chronic implantation of a fiberoptic connector for light delivery in vivo
Neuron-Specific Expression of Tomosyn1 in the Mouse Hippocampal Dentate Gyrus Impairs Spatial Learning and Memory(2013) NeuroMolecular Medicine. 15, 2, p. 351-363 Abstract
Tomosyn, a syntaxin-binding protein, is known to inhibit vesicle priming and synaptic transmission via interference with the formation of SNARE complexes. Using a lentiviral vector, we specifically overexpressed tomosyn1 in hippocampal dentate gyrus neurons in adult mice. Mice were then subjected to spatial learning and memory tasks and electrophysiological measurements from hippocampal slices. Tomosyn1-overexpression significantly impaired hippocampus-dependent spatial memory while tested in the Morris water maze. Further, tomosyn1-overexpressing mice utilize swimming strategies of lesser cognitive ability in the Morris water maze compared with control mice. Electrophysiological measurements at mossy fiber-CA3 synapses revealed impaired paired-pulse facilitation in the mossy fiber of tomosyn1-overexpressing mice. This study provides evidence for novel roles for tomosyn1 in hippocampus-dependent spatial learning and memory, potentially via decreased synaptic transmission in mossy fiber-CA3 synapses. Moreover, it provides new insight regarding the role of the hippocampal dentate gyrus and mossy fiber-CA3 synapses in swimming strategy preference, and in learning and memory.[All authors]
Optopatcher-An electrode holder for simultaneous intracellular patch-clamp recording and optical manipulation(2013) Journal of Neuroscience Methods. 214, 1, p. 113-117 Abstract
Optogenetics has rapidly become a standard method in neuroscience research. Although significant progress has been made in the development of molecular tools, refined techniques for combined light delivery and recording in vivo are still lacking. For example, simultaneous intracellular recording and light stimulation have only been possible by using two separate positioning systems. To overcome this limitation, we have developed a glass pipette holder which contains an additional port for the insertion of an optical fiber into the pipette. This device, which we called "optopatcher allows whole cell patch-clamp recording simultaneously with direct projection of light from the recording pipette. The holder spares the use of an additional manipulator and, importantly, enables accurate, stable and reproducible illumination. In addition, replacement of standard pipettes is done as easily as with the available commercial holders. Here we used the optopatcher in vivo to record the membrane potential of neurons from different cortical layers in the motor cortex of transgenic mice expressing channelrhodopsin-2 under the Thy1 promoter. We demonstrate the utility of the optopatcher by recording LFP and intracellular responses to light stimulation. (C) 2013 Elsevier B.V. All rights reserved.
Principles for applying optogenetic tools derived from direct comparative analysis of microbial opsins(2012) Nature Methods. 9, 2, p. 159-172 Abstract[All authors]
Diverse optogenetic tools have allowed versatile control over neural activity. Many depolarizing and hyperpolarizing tools have now been developed in multiple laboratories and tested across different preparations, presenting opportunities but also making it difficult to draw direct comparisons. This challenge has been compounded by the dependence of performance on parameters such as vector, promoter, expression time, illumination, cell type and many other variables. As a result, it has become increasingly complicated for end users to select the optimal reagents for their experimental needs. For a rapidly growing field, critical figurer. of merit should be formalized both to establish a framework for further development and so that end users can readily understand how these standardized parameters translate into performance. Here we systematically compared microbial opsins under matched experimental conditions to extract essential principles and identify key parameters for the conduct, design and interpretation of experiments involving optogenetic techniques.
(2012) Biological Psychiatry. 71, 12, p. 1075-1080 Abstract
Cognitive and social deficits lie at the core of many neuropsychiatric diseases and are among the many behavioral symptoms not amenable to pharmacological intervention. Despite significant advances in identifying genes potentially involved in the pathogenesis of complex psychiatric conditions such as autism and schizophrenia, knowledge of the physiological functions that are affected ( and are therefore potential targets for clinical intervention) is scarce. In psychiatric disorders with a strong genetic component, animal models have provided important links between disease-related genes and behavioral impairment. Social dysfunction, for instance, is commonly observed in transgenic rodent disease models. However, the causal relationships between the behavioral and physiological abnormalities in these models are not well-understood. Optogenetic techniques have evolved to provide a wide range of experimental paradigms in which neural circuit activity can be perturbed with high spatial and temporal precision, enabling causal investigation of the function of defined physiological events in neuronal subgroups. With optogenetics, researchers have begun to elucidate the basic neural mechanisms of social behaviors and of disease-relevant social and cognitive dysfunction. The synthesis of optogenetic technology with genetic animal models will allow forward-and reverse-engineering approaches to investigating the neural correlates of psychiatric disease. This review outlines the neural systems known to be involved in social behavior, illustrates how optogenetic technology has been applied to analyze this circuitry, and imagines how it might be further developed in future studies to elucidate these complex circuits both from a basic science perspective and in the context of psychiatric disease.
Recombinase-Driver Rat Lines: Tools, Techniques, and Optogenetic Application to Dopamine-Mediated Reinforcement(2011) Neuron. 72, 5, p. 721-733 Abstract[All authors]
Currently there is no general approach for achieving specific optogenetic control of genetically defined cell types in rats, which provide a powerful experimental system for numerous established neurophysiological and behavioral paradigms. To overcome this challenge we have generated genetically restricted recombinase-driver rat lines suitable for driving gene expression in specific cell types, expressing Cre recombinase under the control of large genomic regulatory regions (200-300 kb). Multiple tyrosine hydroxylase (Th)::Cre and choline acetyltransferase (Chat)::Cre lines were produced that exhibited specific opsin expression in targeted cell types. We additionally developed methods for utilizing optogenetic tools in freely moving rats and leveraged these technologies to clarify the causal relationship between dopamine (DA) neuron firing and positive reinforcement, observing that optical stimulation of DA neurons in the ventral tegmental area (VTA) of Th::Cre rats is sufficient to support vigorous intracranial self-stimulation (ICSS). These studies complement existing targeting approaches by extending the generalizability of optogenetics to traditionally non-genetically-tractable but vital animal models.
(2011) Nature. 477, 7363, p. 171-178 Abstract[All authors]
Severe behavioural deficits in psychiatric diseases such as autism and schizophrenia have been hypothesized to arise from elevations in the cellular balance of excitation and inhibition (E/I balance) within neural microcircuitry. This hypothesis could unify diverse streams of pathophysiological and genetic evidence, but has not been susceptible to direct testing. Here we design and use several novel optogenetic tools to causally investigate the cellular E/I balance hypothesis in freely moving mammals, and explore the associated circuit physiology. Elevation, but not reduction, of cellular E/I balance within the mouse medial prefrontal cortex was found to elicit a profound impairment in cellular information processing, associated with specific behavioural impairments and increased high-frequency power in the 30-80 Hz range, which have both been observed in clinical conditions in humans. Consistent with the E/I balance hypothesis, compensatory elevation of inhibitory cell excitability partially rescued social deficits caused by E/I balance elevation. These results provide support for the elevated cellular E/I balance hypothesis of severe neuropsychiatric disease-related symptoms.
(2011) Cell. 147, 7, p. 1446-1457 Abstract[All authors]
The capture and utilization of light is an exquisitely evolved process. The single-component microbial opsins, although more limited than multicomponent cascades in processing, display unparalleled compactness and speed. Recent advances in understanding microbial opsins have been driven by molecular engineering for optogenetics and by comparative genomics. Here we provide a Primer on these light-activated ion channels and pumps, describe a group of opsins bridging prior categories, and explore the convergence of molecular engineering and genomic discovery for the utilization and understanding of these remarkable molecular machines.