The rostral nucleus of the solitary tract (rNST), the initial CNS site for processing gustatory information, is comprised of two major cell types, glutamatergic excitatory and GABAergic inhibitory neurons. Although many investigators have described taste responses of rNST neurons, the phenotypes of these cells were unknown. To directly compare the response characteristics of both inhibitory and noninhibitory neurons, we recorded from mice expressing Channelrhodopsin-2 (ChR2) under the control of GAD65, a synthetic enzyme for GABA. We observed that chemosensitive profiles of GABAergic taste neurons (G+TASTE) were similar to non-GABA taste neurons (G-TASTE) but had much lower response rates. We further observed a novel subpopulation of GABA cells located more ventrally in the nucleus that were unresponsive to taste stimulation (G+UNR), suggesting pathways for inhibition initiated by centrifugal sources. This preparation also allowed us to determine how optogenetic activation of the rNST GABA network impacted...

In vitro and in vivo experimentation in the central nervous system are effective approaches to study its functioning. Manipulations in vitro are characterized by easy experimental control and stable experimental conditions. However, transferring these advantages to in vivo research remains technically and ethically challenging, preventing many research teams from acquiring critical recordings in their animal models. In order to transfer the benefits of in vitro experimentation to in vivo experimentation, we developed a suite of 3D-printed tools (a superfusion chamber with an independent brain presser and animal stand). Using the immature rat barrel cortex as a model, we show that our set of tools (further “superfusion preparation”) provides stable conditions for electrophysiological and neuroimaging recordings in the neonatal rat neocortex in vivo . Highly correlated intracellular and extracellular activity was recorded during spontaneous and evoked cortical activity, supporting the possibility of simultan...

The Emx1-IRES-Cre transgenic mouse is commonly used to direct genetic recombination in forebrain excitatory neurons. However, the original study reported that Emx1-Cre is also expressed embryonically in peripheral autonomic ganglia, which could potentially affect the interpretation of targeted circuitry contributing to systemic phenotypes. Here, we report that Emx1-Cre is expressed in the afferent vagus nerve system involved in autonomic cardiorespiratory regulatory pathways. Our imaging studies revealed expression of Emx1-Cre driven tdtomato fluorescence in the afferent vagus nerve innervating the dorsal medulla of brainstem, cell bodies in the nodose ganglion, and their potential target structures at the carotid bifurcation such as the carotid sinus and the superior cervical ganglion (SCG). Photostimulation of the afferent terminals in the nucleus tractus solitarius (NTS) in vitro using Emx1-Cre driven ChR2 reliably evoked EPSCs in the postsynaptic neurons with electrophysiological characteristics consis...

Compromised endocytosis in neurons leads to synapse overgrowth and altered organization of synaptic proteins. However, the molecular players and the signaling pathways which regulate the process remain poorly understood. Here, we show that σ2-adaptin, one of the subunits of the AP2-complex, genetically interacts with Mad, Medea and Dad (components of BMP signaling) to control neuromuscular junction (NMJ) growth in Drosophila . Ultrastructural analysis of σ2-adaptin mutants show an accumulation of large vesicles and membranous structures akin to endosomes at the synapse. We found that mutations in σ2-adaptin lead to an accumulation of Tkv receptors at the presynaptic membrane. Interestingly, the level of small GTPase Rab11 was significantly reduced in the σ2-adaptin mutant synapses. However, expression of Rab11 does not restore the synaptic defects of σ2-adaptin mutations. We propose a model in which AP2 regulates Tkv internalization and endosomal recycling to control synaptic growth.

Music induces people to coordinate with one another. Here, we conduct two experiments to examine the underlying mechanism of the interbrain synchronization (IBS) that is induced by interpersonal coordination when people are exposed to musical beat and meter. In experiment 1, brain signals at the frontal cortex were recorded simultaneously from two participants of a dyad by using functional near-infrared spectroscopy (fNIRS) hyperscanning, while each tapped their fingers to aural feedback from their partner (coordination task) or from themselves (independence task) with and without the musical meter. The results showed enhanced IBS at the left-middle frontal cortex in case of the coordination task with musical beat and meter. The IBS was significantly correlated with the participants performance in terms of coordination. In experiment 2, we further examined the IBS while the participants coordinated their behaviors in various metrical contexts, such as strong and weak meters (i.e., high/low loudness of acou...

Dendritic spines are submicron, subcellular compartments whose shape is defined by actin filaments and associated proteins. Accurately mapping the cytoskeleton is a challenge, given the small size of its components. It remains unclear whether the actin-associated structures analyzed in dendritic spines of neurons in vitro apply to dendritic spines of intact, mature neurons in situ. Here, we combined advanced preparative methods with multitilt serial section electron microscopy (EM) tomography and computational analysis to reveal the full three-dimensional (3D) internal architecture of spines in the intact brains of male mice at nanometer resolution. We compared hippocampal (CA1) pyramidal cells and cerebellar Purkinje cells in terms of the length distribution and connectivity of filaments, their branching-angles and absolute orientations, and the elementary loops formed by the network. Despite differences in shape and size across spines and between spine heads and necks, the internal organization was remar...

Oral sensory neurons of the geniculate ganglion (GG) innervate taste papillae and buds on the tongue and soft palate. Electrophysiological recordings of these neurons and fibers revealed complexity in the number of unique response profiles observed, suggesting there are several distinct neuronal subtypes. Molecular descriptions of these subpopulations are incomplete. We report here the identification of a subpopulation of GG oral sensory neurons in mice by expression of tyrosine hydroxylase (TH). TH-expressing geniculate neurons represent 10–20% of oral sensory neurons and these neurons innervate taste buds in fungiform and anterior foliate taste papillae on the surface of the tongue, as well as taste buds in the soft palate. While 35–50% of taste buds on the tongue are innervated by these TH+ neurons, 100% of soft palate taste buds are innervated. These neurons did not have extragemmal processes outside of taste buds and did not express the mechanosensory neuron-associated gene Ret , suggesting they are c...

Oscillatory activity in the human brain is dominated by posterior alpha oscillations (8–14 Hz), which have been shown to be functionally relevant in a wide variety of cognitive tasks. Although posterior alpha oscillations are commonly considered a single oscillator anchored at an individual alpha frequency (∼10 Hz), previous work suggests that individual alpha frequency reflects a spatial mixture of different brain rhythms. In this study, we assess whether independent component analysis (ICA) can disentangle functionally distinct posterior alpha rhythms in the context of visual short-term memory retention. Magnetoencephalography (MEG) was recorded in 33 subjects while performing a visual working memory task. Group analysis at sensor level suggested the existence of a single posterior alpha oscillator that increases in power and decreases in frequency during memory retention. Conversely, single-subject analysis of independent components revealed the existence of two dissociable alpha rhythms: one that incre...

The pathophysiological features of ischemia-related blood–brain barrier (BBB) disruption are widely studied using preclinical stroke models. However, in many of these models, craniectomy is required to confirm arterial occlusion via laser Doppler flowmetry or to enable direct ligation of the cerebral artery. In the present study, mice were used to construct a distal middle cerebral artery occlusion (dMCAO) model, a preclinical stroke model that requires craniectomy to enable direct ligation of the cerebral artery, or were subjected to craniectomy alone. dMCAO but not craniectomy caused neurodegeneration and cerebral infarction, but both procedures induced an appreciable increase in BBB permeability to Evans blue dye, fluorescein, and endogenous albumin but not to 10 kDa dextran-FITC, leading to cerebral edema. Using rats, we further showed that BBB disruption induced by craniectomy with no evidence of dural tearing was comparable to that induced by craniectomy involving tearing of the dura. In conclusion, ...

In real-world decision-making scenarios, negative consequences do not always occur immediately after a choice. This delay between action and outcome drives the underestimation, or “delay discounting,” of punishment. While the neural substrates underlying sensitivity to immediate punishment have been well-studied, there has been minimal investigation of delayed consequences. Here, we assessed the role of lateral orbitofrontal cortex (LOFC) and basolateral amygdala (BLA), two regions implicated in cost/benefit decision-making, in sensitivity to delayed versus immediate punishment. The delayed punishment decision-making task (DPDT) was used to measure delay discounting of punishment in rodents. During DPDT, rats choose between a small, single-pellet reward and a large, three-pellet reward accompanied by a mild foot shock. As the task progresses, the shock is preceded by a delay that systematically increases or decreases throughout the session. We observed that rats avoid choices associated with immediate puni...