Many genetically encoded voltage indicators (GEVIs) rely on fluorescent protein (FP) domains to report changes in membrane potential. Rapid and reversible disruption of steady-state fluorescence during voltage sensor activation revealed transient conformational changes near the chromophore in the FP domain, implicating chromophore flexibility as a potential mechanism of signal modulation. Substitution of a bulky phenylalanine near the chromophore with threonine (F165T) introduced a distinct secondary component in the fluorescence response, consistent with increased chromophore mobility. This effect was tunable: an external, directionally polarized offset (164/166F) reoriented the internal threonine side chain, restoring steric hindrance and eliminating the secondary signal. Thus, threonine can function as a context-sensitive molecular switch shaped by β-can surface chemistry. A second internal threonine (T203) also acted as a molecular switch under modified external conditions, generating a secondary signal that is susceptible to membrane curvature during depolarization suggesting that plasma membrane geometry can modulate GEVI activity under permissive conformational states. Crystal structures of Super Ecliptic pHluorin (SE), SE A227D, and a new FP variant revealed that external residues can influence internal side chain orientation. In the new variant, pH-dependent rearrangement of the seventh β-strand dramatically repositions D147 from the interior interacting with the chromophore to the external surface, while H148 shifts from the exterior to interact with the chromophore in alkaline conditions. These insights led to the development of a new GEVI, Ulla, which inverts the polarity of the optical signal─becoming brighter upon depolarization─displays reduced pH sensitivity in the physiological range, and performs reliably under low-light, high-speed imaging conditions in vitro and in vivo using widefield and 2-photon microscopy. Together, these findings present a new approach to modulating chromophore behavior offering broad potential for FP-based biosensor development.

Neurons exhibit varying electrophysiological properties due to dynamic changes in spatiotemporal molecular networks. In situ cryo-electron tomography (cryo-ET) provides advantages for high-resolution visualization of macromolecular complexes within their cellular context. Although correlation with fluorescent labeling allows cryo-ET to target specific cellular regions, it does not adequately reflect the electrophysiological properties of heterogeneous neurons. To bridge high-resolution molecular imaging with electrophysiological properties of individual neurons, we develop a Correlative Voltage Imaging and cryo-ET (CoVET) technique. The nondestructive nature of voltage imaging is compatible with cryo-ET, enabling a direct correlation between neuronal electrophysiology and molecular structures. Neurons are clustered based on their electrophysiological properties, allowing for single-cell-guided structural analysis using cryo-ET. We analyze the translational landscapes of individual neurons and find distinct structural characteristics and spatial networks among ribosomes from different electrophysiological clusters. Our results highlight the importance of the correlation between the electrophysiological properties and molecular structures.

The striatal direct and indirect pathways constitute the core for basal ganglia function in action control. Although both striatal D1- and D2-spiny projection neurons (SPNs) receive excitatory inputs from the cerebral cortex, whether or not they share inputs from the same cortical neurons, and how pathway-specific corticostriatal projections control behavior remain largely unknown. Here using a G-deleted rabies system in mice, we found that more than two-thirds of excitatory inputs to D2-SPNs also target D1-SPNs, while only one-third do so vice versa. Optogenetic stimulation of striatal D1- vs. D2-SPN-projecting cortical neurons differently regulate locomotion, reinforcement learning, and sequence behavior, implying the functional dichotomy of pathway-specific corticostriatal subcircuits. These results reveal the partially segregated yet asymmetrically overlapping cortical projections on striatal D1- vs. D2-SPNs, and that the pathway-specific corticostriatal subcircuits distinctly control behavior. It has important implications in a wide range of neurological and psychiatric diseases affecting cortico-basal ganglia circuitry.

Recent advances in the field of Voltage Imaging, with a special focus on new constructs and novel implementations.

Basal Ganglia Advances is a collection highlighting research on the structure, function, and disorders of the basal ganglia. It features studies spanning neuroscience, clinical insights, and computational models, serving as a hub for advances in movement, cognition, and behavior.

Work related to place tuning, spatial navigation, orientation and direction. Mainly includes articles on connectivity in the hippocampus, retrosplenial cortex, and related areas.

The precise structural and functional characteristics of input circuits targeting histaminergic neurons remain poorly understood. Here, using a rabies virus retrograde tracing system combined with fluorescence micro-optical sectioning tomography, we construct a 3D monosynaptic long-range input atlas of male mouse histaminergic neurons. We identify that the hypothalamus, thalamus, pallidum, and hippocampus constitute major input sources, exhibiting diverse spatial distribution patterns and neuronal type ratios. Notably, a specific layer distribution pattern and co-projection structures of upstream cortical neurons are well reconstructed at single-cell resolution. As histaminergic system is classically involved in sleep-wake regulation, we demonstrate that the lateral septum (predominantly supplying inhibitory inputs) and the paraventricular nucleus of the thalamus (predominantly supplying excitatory inputs) establish monosynaptic connections, exhibiting distinct functional dynamics and regulatory roles in rapid-eye-movement sleep. Collectively, our study provides a precise long-range input map of mouse histaminergic neurons at mesoscopic scale, laying a solid foundation for future systematic study of histaminergic neural circuits.

Nonpharmaceutical approaches based on gamma entrainment using sensory stimuli (GENUS) have shown promise in reducing Alzheimer's disease pathology in mouse models. While human studies remain limited, GENUS has been shown to alleviate aspects of neurodegeneration in patients with Alzheimer's disease. In this study, we analyze intracranial EEG data from 490 contacts across eleven patients with refractory epilepsy in response to three visual stimulation conditions. We find that 40 Hz visual stimulation successfully entrains neural activity beyond early visual areas, including the hippocampus and other cortical regions such as the temporal and frontal lobes. Additionally, we show that synchronization increases between the hippocampus and other cortical areas in response to the 40 Hz visual stimulation. Furthermore, combining stimulation with a simple visual oddball task alters the direction of information flow from frontal regions to the hippocampus and enhances both the strength and spatial extent of neural entrainment. These findings highlight the potential influence of cognitive engagement during sensory gamma stimulation and provide additional insights into the neurophysiological effects of 40 Hz visual stimulation.

The striatal direct and indirect pathways constitute the core for basal ganglia function in action control. Although both striatal D1- and D2-spiny projection neurons (SPNs) receive excitatory inputs from the cerebral cortex, whether or not they share inputs from the same cortical neurons, and how pathway-specific corticostriatal projections control behavior remain largely unknown. Here using a G-deleted rabies system in mice, we found that more than two-thirds of excitatory inputs to D2-SPNs also target D1-SPNs, while only one-third do so vice versa. Optogenetic stimulation of striatal D1- vs. D2-SPN-projecting cortical neurons differently regulate locomotion, reinforcement learning, and sequence behavior, implying the functional dichotomy of pathway-specific corticostriatal subcircuits. These results reveal the partially segregated yet asymmetrically overlapping cortical projections on striatal D1- vs. D2-SPNs, and that the pathway-specific corticostriatal subcircuits distinctly control behavior. It has important implications in a wide range of neurological and psychiatric diseases affecting cortico-basal ganglia circuitry.