Biology subjects

Rah, J.-C.

Publications and source records attributed to Rah, J.-C..

10 recordsLinked to original sources

bioRxiv2026

Muscarinic signaling sustains delay-period selectivity in prefrontal cortex by preserving thalamic drive

Short-term memory (STM) requires the temporary maintenance of task-relevant information in prefrontal cortex (PFC). Reciprocal interactions between the mediodorsal thalamus (MD) and PFC have been implicated in sustaining this activity, but how thalamofrontal communication is maintained despite the biophysical constraints of repetitive synaptic transmission remains unclear. Here, we show that MD--PFC synapses exhibit profound frequency-dependent short-term depression, causing repetitive thalamic input to progressively lose its ability to drive PFC neurons. During STM performance, acetylcholine (ACh) levels in PFC rose rapidly following cue presentation and remained elevated throughout the delay period. Muscarinic ACh receptor (mAChR) activation did not alleviate synaptic depression, but instead increased the intrinsic excitability of PFC neurons, thereby preserving their responsiveness to weakened thalamic input. Conversely, mAChR blockade impaired STM performance and progressively disrupted delay-period directional representations at both the single-neuron and population levels, while largely sparing initial encoding. These findings identify muscarinic signaling as a postsynaptic gain mechanism that compensates for declining thalamofrontal efficacy and sustains task-relevant prefrontal representations during STM.

neuroscience↗

bioRxiv2025

Master clock-thalamic-prefrontal circuit controls circadian social priority

Social behaviors arise from complex brain operations that adapt to changing social contexts and internal states. However, how internal states guide the resolution of competing social goals remains unclear. Here, we show that prioritization between competing instincts follows a circadian pattern via a circuit linking the suprachiasmatic nucleus (SCN) to the medial prefrontal cortex (mPFC). Specifically, SCNVIP neurons project to Vipr2-expressing neurons in the nucleus reuniens (RE), which innervate the mPFC to regulate social prioritization. Vipr2 signaling in the RE is essential for circadian modulation of appetitive and consummatory social behaviors, aligning social behaviors with clock-regulated reproductive system. Overall, this SCN-RE-mPFC circuit provides a neural principle through which the master clock coordinates the prefrontal cortex to resolve a conflict of motivated behaviors by referencing an internal state.

neuroscience↗

bioRxiv2025

Thalamofrontal synaptic weakening underlies short-term memory deficits from adolescent NMDAR hypofunction

N-methyl-D-aspartate receptor (NMDAR) hypofunction is linked to schizophrenia, but prevailing models centered on reduced number and activity of inhibitory interneurons, and the resulting excitation-inhibition (E-I) imbalance, do not explain selective cognitive impairments. Here, we show that repeated adolescent NMDAR antagonism produces short-term memory (STM) deficits by weakening thalamofrontal (TF) synaptic transmission. In mice repeatedly exposed to ketamine, STM impairment coincided with reduced release probability and vesicle refilling at mediodorsal thalamus (MD) [->] dorsomedial prefrontal cortex (dmPFC) synapses, without detectable changes in layer 2/3 [->] layer 2/3 synaptic release probability, intrinsic excitability, or synaptic ultrastructure. These presynaptic deficits were accompanied by diminished direction-selective population coding in the dmPFC, as revealed by decoding analysis, and impaired delayed alternation performance in the Y-maze. Chemogenetic strengthening of MD [->] dmPFC projections restored both neural selectivity and behavior. Our findings identify a circuit-specific presynaptic mechanism linking adolescent NMDAR hypofunction to cognitive dysfunction, challenging interneuron-centric models and establishing TF synapses as a potential therapeutic target in NMDAR-related disorders.

neuroscience↗

bioRxiv2025

Lamin B1 physically regulates neuronal migration by modulating nuclear deformability in the developing cortex

Neuronal migration is a vital process that positions billions of neurons to create a functional brain. To navigate the constrained microenvironments within the cortex, precise control over the nuclear mechanics in migrating neurons is indispensable. Here, we show that Lamin B1 (LB1) regulates neuronal migration by modulating nuclear deformability. Excess LB1 in neurons halted migration without altering laminar identity or overall gene expressions in vivo, while in vitro, it elevated nuclear stiffness and impaired neuronal motility in confined spaces. Moreover, mispositioned neurons resulted in electrophysiological defects in the brain. Computational modeling predicted a temporal relationship between nuclear deformation and enhanced migration velocity, which was validated experimentally through live imaging. Notably, cerebral organoid assays using iPS cells established from patients with LMNB1 duplication exhibited impaired neuronal migration in a human model. Collectively, these findings demonstrate that LB1 is a critical regulator of nuclear mechanics, ensuring the accurate spatiotemporal positioning of neurons.

neuroscience↗

bioRxiv2024

Short-term memory errors are strongly associated with a drift in neural activity in the posterior parietal cortex

Understanding the neural mechanisms behind short-term memory (STM) errors is crucial for unraveling cognitive processes and addressing deficits associated with neuropsychiatric disorders. This study examines whether STM errors arise from misrepresentation of sensory information or decay in these representations over time. Using 2-photon calcium imaging in the posterior parietal cortex (PPC) of mice performing a delayed match-to-sample task, we identified a subset of PPC neurons exhibiting both directional and temporal selectivity. Contrary to the hypothesis that STM errors primarily stem from mis-encoding during the sample phase, our findings reveal that these errors are more strongly associated with a drift in neural activity during the delay period. This drift leads to a gradual divergence away from the correct representation, ultimately leading to incorrect behavioral responses. These results emphasize the importance of maintaining stable neural representations in the PPC for accurate STM. Furthermore, they highlight the potential for therapeutic interventions aimed at stabilizing PPC activity during delay periods as a strategy for mitigating cognitive impairments in conditions like schizophrenia.

animal behavior and cognition↗

bioRxiv2023

Modulation of premotor cortex excitability mitigates the behavioral and electrophysiological abnormalities in a Parkinson's Disease Mouse Model

The subthalamic nucleus (STN) is important in halting ongoing behaviors, referred to as stop-signal responses. The prefrontal regions innervating the STN exhibit increased activity during the stop-signal responses, and optogenetic activation of these neurons inhibits impulsive actions in rodents. High-frequency electrical stimulation of the STN effectively treats motor symptoms of Parkinsons disease (PD), yet its underlying circuit mechanisms are unclear. Here, we investigated the involvement of STN-projecting premotor (M2) neurons in PD mouse models and the impact of deep brain stimulation targeting the STN (DBS-STN). We found that M2 neurons exhibited enhanced burst firing and synchronous oscillations in the PD mouse model. Remarkably, high-frequency stimulation of STN-projecting M2 neurons, simulating antidromic activation, during DBS-STN relieved motor symptoms and hyperexcitability. These changes were attributed to reduced firing frequency vs. current relationship through normalized hyperpolarization-activated inward current (Ih). The M2 neurons in the PD model mouse displayed increased Ih, which was reversed by high-frequency stimulation. Additionally, the infusion of ZD7288, an HCN channel blocker, into the M2 replicated the effects of high-frequency stimulation. In conclusion, our study unveils excessive excitability and suppressive motor control through M2-STN synapses in the PD mouse model. Antidromic excitation of M2 neurons during deep brain stimulation of the STN alleviates this suppression, thereby improving motor impairment. These findings provide insights into the circuit-level dynamics underlying deep brain stimulations therapeutic effects in PD. Targeting M2-STN synapses may be useful for future therapeutic strategies. Significance StatementOur study provides insight into the mechanisms underlying motor impairment in Parkinsons disease (PD) and the therapeutic effect of deep brain stimulation (DBS). By elucidating the role of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels in modulating the hyperexcitability of M2 neurons, we identify potential targets for future PD treatment strategies. Understanding the excessive excitability and suppressive motor control through M2-STN synapses in PD mouse models contributes to our knowledge of circuit-level dynamics underlying DBS effects. These findings have significant implications for improving motor symptoms and advancing the development of more precise and effective interventions for PD patients. HighlightsO_LISTN-projecting M2 neurons show increased burst firing in PD mice. C_LIO_LIHigh-frequency stimulation relieves M2 hyperexcitability and motor symptoms. C_LIO_LIReduction in M2 hyperexcitability by DBS linked to normalized Ih. C_LIO_LIZD7288 infusion in M2 replicates high-frequency stimulation effects. C_LIO_LITargeted modulation of M2 neurons may alleviate PD symptoms. C_LI

neuroscience↗

bioRxiv2022

High-order thalamic and motor cortex inputs integrate sublinearly into tuft dendrites of pyramidal neurons in mouse somatosensory cortex

Tuft dendrites of pyramidal neurons housed in layer 1 of the neocortex form extensive excitatory synaptic connections with long-range cortical and high-order thalamic axons, along with diverse inhibitory inputs. Recently, we reported that synapses from the vibrissal primary motor cortex (vM1) and posterior medial thalamic nucleus (POm) are spatially clustered together in the same set of distal dendrites, suggesting a close functional interaction. In this study, we evaluated how these two types of synapses interact with each other using in vivo two-photon Ca2+ imaging and electrophysiology. We observed that dendritic Ca2+ responses could be efficiently evoked by electrical stimulation of POm or vM1 in the overlapping set of dendritic branches, rejecting the idea of branch-wise origin-selective synaptic wiring. Surprisingly, the Ca2+ responses upon coincident POm and vM1 stimulation summed sublinearly. We attribute this sublinearity to mutual inhibition via inhibitory neurons because synaptic currents generated by POm and vM1 also integrated sublinearly, but pharmacologically isolated direct synaptic currents summed linearly. Inhibitory neurons receiving POm inputs in the superficial cortical layer negatively regulated vM1-evoked responses. Finally, POm and vM1 innervated overlapping but distinct populations of somatostatin-expressing inhibitory neurons. Thus, POm and vM1 inputs negatively modulate each other in the mouse somatosensory cortex.

neuroscience↗

bioRxiv2021

ICoRD: Iterative Correlation-Based ROI Detection Method for the Extraction of Neural Signals in Calcium Imaging

In vivo calcium imaging is a standard neuroimaging technique that allows selective observation of target neuronal activities. In calcium imaging, neuron activation signals provide key information for the investigation of neural circuits. For efficient extraction of the calcium signals of neurons, selective detection of the region of interest (ROI) pixels corresponding to the active subcellular region of the target neuron is essential. However, current ROI detection methods for calcium imaging data exhibit a relatively low signal extraction performance from neurons with a low signal-to-noise power ratio (SNR). This is problematic because a low SNR is unavoidable in many biological experiments. Therefore, we propose an iterative correlation-based ROI detection (ICoRD) method that robustly extracts the calcium signal of the target neuron from a calcium imaging series with severe noise. ICoRD extracts calcium signals closer to the ground-truth calcium signal than the conventional method from simulated calcium imaging data in all low SNR ranges. Additionally, this study confirmed that ICoRD robustly extracts activation signals against noise, even within in vivo environments. ICoRD showed reliable detection from neurons with a low SNR and sparse activation, which were not detected by conventional methods. ICoRD will facilitate our understanding of neural circuit activity by providing significantly improved ROI detection in noisy images.

neuroscience↗

bioRxiv2021

Dopamine depletion can be predicted by the aperiodic component of subthalamic local field potentials

Electrophysiological biomarkers reflecting the pathological activities in the basal ganglia are essential to gain an etiological understanding of Parkinsons disease (PD) and develop a method of diagnosing and treating the disease. Previous studies that explored electrophysiological biomarkers in PD have focused mainly on oscillatory or periodic activities such as beta and gamma oscillations. Emerging evidence has suggested that the nonoscillatory, aperiodic component reflects the firing rate and synaptic current changes corresponding to cognitive and pathological states. Nevertheless, it has never been thoroughly examined whether the aperiodic component can be used as a biomarker that reflects pathological activities in the basal ganglia in PD. In this study, we examined the parameters of the aperiodic component and tested its practicality as an electrophysiological biomarker of pathological activity in PD. We found that a set of aperiodic parameters, aperiodic offset and exponent, were significantly decreased by the nigrostriatal lesion. To further prove the usefulness of the parameters as biomarkers, acute levodopa treatment reverted the aperiodic offset. We then compared the aperiodic parameters with a previously established periodic biomarker of PD, beta frequency oscillation. We found a significantly low negative correlation with beta power. We showed that the performance of the machine learning-based prediction of pathological activities in the basal ganglia can be improved by using the lowly correlated parameters, beta power and aperiodic component. We suggest that the aperiodic component will provide a more sensitive measurement to early diagnosis PD and have the potential to use as the feedback parameter for the adaptive deep brain stimulation.

neuroscience↗

bioRxiv2020

Synapses from the high-order thalamic nucleus and motor cortex are co-clustered spatially in the distal tuft dendrites of the somatosensory cortex

The posterior medial nucleus of the thalamus (POm) and vibrissal primary motor cortex (vM1) convey essential information to the barrel cortex (S1BF) regarding whisker position and movement. Therefore, understanding the relative spatial relationships of these two inputs is critical prerequisites to acquire insight into how S1 synthesizes information to interpret the location of an object. Using array tomography, we identified the locations of synapses from vM1 and POm on distal tuft dendrites of L5 pyramidal neurons. We found that synapses from vM1 and POm are spatially clustered on the same set of dendrites with unusually high density. Furthermore, the clusters of vM1 and POm synapses colocalize each other. These findings suggest that synaptic clusters, but not dendritic branches, act as functional units and cooperatively contribute to nonlinear dendritic responses.

neuroscience↗