Biology subjects

Negishi, K.

Publications and source records attributed to Negishi, K..

14 recordsLinked to original sources

bioRxiv2026

Ripples precede insight in the right human hippocampus

Insight is a sudden transition from uncertainty to awareness of a solution, often preceded by non-conscious processing. Despite the ubiquity of insights in human cognition, the neural mechanisms underlying this pre-conscious restructuring phase remain largely unknown. Recent theoretical frameworks suggest that the hippocampus, through its capacity for rapid associative retrieval and flexible recombination of stored representations, may facilitate the non-conscious exploration that precedes insight. Hippocampal ripples associated with memory replay and consolidation, represent a promising candidate mechanism for this process. We recorded intracranial local field potentials from depth electrodes in the hippocampus of ten patients with drug-resistant epilepsy while they performed non-verbal reasoning tasks. Participants indicated the moment of solution awareness via button press, enabling precise temporal alignment of neural activity to subjective insight. We observed a significant increase in ripple rate during a pre-response window. Critically, this effect was lateralized to the right hippocampus. These findings provide the first direct human electrophysiological evidence linking right-lateralized hippocampal ripples to the non-conscious phase of insight. We propose that right hippocampal ripples support rapid retrieval and flexible recombination of representations, potentially triggering cortical processes that culminate in conscious solution awareness.

neuroscience↗

bioRxiv2025

A modular, adaptable, and accessible implant kit for chronic electrophysiological recordings in rats

Electrophysiological implants enable exploration of the relationship between neuronal activity and behavior. These technologies evolve rapidly, with multiple iterations of recording systems developed and utilized. Chronic implants must address a litany of complications, including retention of high signal-to-noise ratio in probes and the ability to withstand excess force over the experimental period. To overcome these issues, we designed a chronic implant for rats. Our comprehensive protocol optimizes the entire implant process, from assembling and testing the probes (Neuropixels) to implantation. In addition to addressing the complications previously mentioned, our implant can vertically adjust probes with micron precision and is constructed using modular components, allowing it to be easily modified for various research contexts, electrophysiological recording systems, headstages, and probe types.

neuroscience↗

bioRxiv2025

Elaborating the connections of a closed-loop forebrain circuit in the rat: Circumscribed evidence for novel topography within a cortico-striato-pallidal triple descending projection, with thalamic feedback, to the anterior lateral hypothalamic area

Motivated behaviors are regulated by distributed forebrain networks. Traditional approaches have often focused on individual brain regions and connections that do not capture the topographic organization of forebrain connectivity. We performed co-injections of anterograde and retrograde tract tracers in rats to provide novel high-spatial resolution evidence of topographic connections that elaborate a previously identified closed-loop forebrain circuit implicated in affective and motivational processes. The nodes of this circuit include select regions of the medial prefrontal cortex (defined here more specifically as the cingulate region, CNG), a dorsomedial portion of the nucleus accumbens (ACBdm), a portion of the medial substantia innominata (SIm), and the anterior lateral hypothalamic area (LHAa). The circuit also reportedly receives a feedback loop from the anterior region of the paraventricular thalamic nucleus (PVTa). In this draft report, we provide detailed circumscribed evidence supporting these regions as interconnected nodes, and provide several novel findings concerning the topographic organization of their projections. First, we identified the ACBdm based on its unique connectivity. Anterograde labeling from anterior paraventricular thalamic nucleus (PVTa) and retrograde labeling from medial substantia innominata (SIm) and lateral hypothalamic area (LHA) were restricted to the dorsomedial ACB (ACBdm). Strikingly, this labeling formed a longitudinal column extending along virtually the entire anteroposterior axis of ACBdm. Subsequent analysis revealed a convergence of ACBdm axon terminals and retrogradely labeled neurons from LHA within the anterior SIm. Furthermore, we identified cortical CNG regions related to this circuit. These regions contained retrograde labeling from both ACBdm and LHA, and anterograde labeling from PVTa. These cortical subdomains included regions previously implicated in the circuit but for which detailed organization has been unknown: (1) a region between the posterior prelimbic and infralimbic areas; (2) posterior part of basolateral and basomedial amygdalar nuclei, and (3) anterior pole of ventral subiculum. Our circumscribed findings, which await additional samples and analysis, support the existence of a topographically organized closed-loop circuit and identify two additional novel features: (1) direct evidence for an elaborate core rostrocaudal topography for a cortico-striato-pallidal motif comprising a triple descending projection to the LHA via direct, indirect, and "hyperdirect" pathways, and (2) a thalamic feedback system with specific projections to each cortical and striatal node of the circuit. We discuss the implications of this newly elaborated circuit for understanding the neural basis of motivational processes. Significance StatementWe used a bottom-up approach to identify a distinct longitudinal column of dorsomedial nucleus accumbens (ACBdm) that spans its anteroposterior axis. This region projects to medial substantia innominata (SIm) and lateral hypothalamic area (LHA), resembling the "direct" and "indirect" pathways of the classical basal ganglia circuit. We also identified topographically distinct regions in medial prefrontal cortex (strictly delineated here as the cingulate region, CNG), ventral subiculum (SUBv), and basolateral amygdala (BLA) that project to both ACBdm and LHA, further defining the circuit. Finally, we identified an LHA-to-anterior paraventricular thalamic nucleus (PVTa) feedback projection that selectively targets cortical and striatal nodes within the circuit. Our work provides novel detailed maps that bolster the proposal that this "triple descending projection" (cortico-striato-pallidal) and associated thalamic feedback loop play a role in affective and motivational processes.

neuroscience↗

bioRxiv2024

Computational Primitives for Cost-Benefit Decision-Making

Cost-benefit decision-making is a critical process performed by all organisms, including humans. Various factors, including risk1,2, uncertainty3, age4, sex5, and neuropsychiatric disorders6, can alter decision-making. To explore cost-benefit decision-making in humans, we developed a comprehensive task and analysis framework that presents participants with a series of approach-avoid trade-offs across a variety of contexts. With this system, we found that cost-benefit decisions in humans are made using a set of computational strategies that may be used for integrating costs and rewards, which we term decision-making primitives. We further show that these decision-making primitives are used by rodents performing a similar decision-making task7. We find that utilization of these primitives in both rodents and humans shifts based on factors like hunger and sex, and that individuals use primitives differently. We additionally demonstrate that using a naturally-inspired neural network architecture generates output that overlaps with human and rodent performance over a non-constrained neural network. This novel conceptual framework, by isolating discrete decision-making primitives, has potential to help us identify how different brain regions give rise to decision-making behavior, as well as to facilitate better diagnosis of neuropsychiatric disorders and development of naturally-inspired artificial intelligence systems of decision-making.

neuroscience↗

bioRxiv2024

Topographic organization of bidirectional connections between the cingulate region (infralimbic area and anterior cingulate area, dorsal part) and the interbrain (diencephalon) of the adult male rat

The medial prefrontal cortex [cingulate region (Brodmann, 1909) (CNG)] in the rat is a connectionally and functionally diverse structure. It harbors cerebral nuclei that use long-range connections to promote adaptive changes to ongoing behaviors. The CNG is often described across functional and anatomical gradients, a dorsal-ventral gradient being the most prominent. Topographic organization is a general feature of the nervous system, and it is becoming clear that such spatial arrangements can reflect connectional, functional, and cellular differences. Portions of the CNG are known to form reciprocal connections with cortical areas and thalamus; however, these connectional features have not been described in detail or mapped to standardized rat brain atlases. Here, we used co-injected anterograde (Phaseolus vulgaris leucoagglutinin) and retrograde (cholera toxin B subunit) tracers throughout the CNG to identify zones of reciprocal connectivity in the diencephalon [or interbrain (Baer, 1837) (IB)]. Tracer distributions were observed using a Nissl-based atlas-mapping approach that facilitates description of topographic organization. This draft report describes CNG connections of the infralimbic area (Rose & Woolsey, 1948) (ILA) and the anterior cingulate area, dorsal part (Krettek & Price, 1977) (ACAd) throughout the IB. We found that corticothalamic connections are predominantly reciprocal, and that ILA and ACAd connections tended to be spatially segregated with minimal overlap. In the hypothalamus (Kuhlenbeck, 1927), we found dense and specific ILA-originating terminals in the following Brain Maps 4.0 atlas territories: dorsal region (Swanson, 2004) (LHAd) and suprafornical region (Swanson, 2004) (LHAs) of the lateral hypothalamic area (Nissl, 1913), parasubthalamic nucleus (Wang & Zhang, 1995) (PSTN), tuberal nucleus, terete part (Petrovich et al., 2001) (TUte), and an ill-defined dorsal cap of the medial mammillary nucleus (Gudden, 1881) (MM). We discuss these findings in the context of feeding behaviors.

neuroscience↗

bioRxiv2024

Effect of Acute Alcohol Consumption in a Novel Rodent Model of Decision Making

BackgroundAlcohol use, especially at high consumption levels, can lead to irrational decision-making. In humans, this can lead to harmful outcomes often seen in the context of driving under the influence and or aggressive behavior. To date, the field is lacking comprehensive animal models to examine the impact of alcohol use on decision making in rodents, particularly to examine sex differences in choice behavior. To address this issue, the present study examined the effects of acute alcohol consumption during a behavioral approach-avoidance task that captures momentary changes in decision-making behavior and choice selection in female and male rats. MethodsOur team has developed a novel behavioral protocol involving a concurrent choice to consume four different concentrations of alcohol and sucrose combinations. During the task, female or male rats can approach or avoid drinking solutions in four distinct corners of our test apparatus. The solutions were prepared in inverse concentrations (higher sucrose was paired with lower alcohol and vice versa) so that the rodents pursue minimal alcohol use by consuming the higher sucrose concentrations or higher concentrations of alcohol by drinking the lower sucrose concentrations. The animals also have the option to avoid drinking alcohol by not approaching any of the drinking cups. Behavior and choice were tracked during task performance involving different solution concentrations of alcohol and sucrose. ResultsThe choice of consuming different concentrations of alcohol or sucrose resulted in sex-dependent differences in an approach-avoid trade-off pattern of behavior that was sensitive to different concentrations of alcohol/sucrose combinations. Notably, males were greatly affected by the introduction of alcohol into the task environment, approaching higher alcohol concentrations significantly more often than the non-alcohol containing options. In contrast, females choice patterns and task performance were largely unchanged during alcohol and non-alcohol containing tasks. Regardless of sex, we identify a novel method for identifying individual subject decision-making abnormalities during and after alcohol consumption. ConclusionsThis research reveals a novel approach for examining the effects of acute alcohol exposure during a trade-off task, with decision patterns being more impacted by alcohol use in males as compared to females. We also offer the field a novel approach for identifying individual abnormalities in decision making behavior with the presentation of alcohol. Future research can explore these abnormal patterns in both acute and chronic alcohol conditions to develop methods for identifying subjects at-risk for developing an alcohol use disorder and the deleterious impact of alcohol on rational decision making.

neuroscience↗

bioRxiv2024

Brain-wide projections of mouse dopaminergic zona incerta neurons

The zona incerta (ZI) supports diverse behaviors including binge feeding, sleep/wake cycles, nociception, and hunting. This diversity of functions can be attributed to the heterogenous neurochemicals, cytoarchitecture, and efferent connections that characterize the ZI. The ZI is predominantly GABAergic, but we recently identified a subset of medial ZI GABA cells that co-express dopamine (DA), as marked by the enzyme tyrosine hydroxylase (TH). While the role of GABA within the ZI is well studied, little is understood about the function of ZI DA cells. To identify potential roles of ZI DA cells we mapped the efferent fiber projections from Th-cre ZI cells. We first validated a Th-cre;L10-Egfp mouse line and found that medial Egfp ZI cells were more likely to co-express TH-immunoreactivity (TH-ir). We thus delivered a cre-dependent virus into the medial ZI of Th-cre or Th-cre;L10-Egfp mice and selected two injection cases for full brain mapping. We selected the cases with the lowest (17%) and highest (53%) percentage of colocalization between TH-ir and virus transfected cells labelled with DsRed. Overall, DsRed-labelled fibers were observed throughout the brain and were most prominent within motor-related regions of the midbrain (MBmot), notably the periaqueductal grey area and superior colliculus. We also observed considerable DsRed-labelled fibers within the polymodal cortex associated regions of the thalamus (DORpm), including the paraventricular thalamic nucleus and nucleus of reunions. Overall, ZI DA cells displayed a similar connectivity profile to ZI GABA cells, suggesting that ZI DA cells may perform synergistic or opposing functions at the same target sites. List of RRIDsAB_2201528, AB_10013483, AB_11177031, AB_2340593, AB_2315778, SCR_016477 Three key points- Tyrosine hydroxylase immunoreactivity was more prominent in the medial zona incerta - Intersection points from two Th-cre injection cases revealed common target regions - Dopaminergic zona incerta cells project predominantly to motor-related brain regions

neuroscience↗

bioRxiv2024

Model of a striatal circuit exploring biological mechanisms underlying decision-making during normal and disordered states

Decision-making requires continuous adaptation to internal and external contexts. Changes in decision-making are reliable transdiagnostic symptoms of neuropsychiatric disorders. We created a computational model demonstrating how the striosome compartment of the striatum constructs a mathematical space for decision-making computations depending on context, and how the matrix compartment defines action value depending on the space. The model explains multiple experimental results and unifies other theories like reward prediction error, roles of the direct versus indirect pathways, and roles of the striosome versus matrix, under one framework. We also found, through new analyses, that striosome and matrix neurons increase their synchrony during difficult tasks, caused by a necessary increase in dimensionality of the space. The model makes testable predictions about individual differences in disorder susceptibility, decision-making symptoms shared among neuropsychiatric disorders, and differences in neuropsychiatric disorder symptom presentation. The model reframes the role of the striosomal circuit in neuroeconomic and disorder-affected decision-making. HighlightsO_LIStriosomes prioritize decision-related data used by matrix to set action values. C_LIO_LIStriosomes and matrix have different roles in the direct and indirect pathways. C_LIO_LIAbnormal information organization/valuation alters disorder presentation. C_LIO_LIVariance in data prioritization may explain individual differences in disorders. C_LI eTOCBeck et al. developed a computational model of how a striatal circuit functions during decision-making. The model unifies and extends theories about the direct versus indirect pathways. It further suggests how aberrant circuit function underlies decision-making phenomena observed in neuropsychiatric disorders.

neuroscience↗

bioRxiv2023

Inhibition of hypoxia-inducible factors suppresses subretinal fibrosis

Age-related macular degeneration (AMD) is a common cause of vision loss. The aggressive form of AMD is associated with ocular neovascularization and subretinal fibrosis, representing a responsive outcome against neovascularization mediated by epithelial-mesenchymal transition of retinal pigment epithelium cells. A failure of the current treatment (anti-vascular endothelial growth factor therapy) has also been attributed to the progression of subretinal fibrosis. Hypoxia-inducible factors (HIFs) increase gene expressions to promote fibrosis and neovascularization. HIFs act as a central pathway in the pathogenesis of AMD. HIF inhibitors may suppress ocular neovascularization. Nonetheless, further investigation is required to unravel the aspects of subretinal fibrosis. In this study, we used RPE-specific HIFs or von Hippel-Lindau (VHL, a regulator of HIFs) conditional knockout (cKO) mice, along with pharmacological HIF inhibitors, to demonstrate the suppression of subretinal fibrosis. Fibrosis was suppressed by treatments of HIF inhibitors, and similar suppressive effects were detected in RPE-specific Hif1a/Hif2a- and Hif1a-cKO mice. Promotive effects were observed in RPE-specific Vhl-cKO mice, where fibrosis-mediated pathologic processes were evident. Marine products extracts and their component taurine suppressed fibrosis as HIF inhibitors. Our study shows critical roles of HIFs in the progression of fibrosis, linking them to the potential development of therapeutics for AMD.

molecular biology↗

bioRxiv2023

Tight junction component protein claudin-1 deficiency in retinal pigment epithelium leads to early and intermediate age-related macular degeneration phenotypes in mice.

The early and intermediate age-related macular degeneration (AMD) is characterized by the presence of drusen and pigmentary abnormalities in the retinal pigment epithelial (RPE) cells which form the outer blood retinal barrier (oBRB). Fluid leakage through the disrupted oBRB from the choroid to the neural retina has been implicated in the pathogenesis of AMD, however; the molecular mechanisms still remain unclear. The family of four transmembrane proteins, claudins are known to form tight junctions (TJs) in the oBRB. Nonetheless, there are few reports showing how they function in the oBRB in vivo. We found that claudin-1 is dominantly expressed in TJs of the mouse RPE. To investigate the role of claudin-1 in the RPE, we generated RPE-specific Cldn1 conditional knockout mice (Best1-Cre+/- Cldn1flox/flox mice: Cldn1 cKO mice). Deficiency of Cldn1 led to age-related lipid deposits such as subretinal drusenoid deposits (SDD), increased lipid droplets in the RPE, basal lamellar deposits (BlamD) and membranous debris in the Bruchs membrane. In addition, pigmentary abnormalities such as RPE hypertrophy, multilayered-RPE cells, and ectopic pigment granules outside the RPE were observed in Cldn1 cKO mice. Our study provides new insights into the possible association of the TJ protein claudin-1 with lipid metabolism and cellular ageing in the RPE contributing to the early onset of AMD.

molecular biology↗

bioRxiv2023

The orientation of choroidal macrophage polarization significantly influences the development of myopia in murine models

Myopia is a primary contributor to visual impairment and has emerged as a global public health concern. Evidence indicates that one of the main structural features of myopia is the corresponding decrease in choroidal thickness, and choroidal macrophages play an important role in maintaining the choroidal thickness. Nevertheless, the effect of choroidal macrophages on myopia remains unclear. Here, we discovered that the continuous intraperitoneal injection of clodronate liposomes depleted choroidal macrophages and leads to myopia, which confirmed that the presence of choroidal macrophages plays an important role in myopia development. Subsequently, based on the phenotypic characteristics of macrophages, experiments were designed to study the effects of different polarization directions of macrophages on myopia development. We found that lipopolysaccharides (LPS) injection can induce the polarization of choroidal M1 macrophages, thinning the choroidal thickness and resulting in myopia. Conversely, IL-4 or IL-13 injection causes choroidal M2 macrophage polarization, thickens the choroid, and suppresses the progression of myopia. Additionally, we demonstrated that the opposite effects of M1 and M2 macrophages on myopia development may be related to their impacts on choroidal thickness, inflammation, and oxidative stress response. These findings establish that choroidal macrophages are critically important in the development of myopia and provide new strategies for the development of myopic therapies.

immunology↗

bioRxiv2022

Withdrawal from repeated nicotine vapor exposure increases somatic signs of physical dependence, anxiety-like behavior, and brain reward thresholds in adult male rats.

In recent years, there has been a dramatic increase in nicotine vapor consumption via electronic nicotine delivery systems (i.e., e-cigarettes), particularly in adolescents. While recent work has focused on the health effects of nicotine vapor exposure, its effects on the brain and behavior remain unclear. In this study, we assessed the effects that cessation from repeated nicotine vapor exposure had on behavioral and neuronal measures of withdrawal. For Experiment 1, fifty-six adult male rats were tested for plasma cotinine levels, somatic withdrawal signs, and anxiety-like behavior in the elevated plus maze, immediately following precipitated withdrawal from repeated exposure to 12 or 24 mg/mL nicotine vapor. In Experiment 2, twelve adult male rats were tested for intracranial self-stimulation (ICSS) across 14 days of exposure to 24 mg/mL nicotine vapor and across the 14 days immediately following nicotine exposure. Results revealed that plasma cotinine, somatic signs, anxiety-like behavior, and ICSS stimulation thresholds were all observed to be elevated during withdrawal in the 24 mg/mL nicotine group, when compared to vehicle controls (50/50 vegetable glycerin/propylene glycol). The data suggest that cessation from repeated nicotine vapor exposure using our preclinical model leads to nicotine dependence and withdrawal, and demonstrates that the vapor system described in these experiments is a viable pre-clinical model of e-cigarette use in humans. Further characterization of the mechanisms driving nicotine vapor abuse and dependence is needed to improve policies and educational campaigns related to e-cigarette use. HighlightsO_LIA rodent model of nicotine e-cigarette vapor use was utilized to assess effects of cessation from repeated nicotine vapor exposure on behavioral and neuronal measures of drug withdrawal. C_LIO_LICessation of repeated nicotine vapor exposure resulted in increased plasma cotinine levels, somatic withdrawal signs, and anxiety-like behavior. C_LIO_LICessation of repeated nicotine vapor exposure resulted in elevations of ICSS reward threshold. C_LIO_LIElectrode implantations for ICSS were mapped by location and threshold to a standardized reference atlas of the rat brain to facilitate comparisons with the published literature. C_LI

neuroscience↗

bioRxiv2020

Leaf trichome distribution pattern in Arabidopsis reveals gene expression variation associated with environmental adaptation

Gene expression varies stochastically even in both heterogenous and homogeneous cell populations. This variation is not simply useless noise; rather, it is important for many biological processes. Unicellular organisms or cultured cell lines are useful for analyzing the variation in gene expression between cells; however, owing to technical challenges, the biological relevance of this variation in multicellular organisms such as higher plants remains unclear. Here, we addressed the biological relevance of this variation between cells by examining the genetic basis of trichome distribution patterns in Arabidopsis thaliana. The distribution pattern of a trichome on a leaf is stochastic and can be mathematically represented using Turings reaction-diffusion (RD) model. We analyzed simulations based on the RD model and found that the variability in the trichome distribution pattern increased with the increase in stochastic variation in a particular gene expression. Moreover, differences in heat-dependent variability of the trichome distribution pattern between the accessions showed a strong correlation with environmental factors to which each accession was adapted. Taken together, we successfully visualized variations in gene expression by quantifying the variability in the Arabidopsis trichome distribution pattern. Thus, our data provide evidence for the biological importance of variations in gene expression for environmental adaptation.

plant biology↗

bioRxiv2019

Distributions of hypothalamic neuron populations co-expressing tyrosine hydroxylase and the vesicular GABA transporter in the mouse

The hypothalamus contains catecholaminergic neurons marked by the expression of tyrosine hydroxylase (TH). As multiple chemical messengers coexist in each neuron, we determined if hypothalamic TH-immunoreactive (ir) neurons express glutamate or GABA. We used Cre/loxP recombination to express enhanced GFP fluorescence (EGFP) in neurons that express the vesicular glutamate (vGLUT2) or GABA transporter (vGAT), then determined TH immunoreactivity in glutamatergic or GABAergic neurons, respectively. EGFP-positive vGLUT2 neurons were not TH-ir. However, discrete TH-ir signals colocalized with EGFP-positive vGAT neurons, which we validated by in situ hybridization for Vgat mRNA. In order to contextualize the observed pattern of TH+EGFP colocalization in vGAT neurons, we first performed Nissl-based parcellation and plane-of-section analysis, and then mapped the distribution of TH-ir vGAT neurons onto atlas templates from the Allen Reference Atlas (ARA) of the mouse brain. TH-ir vGAT neurons were distributed throughout the rostrocaudal extent of the hypothalamus. Within the ARA ontology of gray matter regions, TH-ir neurons localized primarily to the periventricular hypothalamic zone, periventricular hypothalamic region, and lateral hypothalamic zone. There was a very strong presence of EGFP fluorescence in TH-ir neurons across all brain regions, but the most striking colocalization was found in the zona incerta (ZI) - a region assigned to the hypothalamus in the ARA - where every TH-ir neuron was EGFP-positive. Neurochemical characterization of these ZI neurons revealed that they display immunoreactivity for dopamine but not dopamine {beta}-hydroxylase. In aggregate, these findings indicate the existence of a novel hypothalamic population in the mouse that may signal through the release of GABA and/or dopamine.

neuroscience↗