Biology subjects

Lind, B. L.

Publications and source records attributed to Lind, B. L..

8 recordsLinked to original sources

bioRxiv2026

Patient-Derived Air-Liquid Interface Forebrain Organoids Reveal Functional Synaptic Deficits in Schizophrenia

Schizophrenia (SCZ) is a severe and debilitating neurodevelopmental disorder with lifelong impact on everyday life. Disruptions in synapse functions play a key role in its complex and poorly understood etiological and pathological mechanisms. Here, we investigated both the molecular composition and the spontaneous and stimulated functional properties of synapses in neural organoids from SCZ individuals. Air-liquid interface forebrain organoids (ALI-FOs) were generated from induced pluripotent stem cells (iPSCs) derived from three individuals with SCZ and three healthy controls. At day 170 synaptosomes were enriched and analyzed by data-independent acquisition mass spectrometry to profile the proteome, alongside with TMT-labeled phosphoproteomics both before and after acute KCl-induced depolarization. In parallel, we characterized the PTMome of the surrounding cellular environment, comprising phosphorylation, peptides with free and reversibly modified cysteines, and sialylated N-linked glycopeptides. Functional glutamatergic and GABAergic activity was assessed using calcium imaging to capture spontaneous neuronal signaling. Both conditions exhibited mature synaptic structures, while growth cones were observed only in SCZ-derived ALI-FOs, indicative of ongoing or delayed synaptogenesis. Proteomic analysis of synaptosome preparations revealed 358 differentially regulated proteins between SCZ and controls and 125 phophoproteins with altered phosphorylation, which clustered into three major categories: (1) synaptogenesis and synapse signaling; (2) cytoskeleton and cell junctions; (3) growth cone dynamics and neurite outgrowth. Analysis of the PTMs in the surrounding cellular environment revealed regulation of key regulatory mechanisms in 526 proteins, supporting the synaptic alterations observed. Notably, components of the Wnt signaling pathway were consistently dysregulated across both the synaptosome preparation and the PTMome in SCZ-derived ALIFOs as compared to controls. Depolarization-induced phospho-signaling revealed SCZ-specific response enriched in synaptic vesicle trafficking pathways. Together, these findings provide new insights into early synaptic alterations in SCZ, highlighting changes not only in protein composition, but more in protein regulatory mechanisms underlying synaptic signaling.

neuroscience↗

bioRxiv2026

Spatiotemporally distinctive astrocytic and neuronal responses to repetitive intracortical microstimulation

Astrocytes are increasingly recognized as active modulators of neuronal synaptic transmission. Intracortical microstimulation (ICMS) is widely used to manipulate neuronal activity, yet the accompanying astrocytic responses remain poorly characterized. Using dual-color in vivo two-photon calcium imaging to simultaneously monitor neurons and astrocytes, we show that ICMS elicits astrocytic activation with spatiotemporal features that diverge from those of neurons. Astrocytes were recruited at stimulation intensities as low as 10A, thresholds sufficient to activate neurons, indicating that astrocytes robustly sense electrical perturbation. Unlike neurons, however, astrocytic responses were spatially heterogeneous and temporally variable across trials. At higher stimulation intensities (>=50A), astrocytic responsiveness, i.e., response peak amplitude, and number of responsive trials, progressively attenuated across repeated trials, in contrast to the stable and consistent neuronal responses. Although neuronally driven, astrocytes exhibited a distinct response profile under the same stimulation parameter, revealing a unique component of electrically evoked cortical activity that underscores the importance of incorporating glial physiology into future neuroprosthetic strategies.

neuroscience↗

bioRxiv2025

Single-Cell and Population-Level Neuromodulation Dynamics in Dual-Electrode Intracortical Stimulation

In neuroprosthetics, intracortical microstimulation (ICMS) recruits cortical networks to evoke brain responses and sensory perceptions. However, multi-electrode ICMS often generates suboptimal percepts compared to single-electrode ICMS, suggesting nonlinear neuromodulation rather than simple summation by multi-electrode ICMS. Yet, the factors and mechanisms underlying this modulation remain poorly understood. To investigate multi-electrode ICMS, we combined two-photon calcium imaging with a well-controlled dual-electrode ICMS in the mouse visual cortex to investigate how neurons integrate converging ICMS inputs at varying intensities. We found that stimulation intensity significantly shapes neuromodulation at both single-cell and population levels. Specifically, low intensities (5-7 {micro}A) have a minimal effect on neural responses. At intermediate intensities (10-15 {micro}A), we observed diverse, nonlinear bipolar modulation--both enhancement and attenuation--at the single-cell level. However, we achieved net enhancement at the population level. At higher intensities (15-20 {micro}A), although the proportion of modulated neurons increased in both enhancement and attenuation directions, the net effect at the population level was neutral (zero modulation). Furthermore, neurons strongly responsive to single-electrode ICMS were more likely to be attenuated, while weaker responding cells exhibited enhanced modulation. The strongest neuromodulatory effects occur at intermediate spatial distances in between the two electrodes. Computational modeling based on spiking neural network composed of adaptive exponential integrate-and-field neurons implicated the importance of inhibitory network dynamics and network variability as key mechanisms. Our experimental data was used to train an advanced deep learning approach, which successfully predicted the neuromodulation patterns induced by dual-electrode ICMS. Our findings reveal intensity- and spatial-dependent rules of neuromodulation by ICMS, providing necessary insights to optimize multi-electrode ICMS for neuroprosthetic applications. Significance statementUnderstanding how cortical neurons integrate concurrent inputs from multi-electrode intracortical microstimulation (ICMS) is essential for advancing neuroprosthetic technologies. We show that dual-electrode ICMS evokes distinct, predictable neuromodulatory effects that depend on (i) stimulation intensity, (ii) a neurons baseline responsiveness to single electrode input, and (iii) its proximity to the electrodes. Low and intermediate intensity dual-electrode ICMS amplifies neural activity compared to single-electrode ICMS, whereas high-intensity stimulation leads to attenuation, limiting net activation.

neuroscience↗

bioRxiv2024

Spatially mismatched cerebral blood flow and neuronal activity by intracortical microstimulation

Intracortial microstimulation (ICMS) is widely used in brain-machine interface for neuroprosthetics, particularly with aims of restoring lost sensory and motor functions. However, it remains poorly understood whether neuronal and blood flow responses by ICMS are spatially and temporally matched, as well as their underlying mechanism. Neurovascular coupling (NVC) is the process by which neuronal activity regulates blood flow in the brain to meet local metabolic demands. A hypothetically suboptimal NVC by ICMS may exacerbate the neuronal survival near electrode, contributing to neurodegeneration. In this study, we used wide-field imaging, laser speckle imaging and two-photon imaging in transgenic mice expressing calcium fluorescent indicators in neurons or vascular mural cells to examine this hypothesis. Our results showed blood flow responses are delayed at peak time and prolonged in duration compared with neuronal responses. By varying the stimulation amplitudes, we found that low stimulation intensity lower than 50A preserved NVC. In contrast, high intensity stimulation caused spatially mismatched NVC, i.e. in the adjacent range within 200[~]400 m from electrode tip, elicited blood flow compromises but neuronal activities increase. Ca2+ is the key regulator of contractile tone of vascular mural cells. Our results showed that Ca2+ sensitivity at vascular mural cells, i.e. vessel diameter change per unit of Ca2+ change, was decreased in the adjacent region of electrode, which partially explained the compromised and mismatched NVC, and which likely further lead to ischemia and neurodegeneration. This study offers a new insight into ICMS-associated neuronal and vascular physiology, and provides an important implication towards optimal design of ICMS: low intensities is more neuroprotective than high intensities by preserving NVC and preventing ischemia. Our discoveries pave the way for new research consideration and contribute to the development of more advanced brain-machine interface.

neuroscience↗

bioRxiv2024

Fast 3D imaging in the auditory cortex of awake mice reveals that astrocytes control neurovascular coupling responses locally at arteriole-capillary junctions.

Neurovascular coupling (NVC) increases blood flow, assuring adequate supply to active cortical regions by local redistribution via penetrating arterioles (PA) and branching capillaries. Astrocyte end-feet enwrapping these vascular structures possess machinery to regulate blood flow, but their participation in NVC is controversial. Via a new 3D+t two-photon imaging approach we visualized PA and capillaries simultaneously during naturally-occurring and tone-evoked dilations in the auditory cortex of awake mice. We observed that dilations occurred bidirectionally, and a fraction of them extended between compartments across the interconnecting sphincter, depending on the animal activity states. These multi-compartment dilations were preceded by rapid astrocyte end-foot Ca2+ signals around the sphincter. Reduction of this astrocytic Ca2+ activity in IP3R2KO mice suppressed multi-compartment dilations, revealing a pivotal role of pre-capillary sphincters in their bidirectional spread between vascular compartments under local control by astrocytes. This novel mechanism contributes to physiological regulation of laminar blood flow during NVC.

neuroscience↗

bioRxiv2024

Astrocyte Contribution to Brain State-Dependent Neurovascular Coupling

Neurovascular coupling (NVC) ensures sufficient and targeted blood flow during increased neuronal activity. Astrocytic participation in NVC has long been debated, likely due to the intricacy of the intracellular Ca2+ fluxes and the diversity of their regulatory capacities. As astrocyte signaling changes with brain states, we focused on their involvement in voluntary sensing in freely behaving mice. We used 2-photon microscopy to record cellular and vascular activity in the whisker barrel cortex of awake head-fixed animals. The NVC initiated by volitional whisking in the resting mouse was compared to the whisking preceding locomotion and experimenter-evoked whisker deflections. We developed an analysis method to detect early, subcellular astrocytic activity and found it corresponded with neuronal and vascular responses under all three conditions. After the depletion of noradrenaline (NA), the early astrocytic Ca2+ response to volitional whisking was only moderately reduced and primarily in astrocytic processes closest to the blood vessels. Meanwhile, the dilation of 1st order capillaries was also reduced. Together, these findings demonstrate significant disruptions in the focal regulation of cerebral blood flow, potentially limiting the sustenance of activated neurons. This disruption appeared to translate into behavioral aberrations, as NA-depleted mice exhibited an extended period of exploratory whisking prior to locomotion. Remarkably, NA-depletion did not alter cellular or blood flow responses to locomotion or experimenter-evoked whisking. Our study confirms an astrocytic contribution to NVC, which is relevant during volitional sensing. It also suggests that self-directed sensory processing depends on an appropriate NVC response, which itself depends on NA and astrocyte activity.

neuroscience↗

bioRxiv2022

Astrocytic Ca2+ signals partake in inhibitory neurovascular coupling in a brain state-dependent manner.

Neurovascular coupling (NVC) modulates cerebral blood flow to match increased metabolic demand during neuronal excitation. Activation of inhibitory interneurons also increase blood flow, but the basis for this inhibitory NVC is unclear. We performed two-photon microscopy in awake mice to examine the correlation between astrocytic Ca2+ and NVC, evoked by activity in either all (VGATIN) or parvalbumin-positive GABAergic interneurons (PVIN). Optogenetic stimulation of VGATIN and PVIN in the somatosensory cortex triggered astrocytic Ca2+ increases that were abolished by anaesthesia. PVIN evoked astrocytic Ca2+ responses with a short latency that preceded NVC, whereas VGATIN evoked Ca2+ increases that were delayed relative to the NVC response. The early onset in PVIN evoked Ca2+ increases dependent on noradrenaline release from locus coeruleus, which also affected inhibitory NVC. Therefore, NVC mechanisms should be studied in awake mice and, though the relationship between interneuron activity and astrocytic Ca2+ is complex, we found a correlation between astrocyte activity and NVC in PVIN.

neuroscience↗

bioRxiv2021

Impaired dynamics of brain precapillary sphincters and first order capillaries explains reduced neurovascular functions in aging

The microvascular inflow tract (MIT), comprising the penetrating arterioles, precapillary sphincters, and first order capillaries, is the bottleneck for brain blood flow and energy supply. However, the exact structural and functional alterations of the MIT during aging remain elusive. In vivo 4-dimensional two-photon imaging showed an age-dependent decrease in vaso-responsivity, with reduced sensitivity of the MIT to pinacidil and papaverine, vasoconstrictor endothelin-1, and nitric oxide synthase inhibitor L-NAME. This was accompanied by an age-dependent decrease in capillary density close to the arterioles and loss of pericyte processes, though the number of pericyte somas and pericyte SMA density were preserved. The age-related reduction in vascular reactivity was most pronounced at precapillary sphincters, highlighting their crucial role in capillary blood flow regulation. Mathematical modeling revealed dysregulated but preserved pressure and flow in aged mice during vasoconstriction. Preventing reduced responsivity of the MIT may ameliorate the blood flow decrease associated with aging-related brain frailty.

neuroscience↗