Biology subjects

Kang, J. U.

Publications and source records attributed to Kang, J. U..

7 recordsLinked to original sources

bioRxiv2025

A causal role for the posterior corpus callosum in bimanual coordination

Inter-areal communication is crucial for brain function. Given the largely contralateral organization of the brain, bimanual coordination likely involves interactions across the two cerebral hemispheres for motor planning and execution. The parietal reach region (PRR) is an early node in the sensorimotor transformation stream. Here we examine the contributions of direct callosal connections between left and right PRR to bimanual coordination. Using manganese-enhanced magnetic resonance imaging, we traced callosal pathways crossing the midline and found that PRR-PRR connections are restricted to the splenium. We then temporarily blocked these fibers with lidocaine while measuring behavioral performance and interhemispheric coherence. Blockade reduced task-specific PRR-PRR coherence during bimanual movements. Behaviorally, blockade sped movement initiation across tasks, consistent with an inhibitory role of interhemispheric communication, reduced the temporal synchrony of bimanual movements to a common target and reduced errors for bimanual movements to separate targets. These findings provide causal evidence that posterior callosal communication supports spatial coordination of bimanual actions but may also constrain independent limb control. Significance StatementClassic split-brain studies revealed that severing the corpus callosum impairs bimanual coordination, but the specific pathways and mechanisms remain unclear. In macaques, we transiently disrupted the posterior corpus callosum connecting left and right parietal reach regions (PRR), which encode planned contralateral arm movements. This targeted blockade reduced task-specific neural synchrony between PRRs and selectively impaired coordination when both arms reached to a common target, while improving performance when the arms moved to separate targets. Movement initiation was also sped up across tasks, consistent with an inhibitory role of interhemispheric communication. These findings provide causal evidence that posterior callosal communication enables spatially coordinated bimanual movements, extending foundational split-brain insights to defined cortical circuits in a non-human primate model.

neuroscience↗

bioRxiv2025

Parietal cortex is recruited by frontal and cingulate areas to support action monitoring and updating during stopping

Recent evidence indicates that the intraparietal sulcus (IPS) may play a causal role in action stopping, potentially representing a novel neuromodulation target for inhibitory control dysfunctions. Here, we leverage intracranial recordings in human subjects to establish the timing and directionality of information flow between IPS and prefrontal and cingulate regions during action stopping. Prior to successful inhibition, information flows primarily from the inferior frontal gyrus (IFG), a critical inhibitory control node, to IPS. In contrast, during stopping errors the communication between IPS and IFG is lacking, and IPS is engaged by posterior cingulate cortex, an area outside of the classical inhibition network and typically associated with default mode. Anterior cingulate and orbitofrontal cortex also display performance-dependent connectivity with IPS. Our functional connectivity results provide direct electrophysiological evidence that IPS is recruited by frontal and anterior cingulate areas to support action plan monitoring/updating, and by posterior cingulate during control failures. In briefFunctional connectivity between the intraparietal sulcus (IPS) and a set of frontal and cingulate regions indicates that IPS is recruited to aid inhibitory control. Control failures are associated with increased communication with posterior cingulate. IPS could be a novel and tractable neuromodulation target for control-related neuropsychiatric disorders. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=107 SRC="FIGDIR/small/640787v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@e04699org.highwire.dtl.DTLVardef@3b1ea6org.highwire.dtl.DTLVardef@15961f4org.highwire.dtl.DTLVardef@12e144f_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIParietal cortex displays performance-dependent activity in action stopping C_LIO_LIFunctional connectivity between IPS and IFG underlies successful stopping C_LIO_LIEarly communication from ACC and OFC to IPS is also specific to successful stopping C_LIO_LICommunication from PCC to IPS is higher during lapses in control C_LI

neuroscience↗

bioRxiv2023

Multicore fiber optic imaging reveals that astrocyte calcium activity in the cerebral cortex is modulated by internal motivational state

Astrocytes are a direct target of neuromodulators and can influence neuronal activity on broad spatial and temporal scales through their close proximity to synapses. However, our knowledge about how astrocytes are functionally recruited during different animal behaviors and their diverse effects on the CNS remains limited. To enable measurement of astrocyte activity patterns in vivo during normative behaviors, we developed a high-resolution, long working distance, multi-core fiber optic imaging platform that allows visualization of cortical astrocyte calcium transients through a cranial window in freely moving mice. Using this platform, we defined the spatiotemporal dynamics of astrocytes during diverse behaviors, ranging from circadian fluctuations to novelty exploration, showing that astrocyte activity patterns are more variable and less synchronous than apparent in head-immobilized imaging conditions. Although the activity of astrocytes in visual cortex was highly synchronized during quiescence to arousal transitions, individual astrocytes often exhibited distinct thresholds and activity patterns during explorative behaviors, in accordance with their molecular diversity, allowing temporal sequencing across the astrocyte network. Imaging astrocyte activity during self-initiated behaviors revealed that noradrenergic and cholinergic systems act synergistically to recruit astrocytes during state transitions associated with arousal and attention, which was profoundly modulated by internal state. The distinct activity patterns exhibited by astrocytes in the cerebral cortex may provide a means to vary their neuromodulatory influence in response to different behaviors and internal states.

neuroscience↗

bioRxiv2023

Inferring functional organization of posterior parietal cortex circuitry based on information flow

Many studies infer the role of neurons by asking what information can be decoded from their activity or by observing the consequences of perturbing their activity. An alternative approach is to consider information flow between neurons. We applied this approach to the Parietal Reach Region (PRR) and the Lateral Intraparietal area (LIP) in posterior parietal cortex. Two complementary methods show that, across a range of reaching tasks, information flows primarily from PRR to LIP but not vice versa. This suggests that PRR determines the spatial goals of coordinated eye and arm movements and instructs LIP of those goals. Based on these findings, we conclude that PRR and LIP operate in a parallel rather than hierarchical manner to plan arm and eye movements, respectively. Similar methodology can be applied to other areas to infer their relative relationships.

neuroscience↗

bioRxiv2019

Functional intra-operative guidance of the cavernous nerve network using near-infrared cyanine voltage-sensitive dye imaging: relevance for nerve-sparing radical prostatectomy

Despite current progress achieved in the surgical technique of radical prostatectomy, post-operative complications such as erectile dysfunction and urinary incontinence persist at high incidence rates. In this paper, we present a methodology for functional intra-operative localization of the cavernous nerve (CN) network for nerve-sparing radical prostatectomy using near-infrared cyanine voltage-sensitive dye (VSD) imaging, which visualizes membrane potential variations in the CN and its branches (CNB) in real time. As a proof-of-concept experiment, we demonstrate a functioning complex nerve network in response to electrical stimulation of the CN, which was clearly differentiated from surrounding tissues in an in vivo rat prostate model. Stimulation of an erection was confirmed by correlative intracavernosal pressure (ICP) monitoring. Within 10 minutes, we performed trans-fascial staining of the CN by direct VSD administration. Our findings suggest the applicability of VSD imaging for real-time, functional imaging guidance during nerve-sparing radical prostatectomy.

biophysics↗

bioRxiv2018

Voltage-sensitive dye delivery through the blood brain barrier using adenosine receptor agonist Regadenoson

Optical imaging of brain activity has mostly employed genetically manipulated mice, which cannot be translated to clinical human usage. Observation of brain activity directly is challenging due to difficulty in delivering dyes and other agents through the blood brain barrier (BBB). Using fluorescence imaging, we have demonstrated the feasibility of delivering the near-infrared voltage-sensitive dye (VSD) IR-780 perchlorate to the brain tissue through pharmacological techniques, via an adenosine agonist (Regadenoson). Comparison of VSD fluorescence of mouse brains without and with Regadenoson showed significantly increased residence time of the fluorescence signal in the latter case, indicative of VSD diffusion into the brain tissue. Dose and timing of Regadenoson were varied to optimize BBB permeability for VSD delivery.

bioengineering↗

bioRxiv2017

Transcranial real-time in vivo recording of electrophysiological neural activity in the rodent brain with near-infrared photoacoustic voltage-sensitive dye imaging

Minimally-invasive monitoring of electrophysiological neural activities in real-time--that enables quantification of neural functions without a need for invasive craniotomy and the longer time constants of fMRI and PET--presents a very challenging yet significant task for neuroimaging. In this paper, we present in vivo functional PA (fPA) imaging of chemoconvulsant rat seizure model with intact scalp using a fluorescence quenching-based cyanine voltage-sensitive dye (VSD) characterized by a lipid vesicle model mimicking different levels of membrane potential variation. The framework also involves use of a near-infrared VSD delivered through the blood-brain barrier (BBB), opened by pharmacological modulation of adenosine receptor signaling. Our normalized time-frequency analysis presented in vivo VSD response in the seizure group significantly distinguishable from those of the control groups at sub-mm spatial resolution. Electroencephalogram (EEG) recording confirmed the changes of severity and frequency of brain activities, induced by chemoconvulsant seizures of the rat brain. The findings demonstrate that the near-infrared fPA VSD imaging is a promising tool for in vivo recording of brain activities through intact scalp, which would pave a way to its future translation.

neuroscience↗