https://scholar.dgist.ac.kr/handle/20.500.11750/265 2026-11-11T10:56:43Z https://scholar.dgist.ac.kr/handle/20.500.11750/61169 Title: Graded prefrontal–sensory connectivity underlies cross-modal hierarchical control Author(s): Yoo, Taehyun; Jeon, Hyeon-Ae Abstract: Does the rostro–caudal architecture of the prefrontal cortex (PFC) generalize to support hierarchical control across sensory modalities? To address this question, we used functional magnetic resonance imaging while participants performed three cue-based tasks integrating auditory and visual modalities, requiring policy abstraction from auditory cues to motor responses, visual features, or visual dimensions. Behaviorally, increasing abstraction and complexity produced robust costs in accuracy and reaction time, underscoring the computational demands of cross-modal control. Univariate analyses revealed complexity-modulated effects within each level of abstraction and a corresponding anterior shift in PFC activation paralleling the hierarchical gradient. Multivoxel pattern analysis further demonstrated a representational shift, where caudal PFC encoded concrete motor responses, whereas rostral PFC represented abstract dimensions. Functional connectivity analyses revealed a complementary dissociation: caudal subregions showed selective, complexity-modulated coupling with primary sensory cortices during lower-level control, whereas rostral PFC exhibited functional independence from direct sensory coupling at the highest level of abstraction. Instead, increasing abstraction was associated with enhanced coupling among higher-order association areas, particularly between the superior temporal and intraparietal regions. Together, these findings extend prior unimodal research by demonstrating that hierarchical control is instantiated along a rostro–caudal gradient that flexibly reconfigures prefrontal–sensory interactions to meet multiple sensory demands. This cross-modal hierarchical architecture enables a transition from direct sensorimotor mappings to abstract regulation, providing a neural basis for adaptive cognition in the complex, multisensory environments of everyday life. © 2026 The Author(s). 2026-06-30T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/61155 Title: SCORE beamforming: Spectral COherence REfinement for high-contrast ultrafast Doppler imaging Author(s): Guezzi, Nizar; Lee, Sangheon; Nam, Sangwoo; Seo, Youngho; Kim, Myeongchan; Eom, Kisang; Hyun, Jung Ho; Yu, Jaesok Abstract: Delay-and-sum (DAS) beamforming is widely used in ultrasound flow imaging due to its computational simplicity; however, its high sidelobe levels significantly degrade image contrast. Coherence factor (CF) beamforming partially alleviates this limitation by emphasizing spatial coherence, yet residual incoherent energy remains and continues to impair image quality. In this study, we propose a dual-stage beamforming approach that integrates CF weighting with a frequency-domain filtering stage designed to discriminate and suppress incoherent energy while preserving coherent signal components. The proposed method, termed SCORE (Spectral COherence REfinement), introduces an additional coherence-based discrimination mechanism beyond conventional CF beamforming. Simulation experiments involving single-target, multi-target, and vascular scenarios demonstrate that SCORE achieves substantial sidelobe suppression while maintaining signal integrity. In vivo validation using an open-source contrast-enhanced rat brain and kidney dataset, as well as contrast-free human spleen further confirms improved flow detectability, reduced background noise, and enhanced power Doppler imaging performance, as evidenced by increases in SNR and CNR approaching 10 dB compared to CF and GCF beamforming. Overall, the SCORE beamformer provides a robust framework for high-contrast vascular ultrasound imaging, offering superior sidelobe and noise suppression relative to DAS, CF and GCF. To enhance computational efficiency, the beamforming pipeline was implemented on a graphics processing unit (GPU) using an optimized CUDA framework, achieving real-time beamforming performance with processing times below 30 ms per frame. 2026-12-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/61151 Title: Why behavior lasts while neurons drift Author(s): Kim, Kyuhyung Abstract: Traditional dogmas assume that executing a stable behavior requires neural circuits to remain in a fixed, steady state. However, recent population imaging reveals “representational drift”, a continuous, unprompted shifting of neural activity over time despite invariant behavioral outputs. This introduces a profound paradox where behavioral permanence must emerge from a volatile physical substrate. Here, I review how nervous systems maintain dynamic stability across diverse biological scales. In Caenorhabditis elegans, a structurally fixed connectome achieves functional invariance amid intrinsic whole-brain drift by dynamically reweighting sensory-to-motor paths via acute neuromodulation, metabolic gates, and intergenerational RNA cascades. In mammals, behavioral constancy emerges through collective population dynamics constrained within low-dimensional neural manifolds and stabilized by homeostatic compensation. Far from a biological flaw, representational drift acts as an active computational feature to explore degenerate solution spaces. Together, these multiscale insights demonstrate that behavioral permanence is anchored not in structural rigidity, but in the regulated preservation of network-level dynamics. 2026-11-30T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/61143 Title: Pharmacological inhibition of REV-ERBα ameliorates motor deficits in the 6-OHDA-lesioned mouse model of Parkinson's disease Author(s): Kim, Jeongah; Choe, Mijeong; Jang, Sangwon; Park, Inah; Oh, Sungjoon; Kim, Eun-Kyoung; Choe, Youngshik; Sun, Woong; Kim, Kyungjin Abstract: Parkinson's disease (PD) is characterized by nigrostriatal dopaminergic (DAergic) degeneration and motor dysfunction. Many PD patients also show circadian rhythm disturbances. Increasing evidence links circadian clock dysfunction to PD pathology. REV-ERB alpha is a circadian nuclear receptor that regulates DAergic genes under physiological conditions. However, its role in nigrostriatal dopamine (DA) homeostasis and motor function in PD remains unclear. In this study, we found elevated Rev-erb alpha mRNA expression in tyrosine hydroxylase (TH)-positive neurons of the substantia nigra (SN) in a 6-hydroxydopamine (6-OHDA) mouse model of PD. To test its functional role, we assessed the acute effects of local SN microinjection of the REV-ERB alpha antagonist SR8278. We found that SR8278 partially recovered motor performance and improved fine motor function. These effects occurred regardless of circadian timing. SR8278 administration did not restore TH expression or tissue DA levels in the striatum and SN. However, in vivo microdialysis showed enhanced extracellular DA turnover in the striatum. Specifically, while extracellular DA metabolites level increased, basal extracellular DA levels showed no change. Together, these findings identify REV-ERB alpha as a potential therapeutic target that modulates extracellular nigrostriatal DA dynamics and improves motor function in PD. 2026-11-30T15:00:00Z