Publications by authors named "Sung Phil Kim"

Unlabelled: Patients suffering from various neurological disorders, including major depressive disorder (MDD), often exhibit abnormal brain connectivity. In particular, patients with MDD show atypical brain oscillations propagation. This study aims to investigate an association between abnormal brain connectivity and atypical oscillatory propagation of electroencephalogram (EEG) signals in patients with a history of MDD.

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Objective: In the pursuit of refining P300-based brain-computer interfaces (BCIs), our research aims to propose a novel stimulus design focused on selective attention and task relevance to address the challenges of P300-based BCIs, including the necessity of repetitive stimulus presentations, accuracy improvement, user variability, and calibration demands.

Approach: In the oddball task for P300-based BCIs, we develop a stimulus design involving task-relevant dynamic stimuli implemented as finger-tapping to enhance the elicitation and consistency of event-related potentials (ERPs). We further improve the performance of P300-based BCIs by optimizing ERP feature extraction and classification in offline analyses.

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Article Synopsis
  • Sorting spikes from extracellular recordings is crucial for understanding neural coding, but identifying overlapping spikes remains challenging due to the complexity of neuronal activity.
  • This study introduces a novel method for detecting and decomposing overlapping spikes using estimated spike templates and a particle swarm optimization technique, leading to improved identification accuracy.
  • Results show the proposed approach can effectively classify overlapping spikes, achieving a high F1 score, and also infer the synchronization of hidden spikes, enhancing tools for neural activity analysis.
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Black rice bran, a waste product from the commercial milling of black rice that removes the bran and germ leaving the starchy endosperm, contains bioactive anthocyanin, phenolic, and phytosteroid compounds that may have health benefits. This study determined the effect of a polysaccharide-rich bioprocessed (fermented) black rice bran and a green tea extract individually and in combination on weight loss in orally fed mice on a high-fat diet and on concurrent changes in blood glucose and insulin as well as in cholesterol, triglyceride, and high-density and low-density lipoproteins (HDL and LDL). At the end of the eight-week feeding study, the combination diet resulted in a 67% lower weight gain than mice on a high-fat diet alone, a greater effect than that of bioprocessed black rice bran or green tea extract individually.

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The temporal order of propagation in the blood-oxygen-level-dependent (BOLD) infra-slow activity (ISA, 0.01-0.1 Hz) of functional magnetic resonance imaging (fMRI) can indicate the functional organization of the brain.

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Article Synopsis
  • The study aimed to explore the differences in brain activity between patients with drug-induced parkinsonism (DIP) and those with Parkinson’s disease (PD) using resting-state electroencephalography (rsEEG).
  • Researchers analyzed rsEEG data from 15 DIP patients, 41 PD patients, and 12 healthy controls, finding distinct EEG patterns: DIP patients had higher theta band power and greater delta band coherence compared to PD patients.
  • The findings indicate that rsEEG could serve as an effective method for distinguishing between DIP and PD, potentially aiding in more accurate diagnoses.
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Meditation induces changes in the nervous system, which presumably underpin positive psychological and physiological effects. Such neural changes include alterations in the arousal fluctuation, as well as in infraslow brain activity (ISA, <0.1 Hz).

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This study investigates the impact of conversation on the performance of visual event-related potential (ERP)-based brain-computer interfaces (BCIs), considering distractions in real life environment. The research aims to understand how cognitive distractions from speaking and listening activities affect ERP-BCI performance.The experiment employs a dual-task paradigm where participants control a smart light using visual ERP-BCIs while simultaneously conducting speaking or listening tasks.

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Introduction: Behaviors often involve a sequence of events, and learning and reproducing it is essential for sequential memory. Brain loop structures refer to loop-shaped inter-regional connection structures in the brain such as cortico-basal ganglia-thalamic and cortico-cerebellar loops. They are thought to play a crucial role in supporting sequential memory, but it is unclear what properties of the loop structure are important and why.

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Purpose: Meditation is renowned for its positive effects on cognitive abilities and stress reduction. It has been reported that the amplitude of electroencephalographic (EEG) infra-slow activity (ISA, < 0.1 Hz) is reduced as the stress level decreases.

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Background: The across-trial correlation of neurons' coactivity patterns emerges to be important for information coding, but methods for finding their temporal structures remain largely unexplored.

New Method: In the present study, we propose a method to find time clusters in which coactivity patterns of neurons are correlated across trials. We transform the multidimensional neural activity at each timing into a coactivity pattern of binary states, and predict the coactivity patterns at different timings.

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Group-level analyses have typically associated behavioral signatures with a constrained set of brain areas. Here we show that two behavioral metrics - reaction time (RT) and confidence - can be decoded across the cortex when each individual is considered separately. Subjects (N=50) completed a perceptual decision-making task with confidence.

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Objective: Propagation of electroencephalogram (EEG) oscillations, often referred to as traveling waves, reflects the role of brain oscillations in neural information transmission. This propagation can be distorted by brain disorders such as schizophrenia that features disconnection of neural information transmission (i.e.

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Achieving long-lasting neuronal modulation with low-intensity, low-frequency ultrasound is challenging. Here, we devised theta burst ultrasound stimulation (TBUS) with gamma bursts for brain entrainment and modulation of neuronal plasticity in the mouse motor cortex. We demonstrate that two types of TBUS, intermittent and continuous TBUS, induce bidirectional long-term potentiation or depression-like plasticity, respectively, as evidenced by changes in motor-evoked potentials.

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Brain-computer interfaces (BCIs) have a potential to revolutionize human-computer interaction by enabling direct links between the brain and computer systems. Recent studies are increasingly focusing on practical applications of BCIs-e.g.

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The motor cortex not only executes but also prepares movement, as motor cortical neurons exhibit preparatory activity that predicts upcoming movements. In movement preparation, animals adopt different strategies in response to uncertainties existing in nature such as the unknown timing of when a predator will attack-an environmental cue informing "go." However, how motor cortical neurons cope with such uncertainties is less understood.

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This comprehensive review explores the broad landscape of brain-computer interface (BCI) technology and its potential use in intensive care units (ICUs), particularly for patients with motor impairments such as quadriplegia or severe brain injury. By employing brain signals from various sensing techniques, BCIs offer enhanced communication and motor rehabilitation strategies for patients. This review underscores the concept and efficacy of noninvasive, electroencephalogram-based BCIs in facilitating both communicative interactions and motor function recovery.

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Unlabelled: Non-invasive brain-computer interfaces (BCIs) based on an event-related potential (ERP) component, P300, elicited via the oddball paradigm, have been extensively developed to enable device control and communication. While most P300-based BCIs employ visual stimuli in the oddball paradigm, auditory P300-based BCIs also need to be developed for users with unreliable gaze control or limited visual processing. Specifically, auditory BCIs without additional visual support or multi-channel sound sources can broaden the application areas of BCIs.

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Research in neuroscience often assumes universal neural mechanisms, but increasing evidence points toward sizeable individual differences in brain activations. What remains unclear is the extent of the idiosyncrasy and whether different types of analyses are associated with different levels of idiosyncrasy. Here we develop a new method for addressing these questions.

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Decision-making is a complex process that involves the integration and interpretation of sensory information to guide actions. The rodent motor cortex, which is generally involved in motor planning and execution, also plays a critical role in decision-making processes. In perceptual delayed-response tasks, the rodent motor cortex can represent sensory cues, as well as the decision of where to move.

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Spontaneous gaze following and the concomitant joint attention enable us to share representations of the world with others, which forms a foundation of a broad range of social cognitive processes. Although this form of social orienting has long been suggested as a critical starting point for the development of social and communicative behavior, there is limited evidence directly linking it to higher-level social cognitive processes among healthy adults. Here, using a gaze-cuing paradigm, we examined whether individual differences in gaze following tendency predict higher-order social cognition and behavior among healthy adults.

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Article Synopsis
  • The study explores how the brain processes pitch, focusing on event-related potentials (ERPs) in response to sounds of varying frequencies, particularly looking at comparisons between musically-trained and non-trained individuals.
  • Participants listened to notes from the C major scale, revealing that brain responses varied significantly with pitch, showing anti-symmetric patterns between the left and right hemispheres.
  • Results indicated that musically-trained individuals had quicker and stronger brain responses to pitch changes, suggesting that musical training enhances the brain's ability to process and discriminate pitch frequencies more effectively.
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To develop a biomimetic artificial tactile sensing system capable of detecting sustained mechanical touch, we propose a novel biological neuron model (BNM) for slowly adapting type I (SA-I) afferent neurons. The proposed BNM is designed by modifying the Izhikevich model to incorporate long-term spike frequency adaptation. Adjusting the parameters renders the Izhikevich model describing various neuronal firing patterns.

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Article Synopsis
  • - Efficient coding is a principle that reduces redundancy in neural representations but can increase vulnerability to noise; smoothing neural responses may help improve robustness against such noise in complex brain systems.
  • - The study shows that using spatio-temporally efficient coding in a hierarchical neural network can enhance both efficiency and robustness when processing dynamic visual stimuli, effectively managing noise and delays.
  • - Simulation results indicate that this coding approach allows neural responses to dynamic stimuli to closely resemble responses to static stimuli, suggesting that it helps maintain the structure of visual information in the brain.
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Introduction: Identifying biomarkers for depression from brain activity is important for the diagnosis and treatment of depression disorders. We investigated spatial correlations of the amplitude fluctuations of electroencephalography (EEG) oscillations as a potential biomarker of depression. The amplitude fluctuations of EEG oscillations intrinsically reveal both temporal and spatial correlations, indicating rapid and functional organization of the brain networks.

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