Publications by authors named "Chany Lee"

Article Synopsis
  • - Biomedical research on the brain has made significant strides in understanding consciousness and addressing brain diseases, but has historically faced challenges like complex interpretations and limited collaboration among researchers from different fields.
  • - The progression of brain research has been slower than other biomedical areas due to these complexities, but recent advancements in high-throughput analysis tools have initiated a significant shift towards patient-centered, large-scale studies.
  • - Innovations in neuroimaging, multiomics, and artificial intelligence are leading the way for transformative changes in brain research, while interdisciplinary approaches are helping to tackle unresolved biomedicine questions.
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Purpose: Transscleral ocular iontophoresis has been proposed to deliver charged particulate drugs to ocular tissues effectively by transmitting a weak electrical current through the sclera. The electric fields formed are influenced by the electrode conditions, thus affecting the amount of particulate drugs delivered to the ocular tissues via iontophoresis. Computational simulation is widely used to simulate drug concentrations in the eye; therefore, reflecting the characteristics of the drugs in living tissues to the simulations is important for a more precise estimation of drug concentration.

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An early diagnosis of Alzheimer's disease is crucial as treatment efficacy is limited to the early stages. However, the current diagnostic methods are limited to mid or later stages of disease development owing to the limitations of clinical examinations and amyloid plaque imaging. Therefore, this study aimed to identify molecular signatures including blood plasma extracellular vesicle biomarker proteins associated with Alzheimer's disease to aid early-stage diagnosis.

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Article Synopsis
  • Multichannel transcranial electrical stimulation (tES) aims to enhance the precision of brain stimulation by using current patterns tailored through individual head models derived from MRIs; however, obtaining these individual models can be challenging.
  • A new method was proposed that utilizes multiple head models to derive an optimal injection current pattern, improving stimulation accuracy compared to relying solely on a standard model.
  • Results indicated that averaging current patterns from at least 13 head models significantly enhanced stimulation focality when compared to patterns derived from a single standard model, indicating the advantages of this multicentric approach.
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While zero-phase lag synchronization between multiple brain regions has been widely observed, relatively recent reports indicate that systematic phase delays between cortical regions reflect the direction of communications between cortical regions. For example, it has been suggested that a non-zero phase delay of electroencephalography (EEG) signals at the gamma frequency band between the bilateral parietal areas may reflect the direction of communication between these areas. We hypothesized that the direction of communication between distant brain areas might be modulated by multi-site transcranial alternating current stimulation (tACS) with specific phase delays other than 0° and 180°.

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Background: Electroencephalography (EEG) is a supplementary diagnostic tool in psychiatry but lacks practical usage. EEG has demonstrated inconsistent diagnostic ability because major depressive disorder (MDD) is a heterogeneous psychiatric disorder with complex pathologies. In clinical psychiatry, it is essential to detect these complexities using multiple EEG paradigms.

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Article Synopsis
  • - Adult neurogenesis involves the creation of new neurons from neural stem cells in areas like the hippocampus, and dietary components can influence this process.
  • - A study examined the effects of different doses of curcumin, a compound found in curry, on mouse brain function, finding that low doses (0.4 mg/kg) increased the growth and survival of new neurons while high doses (10 mg/kg) did not have the same effect.
  • - Results indicated that low-dose curcumin improved memory retention in tests and boosted levels of brain-derived neurotrophic factor (BDNF) and certain cellular activity markers, suggesting its potential to counteract cognitive decline related to aging or neurodegenerative diseases.
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Article Synopsis
  • Transcranial temporal interfering stimulation (tTIS) effectively targets deep brain areas by using high-frequency beats that don't impact the brain alone, but its complexity complicates fast calculations and precision.
  • A new approach employs an unsupervised neural network (USNN) to optimize the electrode currents for tTIS, linking two networks to enhance the stimulation's accuracy and efficiency in just 3 minutes.
  • In comparison to transcranial alternating current stimulation (tACS), the USNN-optimized tTIS provides stronger and more precise stimulation even in deep brain regions, reducing mis-stimulation and improving targeting capabilities.
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Working memory (WM) is a complex cognitive function involved in the temporary storage and manipulation of information, which has been one of the target cognitive functions to be restored in neurorehabilitation. WM capacity is known to be proportional to the number of gamma cycles nested in a single theta cycle. Therefore, gamma-band transcranial alternating current stimulation (tACS) should be dependent of the stimulation frequency; however, the results of previous studies that employed 40 Hz tACS have not been consistent.

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Objective: Although serotonergic dysfunction is significantly associated with major depressive disorder (MDD) and schizophrenia (SCZ), comparison of serotonergic dysfunction in both diseases has received little attention. Serotonin hypotheses have suggested diminished and elevated serotonin activity in MDD and SCZ, respectively. However, the foundations underlying these hypotheses are unclear regarding changes in serotonin neurotransmission in the aging brain.

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Temporal interference stimulation (TIS) has been proved to be effective in stimulating deep brain regions while avoiding the stimulation of neocortical regions in animal experiments. In the traditional TIS, two alternating currents are injected with different frequencies via two electrode pairs attached to the scalp. In the human brain, however, it is difficult to achieve a focal stimulation of deep brain structures due to the high complexity of human brain structures.

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Psychiatric diagnosis is formulated by symptomatic classification; disease-specific neurophysiological phenotyping could help with its fundamental treatment. Here, we investigated brain phenotyping in patients with schizophrenia (SZ) and major depressive disorder (MDD) by using electroencephalography (EEG) and conducted machine-learning-based classification of the two diseases by using EEG components. We enrolled healthy controls (HCs) ( = 30) and patients with SZ ( = 34) and MDD ( = 33).

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Precise estimation of electrical conductivity of the eyes is important for the accurate analysis of electric field distributions in the eyes during ocular iontophoresis. In this study, we estimated the tissue electrical conductivities of a rabbit eye, which has been widely employed for neuro-ophthalmological experiments, through an in vivo experiment for the first time. Electrical potentials were measured at multiple locations on the skin, while weak currents were transmitted into the skin via two surface electrodes attached to the skin around the eye.

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Background: Electroencephalography (EEG) frontal alpha asymmetry (FAA) has been observed in several psychiatric disorders. Dominance in left or right frontal alpha activity remains inconsistent in patients with major depressive disorder (MDD), patients with schizophrenia, and healthy controls. This study compared FAA among patients with MDD and schizophrenia, and healthy controls.

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Temporal interference (TI) stimulation was recently proposed that allows for the stimulation of deep brain structures with neocortical regions being minimally stimulated. For human brain modulation, TI current patterns are known to be considerably affected by the complex structures of the human head, and thus, it is hard to deliver TI current to a specific deep brain region. In this study, we optimized scalp electrode configurations and injection currents that can deliver maximum TI stimulation currents to a specific deep brain region, the head of the right hippocampus in this study, considering the real anatomical head structures of each individual.

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Background: It has been frequently reported that non-negligible numbers of individuals have steady-state visual evoked potential (SSVEP) responses of low signal-to-noise-ratio (SNR) to specific stimulation frequencies, which makes detection of the SSVEP difficult especially in brain-computer interface applications. We investigated whether SSVEP can be modulated by anodal transcranial direct-current stimulation (tDCS) of the visual cortex.

Methods: Each participant participated in two 20-min experiments-an actual tDCS experiment and a sham tDCS experiment-that were conducted on different days.

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Recent experimental studies have shown that static magnetic field can be effective in modulating human brain functions. Following this discovery, a new noninvasive brain stimulation technique was developed: the transcranial static magnetic stimulation (tSMS). Various types of permanent magnets have been used in previous experimental studies, with the aim of validating the effectiveness of tSMS; nevertheless, the spatial distributions of magnetic field generated by these permanent magnets have not been fully investigated.

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Background: Percutaneous occipital nerve stimulation (ONS) is effective in refractory chronic cluster headache (rCCH) patients. Responders to ONS differ from non-responders by greater glucose metabolism in subgenual anterior cingulate cortex (sgACC). We reasoned that transcranial direct current stimulation (tDCS), a non-invasive approach, might be able to activate this area and thus improve rCCH patients.

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The finite element method (FEM) is a numerical method that is often used for solving electroencephalography (EEG) forward problems involving realistic head models. In this study, FEM solutions obtained using three different mesh structures, namely coarse, densely refined, and adaptively refined meshes, are compared. The simulation results showed that the accuracy of FEM solutions could be significantly enhanced by adding a small number of elements around regions with large estimated errors.

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Background: Since there is no way to measure electric current generated by transcranial direct current stimulation (tDCS) inside the human head through in vivo experiments, numerical analysis based on the finite element method has been widely used to estimate the electric field inside the head. In 2013, we released a MATLAB toolbox named COMETS, which has been used by a number of groups and has helped researchers to gain insight into the electric field distribution during stimulation. The aim of this study was to develop an advanced MATLAB toolbox, named COMETS2, for the numerical analysis of the electric field generated by tDCS.

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Ictal epileptiform discharges (EDs) are characteristic signal patterns of scalp electroencephalogram (EEG) or intracranial EEG (iEEG) recorded from patients with epilepsy, which assist with the diagnosis and characterization of various types of epilepsy. The EEG signal, however, is often recorded from patients with epilepsy for a long period of time, and thus detection and identification of EDs have been a burden on medical doctors. This paper proposes a new method for automatic identification of two types of EDs, repeated sharp-waves (sharps), and runs of sharp-and-slow-waves (SSWs), which helps to pinpoint epileptogenic foci in secondary generalized epilepsy such as Lennox-Gastaut syndrome (LGS).

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Epilepsy is a disease marked by hypersynchronous bursts of neuronal activity; therefore, identifying the network characteristics of the epileptic brain is important. Juvenile myoclonic epilepsy (JME) represents a common, idiopathic generalized epileptic syndrome, characterized by spike-and-wave discharge (SWD) electroencephalographic (EEG) waveforms. We compare herein the network properties of periods of SWD and baseline activity using graph theory.

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Objectives: We recently reported that the P300 amplitude related to the Sternberg working memory (WM) task was significantly lower in drug-naïve severe restless legs syndrome (RLS) patients than controls. Here, we evaluated the effects of pramipexole on the Sternberg WM task performance by event-related potential (ERP) study.

Methods: Thirteen drug-naïve RLS patients (52.

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Purpose: Although glucose is the primary source of energy for the human brain, only a few studies have quantitatively evaluated the effects of glucose supply in healthy fasting subjects. Thus, this study used an EEG power spectral analysis to investigate whether alterations in EEG are associated with changes in blood glucose levels in healthy fasting subjects.

Methods: This study included 24 healthy volunteers who underwent resting-state EEG and completed two attention examinations following a fasting period of at least 8 hours.

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Synopsis of recent research by authors named "Chany Lee"

  • - Chany Lee's research primarily focuses on advancing techniques in neurostimulation and drug delivery systems, particularly relating to the brain and ocular tissues, utilizing computational modeling and simulations to enhance treatment efficacy and precision in targeting affected areas.
  • - Recent studies explore innovative methods like transcranial electrical stimulation and iontophoresis, investigating the influence of electrode conditions on drug delivery and employing machine learning techniques to differentiate between patient populations, such as those with depression.
  • - Additional contributions include identifying molecular signatures for early-stage Alzheimer's diagnosis and examining the effects of dietary components on neurogenesis, emphasizing the importance of interdisciplinary approaches in addressing complex biomedical challenges.