Seongkyun Kim

Increased Frontomotor Oscillations During Tic Suppression in Children With Tourette Syndrome

This work investigated whether Tourette syndrome patients exhibit alterations in neural oscillations during spontaneous expression and suppression of tics. Electroencephalograms (EEGs) were recorded from 9 medication-naïve children with Tourette syndrome and 10 age-matched healthy subjects in resting conditions and during tic suppression. Their cortical oscillations were examined using the power spectral method and partial directed coherence. The authors found increased oscillations of broad frequency bands in the frontomotor regions of patients during tic expression, suggesting the involvement of aberrant cortical oscillations in Tourette syndrome. More significantly, prominent increases in theta oscillation in the prefrontal area and directed frontomotor interactions in the theta and beta bands were observed during tic suppression. Furthermore, the directed EEG interaction from the frontal to motor regions was positively correlated with the severity of tic symptoms. These findings suggest that the frontal to motor interaction of cortical oscillations plays a significant role in tic suppression.

Vulnerability-Based Critical Neurons, Synapses, and Pathways in the Caenorhabditis elegans Connectome

Determining the fundamental architectural design of complex nervous systems will lead to significant medical and technological advances. Yet it remains unclear how nervous systems evolved highly efficient networks with near optimal sharing of pathways that yet produce multiple distinct behaviors to reach the organism’s goals. To determine this, the nematode roundworm Caenorhabditis elegans is an attractive model system. Progress has been made in delineating the behavioral circuits of the C. elegans, however, many details are unclear, including the specific functions of every neuron and synapse, as well as the extent the behavioral circuits are separate and parallel versus integrative and serial. Network analysis provides a normative approach to help specify the network design. We investigated the vulnerability of the Caenorhabditis elegans connectome by performing computational experiments that (a) “attacked” 279 individual neurons and 2,990 weighted synaptic connections (composed of 6,393 chemical synapses and 890 electrical junctions) and (b) quantified the effects of each removal on global network properties that influence information processing. The analysis identified 12 critical neurons and 29 critical synapses for establishing fundamental network properties. These critical constituents were found to be control elements—i.e., those with the most influence over multiple underlying pathways. Additionally, the critical synapses formed into circuit-level pathways. These emergent pathways provide evidence for (a) the importance of backward locomotion, avoidance behavior, and social feeding behavior to the organism; (b) the potential roles of specific neurons whose functions have been unclear; and (c) both parallel and serial design elements in the connectome—i.e., specific evidence for a mixed architectural design.

Lethality of complex neuronal network in Caenorhabditis elegans nervous system based on cell attacks

The aim of this study was to investigate changes in network structural properties and functional perturbations of the C. elegans network which were induced by simulated lesions of the neural network through removals of each single neuron (attacks). We analyzed complete neuronal wiring data (i.e. connectome) of the nematode C. elegans [1] consisting of 279 neurons (nodes) and their connections (edges). We constructed the circular wiring diagram of simply combined network of gap junctions and chemical synapses as shown Figure ​Figure1.1. Then, we measured several measures of complex network properties of directed weighted neuronal network of C. elegans to examine the effect of single node attack: the clustering coefficient, global efficiency, isolated nodes, and reachability [2]. We found that the deletions of motor neurons and interneurons were more effective to the clustering coefficient of the network than the sensory neurons. Eliminations of some interneurons mainly decreased global efficiency, and remarkably increased global efficiencies were induced by each removal of sensory neurons (see Table ​Table1).1). We suggest that this complex network analysis of the c. elegans connectome is helpful for understanding the potential functions of all neurons, and provide insight into which neurons are crucial for specific functions and which neurons are critical for lethality of the network information processing. Figure 1 Directed circular wiring diagram of the C. elegans combined network. The colors of the links showed the weights of each connection (Color: Weight ranges; light grey: 1-5, grey: 6-10, green: 11-15, blue: 16-20, orange: 21-25, pink: 26-30, and red: over ... Table 1 The average clustering coefficient and the average global efficiency when a target node deleted. A deletion of one of listed neurons induced remarkable changes in each measure.

The Effect of Alcohol on Cortical Complexity in Healthy Subjects Measured by Approximate Entropy

The aim of this study was to examine the effect of alcohol on cortical information processing estimated by EEG using Approximate Entropy (ApEn). The EEG was recorded before alcohol consumption as a baseline and 1 hour after alcohol consumption (alcohol dose: 1.5g/kg) from fourteen healthy males (mean age: 24.14 ± 2.96) during resting state and mental arithmetic task. ApEn was estimated for the EEG recordings as a measure of complexity, and the surrogate data method was used to test the validity of the nonlinearity in the EEG. In a resting condition, EEGs one hour after alcohol administration exhibited significantly lower ApEn in the left frontal (F3), right central and right parietal (C4 and P4), temporal (T4, T5, and T6), and occipital lobes (O1 and O2). More interestingly, during mental arithmetic tasks, alcohol significantly reduced the ApEn values in the left frontal (Fp1 and F3), left central (C3), right temporal (T6), and occipital (O1 and O2) regions. These results suggest that alcohol intake gives rise to reduced cortical complexity, which is possibly associated with cortical and behavioral impairments during alcohol consumption. These findings also suggest that the ApEn is useful in evaluating the effect of alcohol on the brain electrical activity.