Graph Theoretical Analysis of Brain Structural Connectivity in Patients with Alcohol Dependence

This study aimed to compare brain structural connectivity using graph theory between patients with alcohol dependence and social drinkers. The participants were divided into two groups; the alcohol group (N=23) consisting of patients who had been hospitalized and had abstained from alcohol for at least three months and the control group (N=22) recruited through advertisements and were social drinkers. All participants were evaluated using 3T magnetic resonance imaging. A total of 1000 repeated whole-brain tractographies with random parameters were performed using DSI Studio. Four hundred functionally defined cortical regions of interest (ROIs) were parcellated using FreeSurfer based on the Schaefer Atlas.The ROIs were overlaid on the tractography results to generate 1000 structural connectivity matrices per person, and 1000 matrices were averaged into a single matrix per subject. Graph analysis was performed through igraph R package. Graph measures were compared between the two groups using analysis of covariance, considering the effects of age and smoking pack years. The alcohol group showed lower local efficiency than the control group in the whole-brain (F=5.824, p=0.020), somato-motor (F=5.963, p=0.019), and default mode networks (F=4.422, p=0.042). The alcohol group showed a lower global efficiency (F=5.736, p=0.021) in the control network. The transitivity of the alcohol group in the dorsal attention network was higher than that of the control (F=4.257, p=0.046). Our results imply that structural stability of the whole-brain network is affected in patients with alcohol dependence, which can lead to ineffective information processing in cases of local node failure.

Disrupted Association Between Empathy and Brain Structure in Attention-Deficit/Hyperactivity Disorder

Objectives@#To investigate the relationship between brain structure and empathy in early adolescents with attention-deficit/hyperactivity disorder (ADHD). @*Methods@#Nineteen early adolescents with ADHD and 20 healthy controls underwent 3T MRI. All the participants were assessed for different aspects of empathy using measures including the Interpersonal Reactivity Index and Empathy Quotient. Cortical thickness and subcortical structural volume based on T1-weighted scans were analyzed using FreeSurfer. @*Results@#Cognitive empathy (t=-2.52, p=0.016) and perspective taking (t=-2.10, p=0.043) were impaired in the ADHD group compared with the control group. The cluster encompassing the left posterior insular, supramarginal, and transverse temporal cortices [cluster-wise p-value (CWP)=0.001], which are associated with emotional empathy, was significantly smaller in the ADHD group, and the volume of the left nucleus accumbens was greater than that of the control group (F=10.12, p=0.003, effect size=0.22). In the control group, the left superior temporal (CWP=0.002) and lingual cortical (CWP=0.035) thicknesses were positively associated with cognitive empathy, while the right amygdala volume was positively associated with empathic concern (Coef=14.26, t=3.92, p=0.001). However, there was no significant correlation between empathy and brain structure in the ADHD group. @*Conclusion@#The ADHD group had a smaller volume of the cortical area associated with emotional empathy than the control group, and there was no brain region showing significant correlation with empathy, unlike in the control group.

Disrupted Association Between Empathy and Brain Structure in Attention-Deficit/Hyperactivity Disorder

Objectives@#To investigate the relationship between brain structure and empathy in early adolescents with attention-deficit/hyperactivity disorder (ADHD). @*Methods@#Nineteen early adolescents with ADHD and 20 healthy controls underwent 3T MRI. All the participants were assessed for different aspects of empathy using measures including the Interpersonal Reactivity Index and Empathy Quotient. Cortical thickness and subcortical structural volume based on T1-weighted scans were analyzed using FreeSurfer. @*Results@#Cognitive empathy (t=-2.52, p=0.016) and perspective taking (t=-2.10, p=0.043) were impaired in the ADHD group compared with the control group. The cluster encompassing the left posterior insular, supramarginal, and transverse temporal cortices [cluster-wise p-value (CWP)=0.001], which are associated with emotional empathy, was significantly smaller in the ADHD group, and the volume of the left nucleus accumbens was greater than that of the control group (F=10.12, p=0.003, effect size=0.22). In the control group, the left superior temporal (CWP=0.002) and lingual cortical (CWP=0.035) thicknesses were positively associated with cognitive empathy, while the right amygdala volume was positively associated with empathic concern (Coef=14.26, t=3.92, p=0.001). However, there was no significant correlation between empathy and brain structure in the ADHD group. @*Conclusion@#The ADHD group had a smaller volume of the cortical area associated with emotional empathy than the control group, and there was no brain region showing significant correlation with empathy, unlike in the control group.

The Relationship between Insomnia and Somatization According to Types of Work of Firefighters / 정신신체의학

Objectives@#：Firefighters are always under stress due to their job environment, and they are likely to become psychologically vulnerable due to continuous exposure to traumatic events, which is a stressful situation that requires emergency standby at all times. The aims of this study were to examine mental health factors for each division of firefighters and to see the relationship between sleep and somatization symptoms among them. @*Methods@#：General characteristics and related inspections were conducted through self-reporting questionnaires for 1,264 firefighters working at Chungbuk fire stations. Several mental health factors were investigated by the Insomnia Severity Index, Severity of somatic symptoms, Impact of Event Scale, Perceived Stress Scale, Resilience Scale, Alcohol Dependent Screening Scale, and the Center for Epidemiologic Studies Depression Scale Depression Scale and Mini-International Neuropsychiatric Interview. @*Results@#：Among the mental health variables, the relationship between insomnia and somatization varies significantly depending on types of work. It was reported that the first aid team was significantly higher than the fire suppression and rescue team. Post-traumatic stress, depression and drinking also differ significantly depending on types of work. The first aid team reported more posttraumatic stress than the fire suppression team and more depressed mood than the rescue team. The administration part had more alcohol consumption than the fire suppression or first aid team. Resilience was significantly higher in the rescue team than the first aid team. No significant differences between the types of work about stress and suicide risks. Insomnia, stress, and post-traumatic stress were significant predictors of somatization among firefighters. Above all, insomnia was significant mental health variable affecting somatization. @*Conclusions@#：Various mental health factors were different according to the types of work in firefighters. The First aid team was more vulnerable to mental health variables such as insomnia and somatization than other divisions. Insomnia is the most important cause of somatization in firefighters, so it is recommended that they be treated for insomnia and to prepare institutional policies.

Atrophy of Thalamic Nuclei in Patients with Alcohol Dependence / 생물치료정신의학

Objectives@#：Chronic alcohol ingestion is associated with structural alterations in the brain. In patients with alcohol dependence, thalamic volume is frequently diminished, commensurate with the amount of alcohol consumption, duration of illness, and cognitive impairment. Since the thalamus is composed of histologically and functionally distinct nuclei, we aimed to investigate volumetric changes of these nuclei in patients with alcohol dependence. @*Methods@#：Twenty-three participants with alcohol dependence who had abstained from drinking for at least 3 months (alcohol group) and 21 age-matched healthy controls (control group) underwent 3T magnetic resonance imaging. The volumes of 50 individual thalamic nuclei were reconstructed using FreeSurfer 6.0.0. We compared normalized volumes of thalamic nuclei between the two groups using analysis of covariance, controlling for age. The p-values were corrected using False Discovery Rate (p<0.05). @*Results@#：The alcohol group demonstrated atrophy of the whole thalamus and nuclei in the anterior, ventral, intralaminar, and medial thalamus. However, the volumes of bilateral lateral geniculate, medial geniculate, suprageniculatelimitans, pulvinar lateral, and right pulvinar inferior nuclei which are included in posterior thalamus, were not significantly different between the two groups. @*Conclusion@#：In the alcohol group, atrophy of most thalamic nuclei which are associated with language processing, visuospatial memory, autobiographical memory, executive function and attention were not normalized after 3 months of sobriety. Furthermore, thalamic nuclei volumes, which are associated with visual and auditory information processing, were not significantly different compared to controls. We suggest that this could be microstructural evidence of relatively preserved visual attention and auditory startle response in patients with alcohol dependence.

Cognitive and Emotional Empathy in Young Adolescents: an fMRI Study

Objectives@#We investigated the differences in cognitive and emotional empathic ability between adolescents and adults, and the differences of the brain activation during cognitive and emotional empathy tasks. @*Methods@#Adolescents (aged 13–15 years, n=14) and adults (aged 19–29 years, n=17) completed a range of empathic ability questionnaires and were scanned functional magnetic resonance imaging (fMRI) during both cognitive and emotional empathy task. Differences in empathic ability and brain activation between the groups were analyzed. @*Results@#Both cognitive and emotional empathic ability were significantly lower in the adolescent compared to the adult group. Comparing the adolescent to the adult group showed that brain activation was significantly greater in the right transverse temporal gyrus (BA 41), right insula (BA 13), right superior parietal lobule (BA 7), right precentral gyrus (BA 4), and right thalamus whilst performing emotional empathy tasks. No brain regions showed significantly greater activation in the adolescent compared to the adult group while performing cognitive empathy task. In the adolescent group, scores of the Fantasy Subscale in the Interpersonal Reactivity Index, which reflects cognitive empathic ability, negatively correlated with activity of right superior parietal lobule during emotional empathic situations (r=-0.739, p=0.006). @*Conclusion@#These results strongly suggest that adolescents possess lower cognitive and emotional empathic abilities than adults do and require compensatory hyperactivation of the brain regions associated with emotional empathy or embodiment in emotional empathic situation. Compensatory hyperactivation in the emotional empathy-related brain areas among adolescents are likely associated with their lower cognitive empathic ability.

Brain Activation Related to Perspective-Taking in Adolescents: Differences from Adults

OBJECTIVES: The purpose of this study was to investigate the differences between adolescents and adults, in the perspective-taking ability, as well as the brain activation patterns during the perspective-taking situation.METHODS: We recruited healthy adolescents aged 13 years to 15 years (n = 20) and adults aged 19 years to 29 years (n = 20). All the subjects were scanned while performing the perspective-taking task, in which an emotional situation was presented in the form of statements comprising first person, as well as third person perspectives. Differences in brain activation between groups were assessed by contrasting neural activity during the tasks.RESULTS: In the between-group analysis, while performing the third-person perspective-taking task, the adolescent group showed greater neural activities in the middle frontal gyrus and precentral gyrus as compared to the adult group. Positive correlation was observed between the activity in the frontal areas (Brodmann area 6/9) and the score of scales related to perspective-taking and social cognition in the adolescent group.CONCLUSIONS: This study suggests that several frontal brain areas of adolescents needs to be overactivated in order to compensate for low perspective-taking ability when they ought to take another person's point of view.

Autism and Beauty: Neural Correlates of Aesthetic Experiences in Autism Spectrum Disorder

OBJECTIVES: The purpose of this study was to investigate whether the neural activity of autism spectrum disorder (ASD) patients is different from that of normal individuals when performing aesthetic judgments. METHODS: We recruited typical ASD patients without savant skills (ASD group, n=17) and healthy controls (HC group, n=19) for an functional magnetic resonance imaging study. All subjects were scanned while performing aesthetic judgment tasks on two kinds of artwork (magnificent landscape images and fractal images). Differences in brain activation between the two groups were assessed by contrasting neural activity during the tasks. RESULTS: The aesthetic judgment score for all images was significantly lower in the ASD group than in the HC group. During the aesthetic judgment tasks, the ASD group showed less activation than the HC group in the anterior region of the superior frontal gyrus, and more activation in the temporoparietal area and insula, regardless of the type of images being judged. In addition, during the aesthetic judgment task for the fractal images, the ASD group exhibited greater neural activity in the amygdala and the posterior region of the middle/inferior temporal gyrus (Brodmann area 37) than the HC group. CONCLUSION: The results of this study suggest that the brain activation patterns associated with aesthetic experiences in ASD patients may differ from those of normal individuals.

The Relationship between Insomnia and Suicidal Idea Through Resilience / 정신신체의학

OBJECTIVES: Insomnia may be one of the risk factor for suicidal ideation, but little is known about the mechanism by which sleep disturbances confer risk for suicide. The aim of this study was to investigate examine whether insomnia severity would be associated with resilience and suicidal ideation, and whether resilience would mediate the relationship between insomnia and suicidal ideation. METHODS: A total of 432 community-dwelling adults(227 male, 205 female,) completed the self-report questionnaire that covered basic socio-demographic data. To assess the psychological variables, the following instruments were applied: Insomnia Severity Index(ISI), Korean Version of the Connor-Davidson Resilience Scale(K-CD-RISC), Beck Hopelessness Scale(BHOP) and Scale for Suicidal Ideation(SSI-Beck). People with an ISI score of 8 or higher were defined as insomnia. RESULTS: Greater insomnia symptom severity was significantly associated with higher level of suicidal ideation and lower level of resilience, adjusting for hopelessness, age, sex, presence of family members living together, and household income. Additional analysis revealed that disturbance of sleep initiation and disturbance of sleep maintenance were significantly associated with suicidal ideation. Mediation analyses revealed that resilience significantly accounted for the relationship between insomnia symptom severity and suicidal ideation. CONCLUSIONS: These findings suggest that the evaluation and control of insomnia and resilience may be needed to reduce the risk of suicide.

Asymmetrical Electroencephalographic Change of Human Brain During Sleep Onset Period

OBJECTIVE: Human cerebral hemisphere is known to function asymmetrically with daytime left hemisphere superiority in most right-handed persons. It may have relevance to the localization of specific function of the brain. This study attempted to reveal whether the functional cerebral asymmetry in the wakeful state is still maintained throughout the sleep onset period. METHODS: Thirty-channel EEG was recorded in 61 healthy subjects. The EEG power spectra of each of the seven frequencies were compared between the two kinds of 30-second states; the wakeful stage and the late-sleep stage 1. RESULTS: The asymmetrical indices of sleep stage 1 at several fronto-central leads were decreased in the delta, theta, alpha-2, and all beta bands. Conversely, at parts of parieto-occipital leads showed an increase in the indices of the theta, alphas, beta-1, and beta-2 bands. Any fronto-central leads did not show an increase in the index, and no parieto-occipital leads showed a decrease. CONCLUSION: During the sleep onset period, power spectral asymmetry of the brain showed a different pattern from the wakeful stage. This asymmetrical pattern of EEG powers may suggest a reversal of the left hemispheric dominance during sleep.

Neural Correlates of Cognitive and Emotional Empathy in Patients with Autism Spectrum Disorder

OBJECTIVES: Individuals with autism spectrum disorder (ASD) are considered to have problems with empathy. It has recently been suggested that there are two systems for empathy; cognitive and emotional. We aimed to investigate the neural response to cognitive and emotional empathy and elucidate the neurobiological aspects of empathy in patients with ASD. METHODS: We recruited patients with ASD (N=17, ASD group) and healthy controls (HC) (N=22, HC group) for an functional magnetic resonance imaging study. All of the subjects were scanned while performing cognitive and emotional empathy tasks. The differences in brain activation between the groups were assessed by contrasting their neural activity during the tasks. RESULTS: During both tasks, the ASD group showed greater neural activities in the bilateral occipital area compared to the HC group. The ASD group showed more activation in the bilateral precunei only during the emotional empathy task. No brain regions were more activated in the HC group than in the ASD group during the cognitive empathy task. While performing the emotional empathy task, the HC group exhibited greater neural activities in the left middle frontal gyrus and right anterior cingulate gyrus than the ASD group. CONCLUSION: This study showed that the brain regions associated with cognitive and emotional empathy in ASD patients differed from those in healthy individuals. The results of this study suggest that individuals with ASD might have defects both in cognitive empathy and in emotional empathy.

Surface-Based Parameters of Brain Imaging in Male Patients with Alcohol Use Disorder

OBJECTIVE: The structural alteration of brain shown in patients with alcohol use disorder (AUD) can originate from both alcohol effects and genetic or developmental processes. We compared surface-based parameters of patients with AUD with healthy controls to prove the applicability of surface-based morphometry with head size correction and to determine the areas that were sensitive to brain alteration related to AUD. METHODS: Twenty-six abstinent male patients with AUD (alcohol group, mean abstinence=13.2 months) and twenty-eight age-matched healthy participants (control group) were recruited from an inpatient mental hospital and community. All participants underwent a 3T MRI scan. Surface-based parameters were determined by using FreeSurfer. RESULTS: Every surface-based parameter of the alcohol group was lower than the corresponding control group parameter. There were large group differences in the whole brain, grey and white matter volume, and the differences were more prominent after head size correction. Significant group differences were shown in cortical thicknesses in entire brain regions, especially in parietal, temporal and frontal areas. There were no significant group differences in surface areas, but group difference trends in surface areas of the frontal and parietal cortices were shown after head size correction. CONCLUSION: Most of the surface-based parameters in alcohol group were altered because of incomplete recovery from chronic alcohol exposure and possibly genetic or developmental factors underlying the risk of AUD. Surface-based morphometry with controlling for head size is useful in comparing the volumetric parameters and the surface area to a lesser extent in alcohol-related brain alteration.

Evolutionary Meaning of Sadness, Depression, and Suicide

Depression has a relatively high lifetime prevalence rate in spite of a genetic influence on its etiology and a high mortality rate in untreated cases. This suggests the possibility that depression gives us evolutionary benefits which we do not exactly know yet. There have been several hypotheses which tell us what evolutionary advantages depression could give us. The psychic pain hypothesis considers sad or depressed mood as a negative reward just like physical pain which we have to avoid for our protection and survival. The social rank hypothesis holds that depressed mood is very similar to the emotional state of the defeated in social competition which prevents him from further protesting or fighting that might cause additional damage to him. The inclusive fitness hypothesis views suicide as a sacrifice phenomenon to contribute to inclusive fitness. These hypotheses gives us new insights into mood disorders and also some suggestions about the conditions in which depressed mood or suicidal behaviors increase and the ways to reduce them.

Effects of Silver-Care-Robot Program on Cognitive Function, Depression, and Activities of Daily Living for Institutionalized Elderly People

PURPOSE: The purpose of this study was to identify the effects on cognitive function, depression, and activities of daily living of Silver-Care-Robot Program for institutionalized elders. METHODS: This study was a nonequivalent control group pretest-posttest design. The participants were 42 institutionalized elders (17 in the experimental group and 25 in the control group). The Silver-Care-Robot Program was provided as an intervention which was conducted twice a week for 5 weeks. The Silver-Care-Robot Program is an integrated entertainment program to help the mental, emotional, and physical health of elderly people. Pre-test was conducted on the two groups, and, in order to examine the effects of intervention, a post-test was conducted after 5 weeks. RESULTS: There were significant differences in cognitive function and ADL (activities of daily living) between two groups after the program. But the difference in depression in the institutionalized elders was not statistically significant between the two groups. CONCLUSION: The Silver-Care-Robot Program should be considered as a regular program for cognitive function and activities of daily living for institutionalized elders.

Electroencephalographic Characteristics of Alcohol Dependent Patients: 3-Dimensional Source Localization

OBJECTIVES: The power spectral analysis of electroencephalogram has been widely used to reveal the pathophysiology of the alcoholic brain. However, the results were not consistent and the three dimensional study can be hardly found. The purpose of this study was to investigate characteristics of the three dimensional electroencephalographic (EEG) activity of alcohol dependent patients using standardized low resolution electromagnetic tomography (sLORETA). METHODS: The participants consisted of 30 alcohol dependent patients and 30 normal healthy controls. All the participants were males who had refrained from alcohol at least one month and were not taking any medications. Thirty two channel EEG data was collected in the resting state with eyes-closed condition during 30 seconds. The three dimensional data was compared between two groups using sLORETA for delta, theta, alpha, beta1, beta2, and beta3 frequency bands. RESULTS: sLORETA revealed significantly increased brain cortical activity in alpha, beta1, beta2, and beta3 bands each in alcohol dependent patients compared to normal controls. The voxels showing the maximum significance were in the left transverse temporal gyrus, left superior temporal gyrus, left anterior cingulate, and left fusiform gyrus in alpha, beta1, beta2, and beta3 bands respectively. CONCLUSIONS: These results suggest that chronic alcohol intake may cause neurophysiological changes in cerebral activity. Therefore, the measuring of EEG can be helpful in understanding the pathophysiology of cognitive impairements in alcohol dependence.

Total Intracranial Volume Measurement for Children by Using an Automatized Program

OBJECTIVES: Total intracranial volume (TIV) is a major nuisance of neuroimaging research for interindividual differences of brain structure and function. Authors intended to prove the reliability of the atlas scaling factor (ASF) method for TIV estimation in FreeSurfer by comparing it with the results of manual tracing as reference method. METHODS: The TIVs of 26 normal children and 26 children with attention-deficit hyperactivity disorder (ADHD) were obtained by using FreeSurfer reconstruction and manual tracing with T1-weighted images. Manual tracing performed in every 10th slice of MRI dataset from midline of sagittal plane by one researcher who was blinded from clinical data. Another reseacher performed manual tracing independently for randomly selected 20 dataset to verify interrater reliability. RESULTS: The interrater reliability was excellent (intraclass coefficient = 0.91, p < 7.1e-07). There were no significant differences of age and gender distribution between normal and ADHD groups. No significant differences were found between TIVs from ASF method and manual tracing. Strong correlation between TIVs from 2 different methods were shown (r = 0.90, p < 2.2e-16). CONCLUSIONS: The ASF method for TIV estimation by using FreeSurfer showed good agreement with the reference method. We can use the TIV from ASF method for correction in analysis of structural and functional neuroimaging studies with not only elderly subjects but also children, even with ADHD.

Survey of Influencing Factors on Depression and Anxiety in Vietnamese Marriage Immigrant Women

OBJECTIVES: The number of marriage immigrant women has been increasing in the past several years in Korea and their adaptations to the new environment have been an important social issue. The aims of this study were to evaluate the psychosocial and mental health statuses of Vietnamese marriage immigrant women (VMIW). We intended to compare the mental health of VMIW with married Vietnamese women living in Vietnam and reveal the demographic or psychosocial factors affecting their mental health. METHOD: Subjects comprised one-hundred-forty-three VMIW who enrolled in multiculture family support centers in Chungbuk Province and forty-eight women from Vinh Phuc province in Vietnam. Marital satisfaction, domestic violence and social support were evaluated as psychosocial factors, and the Beck Depression Inventory (BDI), Beck Anxiety Inventory (BAI) and General Health Questionnaire (GHQ) were used to evaluate mental health. RESULTS: VMIW had a larger age gap with their husbands but better psychosocial statuses. BDI (p = 0.20), BAI (p = 0.08), GHQ (p = 0.13) scores of VMIW were not significantly different compared to Vietnamese residents. Marriage duration of VMIW affects significantly their marital satisfaction, social support and depressive levels (p < 0.01). The level of domestic violence showed a significant difference according to the educational levels of their husbands, composition of family members and marriage process (p < 0.05). VMIW with older husbands and jobless VMIW had low levels of anxiety (p < 0.01). CONCLUSION: The results suggest that VMIW have no difference in mental health compared to Vietnamese women living in Vietnam which is contrary to general expectations. However, various environmental factors, such as marriage duration, have an effect on the mental health of VMIW. As marriage duration is proven to be important factor on mental health of VMIW, more extended duration of care and interventions are needed to maintain good mental health. Networking system connecting mental health screenings by the multiculture family support center to the local mental healthcare center is needed to care those with poor screening outcomes.

An fMRI Study Investigating Adolescent Brain Activation by Rewards and Feedback

OBJECTIVE: This study aimed to investigate the adolescent brain activation patterns in response to performance feedback (PF), social reward (SR) and monetary reward (MR) and their association with psychological factors. METHODS: Functional magnetic resonance imaging (fMRI) was performed while middle school boys (n=15) performed tests pertained to PF, SR and MR. The brain activation pattern in each condition was investigated, and the extent of brain activation in each of the three conditions was compared at once. RESULTS: The caudate and the dorsal prefrontal area were activated in all three conditions. Furthermore, the cuneus showed significantly greater activation in the PF condition than the SR or MR condition. And the self - related areas, such as the right precentral gyrus and paracenral lobule, were more activated in the SR condition than the PF or MR condition. The left middle frontal gyrus was more activated in the MR condition than the PF or SR condition. CONCLUSION: Not only various reward stimuli but also feedback stimulus might commonly activate dorsal prefrontal and subcortical area in adolescents. Moreover, several different brain activation patterns were also observed in each condition. The results of this study could be applied to planning of learning and teaching strategy for adolescents in various ways.

Application of Detrended Fluctuation Analysis of Electroencephalography during Sleep Onset Period

OBJECTIVES: Much is still unknown about the neurophysiological mechanisms or dynamics of the sleep onset process. Detrended fluctuation analysis (DFA) is a new tool for the analysis of electroencephalography (EEG) that may give us additional information about electrophysiological changes. The purpose of this study is to analyze long-range correlations of electroencephalographic signals by DFA and their changes in the sleep onset process. METHODS: Thirty channel EEG was recorded in 61 healthy subjects (male : female = 34 : 27, age = 27.2 +/- 3.0 years). The scaling exponents, alpha, were calculated by DFA and compared between four kinds of 30s sleep-wakefulness states such as wakefulness, transition period, early sleep, and late sleep (stage 1). These four states were selected by the distribution of alpha and theta waves in O1 and O2 electrodes. RESULTS: The scaling exponents, alpha, were significantly different in the four states during sleep onset periods, and also varied with the thirty leads. The interaction between the sleep states and the leads was significant. The means (+/- standard deviation) of alphas for the states were 0.94 (+/- 0.12), 0.98 (+/- 0.12), 1.10 (+/- 0.10), 1.07 (+/- 0.07) in the wakefulness, transitional period, early sleep and late sleep state respectively. The mean alpha of anterior fifteen leads was greater than that of posterior fifteen leads, and the two regions showed the different pattern of changes of the alpha during the sleep onset periods. CONCLUSIONS: The characteristic findings in the sleep onset period were the increasing pattern of scaling exponent of DFA, and the pattern was slightly but significantly different between fronto-temporal and parieto-occipital regions. It suggests that the long-range correlations of EEG have a tendency of increasing from wakefulness to early sleep, but anterior and posterior brain regions have different dynamical process. DFA, one of the nonlinear analytical methods for time series, may be a useful tool for the investigation of the sleep onset period.

The Role of Job Stress and Brain-Derived Neurotrophic Factor Gene Polymorphism on the Severity of Alcohol Drinking in Korean Office Workers in Their Twenties

OBJECTIVES: The aim of this study was to examine the effects of brain-derived neurotrophic factor (BDNF) genetic polymorphism and job stress on the severity of alcohol drinking. It was hypothesized that individuals with the Met/Met BDNF genotype would be more vulnerable than those carrying the Val allele. METHODS: Participants were 133 healthy Korean adults (mean age 28.2 +/- 1.1). Job stress and the severity index of drinking were investigated through self-reported questionnaires. BDNF (rs6265) gene was genotyped. RESULTS: There was no significant association between job stress and the severity of alcohol drinking. Although the severity of alcohol drinking was not associated with BDNF genetic polymorphism, there was a significant difference in men according to genotype and job stress. Men with homozygous BDNF Met allele were more severe in alcohol drinking when job stress was high, less severe in alcohol drinking when job stress was low than those carrying the Val allele (F = 4.47, p = 0.038). Also higher level of job stress was correlated with higher severity of alcohol drinking in men homozygous for BDNF Met allele (rs = 0.620, p = 0.005). CONCLUSIONS: These findings suggest the possibility that Met allele could have differential susceptibility, with men homozygous for BDNF Met allele being more susceptible to both more adverse and less adverse environmental influences.