The Influence of Life Stress and Sleep Disturbance on White Matter Integrity

Objective@#This study investigated whether sleep and stress mutually interact to induce changes in white matter integrity. @*Methods@#Diffusion tensor imaging (DTI) was conducted on 36 participants (male=22, female=14; mean age=38.33±12.78 years). Participants were divided into three groups depending on their sleep quality and stress levels: poor sleepers with stress, poor sleepers without stress, and good sleepers. Sleep quality and stress level were evaluated using the Pittsburgh Sleep Quality Index and the Life Experiences Survey, respectively. Fractional anisotropy (FA) values were calculated employing DTI tractography. @*Results@#After controlling for age and sex, poor sleepers with stress exhibited a lower FA of the left inferior cerebellar peduncle (ICP) than did poor sleepers without stress (t=2.81, p=0.02). Poor sleepers without stress showed a higher FA of the right middle longitudinal fasciculus (MdLF) than did good sleepers (t=3.35, p=0.006). @*Conclusion@#The current study reports the effects of sleep, stress, and their interaction on the white matter integrities of the ICP and MdLF. ICP change seems to be associated with sleep disturbances related to stress, while MdLF change would be associated with sleep disturbances unrelated to stress.

Effect of Lifetime Cognitive Reserve on Functional Connectivity in the Default Mode Network at the Predementia Stage

Objective@#Cognitive reserve (CR) protects against cognitive decline by utilizing functional connectivity (FC) in the brain, such as the default mode network (DMN). We studied whether CR in individuals with predementia would correlate with better cognition and increased DMN FC in the resting brain. @*Methods@#Fifty-four participants with subjective cognitive decline or mild cognitive impairment completed the Cognitive Reserve Index (CRI) questionnaire, and underwent a comprehensive neuropsychological test battery and resting state functional magnetic resonance imaging. Correlation and regression analyses for clinical variables and seed-to-voxel analyses of CR-related FC in the DMN were conducted. @*Results@#CRI total (β=0.42, p=0.001), education (β=0.39, p=0.001), and leisure time (β=0.33, p=0.009) predicted the MiniMental State Examination. The CRI education predicted verbal memory recall (β=0.32, p=0.017), confrontational naming (β=0.57, p<0.001), and phonemic fluency (β=0.43, p=0.004). In the DMN in the resting brain, the CRI total correlated with increased FC, based on the posterior cingulate to both lateral parietal cortices. @*Conclusion@#In individuals with predementia, comprehensive CR correlated with an enhanced network in the DMN in the resting state. These results may support the neural correlate of CR during the initial stage of cognitive decline.

Functional Magnetic Resonance Imaging of Brain Reactivity to Insomnia-Related vs. General Anxiety-Inducing Stimuli in Insomnia Patients with Subjective-Objective Discrepancy of Sleep / 수면정신생리

Objectives@#Subjective-objective discrepancy of sleep (SODS) is a common symptom and one of the major phenotypes of insomnia. A distorted perception of sleep deficit might be related to abnormal brain reactivity to insomnia-related stimuli. We aimed to investigate differences in brain activation to insomnia-related stimuli vs. general anxiety-inducing stimuli among insomnia patients with SODS, insomnia patients without SODS, and healthy controls (HCs). @*Methods@#All participants were evaluated for subjective sleep status using a sleep diary and questionnaires; occult sleep disorders and objective sleep status were assessed using polysomnography and actigraphy. Task functional magnetic resonance imaging was performed during insomnia-related stimuli (Ins) and general anxiety-inducing stimuli (Gen). Brain reactivity to Ins versus Gen was compared among insomnia with SODS, insomnia without SODS, and HC groups, and a combined insomnia disorder group (ID, insomnia with and without SODS) was also compared with HCs. @*Results@#In the insomnia with SODS group compared to the insomnia without SODS group, the right precuneus and right supplementary motor areas showed significantly increased BOLD signals in response to Ins versus Gen. In the ID group compared to the HC group, the left anterior cingulate cortex showed significantly increased BOLD signals in response to Ins versus Gen. @*Conclusion@#The insomnia with SODS and ID groups showed higher brain activity in response to Ins versus Gen, while this was not observed in the insomnia without SODS and HC groups, respectively. These results suggest that insomnia patients with sleep misperception are more sensitive to sleep-related threats than general anxiety-inducing threats.

Shoe-Type Wearable Sensors Measure Gait Parameters in Vestibular Neuritis: A Preliminary Study / 대한평형의학회지

OBJECTIVES: Despite patients with dizziness were reported of revealing gait problems, there is still lack of objective quantitative measurement of gait patterns of peripheral vestibular disorders. To demonstrate gait variability in acute unilateral peripheral vestibular deficit, we evaluated the differences in gait patterns between vestibular neuritis (VN) patients and healthy subjects by the use of shoe-type inertial measurement unit (IMU) with sensors mounted. METHODS: Between April 2017 and January 2019, 30 patients diagnosed with unilateral peripheral vestibular deficit presumed to be caused by VN were enrolled in this study. The shoe-type IMU was used to analysis subjects. We assessed gait speed, cadence, stride length, stance phase, normalized stride length, normalized step length, phase coordination index and gait asymmetry of data from shoe-type IMU sensors with the walking protocol. We tested 30 healthy volunteers as control group. RESULTS: We identified spatiotemporal parameters of human gait. The gait speed of patients with VN was decreased to 3.82±0.8 compared to 4.93±1.08 in control group. In addition, there were differences in normalized stride length, normalized gait speed and related gait parameters, when comparing VN group and control group. CONCLUSION: Gait analysis by the use of shoe-type IMU could provide important information regarding vestibular pathophysiology in patients with VN. Gait performance tests can examine gait variability quantitatively. It will be taken into consideration as a vestibular function test for patients with vertigo.

Development of Korean Social Affective Visual Stimuli / 수면정신생리

OBJECTIVES: The current study aims to develop Korean Social Affective Visual Stimuli (K-SAVS) to arouse social affect. METHODS: K-SAVS is composed of pictures of social situations among East Asians. Each picture contains a negative, positive, or neutral affect. Positive and negative stimuli were presented to one group of subjects. Negative and neutral stimuli were presented to another group of subjects. All subjects were required to fill out Affective Valence and Arousal Manikin. RESULTS: In the initial test, 18 positive affective stimuli pictures (1 set) and 36 negative affective stimuli pictures (2 sets) were chosen from 95 stimuli pictures. Positive affective stimuli pictures showed higher valence (p < 0.001) and lower arousal (p < 0.001) than negative affective stimuli pictures. In the confirmatory test, 18 neutral stimuli pictures (1 set) were additionally selected out of the total of 79 pictures of neutral stimuli pictures and the pictures used in the former experiment. Neutral stimuli pictures showed higher valence (p < 0.001) and lower arousal (p < 0.001) than negative affective stimuli pictures. CONCLUSION: K-SAVS can be a valid and useful tool for inducing specific social affects of Koreans.

Ideographic Alexia without Involvement of the Fusiform Gyrus in a Korean Stroke Patient: A Serial Functional Magnetic Resonance Imaging Study

BACKGROUND: Korean orthography is composed of Hanja (ideograms) and Hangul (phonograms). Based on previous studies, the fusiform gyrus has been associated with ideogram reading. We examine serial functional magnetic resonance imaging (fMRI) images in a patient exhibiting dissociation of Hanja and Hangul reading to identify brain areas associated with Hanja reading. CASE REPORT: fMRI were taken of a 63-year-old man showing profound Hanja alexia with normal Hangul reading after an acute stroke involving the left frontal and parietal lobes, who later spontaneously recovered his Hanja reading ability. Scans were taken while performing Hanja and Hangul reading tasks on three occasions. As a result, in spite of having profound Hanja alexia, partial activation of the fusiform gyrus was observed on the first fMRI. Serial fMRI scans showed activation of the bilateral middle frontal gyri that increased in parallel with the patient's recovery of Hanja reading. CONCLUSIONS: The frontal lobe, not only fusiform gyrus, may play role in reading Hanja, although more evidence is needed.

Neural Substrates of Hanja (Logogram) and Hangul (Phonogram) Character Readings by Functional Magnetic Resonance Imaging

The two basic scripts of the Korean writing system, Hanja (the logography of the traditional Korean character) and Hangul (the more newer Korean alphabet), have been used together since the 14th century. While Hanja character has its own morphemic base, Hangul being purely phonemic without morphemic base. These two, therefore, have substantially different outcomes as a language as well as different neural responses. Based on these linguistic differences between Hanja and Hangul, we have launched two studies; first was to find differences in cortical activation when it is stimulated by Hanja and Hangul reading to support the much discussed dual-route hypothesis of logographic and phonological routes in the brain by fMRI (Experiment 1). The second objective was to evaluate how Hanja and Hangul affect comprehension, therefore, recognition memory, specifically the effects of semantic transparency and morphemic clarity on memory consolidation and then related cortical activations, using functional magnetic resonance imaging (fMRI) (Experiment 2). The first fMRI experiment indicated relatively large areas of the brain are activated by Hanja reading compared to Hangul reading. The second experiment, the recognition memory study, revealed two findings, that is there is only a small difference in recognition memory for semantic transparency, while for the morphemic clarity was much larger between Hanja and Hangul. That is the morphemic clarity has significantly more effect than semantic transparency on recognition memory when studies by fMRI in correlation with behavioral study.