Asymmetric lateral inhibitory neural activity in the auditory system: a magnetoencephalographic study

<p>Abstract</p> <p>Background</p> <p>Decrements of auditory evoked responses elicited by repeatedly presented sounds with similar frequencies have been well investigated by means of electroencephalography and magnetoencephalography (MEG). However the possible inhibitory interactions between different neuronal populations remains poorly understood. In the present study, we investigated the effect of proceeding notch-filtered noises (NFNs) with different frequency spectra on a following test tone using MEG.</p> <p>Results</p> <p>Three-second exposure to the NFNs resulted in significantly different N1m responses to a 1000 Hz test tone presented 500 ms after the offset of the NFNs. The NFN with a lower spectral edge closest to the test tone mostly decreased the N1m amplitude.</p> <p>Conclusion</p> <p>The decrement of the N1m component after exposure to the NFNs could be explained partly in terms of lateral inhibition. The results demonstrated that the amplitude of the N1m was more effectively influenced by inhibitory lateral connections originating from neurons corresponding to lower rather than higher frequencies. We interpret this effect of asymmetric lateral inhibition in the auditory system as an important contribution to reduce the asymmetric neural activity profiles originating from the cochlea.</p

The Relationship between Time Perspective and Mental Health in Middle Age

中年期は人生の後半へと向かい,老いや自己の有限性の自覚など負の要因に直面する時期であるとされ,臨床的な問題もこのような状況の変化によって過去から未来への連続した自己の展望が持てないことによるものが多い。本研究では中年期を対象に,どのように自己の過去・現在・未来を展望し,現在の自己を意味づけているのかということに注目し,精神的健康との関連から,中年期の時間的展望の様相を,量的な側面と質的な側面からとらえた。その結果,40歳代では未来志向であり,50歳代に現在志向への転換が見られることが示された。精神的健康との関連では,40歳代では現在の充実感,50歳代では過去の受容と現在の充実感,60歳代では,現在の充実感と,未来への希望が,精神的健康と関連することが示唆された。それらの様相を,半構造化面接による語りから質的に分析した結果,中年期の身体的心理的変化の気づきや受容に伴って,40歳代では過去を土台としてとらえ,50歳代では未来を志向する中で過去の出来事に対する必然感が生じ,それに続く現在として現在の出来事に深くコミットし,60歳代では,作り上げたものとしての自己を受容し,それを表現する場としての未来を志向していることが示された。The results of a questionnaire survey indicated that the time perspective of people in their 40s was oriented toward the future, whereas people in their 50s were oriented to the present. The relationship between time perspective and mental health indicated the need to maintain a broad time orientation, in order to maintain positive mental health during middle age, The interview data suggested that feelings regarding the past, present, and future differed between people in their 40s, 50s and 60s. These group differences were related to time orientations and to the relations between time perspective and mental health. Finally, the results of this study suggested differences in the quality of acceptance of the past, satisfaction with the present, and goal directedness and hope in each age group

Enhancement of DNA synthesis of mouse myelogenous cells by cyclic adenosine 3',5'-monophosphate (cAMP)

To observe the possible role of cAMP on the DNA synthesis during specialization-division of myelogenous precursor cells, the authors observed the DNA and RNA synthesis of the cells by in vitro autoradiography. And it is concluded that cAMP or its dibutyryl derivative added to the media penetrated into myelogenous precursor cells and metamyelocytes of mice and enhanced the DNA synthetic capacity of them. cAMP hardly enhanced RNA synthesis. Discussion is made on relation between enhancement of DNA synthesis of metamyelocytes and their possible rejuvenation.</p

Disturbed hippocampal intra-network in first-episode of drug-naïve major depressive disorder

Complex networks inside the hippocampus could provide new insights into hippocampal abnormalities in various psychiatric disorders and dementia. However, evaluating intra-networks in the hippocampus using MRI is challenging. Here, we employed a high spatial resolution of conventional structural imaging and independent component analysis to investigate intra-networks structural covariance in the hippocampus. We extracted the intra-networks based on the intrinsic connectivity of each 0.9 mm isotropic voxel to every other voxel using a data-driven approach. With a total volume of 3 cc, the hippocampus contains 4115 voxels for a 0.9 mm isotropic voxel size or 375 voxels for a 2 mm isotropic voxel of high-resolution functional or diffusion tensor imaging. Therefore, the novel method presented in the current study could evaluate the hippocampal intra-networks in detail. Furthermore, we investigated the abnormality of the intra-networks in major depressive disorders. A total of 77 patients with first-episode drug-naïve major depressive disorder and 79 healthy subjects were recruited. The independent component analysis extracted seven intra-networks from hippocampal structural images, which were divided into four bilateral networks and three networks along the longitudinal axis. A significant difference was observed in the bilateral hippocampal tail network between patients with major depressive disorder and healthy subjects. In the logistic regression analysis, two bilateral networks were significant predictors of major depressive disorder, with an accuracy of 78.1%. In conclusion, we present a novel method for evaluating intra-networks in the hippocampus. One advantage of this method is that a detailed network can be estimated using conventional structural imaging. In addition, we found novel bilateral networks in the hippocampus that were disturbed in patients with major depressive disorders, and these bilateral networks could predict major depressive disorders

Gyrification patterns in first-episode, drug-naïve major depression: Associations with plasma levels of brain-derived neurotrophic factor and psychiatric symptoms

Background and objectivesCortical structural changes in major depressive disorder (MDD) are usually studied using a voxel-based morphometry approach to delineate the cortical gray matter volume. Among cortical structures, gyrification patterns are considered a relatively stable indicator. In this study, we investigated differences in gyrification patterns between MDD patients and healthy controls (HCs) and explored the association of gyrification patterns with plasma brain-derived neurotrophic factor (BDNF) levels and depressive symptoms in MDD patients.MethodsWe evaluated 79 MDD patients and 94 HCs and assessed depression severity in the patients using the 17-item Hamilton Depression Rating Scale (HAM-D). Blood samples of both groups were collected to measure plasma BDNF levels. Magnetic resonance imaging (MRI) data were obtained using three-dimensional fast-spoiled gradient-recalled acquisition. Differences in plasma BDNF levels between groups were examined using the Mann–Whitney U test. Principal component analysis and orthogonal partial least squares discriminant analysis (OPLS-DA) were conducted to investigate the gyrification patterns which were significantly different between the groups, i.e., those with variable importance in projection (VIP) scores of &gt;1.5 and p-value &lt; 0.05 in multiple regression analyses adjusted for age and sex. Finally, multiple regression analysis was performed on the selected gyrification patterns to examine their association with BDNF levels in the two groups and HAM-D in the patients.ResultsThere were no significant differences in plasma BDNF levels between the groups. We found that 108 (71.0%) of 152 total local gyrification indices were MDD &lt; HC. We identified 10 disease-differentiating factors based on critical gyrification features (VIP &gt; 1.5 and p-value adjusted for age and sex &lt; 0.05). However, we found no significant correlations between the 10 gyrification patterns and plasma BDNF levels and no interaction with group. Moreover, no significant correlations were observed between the local gyrification indices and HAM-D total scores.ConclusionThese results suggest that abnormal early cortical neurodevelopment may mediate vulnerability to MDD, independent of plasma BDNF levels and depressive symptoms

Immunohistochemical analysis of brain lesions using S100B and glial fibrillary acidic protein antibodies in arundic acid- (ONO-2506) treated stroke-prone spontaneously hypertensive rats

Stroke-prone spontaneously hypertensive rats (SHRSP) used as a model of essential hypertension cause a high incidence of brain stroke on the course of hypertension. Incidences and sizes of brain lesions are known to relate to the astrocyte activities. Therefore, relation between brain damage and the expression profile of the astrocytes was investigated with morphometric and immunohistochemical analyses using astrocyte marker antibodies of S100B and glial fibrillary acidic protein (GFAP) with or without arundic acid administration, a suppressor on the activation of astrocytes. Arundic acid extended the average life span of SHRSP. An increase in brain tissue weight was inhibited concomitant with a lower rate of gliosis/hemosiderin deposit/scarring in brain lesions. S100B- or GFAP-positive dot and filamentous structures were decreased in arundic acid-treated SHRSP, and this effect was most pronounced in the cerebral cortex, white matter, and pons, and less so in the hippocampus, diencephalon, midbrain, and cerebellum. Blood pressure decreased after administration of arundic acid in the high-dose group (100 mg/kg/day arundic acid), but not in the low-dose group (30 mg/kg/day). These data indicate that arundic acid can prevent hypertension-induced stroke, and may inhibit the enlargement of the stroke lesion by preventing the inflammatory changes caused by overproduction of the S100B protein in the astrocytes

In Vivo Diagnostic Imaging Using Micro-CT: Sequential and Comparative Evaluation of Rodent Models for Hepatic/Brain Ischemia and Stroke

BACKGROUND: There is an increasing need for animal disease models for pathophysiological research and efficient drug screening. However, one of the technical barriers to the effective use of the models is the difficulty of non-invasive and sequential monitoring of the same animals. Micro-CT is a powerful tool for serial diagnostic imaging of animal models. However, soft tissue contrast resolution, particularly in the brain, is insufficient for detailed analysis, unlike the current applications of CT in the clinical arena. We address the soft tissue contrast resolution issue in this report. METHODOLOGY: We performed contrast-enhanced CT (CECT) on mouse models of experimental cerebral infarction and hepatic ischemia. Pathological changes in each lesion were quantified for two weeks by measuring the lesion volume or the ratio of high attenuation area (%HAA), indicative of increased vascular permeability. We also compared brain images of stroke rats and ischemic mice acquired with micro-CT to those acquired with 11.7-T micro-MRI. Histopathological analysis was performed to confirm the diagnosis by CECT. PRINCIPAL FINDINGS: In the models of cerebral infarction, vascular permeability was increased from three days through one week after surgical initiation, which was also confirmed by Evans blue dye leakage. Measurement of volume and %HAA of the liver lesions demonstrated differences in the recovery process between mice with distinct genetic backgrounds. Comparison of CT and MR images acquired from the same stroke rats or ischemic mice indicated that accuracy of volumetric measurement, as well as spatial and contrast resolutions of CT images, was comparable to that obtained with MRI. The imaging results were also consistent with the histological data. CONCLUSIONS: This study demonstrates that the CECT scanning method is useful in rodents for both quantitative and qualitative evaluations of pathologic lesions in tissues/organs including the brain, and is also suitable for longitudinal observation of the same animals