Ryoi Goto

Relationship Between Body Mass Index and Gray Matter Volume in 1,428 Healthy Individuals

Objective: To investigate any correlation between BMI and brain gray matter volume, we analyzed 1,428 healthy Japanese subjects by applying volumetric analysis and voxel‐based morphometry (VBM) using brain magnetic resonance (MR) imaging, which enables a global analysis of brain structure without a priori identification of a region of interest.

Voxel-based morphometry of human brain with age and cerebrovascular risk factors.

The objectives of this study were to evaluate the correlations of the volumes of the gray matter and white matter with age, and the correlations of the tissue probabilities of the gray matter and white matter with age and several cerebrovascular risk factors. We obtained magnetic resonance (MR) images of the brain and clinical information from 769 normal Japanese subjects. We processed the MR images automatically by correcting for inter-individual differences in brain size and shape, and by segmenting the MR images into the gray matter and white matter. Volumetry of the brain revealed a significant negative correlation between the gray matter volume and age, which was not observed between white matter volume and age. Voxel-based morphometry showed that age, systolic blood pressure, and alcohol drinking correlated with the regional tissue probabilities of the gray matter and white matter.

Correlation between human personality and neural activity in cerebral cortex.

Personality traits are a variance of behavioral patterns among individuals and may reflect a variance of brain activity, but their neurobiological explanation is still a matter of debate. Cloninger proposed three dimensions of personality traits, each of which has strong correlation with activity in a specific central monoaminergic system. Although this theory has been supported by physiological and genetic studies, it is still unclear how these personality parameters are correlated with the activity of the cortical networks which control human behavior. Here we measured the regional cerebral blood flow (rCBF) at rest in 30 normal volunteers who completed the personality inventory of Cloninger. Voxel-by-voxel analysis was employed to identify cortical regions where the rCBF showed significant correlation with any of the three personality parameters. Statistically significant correlation was observed in several paralimbic and neocortical regions and was consistent with the assumed monoaminergic influence on neural activity and the distribution of its projections, in each personality dimension. The results suggest that activity in a variety of cortical regions is associated with human personality traits and lend support to Cloningers theory concerning central monoaminergic influence on human personality traits.

A PET Study of Visuomotor Learning under Optical Rotation

We measured the regional cerebral blood flow (rCBF) in six healthy volunteers with PET (positron emission tomography) and H(15)(2)O to identify the areas of the human brain involved in sensorimotor learning. The learning task was visually guided reaching with sensorimotor discrepancy caused by optical rotation. PET measurements were performed in the early and late stages of the adaptation to the sensorimotor perturbation. Control measurements were obtained during an eye movement task and a reaching task without optical rotation. The rCBF data of each learning stage were compared to those of both control conditions. During the early stage, rCBF increases were detected in the rostral premotor cortex bilaterally, the posterior part of the left superior parietal lobule (SPL), and the right SPL including the intraparietal sulcus (IPS). During the late stage, rCBF increases were detected in the left caudal premotor area, the left supplementary motor area proper, the left SPL, the right SPL including the IPS, and the right postcentral sulcus extending to the inferior parietal lobule. These results reveal that sensorimotor learning accompanies changes in the recruited cortical areas during different stages of the adaptation, reflecting the different functional roles of each area for different components of adaptation, from learning of new sensorimotor coordination to retention or retrieval of acquired coordination.

Activity in the parietal area during visuomotor learning with optical rotation.

REGIONAL cerebral blood flow (rCBF) was measured in six subjects to study changes of activity in the parietal cortex during learning of a visually guided pointing task with a discrepancy of visuomotor coordination and to determine whether reorganization affects the parietal activity after learning. During the early stage of learning, the right posterior parietal cortex showed a significant increase in rCBF. During the late stage, on the other hand, significant activation was noted in the postcentral gyrus of the right hemisphere. These results support a role for the posterior parietal cortex in remapping visuomotor coordinates and suggest the involvement of the human postcentral gyrus in retaining sensorimotor coordinates, considered to relate to the self image of the hand.

Correlations among Brain Gray Matter Volumes, Age, Gender, and Hemisphere in Healthy Individuals

To determine the relationship between age and gray matter structure and how interactions between gender and hemisphere impact this relationship, we examined correlations between global or regional gray matter volume and age, including interactions of gender and hemisphere, using a general linear model with voxel-based and region-of-interest analyses. Brain magnetic resonance images were collected from 1460 healthy individuals aged 20–69 years; the images were linearly normalized and segmented and restored to native space for analysis of global gray matter volume. Linearly normalized images were then non-linearly normalized and smoothed for analysis of regional gray matter volume. Analysis of global gray matter volume revealed a significant negative correlation between gray matter ratio (gray matter volume divided by intracranial volume) and age in both genders, and a significant interaction effect of age × gender on the gray matter ratio. In analyzing regional gray matter volume, the gray matter volume of all regions showed significant main effects of age, and most regions, with the exception of several including the inferior parietal lobule, showed a significant age × gender interaction. Additionally, the inferior temporal gyrus showed a significant age × gender × hemisphere interaction. No regional volumes showed significant age × hemisphere interactions. Our study may contribute to clarifying the mechanism(s) of normal brain aging in each brain region.

Database of normal human cerebral blood flow measured by SPECT: I. Comparison between I-123-IMP, Tc-99m-HMPAO, and Tc-99m-ECD as referred with O-15 labeled water PET and voxel-based morphometry

ObjectivesThree accumulative tracers, iodine-123-labeledN-isopropyl-p-iodoamphetamine (I-123-IMP), technetium-99m-labeled hexamethylpropyleneamineoxime (Tc-99m-HMPAO), and technetium-99m-labeled ethyl cysteinate dirtier (Tc-99m-ECD) are widely used to measure cerebral blood flow (CBF) in single-photon emission computed tomography (SPECT). In the present study, normal regional distribution of CBF measured with three different SPECT tracers was entered into a database and compared with regional distribution of CBF measured by positron emission tomography (PET) with H215O. The regional distribution of tissue fractions of gray matter determined by voxel-based morphometry was also compared with SPECT and PET CBF distributions.MethodsSPECT studies with I-123-IMP, Tc-99m-HMPAO, and Tc-99m-ECD were performed on 11, 20, and 17 healthy subjects, respectively. PET studies were performed on 11 healthy subjects. Magnetic resonance (MR) imaging studies for voxel-based morphometry were performed on 43 of the 48 subjects who underwent SPECT study. All SPECT, PET, and MR images were transformed into the standard brain format with the SPM2 system. The voxel values of each SPECT and PET image were globally normalized to 50 ml/100 ml/min. Gray matter, white matter, and cerebrospinal fluid images were segmented and extracted from all transformed MR images by applying voxel-based morphometry methods with the SPM2 system.ResultsRegional distribution of all three SPECT tracers differed from that of H215O in the pons, midbrain, thalamus, putamen, parahippocampal gyrus, posterior cingulate gyrus, temporal cortex, and occipital cortex. No significant correlations were observed between the tissue fraction of gray matter and CBF with any tracer.ConclusionDifferences in regional distribution of SPECT tracers were considered to be caused mainly by differences in the mechanism of retention of tracers in the brain. Regional distribution of CBF was independent of regional distribution of gray matter fractions, and consequently the blood flow per gray matter volume differed for each brain region.

A longitudinal study of gray matter volume decline with age and modifying factors.

The rate at which the volume of gray matter declines with normal aging, and whether gender or generational differences affect this rate, remain unclear. Using a longitudinal design over 6 years in 381 healthy community-dwelling individuals, we examined the rate of age-related loss in global gray matter volume, and how gender, generational and cerebrovascular risk factors affected this rate. We collected brain magnetic resonance images of the subjects, and calculated gray matter and intracranial volumes at baseline and follow-up using a fully automated technique. Using these volumes we then calculated the gray matter ratio (GMR), which measures gray matter volume as a percentage of the total intracranial volume. There were significant main effects of age, gender, and body mass index, and an age×gender interaction in the annual percentage change in the GMR (APC(GMR)). The APC(GMR) of younger women was lower than that in older women and men. Our results may help in understanding the mechanism(s) of normal brain aging, and in distinguishing neurodegenerative diseases from normal aging.

The overlapping community structure of structural brain network in young healthy individuals.

Community structure is a universal and significant feature of many complex networks in biology, society, and economics. Community structure has also been revealed in human brain structural and functional networks in previous studies. However, communities overlap and share many edges and nodes. Uncovering the overlapping community structure of complex networks remains largely unknown in human brain networks. Here, using regional gray matter volume, we investigated the structural brain network among 90 brain regions (according to a predefined anatomical atlas) in 462 young, healthy individuals. Overlapped nodes between communities were defined by assuming that nodes (brain regions) can belong to more than one community. We demonstrated that 90 brain regions were organized into 5 overlapping communities associated with several well-known brain systems, such as the auditory/language, visuospatial, emotion, decision-making, social, control of action, memory/learning, and visual systems. The overlapped nodes were mostly involved in an inferior-posterior pattern and were primarily related to auditory and visual perception. The overlapped nodes were mainly attributed to brain regions with higher node degrees and nodal efficiency and played a pivotal role in the flow of informa- tion through the structural brain network. Our results revealed fuzzy boundaries between communities by identifying overlapped nodes and provided new insights into the understanding of the relationship between the structure and function of the human brain. This study provides the first report of the overlapping community structure of the structural network of the human brain.

Correlation between gray/white matter volume and cognition in healthy elderly people

This study applied volumetric analysis and voxel-based morphometry (VBM) of brain magnetic resonance (MR) images to assess whether correlations exist between global and regional gray/white matter volume and the cognitive functions of semantic memory and short-term memory, which are relatively well preserved with aging, using MR image data from 109 community-dwelling healthy elderly individuals. We used the Information and Digit Span subtests of the Wechsler Adult Intelligent Scale-Revised as measures of semantic memory and short-term memory, respectively. We found significant positive correlations between the gray matter ratio, the percentage of gray matter volume in the intracranial volume, and performance on the Digit Span subtest, and between the regional gray matter volumes of the bilateral anterior temporal lobes and performance on the Information subtest. No significant correlations between performance on the cognitive tests and white matter volume were found. Our results suggest that individual variability in specific cognitive functions that are relatively well preserved with aging is accounted for by the variability of gray matter volume in healthy elderly subjects.