Region-based analysis of sensory processing using diffusion tensor imaging.

The caudate nucleus has been thought to be involved in the control of motor commands by the cerebrum, and recent studies suggest that it may play a role in the control of attachment behavior, cognition, emotion, and mental functions. Implied by the basal ganglia's involvement in the execution, planning and control of movement, the caudate nucleus functions in a situation-dependent manner where processing of external stimuli is important on the basis of learning and memory. Sensory processing, which determines the response to external stimuli, has been shown to be related to various brain regions but it remains unknown how sensory processing is associated with the structure of the caudate nucleus and white matter microstructures of the caudate. Using four diffusion parameters derived from diffusion tensor imaging (DTI) (i.e., fractional anisotropy (FA), mean diffusivity (MD), axonal diffusivity (AD), and radial diffusivity (RD)) and the Adolescent/Adult Sensory Profile (AASP) questionnaire of 99 healthy subjects [42 males and 57 females; mean age:26.9 years, standard deviation 6.9], we investigated the relationship between white matter structure in the caudate nucleus and sensory processing. In consistent with what had been suggested by the results of previous studies, we found significant correlations between AD, MD and tactile sensation. Furthermore, we found a significant correlation between AD, MD and tactile sensory avoidance, the AASP sub-scores regarding the tactile senses. To the best of our knowledge, this is the first study to show that DTI diffusion parameters correlate with AASP scores in specific brain regions.

The effects of epigenetic age and its acceleration on surface area, cortical thickness, and volume in young adults.

DNA methylation age has been used in recent studies as an epigenetic marker of accelerated cellular aging, whose contribution to the brain structural changes was lately acknowledged. We aimed to characterize the association of epigenetic age (i.e. estimated DNA methylation age) and its acceleration with surface area, cortical thickness, and volume in healthy young adults. Using the multi-tissue method (Horvath S. DNA methylation age of human tissues and cell types. 2013. Genome Biol 14), epigenetic age was computed with saliva sample. Epigenetic age acceleration was derived from residuals after adjusting epigenetic age for chronological age. Multiple regression models were computed for 148 brain regions for surface area, cortical thickness, and volume using epigenetic age or accelerated epigenetic age as a predictor and controlling for sex. Epigenetic age was associated with surface area reduction of the left insula. It was also associated with cortical thinning and volume reduction in multiple regions, with prominent changes of cortical thickness in the left temporal regions and of volume in the bilateral orbital gyri. Finally, accelerated epigenetic age was negatively associated with right cuneus gyrus volume. Our findings suggest that understanding the mechanisms of epigenetic age acceleration in young individuals may yield valuable insights into the relationship between epigenetic aging and the cortical change and on the early development of neurocognitive pathology among young adults.

Relationship between sensory characteristics and cortical thickness/volume in autism spectrum disorders.

Individuals with autism spectrum disorders (ASDs) exhibit atypical sensory characteristics, impaired social skills, deficits in verbal and nonverbal communication, and restricted and repetitive behaviors. The relationship between sensory characteristics and brain morphological changes in ASD remains unclear. In this study, we investigated the association between brain morphological changes and sensory characteristics in individuals with ASD using brain image analysis and a sensory profile test. Forty-three adults with ASD and 84 adults with typical development underwent brain image analysis using FreeSurfer. The brain cortex was divided into 64 regions, and the cortical thickness and volume of the limbic system were calculated. The sensory characteristics of the participants were evaluated using the Adolescent/Adult Sensory Profile (AASP). Correlation analysis was performed for cortical thickness, limbic area volume, and AASP scores. In the ASD group, there was a significant positive correlation between visual sensory sensitivity scores and the right lingual cortical thickness (r = 0.500). There were also significant negative correlations between visual sensation avoiding scores and the right lateral orbitofrontal cortical thickness (r = -0.513), taste/smell sensation avoiding scores and the right hippocampal volume (r = -0.510), and taste/smell sensation avoiding scores and the left hippocampal volume (r = -0.540). The study identified associations among the lingual cortical thickness, lateral orbitofrontal cortical thickness, and hippocampal volume and sensory characteristics. These findings suggest that brain morphological changes may trigger sensory symptoms in adults with ASD.

Elucidation of the relationship between sensory processing and white matter using diffusion tensor imaging tractography in young adults.

Sensory processing and behaviors are altered during the development of connectivity between the sensory cortices and multiple brain regions in an experience-dependent manner. To reveal the relationship between sensory processing and brain white matter, we investigated the association between the Adolescent/Adult Sensory Profile (AASP) and neural connectivity in the white matter tracts of 84 healthy young adults using diffusion tensor imaging (DTI). We observed a positive relationship between AASP scores (i.e., sensory sensitivity, sensation avoiding, activity level)/subscores (i.e., sensory sensitivity-activity level, sensation avoiding-touch) and DTI parameters in the cingulum-cingulate gyrus bundle (CCG) and between AASP subscores (i.e., sensory sensitivity-auditory) and a diffusion parameter in the uncinate fasciculus (UNC). The diffusion parameters that correlated with AASP scores/subscores and AASP quadrant scores (i.e., sensory avoiding and sensitivity) were axonal diffusivity (AD) and mean diffusivity (MD) in the CCG and MD in the UNC. Moreover, the increased sensory avoiding and sensitivity scores represent the sensitization of sensory processing, and the level of diffusivity parameters indicates white matter microstructure variability, such as axons and myelin from diffusivity of water molecules. Thus, the present study suggests that the CCG and UNC are critical white matter microstructures for determining the level of sensory processing in young adults.

DNA polymorphism at the ACAULIS5 locus of the wild plant Arabidopsis thaliana.

Nucleotide variation in the ACL5 gene region, which encodes spermine synthase, was analyzed for 21 Arabidopsis thaliana ecotypes and one accession of Arabis gemmifera. In A. thaliana, dimorphism was also detected in the ACL5 region, as in other nuclear genes of this plant. The nucleotide diversity (pi) of the entire region, exon and intron was 0.0163, 0.0042 and 0.0293, respectively. The level of nucleotide variation in this region was among the highest of those reported for genes in this plant species. The neutrality tests of Tajima, and Fu and Li did not detect significant deviation from test assumptions for the polymorphism data. However, the HKA test indicated that the level of polymorphism in the intron was significantly high, compared with A. gemmifera. The high nucleotide variation in the intron is responsible for the high level of nucleotide variation in the entire region. These results can be explained by elevated mutation rate in the ACL5 region in the A. thaliana lineage after the two species were split.

Nucleotide polymorphism at the Atmyb2 locus of the wild plant Arabidopsis thaliana.

DNA variation was studied in a 2.2 kb region of the regulatory gene Atmyb2 using 20 ecotypes of Arabidopsis thaliana and one accession each of Arabis gemmifera and Arabidopsis himalaica. Nucleotide diversity (pi) in the region was 0.0027, which was lower than for other loci in A. thaliana. The MYB domain of the Atmyb2 gene (pi = 0.0036) had a larger variation than the non-MYB region (pi = 0.0013). Tajima's test and Fu and Li's test did not give a significant result. In contrast to the low level of polymorphism, the degree of divergence of the Atmyb2 region was higher between A. thaliana and A. gemmifera (K = 0.0730) than for other loci. The MYB domain (K = 0.0436) had smaller divergence than the non-MYB region (K = 0.0939). The HKA test detected significant discordance in the ratio of polymorphism to divergence in some comparisons. The pattern of low polymorphism and high divergence, which is mainly observed in the non-MYB region of the gene, is inconsistent with the neutral mutation theory. Strong purifying selection after establishment of A. thaliana and a species-specific adaptive process could be invoked to account for this pattern of polymorphism and divergence of Atmyb2.