The effect of meditation on brain structure: cortical thickness mapping and diffusion tensor imaging.

A convergent line of neuroscientific evidence suggests that meditation alters the functional and structural plasticity of distributed neural processes underlying attention and emotion. The purpose of this study was to examine the brain structural differences between a well-matched sample of long-term meditators and controls. We employed whole-brain cortical thickness analysis based on magnetic resonance imaging, and diffusion tensor imaging to quantify white matter integrity in the brains of 46 experienced meditators compared with 46 matched meditation-naïve volunteers. Meditators, compared with controls, showed significantly greater cortical thickness in the anterior regions of the brain, located in frontal and temporal areas, including the medial prefrontal cortex, superior frontal cortex, temporal pole and the middle and interior temporal cortices. Significantly thinner cortical thickness was found in the posterior regions of the brain, located in the parietal and occipital areas, including the postcentral cortex, inferior parietal cortex, middle occipital cortex and posterior cingulate cortex. Moreover, in the region adjacent to the medial prefrontal cortex, both higher fractional anisotropy values and greater cortical thickness were observed. Our findings suggest that long-term meditators have structural differences in both gray and white matter.

Phase-specific brain change of spatial working memory processing in genetic and ultra-high risk groups of schizophrenia.

Spatial working memory (WM) processing has 3 distinct phases: encoding, maintenance, and retrieval and its dysfunction is a core feature in schizophrenia. We examined phase-specific brain activations associated with spatial WM in first-degree relatives of schizophrenia (genetic high risk, GHR), ultra-high risk (UHR) subjects, patients with schizophrenia, and healthy controls. We used an event-related functional magnetic resonance imaging in 17 GHR subjects, 21 UHR subjects, 15 clinically stable patients with schizophrenia and 16 healthy controls, while subjects were performing a spatial delayed-response task. During the encoding phase, the GHR group showed increased activation in the fronto-parietal regions, whereas the UHR and schizophrenia groups showed significantly less activation in these regions than did the healthy control group. Especially, frontal activation was strongest in GHR subjects, followed by healthy controls, and occurred to a lesser degree in the UHR group, with the least activation occurring in the schizophrenia group. During the maintenance phase, the thalamus showed a differential activation, similar to frontal activation pattern during the encoding phase. During the retrieval phase, no prominent differential activations were found. Increased activations were observed in the superior temporal gyrus during the encoding and maintenance phases in the GHR, UHR, and schizophrenia groups relative to healthy controls. Our findings suggest that functional deficits associated with spatial WM processing emerge in the UHR before the onset of schizophrenia and compensatory neural processes exist in the GHR with genetic liability to schizophrenia.

Increased default mode network connectivity associated with meditation.

Areas associated with the default mode network (DMN) are substantially similar to those associated with meditation practice. However, no studies on DMN connectivity during resting states have been conducted on meditation practitioners. It was hypothesized that meditators would show heightened functional connectivity in areas of cortical midline activity. Thirty-five meditation practitioners and 33 healthy controls without meditation experience were included in this study. All subjects received 4.68-min resting state functional scanning runs. The posterior cingulate cortex and medial prefrontal cortex were chosen as seed regions for the DMN map. Meditation practitioners demonstrated greater functional connectivity within the DMN in the medial prefrontal cortex area (xyz=339-21) than did controls. These results suggest that the long-term practice of meditation may be associated with functional changes in regions related to internalized attention even when meditation is not being practiced.

Integration of cross-modal emotional information in the human brain: an fMRI study.

The interaction of information derived from the voice and facial expression of a speaker contributes to the interpretation of the emotional state of the speaker and to the formation of inferences about information that may have been merely implied in the verbal communication. Therefore, we investigated the brain processes responsible for the integration of emotional information originating from different sources. Although several studies have reported possible sites for integration, further investigation using a neutral emotional condition is required to locate emotion-specific networks. Using functional magnetic resonance imaging (fMRI), we explored the brain regions involved in the integration of emotional information from different modalities in comparison to those involved in integrating emotionally neutral information. There was significant activation in the superior temporal gyrus (STG); inferior frontal gyrus (IFG); and parahippocampal gyrus, including the amygdala, under the bimodal versus the unimodal condition, irrespective of the emotional content. We confirmed the results of previous studies by finding that the bimodal emotional condition elicited strong activation in the left middle temporal gyrus (MTG), and we extended this finding to locate the effects of emotional factors by using a neutral condition in the experimental design. We found anger-specific activation in the posterior cingulate, fusiform gyrus, and cerebellum, whereas we found happiness-specific activation in the MTG, parahippocampal gyrus, hippocampus, claustrum, inferior parietal lobule, cuneus, middle frontal gyrus (MFG), IFG, and anterior cingulate. These emotion-specific activations suggest that each emotion uses a separate network to integrate bimodal information and shares a common network for cross-modal integration.

Proton magnetic resonance spectroscopy in subjects with high genetic risk of schizophrenia: investigation of anterior cingulate, dorsolateral prefrontal cortex and thalamus.

OBJECTIVE: Reduced N-acetylaspartate levels in regions of the frontal cortex, including the anterior cingulate cortex, dorsolateral prefrontal cortex, and thalamus, involved in the pathophysiology of schizophrenia suggest that brain metabolite abnormalities may be a marker of genetic vulnerability to schizophrenia. We used proton magnetic resonance spectroscopy (H-MRS) to acquire absolute concentrations of brain metabolites in subjects with a high genetic risk of schizophrenia to investigate the potential relationship between unexpressed genetic liability to schizophrenia and neuronal dysfunction. METHOD: Included in the study were 22 subjects who had at least two relatives with schizophrenia (high genetic risk group) and 22 controls with no second-degree relatives with schizophrenia. Absolute concentrations of N-acetylaspartate, creatine, choline, glutamate/glutamine, and myo-inositol and the ratios of metabolites in the anterior cingulate cortex, left dorsolateral prefrontal cortex, and left thalamus were measured using H-MRS at 1.5 Tesla. RESULTS: Relative to the controls, the high genetic risk group showed significant differences in absolute metabolite levels in the spectra of the regions of the left thalamus, including significant decreases in N-acetylaspartate, creatine, and choline concentrations. CONCLUSIONS: The study points to neuronal dysfunction, and in particular thalamic dysfunction, as a key region of the vulnerability marker of schizophrenia. Further studies should examine the nature of the thalamus more intensively to further our understanding of thalamic dysfunction as a vulnerability marker.