Tactile priming modulates the activation of the fronto-parietal circuit during tactile angle match and non-match processing: an fMRI study

The repetition of a stimulus task reduces the neural activity within certain cortical regions responsible for working memory (WM) processing. Although previous evidence has shown that repeated vibrotactile stimuli reduce the activation in the ventrolateral prefrontal cortex, whether the repeated tactile spatial stimuli triggered the priming effect correlated with the same cortical region remains unclear. Therefore, we used event-related functional magnetic resonance imaging (fMRI) and a delayed match-to-sample task to investigate the contributions of the priming effect to tactile spatial WM processing. Fourteen healthy volunteers were asked to encode three tactile angle stimuli during the encoding phase and one tactile angle stimulus during the recognition phase. Then, they answered whether the last angle stimulus was presented during the encoding phase. As expected, both the Match and Non-Match tasks activated a similar cerebral network. The critical new finding was decreased brain activity in the left inferior frontal gyrus (IFG), the right posterior parietal cortex (PPC) and bilateral medial frontal gyri (mFG) for the match task compared to the Non-Match task. Therefore, we suggest that the tactile priming engaged repetition suppression mechanisms during tactile angle matching, and this process decreased the activation of the fronto-parietal circuit, including IFG, mFG and PPC.

The anodal tDCS over the left posterior parietal cortex enhances attention toward a focus word in a sentence

The posterior parietal cortex (PPC) has two attentional functions: top-down attentional control and stimulus-driven attentional processing. Using the focused version of the reading span test (RST), in which the target word to be remembered is the critical word for comprehending a sentence (focused word) or a non-focused word, we examined the effect of tDCS on resolution of distractor interference by the focused word in the non-focus condition (top-down attentional control) and on augmented/shrunk attentional capture by the focused word in both the focus and non-focus conditions (stimulus-driven attentional processing). Participants were divided into two groups: anodal tDCS (atDCS) and cathodal tDCS (ctDCS). Online stimulation was given while participants performed the RST. A post-hoc recognition task was also administered in which three kinds of words were presented: target words in the RST, distractor words in the RST, and novel words. atDCS augmented the effect of the focused word by increasing differences in performance between the focus and non-focus conditions. Such an effect was not observed in the ctDCS group. As for the recognition task, atDCS again produced the augmented effect of the focused words in the distractor recognition. On the other hand, ctDCS brought less recognition of non-focused target words in comparison to sham. The results indicate that atDCS promotes stimulus-driven attentional processing, possibly by affecting neural firing in the inferior parietal regions. In contrast, ctDCS appears to prevent retrieval of less important information from episodic memory, which may require top-down attentional processing.

Fiber tract associated with autistic traits in healthy adults

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder with impairment of social communication and restricted and repetitive behaviors. Reduced fractional anisotropy (FA), a measure of white matter integrity, in the posterior superior temporal sulcus (pSTS) is related to ASD. However, there are several major fibers in pSTS, and it is unknown which of them is associated with ASD. We investigated FA in correlation with autistic traits assessed by autism spectrum quotient (AQ) in 91 healthy adults using tract-based spatial statistics (TBSS). Then, of the fibers in pSTS, we identified the one in which FA was linked to the AQ score using tractography. TBSS revealed that AQ was correlated with FA of white matter in several regions such as the frontal lobe, parietal lobe, occipital lobe and temporal lobe including pSTS. With further analysis using tractography, we confirmed that FA alteration in pSTS was located on the inferior fronto-occipital fasciculus (IFOF). IFOF has a critical role in processing socio-emotional information. Our findings suggest that of the fibers in pSTS, IFOF is a key fiber that links to autistic traits in healthy adults.

Neural correlates of perceptual grouping effects in the processing of sound omission by musicians and nonmusicians

Perceptual grouping is the process of organizing sounds into perceptually meaningful elements. Psychological studies have found that tones presented as a regular frequency or temporal pattern are grouped according to gestalt principles, such as similarity, proximity, and good continuity. Predictive coding theory suggests that this process helps create an internal model for the prediction of sounds in a tone sequence and that an omission-related brain response reflects the violation of this prediction. However, it remains unclear which brain areas are related to this process, especially in paying attention to the stimuli. To clarify this uncertainty, the present study investigated the neural correlates of perceptual grouping effects. Using magnetoencephalography (MEG), we recorded the evoked response fields (ERFs) of amateur musicians and nonmusicians to sound omissions in tone sequences with a regular or random pattern of three different frequencies during an omission detection task. Omissions in the regular sequences were detected faster and evoked greater activity in the left Heschl's gyrus (HG), right postcentral gyrus, and bilateral superior temporal gyrus (STG) than did omissions in the irregular sequences. Additionally, an interaction between musical experience and regularity was found in the left HG/STG. Tone-evoked responses did not show this difference, indicating that the expertise effect did not reflect the superior tone processing acquired by amateur musicians due to musical training. These results suggest that perceptual grouping based on repetition of a pattern of frequencies affects the processing of omissions in tone sequences and induces more activation of the bilateral auditory cortex by violating internal models. The interaction in the left HG/STG may suggest different styles of processing for musicians and nonmusicians, although this difference was not reflected at the behavioral level.

Functional relevance of the precuneus in verbal politeness

Non-competitive and non-threatening aspects of social hierarchy, such as politeness, are universal among human cultures, and might have evolved from ritualized submission in primates; however, these behaviors have rarely been studied. Honorific language is a type of polite linguistic communication that plays an important role in human social interactions ranging from everyday conversation to international diplomacy. Here, functional magnetic resonance imaging (fMRI) revealed selective precuneus activation during a verbal politeness judgment task, but not other linguistic-judgment or social-status recognition tasks. The magnitude of the activation was correlated with the task performance. Functional suppression of the activation using cathodal transcranial direct-current stimulation reduced performance in the politeness task. These results suggest that the precuneus is an essential hub of the verbal politeness judgment.

Task-specific brain reorganization in motor recovery induced by a hybrid-rehabilitation combining training with brain stimulation after stroke

Recently, we have developed a new hybrid-rehabilitation combining 5Hz repetitive transcranial magnetic stimulation and extensor motor training of the paretic upper-limb for stroke patients with flexor hypertonia. We previously showed that the extensor-specific plastic change in M1 was associated with beneficial effects of our protocol (Koganemaru et al., 2010). Here, we investigated whether extensor-specific multiregional brain reorganization occurred after the hybrid-rehabilitation using functional magnetic resonance imaging. Eleven chronic stroke patients were scanned while performing upper-limb extensor movements. Untrained flexor movements were used as a control condition. The scanning and clinical assessments were done before, immediately and 2 weeks after the hybrid-rehabilitation. As a result, during the trained extensor movements, the imaging analysis showed a significant reduction of brain activity in the ipsilesional sensorimotor cortex, the contralesional cingulate motor cortex and the contralesional premotor cortex in association with functional improvements of the paretic hands. The activation change was not found for the control condition. Our results suggested that use-dependent plasticity induced by repetitive motor training with brain stimulation might be related to task-specific multi-regional brain reorganization. It provides a key to understand why repetitive training of the target action is one of the most powerful rehabilitation strategies to help patients.

Silent information regulator 2 homolog 1 counters cerebral hypoperfusion injury by deacetylating endothelial nitric oxide synthase

BACKGROUND AND PURPOSE

Silent information regulator 2 homolog 1 (SIRT1) is a protein deacetylase that has been reported to suppress neurodegenerative and cardiovascular diseases in model organisms. We hypothesized that neurovascular protection is one of the diverse actions of SIRT1. This study was designed to determine whether SIRT1 protects against the consequences of cerebral hypoperfusion in vivo.

METHODS

Sirt1-overexpressing (Sirt1-Tg) mice driven by a prion promoter and their wild-type littermates were subjected to bilateral common carotid artery stenosis using external microcoils. Using Sirt1-Tg mice, we assessed the effect of SIRT1 on cerebral blood flow, cerebral angioarchitecture, histological and ultrastructural changes, and spatial working memory at several time points. We also evaluated the effects of preadministration of SIRT1 inhibitors or endothelial nitric oxide synthase inhibitors on cerebral blood flow after bilateral common carotid artery stenosis in Sirt1-Tg mice. Levels of acetylated and nonacetylated endothelial nitric oxide synthase were measured semiquantitatively with immunoblotting.

RESULTS

Cerebral hypoperfusion induced by bilateral common carotid artery stenosis caused memory impairment and histological changes in wild-type littermates. However, these phenotypes were rescued in Sirt1-Tg mice, where cerebral blood flow was maintained even poststenosis. Electron microscopic analyses showed irregularities in the vascular endothelia, such as tight junction openings in wild-type mice, which were absent in Sirt1-Tg littermates. Brain endothelial nitric oxide synthase was acetylated after cerebral hypoperfusion in wild-type littermates but remained unacetylated in Sirt1-Tg mice. Moreover, treatment with SIRT1 inhibitors and endothelial nitric oxide synthase inhibitors abolished the vasculoprotective effects of SIRT1.

CONCLUSIONS

Our results indicate that neurovascular endothelial SIRT1 potentiation upregulates the nitric oxide system and counters cerebral hypoperfusion injury. This novel cerebral blood flow-preserving mechanism offers potential molecular targets for future therapeutic intervention.

Insular activation during reward anticipation reflects duration of illness in abstinent pathological gamblers

Pathological gambling (PG) is a chronic mental disorder characterized by a difficulty restraining gambling behavior despite negative consequences. Although brain abnormalities in patients with substance use disorders are caused by repetitive drug use and recover partly with drug abstinence, the relationship between brain activity and duration of illness or abstinence of gambling behavior in PG patients remains unclear. Here, using functional magnetic resonance imaging, we compared the brain activity of 23 PG patients recruited from a treatment facility with 27 demographically-matched healthy control subjects during reward anticipation, and examined the correlations between brain activity and duration of illness or abstinence in PG patients. During reward anticipation, PG patients showed decreased activity compared to healthy controls in a broad range of the reward system regions, including the insula cortex. In PG patients, activation in the left insula showed a significant negative correlation with illness duration. Our findings suggest that insular activation during reward anticipation may serve as a marker of progression of pathological gambling.

Alpha-band desynchronization in human parietal area during reach planning

OBJECTIVE

The symptoms with optic ataxia suggest that simple and visually guided hand movements are controlled by 2 different neural substrates. To assess the differential frequency-coded posterior parietal cortex (PPC) role in planning visuo-motor goal-directed tasks, we studied the action specificity of event-related desynchronization (ERD) in this area.

METHODS

We investigated cortical activity by electroencephalography, while 16 healthy subjects performed self-paced reaching or wrist extension (control) movements. Time-frequency representations were calculated for each movement during the preparatory period.

RESULTS

ERD dynamics in upper alpha-band indicated that preparing a goal-directed action activates contralateral PPC to the moving hand around 1.2s before starting the movement, while this activation is later (around 0.7s) in preparing a not-goal-directed action. The posterior dominant rhythm had peak frequency of lower alpha-band at bilateral parietal.

CONCLUSIONS

Posterior parietal cortex encodes goal-directed movement preparation through upper alpha-band activity, whereas general attention is processed via lower alpha-band oscillations.

SIGNIFICANCE

Preparing to reach an object engages posterior parietal cortex earlier than a not-goal directed movement.

Voxel-based clustered imaging by multiparameter diffusion tensor images for glioma grading

Gliomas are the most common intra-axial primary brain tumour; therefore, predicting glioma grade would influence therapeutic strategies. Although several methods based on single or multiple parameters from diagnostic images exist, a definitive method for pre-operatively determining glioma grade remains unknown. We aimed to develop an unsupervised method using multiple parameters from pre-operative diffusion tensor images for obtaining a clustered image that could enable visual grading of gliomas. Fourteen patients with low-grade gliomas and 19 with high-grade gliomas underwent diffusion tensor imaging and three-dimensional T1-weighted magnetic resonance imaging before tumour resection. Seven features including diffusion-weighted imaging, fractional anisotropy, first eigenvalue, second eigenvalue, third eigenvalue, mean diffusivity and raw T2 signal with no diffusion weighting, were extracted as multiple parameters from diffusion tensor imaging. We developed a two-level clustering approach for a self-organizing map followed by the K-means algorithm to enable unsupervised clustering of a large number of input vectors with the seven features for the whole brain. The vectors were grouped by the self-organizing map as protoclusters, which were classified into the smaller number of clusters by K-means to make a voxel-based diffusion tensor-based clustered image. Furthermore, we also determined if the diffusion tensor-based clustered image was really helpful for predicting pre-operative glioma grade in a supervised manner. The ratio of each class in the diffusion tensor-based clustered images was calculated from the regions of interest manually traced on the diffusion tensor imaging space, and the common logarithmic ratio scales were calculated. We then applied support vector machine as a classifier for distinguishing between low- and high-grade gliomas. Consequently, the sensitivity, specificity, accuracy and area under the curve of receiver operating characteristic curves from the 16-class diffusion tensor-based clustered images that showed the best performance for differentiating high- and low-grade gliomas were 0.848, 0.745, 0.804 and 0.912, respectively. Furthermore, the log-ratio value of each class of the 16-class diffusion tensor-based clustered images was compared between low- and high-grade gliomas, and the log-ratio values of classes 14, 15 and 16 in the high-grade gliomas were significantly higher than those in the low-grade gliomas (p < 0.005, p < 0.001 and p < 0.001, respectively). These classes comprised different patterns of the seven diffusion tensor imaging-based parameters. The results suggest that the multiple diffusion tensor imaging-based parameters from the voxel-based diffusion tensor-based clustered images can help differentiate between low- and high-grade gliomas.

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We have developed a novel unsupervised method for voxel-based clustered imaging.

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Each class ratio in clustered images differentiated high from low-grade gliomas.

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The 16-class clustered images showed the best performance for the differentiation.

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Each class comprised different patterns of the seven diffusion tensor-based features.

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Multiple parameters from diffusion tensor images are useful for glioma grading.

Altered brain response to others׳ pain in major depressive disorder

BACKGROUND

Empathy has a central role in successful interpersonal engagement. Several studies have reported altered empathy in major depressive disorder (MDD), which could lead to interpersonal difficulties. However, the neural basis of altered empathy in the disorder is still largely unknown. To address this, we performed functional magnetic resonance imaging that tested empathy for others׳ pain in MDD patients.

METHODS

Eleven patients with MDD and 11 age-, gender-, handedness-, and education level-matched healthy control subjects were studied. We compared MDD patients and healthy controls for their regional hemodynamic responses to visual perception of videos showing human hands in painful situations. We also assessed subjective pain ratings of the videos in each group.

RESULTS

The MDD patients showed lower pain ratings for the painful videos compared with the healthy controls. In addition, the MDD patients showed reduced cerebral activation in the left middle cingulate cortex, and the right somatosensory-related cortices, whereas they showed greater cerebral activation in the left inferior frontal gyrus.

LIMITATIONS

We relied on a relatively small sample size and could not exclude effects of medications.

CONCLUSIONS

These results suggest that in MDD patients the altered neural activations in these regions may be associated with a deficit in the identification of pain in others. This study adds to our understanding of the neural mechanism involved in empathy in MDD.

The contribution of cortical thickness and surface area to gray matter asymmetries in the healthy human brain

Human cortical gray matter (GM) is structurally asymmetrical and this asymmetry has been discussed to be partly responsible for functional lateralization of human cognition and behavior. Past studies on brain asymmetry have shown mixed results so far, with some studies focusing on the global shapes of the brain's surface, such as gyrification patterns, while others focused on regional brain volumes. In this study, we investigated cortical GM asymmetries in a large sample of right-handed healthy volunteers (n = 101), using a surface-based method which allows to analyze brain cortical thickness and surface area separately. As a result, substantially different patterns of symmetry emerged between cortical thickness and surface area measures. In general, asymmetry is more prominent in the measure of surface compared to that of thickness. Such a detailed investigation of structural asymmetries in the normal brain contributes largely to our knowledge of normal brain development and also offers insights into the neurodevelopmental basis of psychiatric disorders, such as schizophrenia.

Independent or integrated processing of interaural time and level differences in human auditory cortex?

Sound localization in the horizontal plane is mainly determined by interaural time differences (ITD) and interaural level differences (ILD). Both cues result in an estimate of sound source location and in many real-life situations these two cues are roughly congruent. When stimulating listeners with headphones it is possible to counterbalance the two cues, so called ITD/ILD trading. This phenomenon speaks for integrated ITD/ILD processing at the behavioral level. However, it is unclear at what stages of the auditory processing stream ITD and ILD cues are integrated to provide a unified percept of sound lateralization. Therefore, we set out to test with human electroencephalography for integrated versus independent ITD/ILD processing at the level of preattentive cortical processing by measuring the mismatch negativity (MMN) to changes in sound lateralization. We presented a series of diotic standards (perceived at a midline position) that were interrupted by deviants that entailed either a change in a) ITD only, b) ILD only, c) congruent ITD and ILD, or d) counterbalanced ITD/ILD (ITD/ILD trading). The sound stimuli were either i) pure tones with a frequency of 500 Hz, or ii) amplitude modulated tones with a carrier frequency of 4000 Hz and a modulation frequency of 125 Hz. We observed significant MMN for the ITD/ILD traded deviants in case of the 500 Hz pure tones, and for the 4000 Hz amplitude-modulated tone. This speaks for independent processing of ITD and ILD at the level of the MMN within auditory cortex. However, the combined ITD/ILD cues elicited smaller MMN than the sum of the MMN induced in response to ITD and ILD cues presented in isolation for 500 Hz, but not 4000 Hz, suggesting independent processing for the higher frequency only. Thus, the two markers for independent processing - additivity and cue-conflict - resulted in contradicting conclusions with a dissociation between the lower (500 Hz) and higher frequency (4000 Hz) bands.

[A case of smoldering anti-leucine-rich glioma-inactivated 1 (LGI1) antibody-associated limbic encephalitis with faciobrachial dystonic seizure]

We report a 59-year-old right-handed woman with smoldering leucine-rich glioma-inactivated 1 (LGI1) antibody-associated limbic encephalitis (LE) following faciobrachial dystonic seizures. During 8 months before her admission, she developed partial seizures manifesting very brief and very frequent dystonia in her right hand sometimes with oral automatism and loss of awareness. In addition, she showed psychiatric disturbances such as emotionally labile condition and personality changes. On admission, neuropsychological examination revealed short-term memory impairment. During electroencephalography (EEG) monitoring, ictal EEG showed rhythmic delta waves and interictal EEG showed intermittent irregular slow waves at the bilateral frontotemporal area. Brain MRI demonstrated high T2/FLAIR signal changes in the left amygdala expanding into the left hippocampus. FDG-PET showed hypermetabolism in the left amygdala, hippocampus and the bilateral basal ganglia. Cerebrospinal fluid analysis was unremarkable. There were no signs of malignant tumor detected on systemic examination. LGI1 antibody was positive in the serum and the cerebrospinal fluid and the clinical diagnosis of LGI1 antibody-associated LE was confirmed. Her symptoms and the abnormalities in the brain MRI/FDG-PET showed immediate improvement after anti-epileptic and steroid therapy.

Effects of mental rotation on acalculia: differences in the direction of mental rotation account for the differing characteristics of acalculia induced by right and left hemispheric brain injury

We observed a 59-year-old right-handed man with an infarction in his right-middle cerebral artery that included the parietal lobe, who abnormally manipulated mental images in the horizontal direction, resulting in calculation disturbances. Three years later, the patient suffered an infarction in the left parietal lobe and displayed abnormalities during the creation of mental images; i.e., he rotated them in the vertical direction, which again resulted in calculation disturbances. These mental imagery disturbances might indicate that a common acalculia mechanism exists between the right and left hemispheres.

Effects of extracranial-intracranial bypass for patients with hemorrhagic moyamoya disease: results of the Japan Adult Moyamoya Trial

BACKGROUND AND PURPOSE

About one half of those who develop adult-onset moyamoya disease experience intracranial hemorrhage. Despite the extremely high frequency of rebleeding attacks and poor prognosis, measures to prevent rebleeding have not been established. The purpose of this study is to determine whether extracranial-intracranial bypass can reduce incidence of rebleeding and improve patient prognosis.

METHODS

This study was a multicentered, prospective, randomized, controlled trial conducted by 22 institutes in Japan. Adult patients with moyamoya disease who had experienced intracranial hemorrhage within the preceding year were given either conservative care or bilateral extracranial-intracranial direct bypass and were observed for 5 years. Primary and secondary end points were defined as all adverse events and rebleeding attacks, respectively.

RESULTS

Eighty patients were enrolled (surgical, 42; nonsurgical, 38). Adverse events causing significant morbidity were observed in 6 patients in the surgical group (14.3%) and 13 patients in the nonsurgical group (34.2%). Kaplan-Meier survival analysis revealed significant differences between the 2 groups (3.2%/y versus 8.2%/y; P=0.048). The hazard ratio of the surgical group calculated by Cox regression analysis was 0.391 (95% confidence interval, 0.148-1.029). Rebleeding attacks were observed in 5 patients in the surgical group (11.9%) and 12 in the nonsurgical group (31.6%), significantly different in the Kaplan-Meier survival analysis (2.7%/y versus 7.6%/y; P=0.042). The hazard ratio of the surgical group was 0.355 (95% confidence interval, 0.125-1.009).

CONCLUSIONS

Although statistically marginal, Kaplan-Meier analysis revealed the significant difference between surgical and nonsurgical group, suggesting the preventive effect of direct bypass against rebleeding.

CLINICAL TRIAL REGISTRATION URL

http://www.umin.ac.jp/ctr/index.htm. Unique identifier: C000000166.

Compact 100Gb/s DP-QPSK integrated receiver module employing three-dimensional assembly technology

We demonstrate a compact 100 Gbit/s DP-QPSK receiver module that is only 18 mm (W) x 16 mm (D) x 2.8 mm (H). The module size is reduced by using a ball grid array (BGA) package with three-dimensional assembly technology and by applying a heterogeneous integrated PLC. Error-free DP-QPSK signal demodulation is successfully demonstrated.

Global association between cortical thinning and white matter integrity reduction in schizophrenia

Previous neuroimaging studies have revealed that both gray matter (GM) and white matter (WM) are altered in several morphological aspects in schizophrenia patients. Although several studies reported associations between GM and WM alterations in restricted regions, the existence of a global association between GM and WM pathologies is unknown. Considering the wide distribution of GM morphological changes and the profound genetic background of WM abnormalities, it would be natural to postulate a global association between pathologies of GM and WM in schizophrenia. In this investigation, we studied 35 schizophrenia patients and 35 healthy control subjects using T1-weighted magnetic resonance imaging and diffusion tensor imaging (DTI) and investigated the association between GM thickness and WM fractional anisotropy (FA) as a proxy of pathology in each tissue. To investigate cortical thickness, surface-based analysis was used. The mean cortical thickness for the whole brain was computed for each hemisphere, and group comparisons were performed. For DTI data, mean FA for the whole brain was calculated, and group comparisons were performed. Subsequently, the correlation between mean cortical thickness and mean FA was investigated. Results showed that the mean cortical thickness was significantly thinner, and the mean FA was significantly lower in schizophrenia patients. Only in the patient group the mean cortical thickness and mean FA showed significant positive correlations in both hemispheres. This correlation remained significant even after controlling for demographic and clinical variables. Thus, our results indicate that the GM and WM pathologies of schizophrenia are intertwined at the global level.