Functional MRI studies have revealed that the brain activity in the anterior temporal cortex during memory retrieval increases over months after memory encoding. Behavioral evidence has demonstrated that long-term memory can sometimes be consolidated more rapidly in one or two days. In the present functional MRI study, we manipulated the relatedness between paired faces to be retrieved in a pair-association task. The brain activity in the anterior temporal cortex during retrieval of paired associates increased rapidly in one day, as shown in previous studies. We found that the speed of the brain activity development was dependent on the level of semantic relatedness of paired faces. The results suggest that the semantic relatedness enhances the speed of formation of memory representation in the anterior temporal cortex.

The orbitofrontal cortex (OFC) is involved in cognitive functions, and is also closely related to autonomic functions. The OFC is densely connected with the hypothalamus, a heterogeneous structure controlling autonomic functions that can be divided into two major parts: the lateral and the medial. Resting-state functional connectivity has allowed us to parcellate the cerebral cortex into putative functional areas based on the changes in the spatial pattern of connectivity in the cerebral cortex when a seed point is moved from one voxel to another. In the present high spatial-resolution fMRI study, we investigate the connectivity-based organization of the OFC with reference to the hypothalamus. The OFC was parcellated using resting-state functional connectivity in an individual subject approach, and then the functional connectivity was examined between the parcellated areas in the OFC and the lateral/medial hypothalamus. We found a functional double dissociation in the OFC: the lateral OFC (the lateral orbital gyrus) was more likely connected with the lateral hypothalamus, whereas the medial OFC (the medial orbital and rectal gyri) was more likely connected with the medial hypothalamus. These results demonstrate the fundamental heterogeneity of the OFC, and suggest a potential neural basis of the OFC hypothalamic functional interaction.

The current data article provides behavioral and neuroimaging data for the research article "Relatedness-dependent rapid development of brain activity in anterior temporal cortex during pair-association retrieval" (Jimura et al., 2016) [1]. Behavioral performance is provided in a table. Fig. 2 of the article is based on this table. Brain regions showing time effect are provided in a table. A statistical activation map for the time effect is shown in Fig. 3C of the article.

During rest, the human brain performs essential functions such as memory maintenance, which are associated with resting-state brain networks (RSNs) including the default-mode network (DMN) and frontoparietal network (FPN). Previous studies based on spiking-neuron network models and their reduced models, as well as those based on imaging data, suggest that resting-state network activity can be captured as attractor dynamics, i.e., dynamics of the brain state toward an attractive state and transitions between different attractors. Here, we analyze the energy landscapes of the RSNs by applying the maximum entropy model, or equivalently the Ising spin model, to human RSN data. We use the previously estimated parameter values to define the energy landscape, and the disconnectivity graph method to estimate the number of local energy minima (equivalent to attractors in attractor dynamics), the basin size, and hierarchical relationships among the different local minima. In both of the DMN and FPN, low-energy local minima tended to have large basins. A majority of the network states belonged to a basin of one of a few local minima. Therefore, a small number of local minima constituted the backbone of each RSN. In the DMN, the energy landscape consisted of two groups of low-energy local minima that are separated by a relatively high energy barrier. Within each group, the activity patterns of the local minima were similar, and different minima were connected by relatively low energy barriers. In the FPN, all dominant local minima were separated by relatively low energy barriers such that they formed a single coarse-grained global minimum. Our results indicate that multistable attractor dynamics may underlie the DMN, but not the FPN, and assist memory maintenance with different memory states.

Recent advancement of resting-state functional connectivity magnetic resonance imaging (MRI) has provided a method for drawing boundaries of brain areas. However, it remains to be elucidated how the parcellated areas in the association cortex relate to the spatial extent of the brain activation which ought to reflect a functional unit in the neural network supporting that particular function. To address this issue, in the present study, we first mapped boundaries and 2 adjacent activations in the human inferior frontal cortex, and then examined the spatial relationship between the boundaries and the 2 activations. The boundaries mapped with high-resolution functional magnetic resonance imaging revealed a collection of micromodules, the size of which was approximately only 12 mm on average, much smaller than the Brodmann areas. Each of the 2 activations associated with 2 functions, response inhibition and feedback processing, was smaller in size than the micromodules. By comparing the spatial patterns between the boundaries and the 2 activations, it was revealed that the brain activations were less likely to be located on the boundaries. These results suggest the functional relevance of the areas in the association cortex delineated by the boundary mapping method based on resting-state functional connectivity MRI.

The resting-state human brain networks underlie fundamental cognitive functions and consist of complex interactions among brain regions. However, the level of complexity of the resting-state networks has not been quantified, which has prevented comprehensive descriptions of the brain activity as an integrative system. Here, we address this issue by demonstrating that a pairwise maximum entropy model, which takes into account region-specific activity rates and pairwise interactions, can be robustly and accurately fitted to resting-state human brain activities obtained by functional magnetic resonance imaging. Furthermore, to validate the approximation of the resting-state networks by the pairwise maximum entropy model, we show that the functional interactions estimated by the pairwise maximum entropy model reflect anatomical connexions more accurately than the conventional functional connectivity method. These findings indicate that a relatively simple statistical model not only captures the structure of the resting-state networks but also provides a possible method to derive physiological information about various large-scale brain networks.

Immunoglobulin (Ig) G4-related disease is a recently designated benign clinical entity histopathologically characterized by sclerosing inflammation and infiltration of numerous IgG4+ plasma cells that affects multiple organs. The purpose of this study is to characterize the imaging findings of patients with histopathologically proven IgG4-related disease in the head, neck, and brain.

Retrieval of remote memory is considered to differentially involve the anterior and posterior temporal neocortices. Previous neuropsychological studies suggest that the different posterior temporal cortical regions are involved in the retrieval of remote memory of different categories of stimuli, whereas the anterior region is involved more generally in remote memory retrieval. In the present study, using functional magnetic resonance imaging of human brains, we tested this dissociation by examining the more precise characteristics of the anterior and posterior temporal cortical regions. Two categories of stimuli, faces and scenes, were used for paired stimuli to be retrieved, and the brain activity during retrieval of paired stimuli that were learned immediately before the scanning was compared with that during retrieval of paired stimuli that were learned ∼8 weeks earlier. We found that the different posterior temporal cortical regions were activated during retrieval of different categories of remote memory in a category-specific manner, whereas the anterior temporal cortical region was activated during retrieval of remote memory in a category-general manner. Furthermore, by applying a multivariate pattern analysis to psychophysiological interactions during retrieval of remote memory relative to recent memory, we revealed the significant interaction from the category-specific posterior temporal cortical regions to the category-general anterior temporal region. These results suggest that the posterior temporal cortical regions are involved in representation and retrieval of category-specific remote memory, whereas the anterior cortical temporal region is involved in category-general retrieval process of remote memory.

OBJECTIVES:To determine the efficacy and safety of 2 doses of gadobutrol 1.0 M (0.1 and 0.2 mmol/kg body weight [BW]), compared with gadoteridol 0.5 M (0.2 mmol/kg BW), in contrast-enhanced magnetic resonance imaging (CE-MRI) of brain metastases in patients with known or suspected brain metastases from systemic malignancies. The study also compared the usefulness of gadobutrol in treatment planning for stereotactic radiosurgery (SRS).MATERIALS AND METHODS:This was a Phase II/III, multicenter, single-blind, randomized, controlled, crossover, intraindividual comparison study. Each patient underwent one MRI study examination with gadobutrol and the other with gadoteridol, each at a dose of 0.1 mmol/kg BW, administered twice, for a total dose of 0.2 mmol/kg BW. Image acquisition was carried out after the first and second doses of gadobutrol, but only after the second dose of gadoteridol. Contrast agents were assigned in a randomized order and their administration separated by an interval of 1 to 14 days. Images were evaluated through blinded readings by 3 independent experienced radiologists. Treatment planning for SRS was assessed in a blinded manner, as a consensus between a diagnostic neuroradiologist and a radiation oncologist, in addition to the clinical investigator's assessment. The safety and tolerability of gadobutrol and gadoteridol were evaluated in all patients who received the study drugs. The primary efficacy variable was the number of lesions detected in CE-MRI images; the secondary efficacy variables were the degree of contrast enhancement and border delineation of lesions, and experts' confidence in treatment planning for SRS.RESULTS:A total of 175 patients were enrolled and randomized, with 164 (93.7%) included in the safety analysis set, and 151 (86.2%) evaluable in the efficacy analysis. The mean number of detected lesions per patient using the average of the 3 blinded readers was 6.28, 6.92, and 6.87 for gadobutrol 0.1 and 0.2 mmol/kg BW, and gadoteridol 0.2 mmol/kg BW, respectively. Noninferiority of gadobutrol (both doses) to gadoteridol 0.2 mmol/kg BW was demonstrated. The degree of contrast enhancement and the border delineation of each lesion were categorized as "good" or "excellent" for most lesions for both agents. Almost all enhanced images were rated as "confident" in treatment planning for SRS. Sixty-five (43%) and 62 (41%) patients in the gadobutrol 0.1 and 0.2 mmol/kg BW groups, respectively, were selected as eligible for SRS treatment. The percentage of images assessed as "gadobutrol was better than gadoteridol" was higher than that assessed as "gadoteridol was better than gadobutrol" for both doses of gadobutrol. Eight adverse events were reported as being related to the study drug in 7 patients (4.3%) in each group.CONCLUSION:In this study, a single dose of gadobutrol was shown to be noninferior to a double dose of gadoteridol at detecting brain metastases, and could be effectively used for treatment planning in patients eligible for SRS. A dose of gadobutrol 0.1 mmol/kg BW is recommended as the clinical dose for the detection of brain metastases.

Application of multivoxel pattern analysis (MVPA) to functional magnetic resonance imaging (fMRI) data enables reconstruction and classification of cognitive status from brain activity. However, previous studies using MVPA have extracted information about cognitive status that is experienced simultaneously with fMRI scanning, but not one that will be observed after the scanning. In this study, by focusing on activity in the medial temporal lobe (MTL), we demonstrate that MVPA on fMRI data is capable of predicting subsequent recognition performance. In this experiment, six runs of fMRI signals were acquired during encoding of phonogram stimuli. In the analysis, using data acquired in runs 1–3, we first conducted MVPA-based voxel-wise search for the clusters in the MTL whose signals contained the most information about subsequent recognition performance. Next, using the fMRI signals acquired in runs 1–3 from the selected clusters, we trained a classifier function in MVPA. Finally, the trained classifier function was applied to fMRI signals acquired in runs 4–6. Consequently, we succeeded in predicting the subsequent recognition performance for stimuli studied in runs 4–6 with significant accuracy. This accurate prediction suggests that MVPA can extract information that is associated not only with concurrent cognitive status, but also with behavior in the near future.

Posttraumatic stress disorder (PTSD) has been widely studied, but its neural mechanism is still unclear. The purpose of this study is to identify dysfunctional areas in PTSD throughout the whole brain to help to elucidate the neural mechanisms of PTSD. Sixteen patients with PTSD and sixteen healthy controls participated in this study. Traumatic images under perceptual threshold including scenes of earthquakes, traffic accidents, ambulances, emergency rooms, and crimes were presented to the participants, and brain activation was measured using functional MRI. Functional brain images of both groups were evaluated with random effect analysis for the whole brain. In the control group, activation in the ventral frontoparietal areas correlated significantly with presentation of the masked traumatic stimuli. In the PTSD group, activation was not observed in these areas, but significant activation correlated with the masked traumatic stimuli in the parahippocampal region including the left parahippocampal gyrus and tail of the left hippocampus. These results suggest that in PTSD patients activation in the ventral frontoparietal network associated with visual attention processing is attenuated, while the left hippocampal area associated with episodic and autobiographical memory is abnormally easily activated. This pattern of activation corresponds well to the clinical characteristics of PTSD, in which even slight traumatic stimuli tend to induce intrusive recollection or flashbacks, despite a general decrease in attention and ability to concentrate.

Background Septal penetration of high-energy photons may degrade the quality of single photon emission computed tomography (SPECT) of the heart with iodine 123-labeled tracers. We investigated the impact of collimator choice on cardiac SPECT with I-123. Methods and Results SPECT of a thoracic phantom containing I-123 solution was performed with a low-energy high-resolution (LEHR) collimator, special LEHR (SLEHR) collimator, and medium-energy (ME) collimator, and the cavity-to-myocardium contrast, wall thickness, and defect contrast were compared among the collimators. For all indices, use of the SLEHR collimator yielded the best results. Comparison between the LEHR and ME collimators revealed that the cavity-to-myocardium contrast and contrast for large defects were better with the ME collimator, whereas wall thickness and contrast for small defects were similar. Scatter correction by the triple-energy window method improved the indices examined; however, the superiority of the SLEHR collimator was still observed after correction. Conclusions Collimator choice substantially influences the quality of cardiac SPECT with I-123-labeled agents, and an appropriate collimator needs to be selected in consideration of septal penetration and spatial resolution.

BACKGROUND:Quantitative accuracy in iodine 123 studies may be impaired by septal penetration. We evaluated the effect of collimator choice on estimation of the heart-to-mediastinum (H/M) ratio in cardiac I-123 metaiodobenzylguanidine (MIBG) imaging.METHODS AND RESULTS:A low-energy high-resolution (LEHR) collimator, special LEHR (SLEHR) collimator, and medium-energy (ME) collimator were used. In experiments in which a phantom of simple geometry was used, the use of the LEHR collimator provided the lowest contrast accuracy, suggesting the effect of septal penetration. Thoracic phantom studies demonstrated contamination of heart and mediastinum counts by lung and liver activities, which was greatest with the LEHR collimator and least with the ME collimator. In 8 patients anterior chest views were acquired successively with the three collimators after I-123 MIBG injection. H/M ratios were significantly higher with the SLEHR collimator than with the LEHR collimator and were still higher with the ME collimator. The difference in H/M ratios between the LEHR and ME collimators showed a high positive correlation with the lung-to-mediastinum ratio.CONCLUSIONS:Collimator choice substantially influences estimation of the H/M ratios in cardiac I-123 MIBG imaging. The use of an ME collimator provides high quantitative accuracy and may enhance reliability in the evaluation of cardiac sympathetic nerve function.

Among several techniques for contrast-enhanced MRA, the elliptical centric view ordering method, originally developed at the Mayo Clinic, is a promising one. It has been difficult to apply a fat-suppression prepulse, mainly because the conventional fat suppression method requires a longer acquisition time during sampling of the low-frequency domain in k-space, and it causes severe image distortion due to the great change in longitudinal magnetization derived from fat tissue. We developed a novel method to append fat saturation to the elliptical centric view ordering technique, and assessed the feasibility of its use. Our method is to apply fat-saturation pulses only at selected sampling points when any gradient is applied in the slice-encoding direction. In this way, we achieved efficient suppression of fat-derived signal within a relatively short time, comparable to that of the conventional fat-saturation method, and succeeded in minimizing artifacts.

The prefrontal cortex plays a critical role in recollecting the temporal context of past events. The present study used event-related functional magnetic resonance imaging (fMRI) and explored the neural correlates of temporal-order retrieval during a recency judgment paradigm. In this paradigm, after study of a list of words presented sequentially, subjects were presented with two of the studied words simultaneously and were asked which of the two words was studied more recently. Two types of such retrieval trials with varied (high and low) levels of demand for temporal-order retrieval were intermixed and compared using event-related fMRI. The intraparadigm comparison of high versus low demand trials revealed brain regions with activation that was modulated on the basis of demand for temporal-order retrieval. Multiple lateral prefrontal regions including the middle and inferior lateral prefrontal cortex were prominently activated. Activation was also observed in the anterior prefrontal cortex and the medial temporal cortex, regions well documented to be related to memory retrieval in general. The modulation of brain activity in these regions suggests a detailed pathway that is engaged during recency judgment.