Echo time dependence of BOLD contrast and susceptibility artifacts

Cleaning up the Brickyard: How Theory and Methodology Shape Experiments in Cognitive Neuroscience of Language

The capacity for language is a defining property of our species, yet despite decades of research, evidence on its neural basis is still mixed and a generalized consensus is difficult to achieve. We suggest that this is partly caused by researchers defining "language" in different ways, with focus on a wide range of phenomena, properties, and levels of investigation. Accordingly, there is very little agreement among cognitive neuroscientists of language on the operationalization of fundamental concepts to be investigated in neuroscientific experiments. Here, we review chains of derivation in the cognitive neuroscience of language, focusing on how the hypothesis under consideration is defined by a combination of theoretical and methodological assumptions. We first attempt to disentangle the complex relationship between linguistics, psychology, and neuroscience in the field. Next, we focus on how conclusions that can be drawn from any experiment are inherently constrained by auxiliary assumptions, both theoretical and methodological, on which the validity of conclusions drawn rests. These issues are discussed in the context of classical experimental manipulations as well as study designs that employ novel approaches such as naturalistic stimuli and computational modeling. We conclude by proposing that a highly interdisciplinary field such as the cognitive neuroscience of language requires researchers to form explicit statements concerning the theoretical definitions, methodological choices, and other constraining factors involved in their work.

Neural substrates of reward anticipation and outcome in schizophrenia: a meta-analysis of fMRI findings in the monetary incentive delay task

Dysfunction of the mesocorticolimbic dopaminergic reward system is a core feature of schizophrenia (SZ), yet its precise contributions to different stages of reward processing and their relevance to disease symptomology are not fully understood. We performed a coordinate-based meta-analysis, using the monetary incentive delay task, to identify which brain regions are implicated in different reward phases in functional magnetic resonance imaging in SZ. A total of 17 studies (368 SZ and 428 controls) were included in the reward anticipation, and 10 studies (229 SZ and 281 controls) were included in the reward outcome. Our meta-analysis revealed that during anticipation, patients showed hypoactivation in the striatum, anterior cingulate cortex, median cingulate cortex (MCC), amygdala, precentral gyrus, and superior temporal gyrus compared with controls. Striatum hypoactivation was negatively associated with negative symptoms and positively associated with the proportion of second-generation antipsychotic users (percentage of SGA users). During outcome, patients displayed hyperactivation in the striatum, insula, amygdala, hippocampus, parahippocampal gyrus, cerebellum, postcentral gyrus, and MCC, and hypoactivation in the dorsolateral prefrontal cortex (DLPFC) and medial prefrontal cortex (mPFC). Hypoactivity of mPFC during outcome was negatively associated with positive symptoms. Moderator analysis showed that the percentage of SGA users was a significant moderator of the association between symptom severity and brain activity in both the anticipation and outcome stages. Our findings identified the neural substrates for different reward phases in SZ and may help explain the neuropathological mechanisms underlying reward processing deficits in the disorder.

Spatially Adjacent Regions in Posterior Cingulate Cortex Represent Familiar Faces at Different Levels of Complexity

Extensive research has shown that perceptual information of faces is processed in a network of hierarchically-organized areas within ventral temporal cortex. For familiar and famous faces, perceptual processing of faces is normally accompanied by extraction of semantic knowledge about the social status of persons. Semantic processing of familiar faces could entail progressive stages of information abstraction. However, the cortical mechanisms supporting multistage processing of familiar faces have not been characterized. Here, using an event-related fMRI experiment, familiar faces from four celebrity groups (actors, singers, politicians, and football players) and unfamiliar faces were presented to the human subjects (both males and females) while they were engaged in a face categorization task. We systematically explored the cortical representations for faces, familiar faces, subcategories of familiar faces, and familiar face identities using whole-brain univariate analysis, searchlight-based multivariate pattern analysis (MVPA), and functional connectivity analysis. Convergent evidence from all these analyses revealed a set of overlapping regions within posterior cingulate cortex (PCC) that contained decodable fMRI responses for representing different levels of semantic knowledge about familiar faces. Our results suggest a multistage pathway in PCC for processing semantic information of faces, analogous to the multistage pathway in ventral temporal cortex for processing perceptual information of faces.SIGNIFICANCE STATEMENT Recognizing familiar faces is an important component of social communications. Previous research has shown that a distributed network of brain areas is involved in processing the semantic information of familiar faces. However, it is not clear how different levels of semantic information are represented in the brain. Here, we evaluated the multivariate response patterns across the entire cortex to discover the areas that contain information for familiar faces, subcategories of familiar faces, and identities of familiar faces. The searchlight maps revealed that different levels of semantic information are represented in topographically adjacent areas within posterior cingulate cortex (PCC). The results suggest that semantic processing of faces is mediated through progressive stages of information abstraction in PCC.

Lessons learned from using fMRI in the early clinical development of a mu-opioid receptor antagonist for disorders of compulsive consumption

Functional magnetic resonance imaging (fMRI) has been widely used to gain a greater understanding of brain circuitry abnormalities in CNS disorders. fMRI has also been used to examine pharmacological modulation of brain circuity and is increasingly being used in early clinical drug development as functional pharmacodynamic index of target engagement, and to provide early indication of clinical efficacy. In this short review, we summarize data from experimental medicine and early clinical development studies of a mu-opioid receptor antagonist, GSK1521498 developed for disorders of compulsive consumption including binge eating in obesity. We demonstrate how fMRI can be used to answer important questions of early clinical drug development relating to; (1) target engagement, (2) dose response relationships, (3) differential efficacy and (4) prediction of behavioural and clinically relevant outcomes. We also highlight important methodological factors that need to be considered when conducting fMRI studies in drug development given the challenges faced with small sample sizes in Phase 1 and early proof of mechanism studies. While these data highlight the value of fMRI as a biomarker in drug development, its use for making Go/No-go decisions is still faced with challenges given the variability of responses, interpretation of brain activation changes and the limited data linking drug induced changes in brain activity to clinical or behavioural outcome. These challenges need to be addressed to fulfil the promise of fMRI as a tool in clinical drug development.

Altered orbitofrontal activation in preterm-born young adolescents during performance of a reality filtering task

Preterm birth is one of the main causes for neurodevelopmental problems, and has been associated with a wide range of impairments in cognitive functions including executive functions and memory. One of the factors contributing to these adverse outcomes is the intrinsic vulnerability of the premature brain. Neuroimaging studies have highlighted structural and functional alterations in several brain regions in preterm individuals across lifetime. The orbitofrontal cortex (OFC) is crucial for a multitude of complex and adaptive behaviours, and its structure is particularly affected by premature birth. Nevertheless, studies on the functional impact of prematurity on the OFC are still missing. Orbitofrontal Reality filtering (ORFi) refers to the ability to distinguish if a thought is relevant to present reality or not. It can be tested using a continuous recognition task and is mediated by the OFC in adults and typically developing young adolescents. Therefore, the ORFi task was used to investigate whether OFC functioning is affected by prematurity. We compared the neural correlates of ORFi in 35 young adolescents born preterm (below 32 weeks of gestation) and aged 10 to 14 years with 25 full term-born controls. Our findings indicate that OFC activation was required only in the full-term group, whereas preterm young adolescents did not involve OFC in processing the ORFi task, despite being able to correctly perform it.

New acquisition techniques and their prospects for the achievable resolution of fMRI

This work reviews recent advances in technologies for functional magnetic resonance imaging (fMRI) of the human brain and highlights the push for higher functional specificity based on increased spatial resolution and specific MR contrasts to reveal previously undetectable functional properties of small-scale cortical structures. We discuss how the combination of MR hardware, advanced acquisition techniques and various MR contrast mechanisms have enabled recent progress in functional neuroimaging. However, these advanced fMRI practices have only been applied to a handful of neuroscience questions to date, with the majority of the neuroscience community still using conventional imaging techniques. We thus discuss upcoming challenges and possibilities for fMRI technology development in human neuroscience. We hope that readers interested in functional brain imaging acquire an understanding of current and novel developments and potential future applications, even if they don't have a background in MR physics or engineering. We summarize the capabilities of standard fMRI acquisition schemes with pointers to relevant literature and comprehensive reviews and introduce more recent developments.

Get real: Orbitofrontal cortex mediates the ability to sense reality in early adolescents

INTRODUCTION

Orbitofrontal reality filtering (ORFi) is a memory mechanism that distinguishes whether a thought is relevant to present reality or not. In adults, it is mediated by the orbitofrontal cortex (OFC). This region is still not fully developed in preteenagers, but ORFi is already active from age 7. Here, we probe the neural correlates of ORFi in early adolescents, hypothesizing that OFC mediates the sense of reality in this population.

METHODS

Functional magnetic resonance images (fMRI) were acquired in 22 early adolescents during a task composed of two runs: run 1 measuring recognition capacity; run 2 measuring ORFi; each containing two types of images (conditions): distractors (D: images seen for the first time in the current run) and targets (T: images seen for the second time in the current run). Group region of interest (ROI) analysis was performed in a flexible factorial design with two factors (run and condition) using SPM12.

RESULTS

We found significant main effects for the experimental run and condition. The bilateral OFC activation was higher during ORFi than during the first run. Additionally, the OFC was more active while processing distractors than targets.

CONCLUSION

These results confirm, for the first time, the role of OFC in reality filtering in early adolescents.

Wave-CAIPI susceptibility-weighted imaging achieves diagnostic performance comparable to conventional susceptibility-weighted imaging in half the scan time

OBJECTIVES

We aimed to evaluate the agreement in the detection of cerebral microbleeds (CMBs) between conventional susceptibility-weighted imaging (SWI) and fast SWI using wave-controlled aliasing in parallel imaging (CAIPI) acceleration. We also scrutinized the diagnostic agreement for intracranial lesions and compared the image quality between both sequences.

METHODS

Institutional review board approval was obtained and informed consent was waived for this retrospective study. We included 181 consecutive patients who had undergone brain MRI with both conventional SWI (scan time, 251 s) and wave-CAIPI SWI (scan time, 113 s) from September 2017 to November 2017. All images were independently reviewed by two radiologists for the detection and counting of CMBs using the Microbleed Anatomical Rating Scale (MARS). One neuroradiologist diagnosed intracranial lesions and scored image quality using visual analysis. The agreement for detection of CMBs and intracranial lesions was calculated, and interobserver agreements were analyzed by using kappa and intraclass correlation.

RESULTS

For detection of CMBs, both the conventional and wave-CAIPI SWI showed significantly high agreement of 100% for the presence of CMBs, and 94.5% using MARS. Wave-CAIPI SWI achieved more than 97% agreement of MARS when divided by anatomical locations, with excellent agreement. Interobserver agreements were also excellent. The diagnosis for intracranial lesions (33 lesions in 28 patients) demonstrated 100% agreement. The image quality of both sequences is not significantly different (p = 0.20).

CONCLUSIONS

Wave-CAIPI SWI achieved high agreement for CMB detection and diagnosis of intracranial lesions compared to conventional SWI within half of the scan time.

KEY POINTS

• Wave-CAIPI SWI achieves a diagnostic performance for the detection of cerebral microbleeds that is comparable to that of conventional SWI in half the scan time. • Interobserver agreement for the detection (presence vs. absence) and counting of cerebral microbleeds of wave-CAIPI SWI was excellent. • Wave-CAIPI SWI demonstrated a 100% agreement for the diagnosis of intracranial lesions and comparable image quality compared to conventional SWI.

Left Posterior Orbitofrontal Cortex Is Associated With Odor-Induced Autobiographical Memory: An fMRI Study

Autobiographical odor memory (AM-odor) accompanied by a sense of realism of a specific memory elicits strong emotions. AM-odor differs from memory triggered by other sensory modalities, possibly because olfaction involves a unique sensory process. Here, we examined the orbitofrontal cortex (OFC), using functional magnetic resonance imaging (fMRI) to determine which OFC subregions are related to AM-odor. Both AM-odor and a control odor successively increased subjective ratings of comfortableness and pleasantness. Importantly, AM-odor also increased arousal levels and the vividness of memories, and was associated with a deep and slow breathing pattern. fMRI analysis indicated robust activation in the left posterior OFC (L-POFC). Connectivity between the POFC and whole brain regions was estimated using psychophysiological interaction analysis (PPI). We detected several trends in connectivity between L-POFC and bilateral precuneus, bilateral rostral dorsal anterior cingulate cortex (rdACC), and left parahippocampus, which will be useful for targeting our hypotheses for future investigations. The slow breathing observed in AM-odor was correlated with rdACC activation. Odor associated with emotionally significant autobiographical memories was accompanied by slow and deep breathing, possibly involving rdACC processing.

Anterior Temporal Lobe Morphometry Predicts Categorization Ability

Categorization is the mental operation by which the brain classifies objects and events. It is classically assessed using semantic and non-semantic matching or sorting tasks. These tasks show a high variability in performance across healthy controls and the cerebral bases supporting this variability remain unknown. In this study we performed a voxel-based morphometry study to explore the relationships between semantic and shape categorization tasks and brain morphometric differences in 50 controls. We found significant correlation between categorization performance and the volume of the gray matter in the right anterior middle and inferior temporal gyri. Semantic categorization tasks were associated with more rostral temporal regions than shape categorization tasks. A significant relationship was also shown between white matter volume in the right temporal lobe and performance in the semantic tasks. Tractography revealed that this white matter region involved several projection and association fibers, including the arcuate fasciculus, inferior fronto-occipital fasciculus, uncinate fasciculus, and inferior longitudinal fasciculus. These results suggest that categorization abilities are supported by the anterior portion of the right temporal lobe and its interaction with other areas.

Scene content is predominantly conveyed by high spatial frequencies in scene-selective visual cortex

In complex real-world scenes, image content is conveyed by a large collection of intertwined visual features. The visual system disentangles these features in order to extract information about image content. Here, we investigate the role of one integral component: the content of spatial frequencies in an image. Specifically, we measure the amount of image content carried by low versus high spatial frequencies for the representation of real-world scenes in scene-selective regions of human visual cortex. To this end, we attempted to decode scene categories from the brain activity patterns of participants viewing scene images that contained the full spatial frequency spectrum, only low spatial frequencies, or only high spatial frequencies, all carefully controlled for contrast and luminance. Contrary to the findings from numerous behavioral studies and computational models that have highlighted how low spatial frequencies preferentially encode image content, decoding of scene categories from the scene-selective brain regions, including the parahippocampal place area (PPA), was significantly more accurate for high than low spatial frequency images. In fact, decoding accuracy was just as high for high spatial frequency images as for images containing the full spatial frequency spectrum in scene-selective areas PPA, RSC, OPA and object selective area LOC. We also found an interesting dissociation between the posterior and anterior subdivisions of PPA: categories were decodable from both high and low spatial frequency scenes in posterior PPA but only from high spatial frequency scenes in anterior PPA; and spatial frequency was explicitly decodable from posterior but not anterior PPA. Our results are consistent with recent findings that line drawings, which consist almost entirely of high spatial frequencies, elicit a neural representation of scene categories that is equivalent to that of full-spectrum color photographs. Collectively, these findings demonstrate the importance of high spatial frequencies for conveying the content of complex real-world scenes.

Monitoring cardiac and respiratory physiology during FMRI

This article will consider how physiological monitoring can be used both as an intrinsic part of an experiment, or for removing unwanted physiological signals from the FMRI time series. As functional MRI is used for a wide variety of applications beyond the identification of regions involved in a task, different sources of noise in the time series become important. The use of arterial spin labelling sequences, either in isolation or combined with BOLD imaging, means that temporal noise must be dealt with differently. Moreover, when these are combined with global cerebrovascular stimuli, such as respiratory challenges, the standard analysis tools must be employed with great care so as not to detrimentally distort the data. Acquiring and analysing physiological data is sometimes more art than science, and this article attempts to provide some insight into common techniques as well as advice on identifying and correcting some of the problems that may be encountered.

A Hitchhiker's Guide to Functional Magnetic Resonance Imaging

Functional Magnetic Resonance Imaging (fMRI) studies have become increasingly popular both with clinicians and researchers as they are capable of providing unique insights into brain functions. However, multiple technical considerations (ranging from specifics of paradigm design to imaging artifacts, complex protocol definition, and multitude of processing and methods of analysis, as well as intrinsic methodological limitations) must be considered and addressed in order to optimize fMRI analysis and to arrive at the most accurate and grounded interpretation of the data. In practice, the researcher/clinician must choose, from many available options, the most suitable software tool for each stage of the fMRI analysis pipeline. Herein we provide a straightforward guide designed to address, for each of the major stages, the techniques, and tools involved in the process. We have developed this guide both to help those new to the technique to overcome the most critical difficulties in its use, as well as to serve as a resource for the neuroimaging community.

Suppressing Respiration Effects when Geometric Distortion Is Corrected Dynamically by Phase Labeling for Additional Coordinate Encoding (PLACE) during Functional MRI

Echo planar imaging (EPI) suffers from geometric distortions caused by magnetic field inhomogeneities, which can be time-varying as a result of small amounts of head motion that occur over seconds and minutes during fMRI experiments, also known as “dynamic geometric distortion”. Phase Labeling for Additional Coordinate Encoding (PLACE) is a promising technique for geometric distortion correction without reduced temporal resolution and in principle can be used to correct for motion-induced dynamic geometric distortion. PLACE requires at least two EPI images of the same anatomy that are ideally acquired with no variation in the magnetic field inhomogeneities. However, head motion and lung ventilation during the respiratory cycle can cause changes in magnetic field inhomogeneities within the EPI pair used for PLACE. In this work, we exploited dynamic off-resonance in k-space (DORK) and averaging to correct the within EPI pair magnetic field inhomogeneities; and hence proposed a combined technique (DORK+PLACE+averaging) to mitigate dynamic geometric distortion in EPI-based fMRI while preserving the temporal resolution. The performance of the combined DORK, PLACE and averaging technique was characterized through several imaging experiments involving test phantoms and six healthy adult volunteers. Phantom data illustrate reduced temporal standard deviation of fMRI signal intensities after use of combined dynamic PLACE, DORK and averaging compared to the standard processing and static geometric distortion correction. The combined technique also substantially improved the temporal standard deviation and activation maps obtained from human fMRI data in comparison to the results obtained by standard processing and static geometric distortion correction, highlighting the utility of the approach.

Intensity-based masking: A tool to improve functional connectivity results of resting-state fMRI

Seed-based functional connectivity (FC) of resting-state functional MRI data is a widely used methodology, enabling the identification of functional brain networks in health and disease. Based on signal correlations across the brain, FC measures are highly sensitive to noise. A somewhat neglected source of noise is the fMRI signal attenuation found in cortical regions in close vicinity to sinuses and air cavities, mainly in the orbitofrontal, anterior frontal and inferior temporal cortices. BOLD signal recorded at these regions suffers from dropout due to susceptibility artifacts, resulting in an attenuated signal with reduced signal-to-noise ratio in as many as 10% of cortical voxels. Nevertheless, signal attenuation is largely overlooked during FC analysis. Here we first demonstrate that signal attenuation can significantly influence FC measures by introducing false functional correlations and diminishing existing correlations between brain regions. We then propose a method for the detection and removal of the attenuated signal ("intensity-based masking") by fitting a Gaussian-based model to the signal intensity distribution and calculating an intensity threshold tailored per subject. Finally, we apply our method on real-world data, showing that it diminishes false correlations caused by signal dropout, and significantly improves the ability to detect functional networks in single subjects. Furthermore, we show that our method increases inter-subject similarity in FC, enabling reliable distinction of different functional networks. We propose to include the intensity-based masking method as a common practice in the pre-processing of seed-based functional connectivity analysis, and provide software tools for the computation of intensity-based masks on fMRI data. Hum Brain Mapp 37:2407-2418, 2016. © 2016 Wiley Periodicals, Inc.

Reducing signal loss of the parahippocampal gyrus improves imaging of the default-mode network in 3.0-T MRI: the effect of susceptibility-induced field gradients

Previous investigations have indicated that the default-mode network (DMN) is highly involved in memory processing in the parahippocampal gyrus (PHC). However, because of susceptibility-related signal loss, parahippocampal activation in the DMN is difficult to detect in resting-state functional MRI experiments that are conducted using a 3.0-T MRI scanner. This study investigated the magnetic field gradients of various brain regions and attempted to compensate for signal loss in the PHC using an optimized slice orientation. The field gradients, signal intensities and DMN functional connectivity (FC) of the PHC were investigated using datasets acquired from 18 healthy volunteers. The results show that the field gradient component parallel to the main magnetic field dominates the PHC. The results indicate that the signal intensities and FC of the DMN are significantly low in the PHC when the slice orientation of the imaging plane is transversal. Whether the voxel dimension is isotropic or anisotropic exerts a minimal effect in altering the slice orientation dependence. In conclusion, the results of this study support the selection of the coronal or sagittal planes for imaging of the DMN.

The selective impairment of resting-state functional connectivity of the lateral subregion of the frontal pole in schizophrenia

OBJECTIVE

Although extensive resting-state functional connectivity (rsFC) changes have been reported in schizophrenia, rsFC changes of the frontal pole (FP) remain unclear. The FP contains several subregions with different connection patterns; however, it is unknown whether the FP subregions are differentially affected in schizophrenia. To explore this possibility, we compared rsFC differences of the FP subregions between schizophrenia patients and healthy controls.

METHOD

One hundred healthy controls and 91 patients with schizophrenia underwent resting-state functional MRI with a sensitivity-encoded spiral-in (SENSE-SPIRAL) imaging sequence to reduced susceptibility-induced signal loss and distortion. The FP was subdivided into the orbital (FPo), medial (FPm), and lateral (FPl) subregions. Mean fMRI time series were extracted for each FP subregion and entered into a seed-based rsFC analysis.

RESULTS

The FP subregions exhibited differential rsFC patterns in both healthy controls and schizophrenia patients. Direct comparison between groups revealed reduced rsFCs between the bilateral FPl and several cognitive-related regions, including the dorsolateral prefrontal cortex, medial prefrontal cortex, anterior cingulate cortex, posterior cingulate cortex/precuneus, temporal cortex and inferior parietal lobule in schizophrenia. Although the FPl exhibited obvious atrophy, rsFC changes were unrelated to volumetric atrophy in the FPl, to duration of illness, and to antipsychotic medication dosage. No significant differences were observed in the rsFCs of other FP subregions.

CONCLUSION

These findings suggest a selective (the lateral subregion) functional disconnection of the FP subregions in schizophrenia.

Successful decoding of famous faces in the fusiform face area

What are the neural mechanisms of face recognition? It is believed that the network of face-selective areas, which spans the occipital, temporal, and frontal cortices, is important in face recognition. A number of previous studies indeed reported that face identity could be discriminated based on patterns of multivoxel activity in the fusiform face area and the anterior temporal lobe. However, given the difficulty in localizing the face-selective area in the anterior temporal lobe, its role in face recognition is still unknown. Furthermore, previous studies limited their analysis to occipito-temporal regions without testing identity decoding in more anterior face-selective regions, such as the amygdala and prefrontal cortex. In the current high-resolution functional Magnetic Resonance Imaging study, we systematically examined the decoding of the identity of famous faces in the temporo-frontal network of face-selective and adjacent non-face-selective regions. A special focus has been put on the face-area in the anterior temporal lobe, which was reliably localized using an optimized scanning protocol. We found that face-identity could be discriminated above chance level only in the fusiform face area. Our results corroborate the role of the fusiform face area in face recognition. Future studies are needed to further explore the role of the more recently discovered anterior face-selective areas in face recognition.

Special considerations/technical limitations of blood-oxygen-level-dependent functional magnetic resonance imaging

In this review, limitations affecting the results of presurgical mapping with blood-oxygen-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) are discussed. There is a great need to standardize fMRI acquisition and analysis methods and establish guidelines to address quality control issues. Several national and international organizations are formulating guidelines and standards for both clinical and research applications of BOLD fMRI. Consensus regarding management of these issues will likely both improve the clinical standard of care and enhance future research applications of fMRI.

Test-retest reliability of amygdala response to emotional faces

In the current study, we evaluated the test-retest reliability of amygdala response using an emotional face-matching task that has been widely used to examine pathophysiology and treatment mechanisms in psychiatric populations. Activation within the fusiform face area (FFA) was also examined. Twenty-seven healthy volunteers completed a variation of the face-matching paradigm developed by Hariri et al. (2000) at two time points approximately 90 days apart. Estimates of test-retest reliability of amygdala response to fearful faces were moderate, whereas angry and happy faces showed poor reliability. Test-retest reliability of the FFA was moderate to strong, regardless of facial affect. Collectively, these findings indicate that the reliability of the BOLD MR signal in the amygdala varies substantially by facial affect. Efforts to improve measurement precision, enlarge sample sizes, or increase the number of assessment occasions seem warranted.

The challenge of localizing the anterior temporal face area: a possible solution

Humans recognize faces exceptionally well. However, the neural correlates of face recognition are still elusive. Accumulated evidence in recent years suggests that the anterior temporal lobe (ATL), in particular face-selective region in the ATL, is a probable locus of face recognition. Unfortunately, functional MRI (fMRI) studies encounter severe signal drop-out in the ventral ATL, where that ATL face area resides. Consequently, all previous studies localized this region in no more than half of the subjects and its volume was relatively small. Thus, a systematic exploration of the properties of the ATL face area is scarce. In the current high-resolution fMRI study we used coronal slice orientation, which permitted us to localize the ATL face area in all the subjects. Furthermore, the volume of the area was much larger than was reported in previous studies. Direct within subjects comparison with data collected with the commonly used axial slice orientation confirmed that the advantage of the coronal slice orientation in revealing a reliable and larger face-selective area in the ATL. Finally, by displaying the face-selective activations resultant from coronal and axial scanning together, we demonstrate an organization principle of a chain of face-selective regions along the posterior-anterior axis in the ventral temporal lobe that is highly reproducible across all subjects. By using the procedure proposed here, a significant progress can be made in studying the neural correlates of face recognition.

Exploring functional connectivity networks with multichannel brain array coils

The use of multichannel array head coils in functional and structural magnetic resonance imaging (MRI) provides increased signal-to-noise ratio (SNR), higher sensitivity, and parallel imaging capabilities. However, their benefits remain to be systematically explored in the context of resting-state functional connectivity MRI (fcMRI). In this study, we compare signal detectability within and between commercially available multichannel brain coils, a 32-Channel (32Ch), and a 12-Channel (12Ch) at 3T, in a high-resolution regime to accurately map resting-state networks. We investigate whether the 32Ch coil can extract and map fcMRI more efficiently and robustly than the 12Ch coil using seed-based and graph-theory-based analyses. Our findings demonstrate that although the 12Ch coil can be used to reveal resting-state connectivity maps, the 32Ch coil provides increased detailed functional connectivity maps (using seed-based analysis) as well as increased global and local efficiency, and cost (using graph-theory-based analysis), in a number of widely reported resting-state networks. The exploration of subcortical networks, which are scarcely reported due to limitations in spatial-resolution and coil sensitivity, also proved beneficial with the 32Ch coil. Further, comparisons regarding the data acquisition time required to successfully map these networks indicated that scan time can be significantly reduced by 50% when a coil with increased number of channels (i.e., 32Ch) is used. Switching to multichannel arrays in resting-state fcMRI could, therefore, provide both detailed functional connectivity maps and acquisition time reductions, which could further benefit imaging special subject populations, such as patients or pediatrics who have less tolerance in lengthy imaging sessions.

Food motivation circuitry hypoactivation related to hedonic and nonhedonic aspects of hunger and satiety in women with active anorexia nervosa and weight-restored women with anorexia nervosa

BACKGROUND

Previous studies have provided evidence of food motivation circuitry dysfunction in individuals with anorexia nervosa. However, methodological limitations present challenges to the development of a cohesive neurobiological model of anorexia nervosa. Our goal was to investigate the neural circuitry of appetite dysregulation across states of hunger and satiety in active and weight-restored phases of anorexia nervosa using robust methodology to advance our understanding of potential neural circuitry abnormalities related to hedonic and nonhedonic state and trait.

METHODS

We scanned women with active anorexia nervosa, weight-restored women with anorexia nervosa and healthy-weight controls on a 3-T Siemens magnetic resonance scanner while they viewed images of high- and low-calorie foods and objects before (premeal) and after (postmeal) eating a 400 kcal meal.

RESULTS

We enrolled 12 women with active disease, 10 weight-restored women with anorexia nervosa and 11 controls in our study. Compared with controls, both weight-restored women and those with active disease demonstrated hypoactivity premeal in the hypothalamus, amygdala and anterior insula in response to high-calorie foods (v. objects). Postmeal, hypoactivation in the anterior insula persisted in women with active disease. Percent signal change in the anterior insula was positively correlated with food stimuli ratings and hedonic and nonhedonic appetite ratings in controls, but not women with active disease.

LIMITATIONS

Our findings are limited by a relatively small sample size, which prevented the use of an analysis of variance model and exploration of interaction effects, although our substantial effect sizes of between-group differences suggest adequate power for our statistical analysis approach. Participants taking psychotropic medications were included.

CONCLUSION

Our data provide evidence of potential state and trait hypoactivations in food motivation regions involved in the assessment of food's reward value and integration of these with interoceptive signalling of one's internal state of well-being, with important relations between brain activity and homeostatic and hedonic aspects of appetite. Our findings give novel evidence of disruption in neurobiological circuits and stress the importance of examining both state and trait characteristics in the investigation of brain phenotypes in individuals with anorexia nervosa.

Distinct neural substrates for semantic knowledge and naming in the temporoparietal network

Patients with anterior temporal lobe (ATL) lesions show semantic and lexical retrieval deficits, and the differential role of this area in the 2 processes is debated. Functional neuroimaging in healthy individuals has not clarified the matter because semantic and lexical processes usually occur simultaneously and automatically. Furthermore, the ATL is a region challenging for functional magnetic resonance imaging (fMRI) due to susceptibility artifacts, especially at high fields. In this study, we established an optimized ATL-sensitive fMRI acquisition protocol at 4 T and applied an event-related paradigm to study the identification (i.e., association of semantic biographical information) of celebrities, with and without the ability to retrieve their proper names. While semantic processing reliably activated the ATL, only more posterior areas in the left temporal and temporal-parietal junction were significantly modulated by covert lexical retrieval. These results suggest that within a temporoparietal network, the ATL is relatively more important for semantic processing, and posterior language regions are relatively more important for lexical retrieval.

Ultrafast bold fMRI using single-shot spin-echo echo planar imaging

The choice of imaging parameters for functional MRI can have an impact on the accuracy of functional localization by affecting the image quality and the degree of blood oxygenation-dependent (BOLD) contrast achieved. By improving sampling efficiency, parallel acquisition techniques such as sensitivity encoding (SENSE) have been used to shorten readout trains in single-shot (SS) echo planar imaging (EPI). This has been applied to susceptibility artifact reduction and improving spatial resolution. SENSE together with single-shot spin-echo (SS-SE) imaging may also reduce off-resonance artifacts. The goal of this work was to investigate the BOLD response of a SENSE-adapted SE-EPI on a three Tesla scanner. Whole-brain fMRI studies of seven healthy right hand-dominant volunteers were carried out in a three Tesla scanner. fMRI was performed using an SS-SE EPI sequence with SENSE. The data was processed using statistical parametric mapping. Both, group and individual subject data analyses were performed. Individual average percentage and maximal percentage signal changes attributed to the BOLD effect in M1 were calculated for all the subjects as a function of echo time. Corresponding activation maps and the sizes of the activated clusters were also calculated. Our results show that susceptibility artifacts were reduced with the use of SENSE; and the acquired BOLD images were free of the typical quadrature artifacts of SS-EPI. Such measures are crucial at high field strengths. SS SE-EPI with SENSE offers further benefits in this regard and is more specific for oxygenation changes in the microvasculature bed. Functional brain activity can be investigated with the help of single-shot spin echo EPI using SENSE at high magnetic fields.

A blood pool contrast aided T1 functional MRI in patients with brain tumors--a preliminary study

INTRODUCTION

The aim of our study was to determine the possibility of using a new functional technique: a T1-dependent sequence with administration of blood pool contrast agent (BPCA), in patients with brain tumors before and after surgical treatment. We also aimed to compare our results with those obtained using the fMRI technique, based on Blood Oxygenation Level-Dependent (BOLD) contrast.

METHODS

For each of our 14 oncologic patients (four before and ten after neurosurgical intervention), we obtained: a T1-3D GRE sequence (TR = 2.6 ms/TE = 1.1 ms/FA = 10°) after intravenous administration of BPCA (0.03 mmol/kg), as well as a T2*EPI sequence (TR = 3 s/TE = 50 ms/FA = 90°). Movement and/or tactile block type paradigms were carried out during both functional runs. SPM5 software was used for analysis.

RESULTS

For both functional techniques, maximum activations were localized in the same areas. There were no significant differences observed in the t values calculated for activations located in the primary motor cortex between groups of pre- and post-intervention patients (in the same functional technique). The mean values for T2* EPI examinations were 10.84 and 9.36, respectively. The mean t values for the T1 technique were lower, especially for the post-intervention patients (5.83 and 3.9, respectively).

CONCLUSIONS

The T1 technique can be used to detect functional areas in patients with brain tumors, pre-, and post-surgical intervention. This technique enables the evaluation of cortical centers that suffer from susceptibility artifacts when using the T2* BOLD technique. Activations found using both techniques have the same localization, with lower values for the T1 technique.

What the left and right anterior fusiform gyri tell us about semantic memory

The study of patients with semantic dementia, a variant of frontotemporal lobar degeneration, has emerged over the last two decades as an important lesion model for studying human semantic memory. Although it is well-known that semantic dementia is associated with temporal lobe degeneration, controversy remains over whether the semantic deficit is due to diffuse temporal lobe damage, damage to only a sub-region of the temporal lobe or even less severe damage elsewhere in the brain. The manner in which the right and left temporal lobes contribute to semantic knowledge is also not fully elucidated. In this study we used unbiased imaging analyses to correlate resting cerebral glucose metabolism and behavioural scores in tests of verbal and non-verbal semantic memory. In addition, a region of interest analysis was performed to evaluate the role of severely hypometabolic areas. The best, indeed the only, strong predictor of semantic scores across a set of 21 patients with frontotemporal lobar degeneration with semantic impairment was degree of hypometabolism in the anterior fusiform region subjacent to the head and body of the hippocampus. As hypometabolism in the patients' rostral fusiform was even more extreme than the abnormality in other regions with putative semantic relevance, such as the temporal poles, the significant fusiform correlations cannot be attributed to floor-level function in these other regions. More detailed analysis demonstrated more selective correlations: left anterior fusiform function predicted performance on two expressive verbal tasks, whereas right anterior fusiform metabolism predicted performance on a non-verbal test of associative semantic knowledge. This pattern was further supported by an additional behavioural study performed on a wider cohort of patients with semantic dementia, in which the patients with more extensive right-temporal atrophy (when matched on degree of naming deficit to a set of cases with more extensive left temporal atrophy) were significantly more impaired on the test of non-verbal semantics. Our preferred interpretation of this laterality effect involves differential strength of connectivity between different regions of a widespread semantic network in the human brain.

Neuroanatomical correlates of cognitive self-appraisal in neurodegenerative disease

Self-appraisal is a critical cognitive function, which helps us to choose tasks based on an accurate assessment of our abilities. The neural mechanisms of self-appraisal are incompletely understood, although a growing body of literature suggests that several frontal and subcortical regions are important for self-related processing. Anosognosia, or lack of awareness of one's deficits, is common in neurodegenerative dementias, offering an important window onto the brain systems involved in self-appraisal. We examined the neuroanatomical basis of self-appraisal in a mixed group of 39 individuals, including 35 with cognitive impairment due to one of several probable neurodegenerative diseases, using voxel-based morphometry and an objective, neuropsychologically-based measure of self-appraisal accuracy. Self-appraisal accuracy was correlated with tissue content in the right ventromedial prefrontal cortex (vmPFC). We hypothesize that emotional/physiological processing carried out by vmPFC is an important factor mediating self-appraisal accuracy in dementia.

Neural representations of faces and body parts in macaque and human cortex: a comparative FMRI study

Single-cell studies in the macaque have reported selective neural responses evoked by visual presentations of faces and bodies. Consistent with these findings, functional magnetic resonance imaging studies in humans and monkeys indicate that regions in temporal cortex respond preferentially to faces and bodies. However, it is not clear how these areas correspond across the two species. Here, we directly compared category-selective areas in macaques and humans using virtually identical techniques. In the macaque, several face- and body part-selective areas were found located along the superior temporal sulcus (STS) and middle temporal gyrus (MTG). In the human, similar to previous studies, face-selective areas were found in ventral occipital and temporal cortex and an additional face-selective area was found in the anterior temporal cortex. Face-selective areas were also found in lateral temporal cortex, including the previously reported posterior STS area. Body part-selective areas were identified in the human fusiform gyrus and lateral occipitotemporal cortex. In a first experiment, both monkey and human subjects were presented with pictures of faces, body parts, foods, scenes, and man-made objects, to examine the response profiles of each category-selective area to the five stimulus types. In a second experiment, face processing was examined by presenting upright and inverted faces. By comparing the responses and spatial relationships of the areas, we propose potential correspondences across species. Adjacent and overlapping areas in the macaque anterior STS/MTG responded strongly to both faces and body parts, similar to areas in the human fusiform gyrus and posterior STS. Furthermore, face-selective areas on the ventral bank of the STS/MTG discriminated both upright and inverted faces from objects, similar to areas in the human ventral temporal cortex. Overall, our findings demonstrate commonalities and differences in the wide-scale brain organization between the two species and provide an initial step toward establishing functionally homologous category-selective areas.

The impact of EPI voxel size on SNR and BOLD sensitivity in the anterior medio-temporal lobe: a comparative group study of deactivation of the Default Mode

OBJECTIVES

To quantify the gain in time-series SNR that can be achieved in the amygdala by reducing EPI voxel size, and to assess the extent to which this advantage is carried through to statistical significance in a group fMRI study, using a cognitive task to trigger task-independent deactivation of anterior medial temporal structures.

MATERIALS AND METHODS

Two groups of seven subjects were posed number-series tasks to induce deactivation of the Default Mode network. This is known from PET work to include the amygdala, which lies in a region of high magnetic field gradient. In 3 T imaging, one group was studied with high resolution EPI with 6 mul voxels, the other with lower resolution EPI with 17 mul voxels. Field maps were acquired to allow field gradients in relevant ROIs to be assessed.

RESULTS

Time-series SNR was 45% higher in the amygdala in the high resolution EPI data than in the low resolution data. In activation results, whilst there was good agreement between other areas, the involvement of the amygdala could only be demonstrated in the high resolution data.

CONCLUSION

We find that reduction in signal dephasing afforded by high resolution EPI is realized as a substantial increase in SNR and BOLD sensitivity in group fMRI data. This has allowed the first demonstration of the involvement of the amygdala in the Default Mode in fMRI.

K-space spatial low-pass filters can increase signal loss artifacts in Echo-Planar Imaging

Effective transverse relaxation rate (T(2)*)-weighted echo-planar imaging (EPI) is extensively used for functional magnetic resonance imaging (fMRI), because of its high speed and good sensitivity to the blood oxygenation level-dependent (BOLD) signal. Nevertheless, its use is limited in areas with severe static magnetic field inhomogeneities that cause frequency shifts and T(2)* relaxation-related distortions of the MR signal along the time-domain (k-space) trajectory, resulting in disperse time-domain signals and generating susceptibility-induced signal losses. Echo planar images are commonly smoothed with k-space spatial low-pass filters to improve the signal-to-noise ratio (SNR) and reduce reconstruction artifacts. Here, we show that when such filters are applied to the dispersed echo-signals (not perfectly centered in k-space), part of the image information from the object is removed, thereby enhancing signal-loss artifacts in the images. To avoid this artifact, the dispersed echo signal has to be refocused before k-space filtering.

fMRI of the temporal lobe of the awake monkey at 7 T

Increasingly 7 T scanners are used for fMRI of humans and non-human primates, promising improvements in signal-to-noise, spatial resolution and specificity. A disadvantage of fMRI at 7 T, but already at 3 T, is that susceptibility artifacts from air-filled cavities like the ear canal and nasal cavity cause signal loss and distortion. This limits the applicability of fMRI in these areas, thereby limiting study of these areas, but it also limits study of processes that span large-scale cortical networks or the entire brain. Our goal is to study the inferior temporal (IT) lobe in awake monkeys because of its importance in object perception and recognition, but the functional signal is degraded by strong susceptibility gradients. To allow fMRI of this region, we used an optimized SE-EPI, which recovers signal lost with GE-EPI and we corrected for susceptibility-induced image distortion. SE-EPI has the added advantage that, in contrast to GE-EPI, where the functional signal derives to a large extent from veins, the SE-EPI signal arises from the microvasculature, and hence it better represents the neural activation. We show fMRI at 7 T of the entire visual pathway in the awake primate with robust and widespread activation in all ventral areas of the brain, including areas adjacent to the ear canal. This allows fMRI of areas that normally suffer from artifact and thus more reliable whole-brain studies.

Improved functional mapping of the human amygdala using a standard functional magnetic resonance imaging sequence with simple modifications

As the amygdala is involved in various aspects of emotional processing, its characterization using neuroimaging modalities, such as functional magnetic resonance imaging (fMRI), is of great interest. However, in fMRI, the amygdala region suffers from susceptibility artifacts that are composed of signal dropouts and image distortions. Various technically demanding approaches to reduce these artifacts have been proposed, and most require alterations beyond a mere change of the acquisition parameters and cannot be easily implemented by the user without changing the MR sequence code. In the present study, we therefore evaluated the impact of simple alterations of the acquisition parameters of a standard gradient-echo echo-planar imaging technique at 3 T composed of echo times (TEs) of 27 and 36 ms as well as section thicknesses of 2 and 4 mm while retaining a section orientation parallel to the intercommissural plane and an in-plane resolution of 2x2 mm(2). In contrast to previous studies, we based our evaluation on the resulting activation maps using an emotional stimulation paradigm rather than on MR raw image quality only. Furthermore, we tested the effects of spatial smoothing of the functional raw data in the course of postprocessing using spatial filters of 4 and 8 mm. Regarding MR raw image quality, a TE of 27 ms and 2-mm sections resulted in the least susceptibility artifacts in the anteromedial aspect of the temporal lobe. The emotional stimulation paradigm resulted in robust bilateral amygdala activation for the approaches with 2-mm sections only -- but with larger activation volumes for a TE of 36 ms as compared with that of 27 ms. Moderate smoothing with a 4-mm spatial filter represented a good compromise between increased sensitivity and preserved specificity. In summary, we showed that rather than applying advanced modifications of the MR sequence, a simple increase in spatial resolution (i.e., the reduction of section thickness) is sufficient to improve the detectability of amygdala activation.

The contribution of neuroimaging to the study of language and aphasia

New structural and functional imaging methods continue to be developed at a rapid pace. In the last 25 years, advanced imaging techniques have provided insights into how language is represented and processed in the brain and how it can be disrupted by damage to, or dysfunction of, various parts of the brain. Imaging studies have also yielded new information regarding how individuals recover language after stroke. We briefly review the strengths and weaknesses of the various radiological methods currently used to study language and aphasia.

Optimized EPI for fMRI studies of the orbitofrontal cortex: compensation of susceptibility-induced gradients in the readout direction

Object Most functional magnetic resonance imaging (fMRI) studies record the blood oxygen leveldependent (BOLD) signal using gradient-echo echo-planar imaging (GE EPI). EPI can suffer from substantial BOLD sensitivity loss caused by magnetic field inhomogeneities. Here, BOLD sensitivity losses due to susceptibility- induced gradients in the readout (RO) direction are characterized and a compensation approach is developed.

Materials and Methods Based on a theory describing the dropout mechanism, an EPI sequence was optimized for maximal BOLD sensitivity in the orbitofrontal cortex (OFC) using a specific combination of an increased spatial resolution in the RO direction and a reduced echo time. Using measured BOLD sensitivity maps and a breath hold experiment, the model and compensation approach were tested.

Results Using typical fMRI EPI parameters, susceptibility-induced gradients in the RO direction caused dropouts in the OFC and the inferior temporal lobe. Optimizing the echo time and spatial resolution effectively reduced the dropout as predicted by the theory.

Conclusion The model-based compensation approach effectively reduces BOLD sensitivity losses due to susceptibility-induced gradients in the RO direction. It retains the high temporal resolution of single-shot EPI and can be readily combined with methods for the compensation of susceptibility-induced field gradients in the phase-encoding and through-plane direction.

Song and speech: Brain regions involved with perception and covert production

This 3-T fMRI study investigates brain regions similarly and differentially involved with listening and covert production of singing relative to speech. Given the greater use of auditory-motor self-monitoring and imagery with respect to consonance in singing, brain regions involved with these processes are predicted to be differentially active for singing more than for speech. The stimuli consisted of six Japanese songs. A block design was employed in which the tasks for the subject were to listen passively to singing of the song lyrics, passively listen to speaking of the song lyrics, covertly sing the song lyrics visually presented, covertly speak the song lyrics visually presented, and to rest. The conjunction of passive listening and covert production tasks used in this study allow for general neural processes underlying both perception and production to be discerned that are not exclusively a result of stimulus induced auditory processing nor to low level articulatory motor control. Brain regions involved with both perception and production for singing as well as speech were found to include the left planum temporale/superior temporal parietal region, as well as left and right premotor cortex, lateral aspect of the VI lobule of posterior cerebellum, anterior superior temporal gyrus, and planum polare. Greater activity for the singing over the speech condition for both the listening and covert production tasks was found in the right planum temporale. Greater activity in brain regions involved with consonance, orbitofrontal cortex (listening task), subcallosal cingulate (covert production task) were also present for singing over speech. The results are consistent with the PT mediating representational transformation across auditory and motor domains in response to consonance for singing over that of speech. Hemispheric laterality was assessed by paired t tests between active voxels in the contrast of interest relative to the left-right flipped contrast of interest calculated from images normalized to the left-right reflected template. Consistent with some hypotheses regarding hemispheric specialization, a pattern of differential laterality for speech over singing (both covert production and listening tasks) occurs in the left temporal lobe, whereas, singing over speech (listening task only) occurs in right temporal lobe.

Precuneus is involved in allocentric spatial location encoding and recognition

Using a declarative memory paradigm, the anatomical correlates of spatial location encoding and retrieval in the healthy human brain as reflected by BOLD fMRI were investigated. During encoding, subjects were instructed to view and keep in mind different locations of an object on a platform seen from different viewpoints in virtual 3D. In retrieval trials, subjects had to recognize previously learned object locations. Comparing activation patterns associated with encoding and recognition on a voxel-by-voxel basis, we found regions in the precuneus bilaterally activated by both processes. To our knowledge, this is the first study that directly compared human brain activation patterns associated with allocentric encoding and retrieval of spatial locations in virtual 3D. Our results provide further information concerning the role of the precuneus in declarative memory processes, pointing to precuneus involvement in encoding and retrieval of spatial locations.

Dependence of amygdala activation on echo time: Results from olfactory fMRI experiments

Echo time dependence of the BOLD sensitivity is an important topic in fMRI whenever brain regions are considered where the EPI data quality suffers from susceptibility gradients. Here, an fMRI study is presented showing that a reduced echo time EPI sequence significantly enhances the statistical inference in subcortical (limbic) brain regions, with special focus on the amygdala. As a consequence, to facilitate whole-brain fMRI with optimal echo times, a sequence with slice-dependent echo time is demonstrated with a focus on structures suffering from susceptibility changes. The applicability of this method is shown in a second fMRI study aimed at both, cortical, and limbic brain regions. The results are in good agreement with theoretical descriptions of the BOLD sensitivity under the influence of susceptibility gradients.

fMRI studies of sensitivity and habituation effects within the auditory cortex at 1.5 T and 3 T

PURPOSE

To assess habituation effects in relation to field strength by fMRI at 1.5 vs. 3.0 T within the auditory cortex of healthy subjects.

MATERIALS AND METHODS

fMRI experiments were performed on 19 healthy subjects at 1.5 T (N = 12) and 3 T (N = 12). The auditory cortex was stimulated binaurally by digitally generated pulsed (nu = 5 Hz) 800 Hz sine tones with three alternating on and off periods.

RESULTS

The mean activation after stimulation (4.4% +/- 1.2% (1.5 T) and 5.3% +/- 2.3% (3 T)) and number of activated pixels (96.7 +/- 49.8 (1.5 T) and 139.9 +/- 101 (3 T)) were higher at 3 T compared to 1.5 T; however, that difference did not reach statistical significance. A characteristic signal decay with repeated stimuli was revealed at both 1.5 and 3 T, and the response to the second and third stimulation blocks was significantly lower compared to the first. The habituation pattern was the same, independently of field strength and age.

CONCLUSION

The mean activation and number of pixels were only modestly higher at 3 T, probably due to higher physiologic noise and higher local macroscopic susceptibility gradients within the temporal lobes at 3 T. Our data reveal that measured auditory habituation is independent of field strength, and data obtained at two different field strengths do not differ fundamentally in this context.

Neuroanatomical correlates of impaired recognition of emotion in dementia

Neurodegenerative diseases frequently affect brain regions important for emotional processing, offering a valuable opportunity to study the effects of brain injury on emotion. The current study examined the neuroanatomical correlates of impaired recognition of emotions in patients with neurodegenerative disease. Performance on recognition of facial expressions, as measured by the Florida Affect Battery, was correlated with regional changes in gray matter tissue content in 50 patients with neurodegenerative disease using voxel-based morphometry. Recognition accuracy in the group was poor for negative emotions (fear, anger and sadness) and good for happiness, consistent with previous studies. For negative emotions, a region in the right lateral inferior temporal gyrus (Brodman's area (BA) 20) extending into the right middle temporal gyrus (BA 21) was correlated with accuracy. This effect appeared to be strongest for sadness, which was also independently correlated with atrophy in the superior temporal gyrus. These data suggest that regions in the right lateral and inferolateral temporal lobe are important for visual processing of negative emotions from faces and that functioning of this right temporal network is most critical for recognition of sad faces.

The reliability of fMRI activations in the medial temporal lobes in a verbal episodic memory task

The test-retest reliability of activation patterns elicited by encoding and recognition of word-pair associates within the whole brain and a predefined medial temporal region of interest (ROI) was investigated. Twenty healthy right-handed subjects were studied within two sessions, either on the same day or 210-308 days later. Three quantitative measures of reliability were calculated for the contrasts encoding and recognition versus a control condition within the ROI and also for the whole brain: A group correlational analysis between the lateralization indices of the first and second session, correlations of the individual SPM(t) maps of the first and the second run, and overlap ratios between both sessions. For the ROI, correlational analysis of lateralization indices during both encoding trials was significant. Eighty percent of the individual positive correlation coefficients of SPM(t) maps during encoding, and 75% during recognition reached significance. The mean percentage of overlapping voxels was 18% during encoding and 19% during recognition. The reproducibility measures evaluated for the whole brain demonstrated significantly higher values compared to the ROI. For the group that stayed inside the scanner, better whole brain test-retest reliability was observed, and no influence of the memory process (encoding or recognition) on reproducibility was found.