Human Brain Imaging Studies Research Articles

MP62-08 FIBERPHOTOMETRY AND OPTOGENETICS AS NOVEL TECHNOLOGIES REVEALED REGULATORY FUNCTION OF THE MOUSE ANTERIOR CINGULATE CORTEX IN MICTURITION REFLEX

INTRODUCTION AND OBJECTIVES:The cerebrum has been considered to regulate micturition reflex. Recently, human brain imaging studies revealed that the ACC (anterior cingulate cortex) may regulate mic...

Neural Mechanisms Linking Emotion with Cardiovascular Disease.

The present review discusses brain circuits that are engaged by negative emotions and possibly linked to cardiovascular disease risk. It describes recent human brain imaging studies that relate activity in these brain circuits to emotional processes, peripheral physiology, preclinical pathophysiology, as well as clinical outcomes. Negative emotions and the regulation of negative emotions reliably engage several brain regions that cross-sectional and longitudinal brain imaging studies have associated with CVD risk markers and outcomes. These brain regions include the amygdala, anterior cingulate cortex, medial prefrontal cortex, and insula. Other studies have applied advanced statistical techniques to characterize multivariate patterns of brain activity and brain connectivity that associate with negative emotion and CVD-relevant peripheral physiology. Brain imaging studies on emotion and cardiovascular disease risk are expanding our understanding of the brain-body bases of psychosocial and behavioral risk for cardiovascular disease.

Trigeminal neuropathic pain: Evidence of central changes from human brain imaging investigations

AbstractChronic neuropathic pain imposes enormous economic and social burden on Australia and can occur following relatively minor surgical procedures. The precise mechanisms that result in one individual developing chronic pain and another individual not, following seemingly identical surgical procedures, remain unknown. However, over the past few decades, numerous preclinical and human brain imaging studies have begun to reveal possible mechanisms responsible for the development of neuropathic pain following nerve injury. In this review, the latest human brain imaging results are canvassed and an overall series of events that might occur following nerve injury and how these events may lead to the development and maintenance of chronic neuropathic pain is outlined.

Lost in translation? Neuroscientific research, advocacy, and the claimed transfer benefits of musical practice

ABSTRACTIn recent decades there has been a proliferation of neuromyths based on oversimplifications and over-generalisations of research findings. As part of a larger project that examines the societal impacts of the arts and arts education practices, this interdisciplinary collaborative study examines the translation of recent neuromusical research into the public domain, one of the main generators of neuromyths. We review the claimed benefits of musical engagement to other domains, and the ways that researchers discuss these claims. To accomplish this, we first provide a thematic analysis of the kinds of claims that are made in research texts. We analysed 76 review articles published between 2006 and 2016 that both concern brain imaging studies in humans and involve music. The analysis highlights the ways that researchers qualify the potential benefits of music. Second, we explore the ways that neuroscientists report their results to the public and the ways that these results are taken into public discourse. In order to do this we analysed the homepages of the researchers who published at least 2 review articles in our dataset, focussing on the media linked to their homepages. We also explored over 100 websites that mention the benefits of music and also refer to brain imaging research. These overviews allow us to show that the same criteria commonly applied in research are almost never applied in public discourse. We conclude that there is an ethical imperative for researchers to take care in presenting the research results of brain imaging studies to the larger public, and furthermore argue that there is an ethical obligation for researchers to speak out against misuse of research findings.

The impact of traditional neuroimaging methods on the spatial localization of cortical areas

Localizing human brain functions is a long-standing goal in systems neuroscience. Toward this goal, neuroimaging studies have traditionally used volume-based smoothing, registered data to volume-based standard spaces, and reported results relative to volume-based parcellations. A novel 360-area surface-based cortical parcellation was recently generated using multimodal data from the Human Connectome Project, and a volume-based version of this parcellation has frequently been requested for use with traditional volume-based analyses. However, given the major methodological differences between traditional volumetric and Human Connectome Project-style processing, the utility and interpretability of such an altered parcellation must first be established. By starting from automatically generated individual-subject parcellations and processing them with different methodological approaches, we show that traditional processing steps, especially volume-based smoothing and registration, substantially degrade cortical area localization compared with surface-based approaches. We also show that surface-based registration using features closely tied to cortical areas, rather than to folding patterns alone, improves the alignment of areas, and that the benefits of high-resolution acquisitions are largely unexploited by traditional volume-based methods. Quantitatively, we show that the most common version of the traditional approach has spatial localization that is only 35% as good as the best surface-based method as assessed using two objective measures (peak areal probabilities and "captured area fraction" for maximum probability maps). Finally, we demonstrate that substantial challenges exist when attempting to accurately represent volume-based group analysis results on the surface, which has important implications for the interpretability of studies, both past and future, that use these volume-based methods.

Functional MRI of brain physiology in aging and neurodegenerative diseases

Brain aging and associated neurodegeneration constitute a major societal challenge as well as one for the neuroimaging community. A full understanding of the physiological mechanisms underlying neurodegeneration still eludes medical researchers, fuelling the development of in vivo neuroimaging markers. Hence it is increasingly recognized that our understanding of neurodegenerative processes likely will depend upon the available information provided by imaging techniques. At the same time, the imaging techniques are often developed in response to the desire to observe certain physiological processes. In this context, functional MRI (fMRI), which has for decades provided information on neuronal activity, has evolved into a large family of techniques well suited for in vivo observations of brain physiology. Given the rapid technical advances in fMRI in recent years, this review aims to summarize the physiological basis of fMRI observations in healthy aging as well as in age-related neurodegeneration. This review focuses on in-vivo human brain imaging studies in this review and on disease features that can be imaged using fMRI methods. In addition to providing detailed literature summaries, this review also discusses future directions in the study of brain physiology using fMRI in the clinical setting.

Missing motoric manipulations: rethinking the imaging of the ventral striatum and dopamine in human reward.

Human neuroimaging studies of natural rewards and drugs of abuse frequently assay the brain's response to stimuli that, through Pavlovian learning, have come to be associated with a drug's rewarding properties. This might be characterized as a 'sensorial' view of the brain's reward system, insofar as the paradigms are designed to elicit responses to a reward's (drug's) sight, aroma, or flavor. A different field of research nevertheless suggests that the mesolimbic dopamine system may also be critically involved in the motor behaviors provoked by such stimuli. This brief review and commentary surveys some of the preclinical data supporting this more "efferent" (motoric) view of the brain's reward system, and discusses what such findings might mean for how human brain imaging studies of natural rewards and drugs of abuse are designed.

An introduction to psychedelic neuroscience.

This chapter is an introduction to the volume "Psychedelic Neuroscience" of Elsevier's Progress in Brain Research addressing the neurobiological mechanisms of psychedelic drugs, the resulting changes in brain activity and integration of traditional viewpoints. As the field is relatively new, there are discrepancies in the literature related to classification, composition and effects of the various psychedelics. Currently, psychedelics are grouped according to their neuro-receptor affinities into classic and atypical psychedelics, each with individual treatment potentials and abilities to elicit potent acute experiences and long-lasting changes in neurobiology through concurrent activation of several neuromodulatory systems. There is disparity in psychedelic brain imaging studies, delineating what is neural activity and hemodynamic needs further investigation for us to understand the brain "state" changes that are apparent. The psychedelic brain "state" is often compared to acute psychosis and we review the psychedelic animal models of psychosis and human brain imaging studies and contrast these to psychosis. The term "psychedelic" means mind-revealing and psychedelics have exceptional anti-amnesic effects and are able to "make conscious" that which was previously unconscious through changes in brain "state," but also there is growing evidence which demonstrates the role of epigenetic mechanisms. This supports traditional therapeutic use of psychedelics to heal ancestral trauma. Details of these mechanisms are provided along with suggestions for further research.

Astrocytic l-Lactate Signaling Facilitates Amygdala-Anterior Cingulate Cortex Synchrony and Decision Making in Rats

Human brain imaging studies have revealed the anterior cingulate cortex (ACC) as a key brain region for mediating visceral-pain-cognitive interactions. Recently, we characterized impairments of long-term potentiation and spike-field coherence in the basolateral amygdala (BLA)-ACC network in association with a decision-making deficit in rats with visceral hypersensitivity (VH). Now, by combining integrative neurobiological approaches, we show that ACC-reactive astrogliosis and activity-dependent impairment of lactate release occur in VH rats. Exogenous lactate supply rescues chronic-visceral-pain-caused impairments of ACC phase locking and decision making, which can be mimicked by optogenetic activation of ACC astrocytes. Large-scale electrophysiological recordings in free-moving animals during a decision-making task indicate that optogenetic astrocytic activation improves decision-making performance and engages ACC phase locking and BLA-to-ACC information flow. Collectively, these observations support the idea of an "astrocyte-neuron l-lactate shuttle" and suggest that targeting astrocytes may help with cognitive dysfunctions under chronic visceral pain.

Subchronic glucocorticoids, glutathione depletion and a postpartum model elevate monoamine oxidase a activity in the prefrontal cortex of rats

Recent human brain imaging studies implicate dysregulation of monoamine oxidase-A (MAO-A), in particular in the prefrontal cortex (PFC) and anterior cingulate cortex (ACC), in the development of major depressive disorder (MDD). This study investigates the influence of four alterations underlying important pathologies of MDD, namely, chronic elevation of glucocorticoid levels, glutathione depletion, changes in female gonadal sex hormones and serotonin concentration fluctuation, on MAO-A and MAO-B activities in rats. Young adult rats exposed chronically to the synthetic glucocorticoid dexamethasone at 0, 0.05, 0.5, and 2.0mg/kg/day (osmotic minipumps) for eight days showed significant dose-dependent increases in activities of MAO-A in PFC (+17%, p<0.001) and ACC (+9%, p<0.01) and MAO-B in PFC (+14%, p<0.001) and increased serotonin turnover in the PFC (+31%, p<0.01), not accounted for by dexamethasone-induced changes in serotonin levels, since neither serotonin depletion nor supplementation affected MAO-A activity. Sub-acute depletion of the major antioxidant glutathione by diethyl maleate (5mmol/kg, i.p.) for three days, which resulted in a 36% loss of glutathione in PFC (p=0.0005), modestly, but significantly, elevated activities of MAO-A in PFC and MAO-B in PFC, ACC and hippocampus (+6–9%, p<0.05). Changes in estrogen and progesterone representing pseudopregnancy were associated with significantly elevated MAO-A activity in the ACC day 4–7 postpartum (10–18%, p<0.05 to p<0.0001) but not the PFC or hippocampus. Hence, our study provides data in support of strategies targeting glucocorticoid and glutathione systems, as well as changes in female sex hormones for normalization of MAO-A activities and thus treatment of mood disorders.

The royal road to the obesity: A case report of food addiction

Increasing prevalence of obesity in the world and increasing role of processed foods in daily life has led to become the focal point of food addiction. In recent years, the animal studies and human brain imaging studies demonstrated the neurobiological and behavioral similarities between drug addiction and food addiction. Here, we aim to present a 13-year-old, female, adolescent who applied with complaints of anger and irritability and shows serious addictive behaviors of chocolate. Our patient with increasing chocolate consumption in the last two years was using atomoxetine 60 mg/day with attention deficit hyperactivity disorder (ADHD). She gradually needs more chocolate to be satisfied. She has complained of nervousness, irritability and serious chocolate-seeking behavior during chocolate deprivation. She gained weight in proportion to the increase in chocolate consumption. Her daily diet was increasingly deteriorated. We used behavioral approach and sertraline in her treatment and were observed that partially benefit from treatment. Combined data from retrospective accounts of adults and prospective observations of youth indicates that juveniles with ADHD are at increased risk for cigarette smoking and substance abuse and behavioral addiction such as Internet addiction, gambling and sex addiction during adolescence. Recognition of the food addiction is important to fight against obesity, strengthening the treatment of choice in the food addiction and take political measures against food addiction are becoming inevitable.Disclosure of interestThe authors have not supplied their declaration of competing interest.

Serotonin receptors in depression: from A to B.

The role of serotonin in major depressive disorder (MDD) is the focus of accumulating clinical and preclinical research. The results of these studies reflect the complexity of serotonin signaling through many receptors, in a large number of brain regions, and throughout the lifespan. The role of the serotonin transporter in MDD has been highlighted in gene by environment association studies as well as its role as a critical player in the mechanism of the most effective antidepressant treatments – selective serotonin reuptake inhibitors. While the majority of the 15 known receptors for serotonin have been implicated in depression or depressive-like behavior, the serotonin 1A (5-HT 1A) and 1B (5-HT 1B) receptors are among the most studied. Human brain imaging and genetic studies point to the involvement of 5-HT 1A and 5-HT 1B receptors in MDD and the response to antidepressant treatment. In rodents, the availability of tissue-specific and inducible knockout mouse lines has made possible the identification of the involvement of 5-HT 1A and 5-HT 1B receptors throughout development and in a cell-type specific manner. This, and other preclinical pharmacology work, shows that autoreceptor and heteroreceptor populations of these receptors have divergent roles in modulating depression-related behavior as well as responses to antidepressants and also have different functions during early postnatal development compared to during adulthood.

Predicting CYP2D6 phenotype from resting brain perfusion images by gradient boosting

The cytochrome P450 enzyme 2D6 is involved in the metabolism of 20% of all commonly used drugs, including many psychotropic drugs and CNS-active substances. CYP2D6 is among the CYP enzymes with the highest expression levels in the brain, suggesting a role in the local brain metabolism of psychotropic drugs and the existence of endogenous substrates. The genetic polymorphism of CYP2D6, which causes individual differences in activity levels of the enzyme, has also been characterized functionally in human brain imaging studies. Here we explore the feasibility of predicting CYP2D6 phenotype using component-wise gradient boosting on fMRI resting brain perfusion images. The images belonged to subjects showing a range of genetic CYP2D6 variants. We achieved sensitivity and specificity values between 85% and 87% for the classification of ultrarapid metabolisers, and between 71% and 79% for poor metabolisers. An extension of the boosting algorithm, developed to improve the clinical plausibility of the inherently sparse models, produced enhanced models in agreement with the results of previous studies, showing some brain regions as positively associated with genotypic variation, most prominently in the prefrontal white matter and the corpus callosum. With further development, such a probabilistic method might constitute a valuable, non-invasive alternative to actual genotyping.

Making the Right Connections

Recent years have seen the application of increasingly powerful transgenic, optogenetic, and chemogenetic methodologies in rodents. Armed with these tools, many studies have shown how perturbations of specific subregions of the rodent frontal cortex can elicit circumscribed behavioral phenotypes that resemble key aspects of psychiatric disorders. For example, the rodent frontal cortex can be broadly divided into motor, medial prefrontal cortex (mPFC), and orbitofrontal cortex (OFC) divisions; the mPFC can be further subdivided into prelimbic (PL), infralimbic (IL), and cingulate (Cg) cortices, while the OFC comprises the medial orbital (MO) and ventral and lateral orbital (VOLO) cortices. Recent studies have specifically linked changes in MO and VOLO activity to the expression of repetitive grooming behavior, which may model aspects of obsessive-compulsive disorder ( 1 Ahmari S.E. Spellman T. Douglass N.L. Kheirbek M.A. Simpson H.B. Deisseroth K. et al. Repeated cortico-striatal stimulation generates persistent OCD-like behavior. Science. 2013; 340: 1234-1239 Crossref PubMed Scopus (325) Google Scholar , 2 Burguiere E. Monteiro P. Feng G. Graybiel A.M. Optogenetic stimulation of lateral orbitofronto-striatal pathway suppresses compulsive behaviors. Science. 2013; 340: 1243-1246 Crossref PubMed Scopus (294) Google Scholar ), while many other studies have linked subregions of the mPFC to aspects of social behavior, cognitive flexibility, working memory, chronic pain, and anxiety. At the same time, a plethora of human brain imaging studies have implicated frontal cortical networks in a variety of neuropsychiatric disorders. Notably, the subcallosal cingulate gyrus—which includes Brodmann area 25 (a25), parts of area 24 (a24), and area 32 (a32)—has been a focus of attention since it was found that deep brain stimulation of this region can alleviate treatment-resistant depression in some patients ( 3 Hamani C. Mayberg H. Stone S. Laxton A. Haber S. Lozano A.M. The subcallosal cingulate gyrus in the context of major depression. Biol Psychiatry. 2011; 69: 301-308 Abstract Full Text Full Text PDF PubMed Scopus (331) Google Scholar ). Taken together, these and numerous other studies across humans, nonhuman primates (NHPs), and rodents suggest that many psychiatric disorders may be reconceptualized as disorders of brain networks within which prefrontal or orbitofrontal regions represent key nodes. In this context, a central challenge is identifying homologies between cortical regions in humans and animal models, so that insights obtained via the use of cutting edge tools in animal models can be translated to those regions of the human brain that have been directly implicated in psychiatric disease. And while many modern neuroscientific tools can be most readily exploited in rodents, the rodent prefrontal and orbitofrontal cortices are vastly underdeveloped compared to their human counterparts. Therefore, NHPs represent a critical bridge that may facilitate the synthesis of findings across rodent and human studies. However, achieving this synthesis has been challenging. In particular, there are many possible ways to identify corresponding brain regions across species [e.g., based on cytoarchitectonic features and corticocortical connectivity ( 4 Ongur D. Price J.L. The organization of networks within the orbital and medial prefrontal cortex of rats, monkeys and humans. Cereb Cortex. 2000; 10: 206-219 Crossref PubMed Scopus (2048) Google Scholar ) or patterns of neuronal activity and behavioral functions ( 5 Seamans J.K. Lapish C.C. Durstewitz D. Comparing the prefrontal cortex of rats and primates: insights from electrophysiology. Neurotox Res. 2008; 14: 249-262 Crossref PubMed Scopus (167) Google Scholar )]. In addition, there is controversy about whether many regions of primate PFC have rodent analogs at all ( 6 Wise S.P. Forward frontal fields: phylogeny and fundamental function. Trends Neurosci. 2008; 31: 599-608 Abstract Full Text Full Text PDF PubMed Scopus (327) Google Scholar ). Circuit-Based Corticostriatal Homologies Between Rat and PrimateBiological PsychiatryVol. 80Issue 7PreviewUnderstanding the neural mechanisms of psychiatric disorders requires the use of rodent models; however, frontal-striatal homologies between rodents and primates are unclear. In contrast, within the striatum, the shell of the nucleus accumbens, the hippocampal projection zone, and the amygdala projection zone (referred to as the striatal emotion processing network [EPN]) are conserved across species. We used the relationship between the EPN and projections from the anterior cingulate cortex (ACC) and orbitofrontal cortex (OFC) to assess network similarities across rats and monkeys. Full-Text PDF

Cortical Plasticity and Olfactory Function in Early Blindness.

Over the last decade, functional brain imaging has provided insight to the maturation processes and has helped elucidate the pathophysiological mechanisms involved in brain plasticity in the absence of vision. In case of congenital blindness, drastic changes occur within the deafferented “visual” cortex that starts receiving and processing non visual inputs, including olfactory stimuli. This functional reorganization of the occipital cortex gives rise to compensatory perceptual and cognitive mechanisms that help blind persons achieve perceptual tasks, leading to superior olfactory abilities in these subjects. This view receives support from psychophysical testing, volumetric measurements and functional brain imaging studies in humans, which are presented here.

Multi-Voxel Decoding and the Topography of Maintained Information During Visual Working Memory.

The ability to maintain representations in the absence of external sensory stimulation, such as in working memory, is critical for guiding human behavior. Human functional brain imaging studies suggest that visual working memory can recruit a network of brain regions from visual to parietal to prefrontal cortex. In this review, we focus on the maintenance of representations during visual working memory and discuss factors determining the topography of those representations. In particular, we review recent studies employing multi-voxel pattern analysis (MVPA) that demonstrate decoding of the maintained content in visual cortex, providing support for a “sensory recruitment” model of visual working memory. However, there is some evidence that maintained content can also be decoded in areas outside of visual cortex, including parietal and frontal cortex. We suggest that the ability to maintain representations during working memory is a general property of cortex, not restricted to specific areas, and argue that it is important to consider the nature of the information that must be maintained. Such information-content is critically determined by the task and the recruitment of specific regions during visual working memory will be both task- and stimulus-dependent. Thus, the common finding of maintained information in visual, but not parietal or prefrontal, cortex may be more of a reflection of the need to maintain specific types of visual information and not of a privileged role of visual cortex in maintenance.

Neurobiología de la depresión mayor y de su tratamiento farmacológico

Resumen Introducción. La depresión mayor (DM) se debe a la interacción de factores ambientales, genéticos y epigenéticos, que atenúan la transmisión monoaminérgica en el cerebro. Sin embargo, poco se conoce sobre los mecanismos fisiopatológicos que subyacen a ella. Objetivo. Proponer una visión integral sobre la fisiopatología de la DM y los mecanismos de acción de los fármacos antidepresivos. Método. Se empleó la base PubMed para la búsqueda bibliográfica. La mayoría son investigaciones experimentales y estudios de genética molecular o de imágenes cerebrales en humanos. Resultados. La DM se asocia con: i) menor volumen de la corteza cingulada anterior; ii) hiper-metabolismo del área Cg25; iii) menor expresión del receptor 5-HT1A; iv) mayor expresión de la monoamino oxidasa A. Algunos polimorfismos están asociados a la fisiopatología. El estrés crónico reduce la expresión del 5-HT1A. Los antidepresivos atenúan el hiper-metabolismo del área Cg25, estimulan la neurogénesis y activan la vía del AMPc. Encontramos que la imipramina aumenta y reduce la expresión de Gαs y Gαz, respectivamente (datos sin publicar). Discusión y conclusión. El déficit en la transmisión monoaminérgica puede deberse a: i) el polimorfismo G1463A en el gen de la enzima hTPH2 que reduce la síntesis de serotonina; ii) el polimorfismo C(-1019)G en el gen del receptor 5-HT1A, aumentando su transcripción en el rafé e implicando menor liberación del neurotransmisor; iii) mayor degradación de las monoaminas. La menor expresión del receptor 5-HT1A se discute considerando su acción inhibitoria en la corteza prefrontal. Los cambios en la expresión de Gαs y Gαz coinciden con la estimulación de la vía del AMPc.

A shared neural network for emotional expression and perception: an anatomical study in the macaque monkey.

Over the past two decades, the insula has been described as the sensory “interoceptive cortex”. As a consequence, human brain imaging studies have focused on its role in the sensory perception of emotions. However, evidence from neurophysiological studies in non-human primates have shown that the insula is also involved in generating emotional and communicative facial expressions. In particular, a recent study demonstrated that electrical stimulation of the mid-ventral sector of the insula evoked affiliative facial expressions. The present study aimed to describe the cortical connections of this “affiliative field”. To this aim, we identified the region with electrical stimulation and injected neural tracers to label incoming and outgoing projections. Our results show that the insular field underlying emotional expression is part of a network involving specific frontal, cingulate, temporal, and parietal areas, as well as the amygdala, the basal ganglia, and thalamus, indicating that this sector of the insula is a site of integration of motor, emotional, sensory and social information. Together with our previous functional studies, this result challenges the classic view of the insula as a multisensory area merely reflecting bodily and internal visceral states. In contrast, it supports an alternative perspective; that the emotional responses classically attributed to the insular cortex are endowed with an enactive component intrinsic to each social and emotional behavior.

The effect of striatal dopamine depletion on striatal and cortical glutamate: A mini-review

Understanding the interplay between the neurotransmitters dopamine and glutamate in the striatum has become the highlight of several theories of neuropsychiatric illnesses, such as schizophrenia. Using in vivo brain imaging in humans, alterations in dopamine and glutamate concentrations have been observed in several neuropsychiatric disorders. However, it is unclear a priori how alterations in striatal dopamine should modulate glutamate concentrations in the basal ganglia. In this selective mini-review, we examine the consequence of reducing striatal dopamine functioning on glutamate concentrations in the striatum and cortex; regions of interest heavily examined in the human brain imaging studies. We examine the predictions of the classical model of the basal ganglia, and contrast it with findings in humans and animals. The review concludes that chronic dopamine depletion (>4months) produces decreases in striatal glutamate levels which are consistent with the classical model of the basal ganglia. However, acute alterations in striatal dopamine functioning, specifically at the D2 receptors, may produce opposite affects. This has important implications for models of the basal ganglia and theorizing about neurochemical alterations in neuropsychiatric diseases. Moreover, these findings may help guide a priori hypotheses for 1H-MRS studies measuring glutamate changes given alterations in dopaminergic functioning in humans.

A diffusion tensor MRI atlas of the postmortem rhesus macaque brain

The rhesus macaque (Macaca mulatta) is the most widely used nonhuman primate for modeling the structure and function of the brain. Brain atlases, and particularly those based on magnetic resonance imaging (MRI), have become important tools for understanding normal brain structure, and for identifying structural abnormalities resulting from disease states, exposures, and/or aging. Diffusion tensor imaging (DTI)-based MRI brain atlases are widely used in both human and macaque brain imaging studies because of the unique contrasts, quantitative diffusion metrics, and diffusion tractography that they can provide. Previous MRI and DTI atlases of the rhesus brain have been limited by low contrast and/or low spatial resolution imaging. Here we present a microscopic resolution MRI/DTI atlas of the rhesus brain based on 10 postmortem brain specimens. The atlas includes both structural MRI and DTI image data, a detailed three-dimensional segmentation of 241 anatomic structures, diffusion tractography, cortical thickness estimates, and maps of anatomic variability among atlas specimens. This atlas incorporates many useful features from previous work, including anatomic label nomenclature and ontology, data orientation, and stereotaxic reference frame, and further extends prior analyses with the inclusion of high-resolution multi-contrast image data.