Distinct Symptom-Specific Treatment Targets for Circuit-Based Neuromodulation

OBJECTIVE

Treatment of different depression symptoms may require different brain stimulation targets with different underlying brain circuits. The authors sought to identify such targets, which could improve the efficacy of therapeutic brain stimulation and facilitate personalized therapy.

METHODS

The authors retrospectively analyzed two independent cohorts of patients who received left prefrontal transcranial magnetic stimulation (TMS) for treatment of depression (discovery sample, N=30; active replication sample, N=81; sham replication sample, N=87). Each patient's TMS site was mapped to underlying brain circuits using functional connectivity MRI from a large connectome database (N=1,000). Circuits associated with improvement in each depression symptom were identified and then clustered based on similarity. The authors tested for reproducibility across data sets and whether symptom-specific targets derived from one data set could predict symptom improvement in the other independent cohort.

RESULTS

The authors identified two distinct circuit targets effective for two discrete clusters of depressive symptoms. Dysphoric symptoms, such as sadness and anhedonia, responded best to stimulation of one circuit, while anxiety and somatic symptoms responded best to stimulation of a different circuit. These circuit maps were reproducible, predicted symptom improvement in independent patient cohorts, and were specific to active compared with sham stimulation. The maps predicted symptom improvement in an exploratory analysis of stimulation sites from 14 clinical TMS trials.

CONCLUSIONS

Distinct clusters of depressive symptoms responded better to different TMS targets across independent retrospective data sets. These symptom-specific targets can be prospectively tested in a randomized clinical trial. This data-driven approach for identifying symptom-specific targets may prove useful for other disorders and facilitate personalized neuromodulation therapy.

Obese patients after gastric bypass surgery have lower brain-hedonic responses to food than after gastric banding

OBJECTIVES

Roux-en-Y gastric bypass (RYGB) has greater efficacy for weight loss in obese patients than gastric banding (BAND) surgery. We hypothesise that this may result from different effects on food hedonics via physiological changes secondary to distinct gut anatomy manipulations.

DESIGN

We used functional MRI, eating behaviour and hormonal phenotyping to compare body mass index (BMI)-matched unoperated controls and patients after RYGB and BAND surgery for obesity.

RESULTS

Obese patients after RYGB had lower brain-hedonic responses to food than patients after BAND surgery. RYGB patients had lower activation than BAND patients in brain reward systems, particularly to high-calorie foods, including the orbitofrontal cortex, amygdala, caudate nucleus, nucleus accumbens and hippocampus. This was associated with lower palatability and appeal of high-calorie foods and healthier eating behaviour, including less fat intake, in RYGB compared with BAND patients and/or BMI-matched unoperated controls. These differences were not explicable by differences in hunger or psychological traits between the surgical groups, but anorexigenic plasma gut hormones (GLP-1 and PYY), plasma bile acids and symptoms of dumping syndrome were increased in RYGB patients.

CONCLUSIONS

The identification of these differences in food hedonic responses as a result of altered gut anatomy/physiology provides a novel explanation for the more favourable long-term weight loss seen after RYGB than after BAND surgery, highlighting the importance of the gut-brain axis in the control of reward-based eating behaviour.

Treatment resistant schizophrenia: Clinical, biological, and therapeutic perspectives

Treatment resistant schizophrenia (TRS) refers to the significant proportion of schizophrenia patients who continue to have symptoms and poor outcomes despite treatment. While many definitions of TRS include failure of two different antipsychotics as a minimum criterion, the wide variability in inclusion criteria has challenged the consistency and reproducibility of results from studies of TRS. We begin by reviewing the clinical, neuroimaging, and neurobiological characteristics of TRS. We further review the current treatment strategies available, addressing clozapine, the first-line pharmacological agent for TRS, as well as pharmacological and non-pharmacological augmentation of clozapine including medication combinations, electroconvulsive therapy, repetitive transcranial magnetic stimulation, deep brain stimulation, and psychotherapies. We conclude by highlighting the most recent consensus for defining TRS proposed by the Treatment Response and Resistance in Psychosis Working Group, and provide our overview of future perspectives and directions that could help advance the field of TRS research, including the concept of TRS as a potential subtype of schizophrenia.

Association of Elevated Reward Prediction Error Response With Weight Gain in Adolescent Anorexia Nervosa

OBJECTIVE

Anorexia nervosa is a psychiatric disorder of unknown etiology. Understanding associations between behavior and neurobiology is important in treatment development. Using a novel monetary reward task during functional magnetic resonance brain imaging, the authors tested how brain reward learning in adolescent anorexia nervosa changes with weight restoration.

METHOD

Female adolescents with anorexia nervosa (N=21; mean age, 16.4 years [SD=1.9]) underwent functional MRI (fMRI) before and after treatment; similarly, healthy female control adolescents (N=21; mean age, 15.2 years [SD=2.4]) underwent fMRI on two occasions. Brain function was tested using the reward prediction error construct, a computational model for reward receipt and omission related to motivation and neural dopamine responsiveness.

RESULTS

Compared with the control group, the anorexia nervosa group exhibited greater brain response 1) for prediction error regression within the caudate, ventral caudate/nucleus accumbens, and anterior and posterior insula, 2) to unexpected reward receipt in the anterior and posterior insula, and 3) to unexpected reward omission in the caudate body. Prediction error and unexpected reward omission response tended to normalize with treatment, while unexpected reward receipt response remained significantly elevated. Greater caudate prediction error response when underweight was associated with lower weight gain during treatment. Punishment sensitivity correlated positively with ventral caudate prediction error response.

CONCLUSIONS

Reward system responsiveness is elevated in adolescent anorexia nervosa when underweight and after weight restoration. Heightened prediction error activity in brain reward regions may represent a phenotype of adolescent anorexia nervosa that does not respond well to treatment. Prediction error response could be a neurobiological marker of illness severity that can indicate individual treatment needs.

Hyperactivity and Reduced Activation of Anterior Hippocampus in Early Psychosis

OBJECTIVE

In schizophrenia, the anterior hippocampus is hyperactive and shows reduced task-related recruitment, but the relationship between these two findings is unclear. The authors tested the hypothesis that hyperactivity impairs recruitment of the anterior hippocampus during scene processing.

METHODS

Functional MRI data from 45 early-psychosis patients and 35 demographically matched healthy control subjects were analyzed using a block-design 1-back scene-processing task. Hippocampal activation in response to scenes and faces compared with scrambled images was measured. In a subset of 20 early-psychosis patients and 31 healthy control subjects, baseline hippocampal activity using cerebral blood volume (CBV) mapping was measured. Correlation analyses were used to examine the association between baseline hippocampal activity and task-related hippocampal activation.

RESULTS

Activation of the anterior hippocampus was significantly reduced and CBV in the anterior hippocampus was significantly increased in the early stages of psychosis. Increased CBV in early-psychosis patients was inversely correlated with task-related activation during scene processing in the anterior hippocampus.

CONCLUSIONS

Anterior hippocampal hyperactivity in early-psychosis patients appears to limit effective recruitment of this region during task performance. These findings provide novel support for the anterior hippocampus as a therapeutic target in the treatment of cognitive deficits in psychosis.

An Electroencephalography Connectomic Profile of Posttraumatic Stress Disorder

OBJECTIVE

The authors sought to identify brain regions whose frequency-specific, orthogonalized resting-state EEG power envelope connectivity differs between combat veterans with posttraumatic stress disorder (PTSD) and healthy combat-exposed veterans, and to determine the behavioral correlates of connectomic differences.

METHODS

The authors first conducted a connectivity method validation study in healthy control subjects (N=36). They then conducted a two-site case-control study of veterans with and without PTSD who were deployed to Iraq and/or Afghanistan. Healthy individuals (N=95) and those meeting full or subthreshold criteria for PTSD (N=106) underwent 64-channel resting EEG (eyes open and closed), which was then source-localized and orthogonalized to mitigate effects of volume conduction. Correlation coefficients between band-limited source-space power envelopes of different regions of interest were then calculated and corrected for multiple comparisons. Post hoc correlations of connectomic abnormalities with clinical features and performance on cognitive tasks were conducted to investigate the relevance of the dysconnectivity findings.

RESULTS

Seventy-four brain region connections were significantly reduced in PTSD (all in the eyes-open condition and predominantly using the theta carrier frequency). Underconnectivity of the orbital and anterior middle frontal gyri were most prominent. Performance differences in the digit span task mapped onto connectivity between 25 of the 74 brain region pairs, including within-network connections in the dorsal attention, frontoparietal control, and ventral attention networks.

CONCLUSIONS

Robust PTSD-related abnormalities were evident in theta-band source-space orthogonalized power envelope connectivity, which furthermore related to cognitive deficits in these patients. These findings establish a clinically relevant connectomic profile of PTSD using a tool that facilitates the lower-cost clinical translation of network connectivity research.

The Physiology of Female Sexual Function and the Pathophysiology of Female Sexual Dysfunction (Committee 13A)

INTRODUCTION

The article consists of six sections written by separate authors that review female genital anatomy, the physiology of female sexual function, and the pathophysiology of female sexual dysfunction but excluding hormonal aspects.

AIM

To review the physiology of female sexual function and the pathophysiology of female sexual dysfunction especially since 2010 and to make specific recommendations according to the Oxford Centre for evidence based medicine (2009) "levels of evidence" wherever relevant.

CONCLUSION

Recommendations were made for particular studies to be undertaken especially in controversial aspects in all six sections of the reviewed topics. Despite numerous laboratory assessments of female sexual function, genital assessments alone appear insufficient to characterise fully the complete sexual response.

Cerebrovascular Events in Systemic Lupus Erythematosus: Diagnosis and Management

Stroke is a major cause of morbidity, mortality and disability in systemic lupus erythematosus (SLE). Patients with SLE have a two-fold increase in the risk of stroke with younger patients (ie, less than 50 years of age) having an ever-higher risk (up to 10-fold). Although the prognosis of SLE has improved, mortality due to cerebrovascular events (CVE) remains unchanged. Cerebrovascular disease may be directly attributed to the disease per se, as a manifestation of neuropsychiatric SLE, or be the result of traditional cardiovascular risk factors accompanying the disease. Elucidation of the underlying mechanism(s) of CVE is essential as it may guide the type of therapy (ie, antithrombotic or anticoagulant therapy versus immunosuppressive). Strokes attributed to lupus usually occur early in the course of the disease and are often accompanied by evidence of activity in other organs; those related to antiphospholipid antibodies can occur at any time, in patients with either active or inactive SLE. In this review, we discuss the epidemiology, work-up, management and primary prevention of CVE in patients with lupus. In view of the effectiveness of thrombolysis, physicians need to educate lupus patients and their families for the early recognition of the signs of stroke and the need to seek prompt attention. To this end acronyms, such as FAST (Facial drooping, Arm weakness, Speech difficulties and Time to call emergency service) can be used as a mnemonic to help detect and enhance responsiveness to the needs of a person having a stroke.

Behavioral and neural inhibitory control moderates the effects of reward sensitivity on adolescent substance use

The developmental period of adolescence is characterized by increasing incidence of health risk behaviors, including experimenting with drugs and alcohol. We examined how inhibitory control interacts with reward and punishment sensitivity to predict substance use severity and age of onset among early adolescents. The sample was comprised of 157 early adolescents (13-14 years of age, 52% male). Composite scores for behavioral activation system (BAS), behavioral inhibition system (BIS), and substance use severity and onset were computed using adolescents' questionnaire data, and inhibitory control was assessed based on adolescents' behavioral performance and brain imaging during the Multiple Source Interference Task (MSIT). Structural equation modeling analyses indicated that for both behavioral performance and neural activity indicators of inhibitory control, high levels of BAS predicted earlier onset of substance use among adolescents with low inhibitory control-but not among adolescents with high inhibitory control. BIS was not related to substance use severity and onset among adolescents. The results support the theoretically hypothesized moderating role of inhibitory control and its associated frontal cortex functioning, and offer new insights into the identification of adolescents with neurobehavioral vulnerabilities to developing maladaptive substance use behaviors.

Living Brain Optical Imaging: Technology, Methods and Applications

Within the last few decades, optical imaging methods have yielded revolutionary results when applied to all parts of the central nervous system. The purpose of this review is to analyze research possibilities and limitations of several novel imaging techniques and show some of the most interesting achievements obtained by these methods. Here we covered intrinsic optical imaging, voltage-sensitive dye, photoacoustic, optical coherence tomography, near-infrared spectroscopy and some other techniques. All of them are mainly applicable for experimental neuroscience but some of them also suitable for the clinical studies.

ULTRAHIGH FIELD and ULTRAHIGH RESOLUTION fMRI

Functional magnetic resonance imaging (fMRI) has become one of the most powerful tools for investigating the human brain. Ultrahigh magnetic field (UHF) of 7 Tesla has played a critical role in enabling higher resolution and more accurate (relative to the neuronal activity) functional maps. However, even with these gains, the fMRI approach is challenged relative to the spatial scale over which brain function is organized. Therefore, going forward, significant advances in fMRI are still needed. Such advances will predominantly come from magnetic fields significantly higher than 7 Tesla, which is the most commonly used UHF platform today, and additional technologies that will include developments in pulse sequences, image reconstruction, noise suppression, and image analysis in order to further enhance and augment the gains than can be realized by going to higher magnetic fields.

Relationship of the serotonin transporter gene promoter polymorphism (5-HTTLPR) genotype and serotonin transporter binding to neural processing of negative emotional stimuli

BACKGROUND

The lower-expressing (S') alleles of the serotonin transporter (5-HTT) gene promoter polymorphism (5-HTTLPR) are linked to mood and anxiety related psychopathology. However, the specific neural mechanism through which these alleles may influence emotional and cognitive processing remains unknown. We examined the relationship between both 5-HTTLPR genotype and in vivo 5-HTT binding quantified via PET with amygdala reactivity to emotionally negative stimuli. We hypothesized that 5-HTT binding in both raphe nuclei (RN) and amygdala would be inversely correlated with amygdala reactivity, and that number of S' alleles would correlate positively with amygdala reactivity.

METHODS

In medication-free patients with current major depressive disorder (MDD; N=21), we determined 5-HTTLPR genotype, employed functional magnetic resonance imaging (fMRI) to examine amygdala responses to negative emotional stimuli, and used positron emission tomography with [(11)C]DASB to examine 5-HTT binding.

RESULTS

[(11)C]DASB binding in RN and amygdala was inversely correlated with amygdala response to negative stimuli. 5-HTTLPR S' alleles were not associated with amygdala response to negative emotional stimuli.

LIMITATIONS

Primary limitations are small sample size and lack of control group.

CONCLUSIONS

Consistent with findings in healthy volunteers, 5-HTT binding is associated with amygdala reactivity to emotional stimuli in MDD. 5-HTT binding may be a stronger predictor of emotional processing in MDD as compared with 5-HTTLPR genotype.

Predicting Brain Functional Connectivity Using Mobile Sensing

Brain circuit functioning and connectivity between specific regions allow us to learn, remember, recognize and think as humans. In this paper, we ask the question if mobile sensing from phones can predict brain functional connectivity. We study the brain resting-state functional connectivity (RSFC) between the ventromedial prefrontal cortex (vmPFC) and the amygdala, which has been shown by neuroscientists to be associated with mental illness such as anxiety and depression. We discuss initial results and insights from the NeuroSence study, an exploratory study of 105 first year college students using neuroimaging and mobile sensing across one semester. We observe correlations between several behavioral features from students' mobile phones and connectivity between vmPFC and amygdala, including conversation duration (r=0.365, p<0.001), sleep onset time (r=0.299, p<0.001) and the number of phone unlocks (r=0.253, p=0.029). We use a support vector classifier and 10-fold cross validation and show that we can classify whether students have higher (i.e., stronger) or lower (i.e., weaker) vmPFC-amygdala RSFC purely based on mobile sensing data with an F1 score of 0.793. To the best of our knowledge, this is the first paper to report that resting-state brain functional connectivity can be predicted using passive sensing data from mobile phones.

A NEW REGISTRATION METHOD BASED ON LOG-EUCLIDEAN TENSOR METRICS AND ITS APPLICATION TO GENETIC STUDIES

In structural brain MRI, group differences or changes in brain structures can be detected using Tensor-Based Morphometry (TBM). This method consists of two steps: (1) a non-linear registration step, that aligns all of the images to a common template, and (2) a subsequent statistical analysis. The numerous registration methods that have recently been developed differ in their detection sensitivity when used for TBM, and detection power is paramount in epidemological studies or drug trials. We therefore developed a new fluid registration method that computes the mappings and performs statistics on them in a consistent way, providing a bridge between TBM registration and statistics. We used the Log-Euclidean framework to define a new regularizer that is a fluid extension of the Riemannian elasticity, which assures diffeomorphic transformations. This regularizer constrains the symmetrized Jacobian matrix, also called the deformation (or strain) tensor. We applied our method to an MRI dataset from 40 fraternal and identical twins, to revealed voxelwise measures of average volumetric differences in brain structure for subjects with different degrees of genetic resemblance.

Normalization of Fronto-Parietal Activation by Cognitive-Behavioral Therapy in Unmedicated Pediatric Patients With Anxiety Disorders

OBJECTIVE

Anxiety disorders are prevalent among youths and are often highly impairing. Cognitive-behavioral therapy (CBT) is an effective first-line treatment. The authors investigated the brain mechanisms associated with symptom change following CBT.

METHODS

Unmedicated youths diagnosed with an anxiety disorder underwent 12 weeks of CBT as part of two randomized clinical trials testing the efficacy of adjunctive computerized cognitive training. Across both trials, participants completed a threat-processing task during functional MRI before and after treatment. Age-matched healthy comparison youths completed two scans over the same time span. The mean age of the samples was 13.20 years (SD=2.68); 41% were male (youths with anxiety disorders, N=69; healthy comparison youths, N=62). An additional sample including youths at temperamental risk for anxiety (N=87; mean age, 10.51 years [SD=0.43]; 41% male) was utilized to test the stability of anxiety-related neural differences in the absence of treatment. Whole-brain regional activation changes (thresholded at p<0.001) were examined using task-based blood-oxygen-level-dependent response.

RESULTS

Before treatment, patients with an anxiety disorder exhibited altered activation in fronto-parietal attention networks and limbic regions relative to healthy comparison children across all task conditions. Fronto-parietal hyperactivation normalized over the course of treatment, whereas limbic responses remained elevated after treatment. In the at-risk sample, overlapping clusters emerged between regions showing stable associations with anxiety over time and regions showing treatment-related changes.

CONCLUSIONS

Activation in fronto-parietal networks may normalize after CBT in unmedicated pediatric anxiety patients. Limbic regions may be less amenable to acute CBT effects. Findings from the at-risk sample suggest that treatment-related changes may not be attributed solely to the passage of time.

A Just Standard: The Ethical Management of Incidental Findings in Brain Imaging Research

Neuroimaging research regularly yields "incidental findings": observations of potential clinical significance in healthy volunteers or patients, but which are unrelated to the purpose or variables of the study.

Recent Developments in Diffusion Tensor Imaging of Brain

Magnetic resonance imaging (MRI) has come to be known as a unique radiological imaging modality because of its ability to perform tomographic imaging of body without the use of any harmful ionizing radiation. The radiologists use MRI to gain insight into the anatomy of organs, including the brain, while biomedical researchers explore the modality to gain better understanding of the brain structure and function. However, due to limited resolution and contrast, the conventional MRI fails to show the brain microstructure. Diffusion tensor imaging (DTI) harnesses the power of conventional MRI to deduce the diffusion dynamics of water molecules within the tissue and indirectly create a three-dimensional sketch of the brain anatomy. DTI enables visualization of brain tissue microstructure, which is extremely helpful in understanding various neuropathologies and neurodegenerative disorders. In this review, we briefly discuss the background and operating principles of DTI, followed by current trends in DTI applications for biomedical and clinical investigation of various brain diseases and disorders.

Brain Regions Identified as Being Associated with Verbal Reasoning through the Use of Imaging Regression via Internal Variation

Brain-imaging data have been increasingly used to understand intellectual disabilities. Despite significant progress in biomedical research, the mechanisms for most of the intellectual disabilities remain unknown. Finding the underlying neurological mechanisms has been proved difficult, especially in children due to the rapid development of their brains. We investigate verbal reasoning, which is a reliable measure of individuals' general intellectual abilities, and develop a class of high-order imaging regression models to identify brain subregions which might be associated with this specific intellectual ability. A key novelty of our method is to take advantage of spatial brain structures, and specifically the piecewise smooth nature of most imaging coefficients in the form of high-order tensors. Our approach provides an effective and urgently needed method for identifying brain subregions potentially underlying certain intellectual disabilities. The idea behind our approach is a carefully constructed concept called Internal Variation (IV). The IV employs tensor decomposition and provides a computationally feasible substitution for Total Variation (TV), which has been considered in the literature to deal with similar problems but is problematic in high order tensor regression. Before applying our method to analyze the real data, we conduct comprehensive simulation studies to demonstrate the validity of our method in imaging signal identification. Then, we present our results from the analysis of a dataset based on the Philadelphia Neurodevelopmental Cohort for which we preprocessed the data including re-orienting, bias-field correcting, extracting, normalizing and registering the magnetic resonance images from 978 individuals. Our analysis identified a subregion across the cingulate cortex and the corpus callosum as being associated with individuals' verbal reasoning ability, which, to the best of our knowledge, is a novel region that has not been reported in the literature. This finding is useful in further investigation of functional mechansims for verbal reasoning.

Altruistic Social Activity, Depressive Symptoms, and Brain Regional Gray Matter Volume: Voxel-Based Morphometry Analysis from 8695 Old Adults

Altruistic social activity, such as giving support to others, has shown protective benefits on dementia risk and cognitive decline. However, the pathological mechanism is unclear. In the present study, we investigated the association between altruistic social activity and brain regional gray matter. Furthermore, to explore the psychological interplay in altruistic social activity, we tested mediating effect of depressive symptoms on brain regional gray matter. We performed a cross-sectional Voxel-Based Morphology (VBM) analysis including 8695 old adults (72.9±6.1 years) from Japan Prospective Studies Collaboration for Aging and Dementia (JPSC-AD) Cohort. We measured altruistic social activities by self-report questionnaire, depressive symptoms by Geriatric Depression Scale (GDS)-short version. We employed the whole-brain VBM method to detect relevant structural properties related to altruistic social activity. We then performed multiple regression models to detect the mediating effect of depressive symptoms on particular brain regional gray matter volume while adjusting possible physical and social lifestyle covariables. We found that altruistic social activity is associated with larger gray matter volume in posterior insula, middle cingulate gyrus, hippocampus, thalamus, superior temporal gyrus, anterior orbital gyrus, and middle occipital gyrus. Depressive symptoms mediated over 10% on altruistic social activity and hippocampus volume, over 20% on altruistic social activity and cingulate gyrus volume. Our results indicated that altruistic social activity might preserve brain regional gray matter where are sensitive to aging and cognitive decline. Meanwhile, this association may be explained by indirect effect on depressive symptoms, suggesting that altruistic social activity may mitigate the neuropathology of dementia.

The Brain: Is it a Next Frontier to Better Understand the Regulation and Control of Hematopoiesis for Future Modulation and Treatment?

We wish to suggest the possibility there is a link between the brain and hematopoiesis in the bone marrow and that in the future it may be possible to use such information for better understanding of the regulation of hematopoiesis, and for efficacious treatment of hematopoietic disorders.

Neuroimaging findings in first unprovoked seizures: a multicentric study in tehran

OBJECTIVE

Seizure is an emergency in pediatrics. It really matters to the parents of the involved child to have information about the causes, management and prognosis. First unprovoked seizures (FUS) are seizures that occur in patients without fever, trauma or infection. Due to the rapid improvement in diagnostic techniques in the last few decades, the etiology will be revealed and this term will no longer exist. This Study was designed to evaluate brain imaging findings in FUS patients.

MATERIALS & METHODS

Ninety-six children with FUS, who were admitted in three major children's hospitals in Tehran, underwent brain imaging and were enrolled into the study. The decision about the type of imaging (CT or MRI) was based on the patient's medical and financial conditions. An expert radiologist in the field of pediatric neuroimaging interpreted the images.

RESULTS

Altogether, 27.1% had abnormal findings of which 29.2% were in the brain MRI group and 14.3% were in the brain CT scan group. Abnormal results were gliosis (10.4%), hemorrhage (4.2%), dysgenesis (2.1%), dysmyelination (7.3%), encephalomalacy (1%), atrophy (5.2%) and infarction (2.1%). In some patients, the lesions were in 2 or 3 sites and some had more than one type of lesion. There was no association between the duration, age and type of seizure and imaging abnormlities. However, we found an association between the location of the lesion and the type of seizure.

CONCLUSION

We recommend brain imaging in all patients with FUS and apart from some exceptions, brain MRI is superior to CT.

Pulsatility analysis of the circle of Willis

Purpose

To evaluate the phenomenological significance of cerebral blood pulsatility imaging in aging research.

Methods

N = 38 subjects from 20 to 72 years of age (24 females) were imaged with ultrafast MRI with a sampling rate of 100 ms and simultaneous acquisition of pulse oximetry data. Of these, 28 subjects had acceptable MRI and pulse data, with 16 subjects between 20 and 28 years of age, and 12 subjects between 61 and 72 years of age. Pulse amplitude in the circle of Willis was assessed with the recently developed method of analytic phase projection to extract blood volume waveforms.

Results

Arteries in the circle of Willis showed pulsatility in the MRI for both the young and old age groups. Pulse amplitude in the circle of Willis significantly increased with age (p = 0.01) but was independent of gender, heart rate, and head motion during MRI.

Discussion and conclusion

Increased pulse wave amplitude in the circle of Willis in the elderly suggests a phenomenological significance of cerebral blood pulsatility imaging in aging research. The physiologic origin of increased pulse amplitude (increased pulse pressure vs. change in arterial morphology vs. re-shaping of pulse waveforms caused by the heart, and possible interaction with cerebrospinal fluid pulsatility) requires further investigation.