Reprint of: Aspects of neuroticism and the amygdala: chronic tuning from motivational styles.

Recent research and theory has highlighted the dynamic nature of amygdala activation. Rather than simply being sensitive to a few limited stimulus categories, amygdala activation appears to be dependent on the goals of the perceiver. In this study, we extend this line of work by demonstrating that the means by which a person seeks to accomplish a goal also modulates the amygdala response. Specifically, we examine the modulatory effects of the aspects of neuroticism (volatility/withdrawal), a personality variable that has been linked to both generalized anxiety and differences in amygdala sensitivity. Whereas Neuroticism-Volatility is proposed to be associated with the fight-flight-freeze system (FFFS) and a sensitivity for any cues of negativity, Neuroticism-Withdrawal is proposed to be associated with the behavioral inhibition system (BIS) and a generalized tendency toward passive avoidance. During fMRI scanning, participants were presented with positive, negative, and neutral images and were required to approach (move perceptually closer) or avoid (move perceptually farther away) stimuli in different blocks of trials. Consistent with hypotheses proposing a dissociation between these two aspects of neuroticism, participants higher in Neuroticism-Volatility had increased amygdala activation to negative stimuli (regardless of whether they were approached or avoided), whereas participants higher in Neuroticism-Withdrawal had increased amygdala activation to all approached stimuli (regardless of stimulus valence). These data provide further support for the motivational salience hypothesis of amygdala function, and demonstrate that both the ends and means of goal pursuit are important for shaping a response.

An endovascular canine middle cerebral artery occlusion model for the study of leptomeningeal collateral recruitment.

OBJECTIVES: This work aimed to refine a large animal in minimally invasive reversible middle cerebral artery (MCA) occlusion (MCAO) model to account for leptomeningeal collateral formation. MATERIALS AND METHODS: An angiographically based methodology allowed for transient MCA and carotid terminus occlusion in 12 mongrel dogs and assessment of pial collateral recruitment. Outcome measures included 1- and 24-hour magnetic resonance imaging-based infarct volume calculation, a behavioral scale and histopathologic sections. RESULTS: MCAO succeeded in 8 of 12 dogs (67% efficiency). One-hour postreperfusion infarct volume predicted 24-hour postreperfusion infarct volume (r = 0.997, P < 0.0001). Pial collateral recruitment varied with time and reproducibly assessed predicted infarct volume on 1-hour postreperfusion mean diffusivity maps (P < 0.0001; r = 0.946) and 24-hour fluid-attenuated inversion recovery FLAIR magnetic resonance imaging (P = 0.0033; r = 0.961). The canine stroke scale score correlated with infarct volumes and pial collateral score. CONCLUSION: This canine MCAO model produces defined cerebral infarct lesions whose volumes correlate with leptomeningeal collateral formation and canine behavior.

Aspects of neuroticism and the amygdala: chronic tuning from motivational styles.

Recent research and theory has highlighted the dynamic nature of amygdala activation. Rather than simply being sensitive to a few limited stimulus categories, amygdala activation appears to be dependent on the goals of the perceiver. In this study, we extend this line of work by demonstrating that the means by which a person seeks to accomplish a goal also modulates the amygdala response. Specifically, we examine the modulatory effects of the aspects of neuroticism (volatility/withdrawal), a personality variable that has been linked to both generalized anxiety and differences in amygdala sensitivity. Whereas Neuroticism-Volatility is proposed to be associated with the fight-flight-freeze system (FFFS) and a sensitivity for any cues of negativity, Neuroticism-Withdrawal is proposed to be associated with the behavioral inhibition system (BIS) and a generalized tendency toward passive avoidance. During fMRI scanning, participants were presented with positive, negative, and neutral images and were required to approach (move perceptually closer) or avoid (move perceptually farther away) stimuli in different blocks of trials. Consistent with hypotheses proposing a dissociation between these two aspects of neuroticism, participants higher in Neuroticism-Volatility had increased amygdala activation to negative stimuli (regardless of whether they were approached or avoided), whereas participants higher in Neuroticism-Withdrawal had increased amygdala activation to all approached stimuli (regardless of stimulus valence). These data provide further support for the motivational salience hypothesis of amygdala function, and demonstrate that both the ends and means of goal pursuit are important for shaping a response.

Characterization of water distribution in bread during storage using magnetic resonance imaging.

A soy bread of fully acceptable quality and containing 49% soy ingredients (with or without 5% almond powder) has been recently developed in our laboratory. An investigation on water distribution and mobility, as probed by proton signal intensity and T2 magnetic resonance images, during storage was designed to examine possible relations between water states and hindered staling rate upon soy or soy-almond addition. Water proton distribution throughout soy-containing loaves was found to be very homogeneous in fresh breads with and without almond, with minimal water migration occurring during prolonged storage. In contrast, traditional wheat bread displayed an inhomogeneous water proton population that tended to change (with higher moisture migration towards the outer perimeter of the slice) during storage. Similar results were found for water mobility throughout the loaves, as depicted in T2 images. On intensity images of all considered bread varieties, the outer perimeter corresponding to the crust exhibited lower signal intensity due to decreased water content. Higher T2 values were found in the crust of soy breads with and without almond, which were attributed to lipids. The results indicated that the addition of soy to bread improved the homogeneous distribution of water molecules, which may hinder the staling rate of soy-containing breads. However, incorporation of almond had little effect on the water proton distribution or mobility of soy breads.

Global and regional effects of type 2 diabetes on brain tissue volumes and cerebral vasoreactivity.

OBJECTIVE: The aim of this study was to evaluate the regional effects of type 2 diabetes and associated conditions on cerebral tissue volumes and cerebral blood flow (CBF) regulation. RESEARCH DESIGN AND METHODS: CBF was examined in 26 diabetic (aged 61.6 +/- 6.6 years) and 25 control (aged 60.4 +/- 8.6 years) subjects using continuous arterial spin labeling (CASL) imaging during baseline, hyperventilation, and CO2 rebreathing. Regional gray and white matter, cerebrospinal fluid (CSF), and white matter hyperintensity (WMH) volumes were measured on a T1-weighted inversion recovery fast-gradient echo and a fluid attenuation inversion recovery magnetic resonance imaging at 3 Tesla. RESULTS: The diabetic group had smaller global white (P = 0.006) and gray (P = 0.001) matter and larger CSF (36.3%, P < 0.0001) volumes than the control group. Regional differences were observed for white matter (-13.1%, P = 0.0008) and CSF (36.3%, P < 0.0001) in the frontal region, for CSF (20.9%, P = 0.0002) in the temporal region, and for gray matter (-3.0%, P = 0.04) and CSF (17.6%, P = 0.01) in the parieto-occipital region. Baseline regional CBF (P = 0.006) and CO2 reactivity (P = 0.005) were reduced in the diabetic group. Hypoperfusion in the frontal region was associated with gray matter atrophy (P < 0.0001). Higher A1C was associated with lower CBF (P < 0.0001) and greater CSF (P = 0.002) within the temporal region. CONCLUSIONS: Type 2 diabetes is associated with cortical and subcortical atrophy involving several brain regions and with diminished regional cerebral perfusion and vasoreactivity. Uncontrolled diabetes may further contribute to hypoperfusion and atrophy. Diabetic metabolic disturbance and blood flow dysregulation that affects preferentially frontal and temporal regions may have implications for cognition and balance in elderly subjects with diabetes.

Cerebral blood flow velocity and periventricular white matter hyperintensities in type 2 diabetes.

OBJECTIVE: Diabetes increases the risk for cerebromicrovascular disease, possibly through its effects on blood flow regulation. The aim of this study was to assess the effects of type 2 diabetes on blood flow velocities (BFVs) in the middle cerebral arteries and to determine the relationship between white matter hyperintensities (WMHs) on magnetic resonance imaging (MRI) and BFVs. RESEARCH DESIGN AND METHODS: We measured BFVs in 28 type 2 diabetic and 22 control subjects (aged 62.3 +/- 7.2 years) using transcranial Doppler ultrasound during baseline, hyperventilation, and CO(2) rebreathing. WMHs were graded, and their volume was quantified from fluid-attenuated inversion recovery images on a 3.0 Tesla MRI. RESULTS: The diabetic group demonstrated decreased mean BFVs and increased cerebrovascular resistance during baseline, hypo- and hypercapnia (P < 0.0001), and impaired CO(2) reactivity (P = 0.05). WMH volume was negatively correlated with baseline BFV (P < 0.0001). A regression model revealed that baseline BFVs were negatively associated with periventricular WMHs, HbA(1c) (A1C), and inflammatory markers and positively associated with systolic blood pressure (R(2) = 0.86, P < 0.0001). CONCLUSIONS: Microvascular disease in type 2 diabetes, which manifests as white matter abnormalities on MRI, is associated with reduced cerebral BFVs, increased resistance in middle cerebral arteries, and inflammation. These findings are clinically relevant as a potential mechanism for cerebrovascular disease in elderly with type 2 diabetes.

Susceptibility-based imaging of glioblastoma microvascularity at 8 T: correlation of MR imaging and postmortem pathology.

BACKGROUND AND PURPOSE: Imaging methods are currently being optimized in an attempt to assess and monitor angiogenesis in vivo. The purpose of this investigation was to determine whether areas of apparently increased tumor vascularity, as identified on 8-T gradient-echo (GE) imaging of a known glioblastoma multiforme (GBM), corresponds to foci of increased microvascularity on histopathologic analysis. METHODS: We performed postmortem in situ, high-resolution GE 8-T MR imaging of the brain in a 53-year-old woman with GBM. Ten histopathologic specimens in the region of the tumor bed were studied by using hematoxylin-eosin and reticulin stains. MR and histopathologic results were assessed and compared for microvascular size and density. RESULTS: 8-T GE images showed small, penetrating vessels in the gray matter and white matter. The images, however, were partly inhomogeneous as a result of local magnetic field inhomogeneities adjacent to the skull base and aerated paranasal sinus structures. 8-T MR images demonstrated serpiginous areas of signal intensity loss, which were thought to represent areas of increased microvascularity. Areas of lower microvascularity in the tumor bed corresponded to areas of lower vascularity on histopathologic sections with smaller vessel diameters. There was concurrence between vascular size predicted by histopathologic analysis and 8-T MR imaging in nine of nine biopsy samples. Vascular density agreed in seven of nine biopsy samples. CONCLUSION: Our pilot data suggest that microvascularity in GBM can be identified by use of high-resolution, GE, 8-T MR imaging.

Enhanced gray and white matter contrast of phase susceptibility-weighted images in ultra-high-field magnetic resonance imaging.

PURPOSE: To evaluate if magnetic susceptibility sensitive phase postprocessed images can be used to enhance the inherent brain/gray white matter contrast in gradient echo (GE) images at 8-Tesla (T) magnetic resonance (MR). MATERIALS AND METHODS: Phase and magnitude images of high-resolution GE MR 8-T images were created. Comparisons were made between the magnitude, the product of the magnitude and phase, and pure phase images. RESULTS: The pure phase images significantly improved the contrast between the gray and white matter structures. In general, the higher the iron content or subvoxel field inhomogeneities, the higher was the contrast, and the greater were the resultant phase shifts. The phase images best demonstrated anatomy that was not apparent on the standard magnitude images. CONCLUSION: Phase imaging can significantly improve the demonstration of the internal anatomical brain structures over standard magnitude GE imaging techniques at high field.

Visualization of microvascularity in glioblastoma multiforme with 8-T high-spatial-resolution MR imaging.

We used 8-T high-spatial-resolution gradient-echo MR imaging to directly visualize microvascularity in pathologically proved glioblastoma multiforme. Images were compared with 1.5-T high-spatial-resolution fast spin-echo T2-weighted images and digital subtraction angiograms. Preliminary data indicate that 8-T high-spatial-resolution MR imaging may enable the identification of areas of abnormal microvascularity in glioblastoma multiforme that are not visible with other routine clinical techniques.

Comparison of 1.5 and 8 tesla high-resolution magnetic resonance imaging of lacunar infarcts.

PURPOSE: We present a case report comparing 1.5 fast spin-echo (FSE) and high-resolution 8 Tesla (T) gradient echo (GE) MRI of a patient with multiple lacunar infarcts. METHODS: A 51-year-old man with a history of previous lacunar infarctions was studied with two-dimensional Fourier transform axial 8 T GE MRI using the following parameters: 3 mm thick slices skip 3 mm, flip-angle approximately 20 degrees, TR 800 milliseconds, TE 12 milliseconds, 1024 x 1024 matrix, field of view (FOV) 20 cm, and bandwidth 50 kHz. These images were then compared with routine clinical 1.5 T T2-weighted FSE images with 5 mm thick sections, 256 x 256, FOV 20, TR 5650, TE 102, and 16 echo train length. RESULTS: The majority of the infarctions were seen as areas of high signal intensity on both the 1.5 and 8 T images. They were seen in the corona radiata or the basal ganglia. More lesions were seen on the 8 T images. Low intensity signal was best demonstrated on the 8 T images at segments of the periphery of a few of the larger infarcts. There were a few small punctate low signal intensity regions localized at the termination of some of the microvessels on the 8 T images only. The foci of decreased signal intensity in regions of chronic hemorrhage appeared larger on the 8 T images compared with the 1.5 T images. The 8 T images demonstrated direct visualization of many small vessels, primarily in the deep white matter, which were not visible on the 1.5 T images. On the 8 T images, some of the infarcts appeared to be located between the medullary veins of the deep white matter. CONCLUSION: This case report indicates that GE 8 T images demonstrate more infarctions compared with the FSE 1.5 T images. It is possible to simultaneously identify the microvessels of the brain, small foci of hemorrhage, and lacunar infarctions using 8 T MRI.

In vivo high resolution coronal MRI of the wrist at 8.0 tesla.

The wrists of asymptomatic volunteers were imaged at 8 and 1.5 T. The signal-to-noise ratio, spatial resolution, and soft tissue contrast of the 8 T images were much greater. The increased signal-to-noise ratio available at 8 T allows acquisition of high quality, high resolution images and visualization of intricate anatomy at scan times acceptable for clinical imaging.