ORIGINAL ARTICLES Can’t Shake that Feeling: Event-Related fMRI Assessment of Sustained Amygdala Activity in Response to Emotional Information in Depressed Individuals

individuals engage in prolonged elaborative processing of emotional information. A computational neural network model of emotional information processing suggests this process involves sustained amygdala activity in response to processing negative features of information. This study examined whether brain activity in response to emotional stimuli was sustained in depressed individuals, even following subsequent distracting stimuli. Methods: Seven depressed and 10 never-depressed individuals were studied using event-related functional magnetic resonance imaging during alternating 15-sec emotional processing (valence identification) and nonemotional processing (Sternberg memory) trials. Amygdala regions were traced on high-resolution structural scans and coregistered to the functional data. The time course of activity in these areas during emotional and nonemotional processing trials was examined. Results: During emotional processing trials, never-depressed individuals displayed amygdalar responses to all stimuli, which decayed within 10 sec. In contrast, depressed individuals displayed sustained amygdala responses to negative words that lasted throughout the following nonemotional processing trials (25 sec later). The difference in sustained amygdala activity to negative and positive words was moderately related to self-reported rumination. Conclusions: Results suggest that depression is associated with sustained activity in brain areas responsible for coding emotional features. Biol Psychiatry 2002;51

Supplemental data 1 Shape analysis

The diameters of our nanoparticles are determined by using the free online image analysis tool ImageJ [1] which includes a particle analysis package. We use the 2D images taken in STEM mode to measure the surface area A of the nanoparticle, whereafter we determine the mean nanoparticle diameter D using the relation A = π ( D /2) 2 . The particle analysis tool also evaluates the maximum D max and minimum D min diameters of the nanoparticle and the difference between these two diameters, i.e., Δ D = D max -D min provides us a measure for error in the nanoparticle diameter (shown as the error bar in Article Supplementary In order to understand the scattering of the SP resonance energies observed in Articl

Spectral decomposition of susceptibility artifacts for spectral-spatial radiofrequency pulse design

Susceptibility induced signal loss is a limitation in gradient echo functional MRI. The through-plane artifact in axial slices is particularly problematic due to the inferior position of air cavities in the brain. Spectral-spatial RF pulses have recently been shown to reduce signal loss in a single excitation. The pulses were successfully demonstrated assuming a linear relationship between susceptibility gradient and frequency, however, the exact frequency and spatial distribution of the susceptibility gradient in the brain is unknown. We present a spiral spectroscopic imaging sequence with a time-shifted RF pulse that can spectrally decompose the through-plane susceptibility gradient for spectral-spatial RF pulse design. Maps of the through-plane susceptibility gradient as a function of frequency were generated for the human brain at 3T. We found that the linear relationship holds well for the whole brain with an optimal slope of −1.0μT/m/Hz

Three-dimensional Fourier encoding of simultaneously excited slices:generalized acquisition and reconstruction framework

PURPOSE: Simultaneous multi-slice (SMS) acquisitions have recently received much attention as a means of increasing single-shot imaging speed. SMS acquisitions combine the advantages of single-shot sampling and acceleration along the slice dimension which was previously limited to 3D volumetric acquisitions. A 2D description of SMS sampling and reconstruction has become established in the literature. Here, we present a more general 3D Fourier encoding and reconstruction formalism for SMS acquisitions that can easily be applied to non-Cartesian SMS acquisitions. THEORY AND METHODS: A “SMS 3D” k-space is defined in which the field of view along the slice select direction is equal to the number of excited slices times their separation. In this picture, SMS acceleration can be viewed as an under sampling of SMS 3D k-space that can be freely distributed between the in-plane and slice directions, as both are effective phase encoding directions. RESULTS: Use of the SMS 3D k-space picture is demonstrated in phantom and in-vivo brain acquisitions including data obtained with blipped-CAIPI sampling. SMS SENSE reconstruction is demonstrated as well as non-Cartesian SMS imaging using blipped spiral trajectories. CONCLUSION: The full framework of reconstruction methods can be applied to SMS acquisitions by employing a 3D k-space approach. The blipped-CAIPI method can be viewed as a special case of undersampling an SMS 3D k-space. The extension of SMS methods to non-Cartesian 3D sampling and reconstruction is straightforward

Single-shot echo-planar imaging with Nyquist ghost compensation:interleaved dual echo with acceleration (IDEA) echo-planar imaging (EPI)

Echo planar imaging is most commonly used for BOLD fMRI, owing to its sensitivity and acquisition speed. A major problem with EPI is Nyquist (N/2) ghosting, most notably at high field. EPI data are acquired under an oscillating readout gradient and hence vulnerable to gradient imperfections such as eddy current delays and off-resonance effects, as these cause inconsistencies between odd and even k-space lines after time reversal. We propose a straightforward and pragmatic method herein termed Interleaved Dual Echo with Acceleration (IDEA) EPI: Two k-spaces (echoes) are acquired under the positive and negative readout lobes, respectively, by performing phase blips only before alternate readout gradients. From these two k-spaces, two almost entirely ghost free images per shot can be constructed, without need for phase correction. The doubled echo train length can be compensated by parallel imaging and/or partial Fourier acquisition. The two k-spaces can either be complex-averaged during reconstruction, which results in near-perfect cancellation of residual phase errors, or reconstructed into separate images. We demonstrate the efficacy of IDEA EPI and show phantom and in vivo images at both 3 and 7 Tesla