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Bioimaging Sciences Seminar Series


October 1, Tuesday (4:00 pm) at TAC N135 (300 Cedar Street)

"New approaches in edited MRS"

Richard Edden (Johns Hopkins University) This talk describes recent efforts to develop edited MRS with a particular focus on improving acquisition efficiency. The "single-voxel-single-metabolite" MEGA-PRESS experiment can be enhanced by Hadamard-encoded editing to selectively detect more than one target metabolite and by multi-volume acquisition strategies. Recent efforts at multi-site and multi-vendor standardization will also be presented.


October 15, Tuesday (4:00 pm) at TAC N135 (300 Cedar Street)

"Microcircuitry of agranular frontal cortex: A stochastic 2-compartment model of neocortical pyramidal cells"

Jorge Riera (Florida International University) An understanding of the circuitry accomplishing executive control depends on knowledge about the properties of neocortical pyramidal cells (PCs). Highly-complicated (hundreds of compartments and dozens of ionic channels) models have been proposed to account for the Ca2+ spike dependent gain and the existence of the critical frequency for Ca2+ spike genesis in PCs (Hay et al., 2011; Bahl et al., 2012; Mäki-Marttunen et al., 2018). However, other features of PCs have not been explained yet with a single theoretical model. Moreover, it has not been possible to evaluate their impact on large population dynamics due to their high computational cost. In this study, we present a simple stochastic 2-compartment model of PCs that reproduces all three principal features. The model comprises a combination of Na+-K+ conductance for the soma/basal-dendrites. The dendritic tuft includes the persistent Na+, the hyperpolarization-activated cation (Ih), the slow inactivation K+ channel and the Ca2+ L-type channel. As for the calcium active control in the dendritic tuft, we assumed single Michaelis–Menten kinetics. Our model was able to replicate the three major phenomena in this type of cells: a) the back-propagating action potential (AP) activated Ca2+ spikes underlying the above-referred changes in dendritic gain, b) the desensitization of their soma, and c) the shifting of the critical frequency via activation of the Ih current, which could be enhanced by GABA-ergic synaptic activity. The results demonstrate that this simple neuronal model can serve as a powerful tool to study the cortical organization of agranular areas, such as the supplementary eye field (SEF). To illustrate the usefulness of our model in this area, we simulated local field potential (LFPs), and calculated the related current source density (CSD) maps, evoked by the activation of an agranular cortical column via NMDA inputs at the apical/basal dendrite and a delayed apical inhibition from intra-cortical connections. We were also able to reproduce the CSD pattern created when the soma of these cells are optogenetically stimulated.


November 19, Tuesday (4:00 pm) at TAC N135 (300 Cedar Street)

"At the Intersection of Mood and Alcohol: Neurophysiological, Environmental, and Genetic Mechanisms of Risk for Alcohol Use Disorders in Youth with Bipolar Disorder"

Elizabeth Lippard (University of Texas, Austin) Alcohol use disorders occur 3-5 times more often in bipolar disorder compared to the general population, with estimates that up to 60% of individuals with bipolar disorder will present with an alcohol use disorder during their lifetime. Despite this prevalence—and that comorbidity is associated with worse illness course—there is limited studies investigating mechanisms that may contribute to elevated risk for, and development of, alcohol use disorders in bipolar disorder. This talk will discuss emerging evidence from my laboratory suggesting neurophysiological, environmental, and genetic mechanisms that may contribute to risk for alcohol use disorders in youth with bipolar disorder. Research studies focus on structural and functional neuroimaging data investigating neural correlates of shared risk factors for bipolar disorder and alcohol use disorders, including alcohol use patterns, individual differences in response to alcohol, stress-related processes, and familial factors. Additionally, emerging pilot longitudinal data modeling relations between neurophysiological markers of risk and associated outcomes will be discussed.


December 17, Tuesday (4:00 pm) at TAC N135 (300 Cedar Street)

"Calibrated fMRI of oxygen metabolism without gas or contrast agent exposure in awake versus anesthetized mice"

Garth Thompson (Shanghai Tech University) In functional brain imaging, neuromodulation and metabolism alter the baseline of brain activity, limiting scientific interpretation and clinical translation. The neuroimaging standard of the Blood Oxygen Level Dependent (BOLD) signal represents a mixture of cerebral blood flow (CBF), cerebral blood volume (CBV) and the cerebral metabolic rate of oxygen consumption (CMRO2). “Calibrated fMRI” methods aim to measure CMRO2 through a metabolic model, but typically require administration of gases which is not possible in many clinical settings. Here, we develop a calibrated fMRI technique called “M-Mapping” which combines CBF and magnetic relaxation (R2') maps together to compare CMRO2 between two states. With quantitative measurement of CBF and R2' maps on a per-subject basis (combined with an average group map of “beta” which quantifies intravascular magnetic susceptibility) we show that awake mice have globally greater CMRO2 than anesthetized mice. This result was recapitulated when measuring global venous oxygen (Yv) using T2-relaxation under spin-tagging (TRUST). Thus, M-mapping is a possible way to compare brain activity across different resting activity levels. Unlike other calibrated fMRI methods, M-mapping does not require additional agents or gases, so it shows a great potential for future clinical use..

*co-sponsored by the Neuroimaging Sciences Training Program Refreshments served 15 minutes prior to start of seminar. Please call 5-6199 / 5-6622 for directions.

Past Bioimaging Sciences Seminar Series