The research of the Alexander group is focused on developing imaging and analysis techniques for the study of human brain function with magnetic resonance imaging (MRI) at 3 tesla. The group is actively involved in the following research areas:
The general goals of my research group are to improve techniques for measuring functional brain organization (specifically, resting-state functional connectivity MRI), and to use these tools in order to understand the changes in the functional organization of the brain during childhood and adolescence.
Methodological improvements for resting-state functional connectivity (rs-fcMRI). We are developing improved methods for reliably mapping functional connections in the brain, particularly those acquired in the absence of a directed task (i.e. at “rest”). This includes optimizing image acquisition parameters as well as improving post-processing methods for dealing with non-neuronal signal changes such as physiological noise and head motion.
Changes in functional connectivity during childhood and adolescence. We are using resting-state functional connectivity MRI (rs-fcMRI), together with structural MRI, diffusion tensor imaging (DTI), and functional MRI (fMRI) to understand the changes in functional brain organization during childhood and adolescence.
Brad Christian's research involves the development and application of PET methodologies to investigate neurochemical changes in the brain, including studying novel radioligands to characterize neurotransmitter-protein interactions and how they are influenced by the effects of neuropsychiatric disease and psychotropic drugs. With strong interdisciplinary collaborations, the group is presently involved in studies on:
Moo Chung is interested in tensor-based morphometry (TBM) in structural MRIs. This is a new morphometric technique that localizes the structural differences between groups without defining the regions of interest (ROI). He has developed a unified statistical framework for TBM that can be used to quantify the amount of tissue growth and atrophy in the brain. Extending TBM further, he is trying to develop fMRI analysis that facilitates the variations in gray matter density. He is also interested in mathematical/statistical modeling of functional and structural changes over time and subjects.
Alex Converse studies the interaction between modulatory neural pathways, particularly dopamine neurons, and other brain circuitry. The goal is to describe the role of dopaminergic neuromodulation at the systems level in the human brain in such processes as movement, reward, and attention. He is currently working on an NIH funded project to develop a dual tracer PET method to simultaneously image and correlate dopamine release and blood flow alteration. Future work in humans may involve sequential PET and MRI scans and possibly simultaneous PET and MRI imaging. Additionally, he is carrying out a PET study funded by Pfizer to determine the dopamine receptor occupancy of a candidate antipsychotic compound. He is responsible for microPET operations and collaborates with a number of investigators using a variety of PET tracers to study the dopamine and serotonin systems, glucose utilization, microglial activation, and other aspects of brain biology.
Richard Davidson is the Director of the Laboratory for Affective Neuroscience (housed in the Department of Psychology) and of the Waisman Laboratory for Brain Imaging and Behavior. Dr. Davidson's labs are engaged in a broad program of research on the brain mechanisms that subserve affective processing in normal adults and children and in children and adults with psychiatric disorders (primarily autism and fragile X in children and mood and anxiety disorders in adults). His research group also studies the neural bases of affect-cognition interactions. In addition, they conduct research on relations between the central circuitry of emotion and emotion regulation and peripheral biology to explore bi-directional communication between the brain and body that may be consequential for health. Finally, they also examine the impact of interventions designed to treat psychiatric disorders and to improve well-being in non-disordered populations.
Current work includes studies on:
The methods used include high-density electrophysiology, functional magnetic resonance imaging (fMRI), structural MRI including diffusion tensor imaging (DTI) and positron emission tomography (PET). Researchers also utilize measure of peripheral autonomic and skeletal-muscular measures, along with endocrine and immune measures.
My research examines the neuroscience of emotion and affective disorders. One of my research goals is to identify the neural circuits involved in distinct forms of anxiety and depression and their comorbidity in an attempt to address the diagnostic heterogeneity so prevalent among individuals with mood and anxiety disorders and to inform treatment strategies. The majority of prior research in this area has treated anxiety and depression as global constructs, which has led to a potpourri of findings that make it difficult to determine the precise neurobiological concomitants involved.
The emphasis of my work is on characterizing the constituent elements that comprise these affective constructs. In service of that, my research has probed subtypes of anxiety and depression, psychometrically and physiologically distinguishable affective dimensions, and laboratory-based models of anticipatory and reactivity processes.
Building on my previous work investigating cortical brain function in anxiety and depression using EEG and neuropsychological methods, my postdoctoral fellowship allowed me the opportunity to learn and employ additional methodologies – fMRI, PET, eye-blink startle, and EEG source localization via LORETA – to further interrogate the brain circuits involved in anxiety and depression.
My current research includes an event-related fMRI study that successfully distinguished brain circuits activated during the anticipation of and reactivity to aversive pictures. We are currently employing the same fMRI paradigm with generalized anxiety disorder patients, with the hypothesis that they will exhibit functional abnormalities in the anticipation circuit that will resolve following successful pharmacological treatment. Both of these projects are part of my NIMH K Award.
I am also conducting research that will help to uncover the neural circuitry of positive emotion, which has received far less attention than negative emotion. A major obstacle for researchers in this area has been the challenge of eliciting robust positive emotion reliably across subjects in a physiological laboratory setting. I was recently awarded a grant by the Fetzer Institute for research plans elaborating on our previous block-design fMRI study imaging new mothers while they viewed photographs of their own infants.
On a separate front, a postdoctoral fellow in the lab and I are currently writing up scalp EEG findings of more left than right frontal activity accompanying high levels of well-being. Finally, of further relevance to the general theme of health that courses through all my research endeavors, we are in the design and pilot phases of an event-related fMRI study investigating the brain structures involved in the placebo effect.