Neurophysiological Research

amygdala

NEUROPHYSIOLOGICAL PROJECTS

There are many components to the Grady Trauma Project. Patients enrolled in the Grady Trauma Project may be eligible for a number of other areas of research. Some of these studies look at biological indices of trauma reactions.

The Neurophysiology Laboratory at the Grady Trauma Project uses psychophysiological measures, including acoustic startle response, skin conductance response, and heart-rate variability, to assess fear-related physiology. We have developed several paradigms that have identified startle-based phenotypes related to PTSD. Specifically, we have found that impaired inhibition of fear-potentiated startle is a robust biomarker of PTSD in survivors of combat and civilian trauma.

Neuroimaging techniques help us learn about the neurobiology of PTSD and fear in humans. We use magnetic resonance imaging (MRI) techniques to study alterations in brain structure and function associated with PTSD. PTSD has been shown to involve heightened emotional responses to threatening stimuli. Our findings, along with those of other groups, indicate that such symptoms depend on changes in a neural circuit involving the amygdala, hippocampus, and medial prefrontal cortex. The amygdala is a brain region that coordinates emotional feelings and physiology, influencing heart rate, breathing, and sweating responses. This region is more active in PTSD. In addition, regulatory signals from the hippocampus and medial prefrontal cortex fail to inhibit amygdala activation and fear.

Through our epidemiological genetic study and research in rodents, we have identified several genetic polymorphisms that predict risk for PTSD. We are currently investigating how these genetic pathways influence the neural circuitry of PTSD. These studies may point to new treatments that specifically target a particular gene-brain pathway, and may help to identify differences in patients’ genetic profiles that will facilitate individually-tailored treatment plans.

 

Effects of Cortisol Suppression on Fear-Potentiated Startle in Trauma and PTSD (NIMH R21)

PI: Tanja Jovanovic

The study uses innovative tools to tease apart the relationship between amygdala-dependent neurophysiology and HPA-axis sensitivity in a human clinical population. Our recent discovery that cortisol suppression reduces fear responses in PTSD coupled with the development of new fear conditioning paradigms, provides a unique opportunity to interrogate amygdala–HPA interactions to determine aspects of the neurobiological underpinnings of PTSD-related pathology.

 

startle1startle2

 

 

 

 

 

 

 

 

Neuroimaging Correlates of Impaired Fear Inhibition in PTSD (NIMH R21)

PI: Tanja Jovanovic

Brain imaging data from our laboratory have shown both structural and functional MRI differences in PTSD are associated with impaired fear inhibition. In this project we will examine the neural underpinnings of fear inhibition as an intermediate phenotype of PTSD. We will use innovative imaging techniques, including fMRI of a Go/NoGo task, resting state fMRI, DTI, and volume and shape analyses in order to better understand the pathophysiology of PTSD.

brain2