Psychiatry: Faculty and Staff
Uniformed Services University of the Health Sciences
Department of Psychiatry
4301 Jones Bridge Road
Bethesda, Maryland 20814-4799
Phone: (301) 295-3294
Fax: (301) 295-1536
Luke R. Johnson, Ph.D.
The Johnson Lab in the department of Psychiatry and interdepartmental Neuroscience program seeks to address fundamental questions in the neurobiology of fear memory with the aim of providing vital basic knowledge into the way the brain encodes normal and pathological fear memories.
Normal fear memory and fear responses are an essential part of any persons or animals survival mechanism. Using fear memory an organism can learn to associate and remember new threats with physical danger. Fear pathology includes the anxiety disorders and post traumatic stress disorder (PTSD). Anxiety and PTSD can be characterized by pathology in fear memory where responses are amplified and become debilitating. These disorders can thus be thought of as either pathology of the acquisition of fear memory or as pathology in the expression of an otherwise normal fear memory.
Knowledge of where and how the brain processes fear and fear learning has greatly increased in the last few decades driven by the work of LeDoux, Davis, Pare, Fanslow, Phelps, Maren and many others. This research has identified neural circuits that mediate synaptic plasticity at input synapses to the lateral amygdala (LA). However, knowledge of the cellular encoding of fear memory within the LA network is crucially lacking. The Johnson Lab seeks to quantify the neural circuits of the LA and also the organization of fear memories encoded by groups of LA neurons. The lab has coined this approach the study of the Micro Anatomy of Fear.
In addition the Johnson Lab also seeks to directly understand the microanatomy of how stress interacts with the fear system. One of the key mechanisms of the stress response is regulation of the HPA axis including modulation of adrenal steroids. The Johnson lab also investigates the microanatomy of glucorticoid receptors and their regulation of LA network behavior.
The Johnson lab studies the microanatomy of fear using Pavlovian Fear Conditioning as a principal behavioral model. Brains subject to Pavlovian conditioning are studied using 3-dimensional reconstruction of LA neural networks. 3D mapping is performed using computerized mapping with Neurolucida (Microbrightfield, VT). Anatomical and electrophysiological data is obtained from neurons and networks using immunocytochemistry and whole cell patch clamp and extra cellular field recordings. Structural data is obtained using transmitted light, fluorescent and electron microscopy.