My work concerns the biological substrates of memory, fear, and anxiety, and drug dependence. Fears can be acquired extremely rapidly and once acquired, can last a lifetime. I use Pavlovian conditioning paradigms to produce fearful memories in rats. To test for the presence and strength of those memories, I measure the startle reflex, the size of which is elevated when a rat (or other mammal, including human) is afraid.
"Fear-potentiated startle" provides us with a tool to identify brain structures, and to study pharmacological and molecular mechanisms involved in different aspects of the formation and retrieval of fearful memories. Moreover, dramatic elevations in startle accompany certain forms of anxiety disorder and the anxiety-related symptoms of drug withdrawal. Thus, understanding the mechanisms through which startle is potentiated provides insights into the pathophysiology and treatment of anxiety and drug abuse.
(For a comprehensive list of recent publications, refer to PubMed, a service provided by the National Library of Medicine.)
Rothwell PE, Thomas MJ, Gewirtz JC. Protracted manifestations of acute dependence after a single morphine exposure. Psychopharmacology (Berl). 2011 Aug 11.
Radke AK, Rothwell PE, Gewirtz JC. An anatomical basis for opponent process mechanisms of opiate withdrawal. J Neurosci. 2011 May 18;31(20):7533-9.
Burman, M.A., Hamilton, K.L., & Gewirtz, J.C. (2010). Role of corticosterone in trace and delay conditioned fear-potentiated startle in Rats. Behavioral Neuroscience, 124, 294-299.
Sun, M., Gewirtz, J.C., Bofenkamp, L., Wickham, R.J., Ge, H., O’Connor, M.B. (2010). Canonical TGF-beta signaling is required for the balance of excitatory/inhibitory transmission within the hippocampus and prepulse inhibition of acoustic startle. Journal of Neuroscience, 30, 6025-6035.
Engelmann, J.M., Radke, A.K., & Gewirtz, J.C. (2009). Potentiated startle as a measure of the negative affective consequences of repeated exposure to nicotine in rats. Psychopharmacology. 2009 Nov;207(1):13-25.
Rothwell, P.E., Thomas, M.J., & Gewirtz, J.C. (2009). Distinct profiles of anxiety and dysphoria during spontaneous withdrawal from acute morphine exposure. Neuropsychopharmacology. 2009 Sep;34(10):2285-95.
Gewirtz, J.C., Hamilton, K.L., Babu, M.A., Wobken, J.D., Georgieff, M.K. (2008). Effects of gestational iron deficiency on fear conditioning in juvenile and adult rats. Brain Research, 1237, 195-203.
Raman, L., Hamilton, K.L., Gewirtz, J.C., & Rao, R. (2008). Effects of chronic hypoxia in developing rats on dendritic morphology the CA1 subarea of the hippocampus and on fear-potentiated startle. Brain Research, 1190, 167-174.
Harris, A.C., Rothwell, P.E., & Gewirtz, J.C. (2008). Effects of the NMDA receptor antagonist memantine on the expression and development of acute opiate dependence as assessed by withdrawal-potentiated startle and hyperalgesia. Psychopharmacology, 196, 649-660.
Current Graduate Students:
Marc Pisansky (Neuroscience, University of Minnesota).
Bruce Kennedy (Neuroscience, University of Minnesota).
Former Graduate Students:
Anna Radke (Ph.D. 2011, Neuroscience, University of Minnesota).