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The Journal of Neuroscience, November 5, 2008, 28(45):11517-11525; doi:10.1523/JNEUROSCI.2265-08.2008

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Behavioral/Systems/Cognitive
From Fear to Safety and Back: Reversal of Fear in the Human Brain

Daniela Schiller,^1,2 Ifat Levy,¹ Yael Niv,³ Joseph E. LeDoux,¹ and Elizabeth A. Phelps^1,2

¹Center for Neural Science and ²Psychology Department, New York University, New York, New York 10003, and ³Department of Psychology and Princeton Neuroscience Institute, Princeton University, Princeton, New Jersey 08544

Correspondence should be addressed to Dr. Elizabeth A. Phelps, Department of Psychology, 6 Washington Place, Room 863, New York, NY 10003. Email: liz.phelps{at}nyu.edu

Fear learning is a rapid and persistent process that promotes defense against threats and reduces the need to relearn about danger. However, it is also important to flexibly readjust fear behavior when circumstances change. Indeed, a failure to adjust to changing conditions may contribute to anxiety disorders. A central, yet neglected aspect of fear modulation is the ability to flexibly shift fear responses from one stimulus to another if a once-threatening stimulus becomes safe or a once-safe stimulus becomes threatening. In these situations, the inhibition of fear and the development of fear reactions co-occur but are directed at different targets, requiring accurate responding under continuous stress. To date, research on fear modulation has focused mainly on the shift from fear to safety by using paradigms such as extinction, resulting in a reduction of fear. The aim of the present study was to track the dynamic shifts from fear to safety and from safety to fear when these transitions occur simultaneously. We used functional neuroimaging in conjunction with a fear-conditioning reversal paradigm. Our results reveal a unique dissociation within the ventromedial prefrontal cortex between a safe stimulus that previously predicted danger and a "naive" safe stimulus. We show that amygdala and striatal responses tracked the fear-predictive stimuli, flexibly flipping their responses from one predictive stimulus to another. Moreover, prediction errors associated with reversal learning correlated with striatal activation. These results elucidate how fear is readjusted to appropriately track environmental changes, and the brain mechanisms underlying the flexible control of fear.

Key words: fear conditioning; prediction error; reversal; amygdala; striatum; vmPFC

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Received May 4, 2008; revised Sept. 5, 2008; accepted Sept. 15, 2008.

Correspondence should be addressed to Dr. Elizabeth A. Phelps, Department of Psychology, 6 Washington Place, Room 863, New York, NY 10003. Email: liz.phelps{at}nyu.edu

This article has been cited by other articles:

				D. Mobbs, J. L. Marchant, D. Hassabis, B. Seymour, G. Tan, M. Gray, P. Petrovic, R. J. Dolan, and C. D. Frith From Threat to Fear: The Neural Organization of Defensive Fear Systems in Humans J. Neurosci., September 30, 2009; 29(39): 12236 - 12243. [Abstract] [Full Text] [PDF]

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