Fear and Memory: A View of the Hippocampus Through the Lens of the Amygdala
Studies of the brain’s fear circuits have significantly advanced our neurobiological understanding of learning and memory systems. Fear and anxiety are often rooted in memories of past experiences and can be aroused by recognition of familiar stimuli that
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Hugh T. Blair and Michael S. Fanselow
Abstract
Studies of the brain’s fear circuits have significantly advanced our neurobiological understanding of learning and memory systems. Fear and anxiety are often rooted in memories of past experiences and can be aroused by recognition of familiar stimuli that predict danger. In this chapter, we examine how the amygdala and hippocampus regulate interactions between fear and memory, with emphasis upon evidence derived from studies of Pavlovian fear conditioning. Convergent behavioral, pharmacological, anatomical, and neurophysiological findings indicate that amygdala circuits can rapidly and permanently store information about which environmental stimuli and events predict danger. These same amygdala circuits are interconnected with the ventral hippocampus (VH), and together, the amygdala and VH may be core components of an emotional memory system in the mammalian brain. The dorsal hippocampus (DH) is not directly connected with the amygdala, but it also makes important contributions to fear conditioning by supporting cognitive memory processes that are essential for recognizing cues and contexts that can predict threats. We discuss how neural representations stored in the amygdala and hippocampus support the mammalian brain’s ability to map states of the world onto expectations of danger.
H.T. Blair (*) UCLA Psychology Department, Los Angeles, CA, USA e-mail: [email protected] M.S. Fanselow Department of Psychology, University of California, Los Angeles, Los Angeles, CA, USA Department of Psychiatry, University of California, Los Angeles, Los Angeles, CA, USA e-mail: [email protected] D. Derdikman and J.J. Knierim (eds.), Space, Time and Memory in the Hippocampal Formation, DOI 10.1007/978-3-7091-1292-2_17, # Springer-Verlag Wien 2014
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H.T. Blair and M.S. Fanselow
Introduction
“Fear” is an emotional state that accompanies anticipation of danger and benefits survival by motivating defensive behaviors that protect against threats (Fanselow and Lester 1988; LeDoux 2000). Humans sometimes experience pathological fear, characterized by recurring anticipation of danger that is out of proportion with available evidence of threat, which is symptomatic of anxiety disorders such as post-traumatic stress and phobias (Craske 1999). Neural circuits that regulate fear and anxiety have become a major focus of research to advance the diagnosis and treatment of such disorders (LeDoux and Muller 1997; Cahill and McGaugh 1998; Garakani et al. 2006). This line of research has also deepened our understanding of learning and memory systems in the mammalian brain.
17.1.1 Learning to Anticipate Danger Fear can be elicited by cues in the environment that signal the presence of danger. Some cues and events are programmed by natural selection to be innately threatening [such as encounters with natural predators, Lester and Fanselow (1985)], but other cues acquire the ability to predict danger through experience-dependent learning. Much of our current knowledge about the br
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