Play fear 2 without updating
Fear extinction is context-dependent and is generally considered to involve the establishment of inhibitory control of the prefrontal cortex over amygdala-based fear processes.In this paper, we review research progress on the neural basis of fear extinction with a focus on the role of the amygdala and the prefrontal cortex.Based on this result, we propose an updated model for integrating hippocampal-based contextual information with prefrontal-amygdala circuitry.In the presence of threatening or painful stimuli, the brain learns and stores information about other stimuli present so that these can be used as warning signals in future situations.This special issue of features many of the key findings. In humans and other primates, these include the lateral prefrontal cortex, orbital frontal cortex, and m PFC. The m PFC itself has several divisions, including the anterior cingulate cortex and several more ventral areas that include the infralimbic (IL) and prelimbic (PL) cortices, and the medial frontal gyrus. The functional contribution of the ventral m PFC (vm PFC: regions below the ventral anterior cingulate, and involving the IL and PL, among other regions) in humans is less clear.In this article, we review the original impetus for pursing the role of the m PFC, and survey some of the findings that have come since. The lateral prefrontal cortex, especially the dorsolateral region, is involved in working memory and executive control functions (Goldman-Rakic 1995; Owen et al. 2000; Levy and Goldman-Rakic 2000; Miller and Cohen 2001; Curtis and D'Esposito 2003). The anterior cingulate is divided into two parts, a dorsal part involved in attention and cognitive control and a more ventral part involved in emotional regulation (Bush et al. In non-primate species, the prefrontal cortex is poorly developed.Next, we return to the original findings that motivated interest in the role of the m PFC in extinction of conditioned fear, and then we consider the evidence that has subsequently accumulated, which has both confirmed and refined our understanding of m PFC involvement in the regulation of fear. Research on the neural basis of fear extinction was stimulated by two studies in the late 1980s showing that damage to sensory processing regions of the cortex (auditory or visual) leads to increased resistance to extinction (Le Doux et al. Follow-up studies systematically examined the effects of damage to the dorsal m PFC (anterior cingulate cortex) and vm PFC (Morgan and Le Doux 1995).
With the dorsal m PFC lesions, it was unclear if the effect on extinction was really due to increased resistance to extinction, because the effect could also be explained by the overall increase in the expression of conditioned fear.Integrating these findings with their observations on fear extinction, Morgan et al.(1993) proposed that the resistance to extinction following m PFC damage represented perseverative tendencies in the emotional domain.We evaluate two competing hypotheses for how the medial prefrontal cortex inhibits amygdala output.In addition, we present new findings showing that lesions of the basal amygdala do not affect fear extinction.