Amygdala–prefrontal interactions in (mal)adaptive learning

Abstract

The study of neurobiological mechanisms underlying anxiety disorders has been shaped by learning models that frame anxiety as maladaptive learning. Pavlovian conditioning and extinction are particularly influential in defining learning stages that can account for symptoms of anxiety disorders. Recently, dynamic and task related communication between the basolateral complex of the amygdala (BLA) and the medial prefrontal cortex (mPFC) has emerged as a crucial aspect of successful evaluation of threat and safety. Ongoing patterns of neural signaling within the mPFCBLA circuit during encoding, expression and extinction of adaptive learning are reviewed. The mechanisms whereby deficient mPFC-BLA interactions can lead to generalized fear are discussed in learned and innate anxiety. Findings with crossspecies validity are emphasized.

Infralimbic cortex controls the activity of the hypothalamus–pituitary–adrenal axis and the formation of aversive memory: Effects of environmental enrichment

“…posttraumatic stress disorder) [11,12]. In this study we show that the infralimbic cortex regulates basal and stress-induced concentrations of corticosterone as well as the acquisition of aversive memories.…”

“…However, most pharmacological and lesion studies are limited to the dorsal part of the medial PFC or do not distinguish between the dorsal and ventral parts [5][6][7][8] and, therefore, the role played by the infralimbic cortex in the regulation of the HPA axis and corticosterone concentrations is still uncertain. A dysfunctional regulation of the HPA axis as well as other limbic areas by the infralimbic cortex (ventral medial PFC in humans) is associated with stress mal adaptation and stress-related disorders [9][10][11][12].…”

“…Moreover, EE enhances the control that the infralimbic cortex exerts on the HPA axis. A stronger interaction between the infralimbic cortex and the HPA axis as well as other limbic areas might facilitate the extinction of fear-related memories [12,31,39] and protect enriched animals to stress-related disorders [9].…”

Resolving the neural circuits of anxiety

“…Direct activation of the BLA by PL inputs mediates freezing responses to CS presentations within six hours of auditory fear conditioning, however, fear memory retrieval greater than 24 hours following conditioning necessitates PL recruitment of PVT inputs to CeL 114 . For a more in-depth consideration of how interactions between the amygdala and mPFC impact fear learning, readers are directed to 115 . Taken together, these findings indicate that PL inputs to the amygdala facilitate responses to threatening stimuli, whereas IL inputs to the amygdala suppress them.…”

Effects of electroacupuncture on stress and anxiety-related responses in rats

“…The amygdala activation also suggests that IMMO might induce anxiety and pathological fear (Le Doux andDamasio 2013, Hyman andCohen 2013). Dysregulation of the interaction between the amygdala and the PFC may lead to fear and generalized anxiety (Duvarci and Pare 2014, Likhtik and Paz 2015, Raio and Phelps 2015 and may alter the role played by the hippocampus in fear conditioning (Rozeske et al 2015). The activation by IMMO of those brain areas was attenuated or even canceled by EEA, either in PC6 or the rat tail.…”