Fear and Safety Engage Competing Patterns of Theta-Gamma Coupling in the Basolateral Amygdala

• Published in: Neuron (Cambridge, Mass.) Mass.), 2014-08, Vol.83 (4), p.919-933
• Main Authors: Stujenske, Joseph M., Likhtik, Ekaterina, Topiwala, Mihir A., Gordon, Joshua A.
• Format: Article
• Language: English
• Subjects: Animals; Basolateral Nuclear Complex - physiology; Conditioning (Psychology) - physiology; Data analysis; Discrimination; Extinction, Psychological - physiology; Fear - physiology; Fourier transforms; Gamma Rhythm - physiology; Hippocampus - physiology; Male; Medical research; Mental health; Mice; Neural Pathways - physiology; Neurons - physiology; Prefrontal Cortex - physiology; Safety; Theta Rhythm - physiology
• ISSN: 0896-6273; 1097-4199
• DOI: 10.1016/j.neuron.2014.07.026

Theta oscillations synchronize the basolateral amygdala (BLA) with the hippocampus (HPC) and medial prefrontal cortex (mPFC) during fear expression. The role of gamma-frequency oscillations in the BLA is less well characterized. We examined gamma- and theta-frequency activity in recordings of neural activity from the BLA-HPC-mPFC circuit during fear conditioning, extinction, and exposure to an open field. In the BLA, slow (40–70 Hz) and fast (70–120 Hz) gamma oscillations were coupled to distinct phases of the theta cycle and reflected synchronous high-frequency unit activity. During periods of fear, BLA theta-fast gamma coupling was enhanced, while fast gamma power was suppressed. Periods of relative safety were associated with enhanced BLA fast gamma power, mPFC-to-BLA directionality, and strong coupling of BLA gamma to mPFC theta. These findings suggest that switches between states of fear and safety are mediated by changes in BLA gamma coupling to competitive theta frequency inputs. •There are two bands of theta-nested gamma in the BLA during fear expression•BLA cells that phase-lock to fast gamma increase firing during safety•Fast gamma couples to BLA theta during fear and to mPFC theta during safety•mPFC-to-BLA fast gamma directionality indicates safety in three behavioral paradigms The medial prefrontal cortex is thought to inhibit fear through interactions with the basolateral amygala (BLA). Stujenske et al. show that, during safety, gamma oscillations in the BLA are modulated by medial prefrontal cortex activity, perhaps mediating this inhibition.