Representation of Fear of Heights by Basolateral Amygdala Neurons.

Abstract

Fear of heights is evolutionarily important for survival, yet it is unclear how and which brain regions process such height threats. Given the importance of the basolateral amygdala (BLA) in mediating both learned and innate fear, we investigated how BLA neurons may respond to high-place exposure in freely behaving male mice. We found that a discrete set of BLA neurons exhibited robust firing increases when the mouse was either exploring or placed on a high place, accompanied by increased heart rate and freezing. Importantly, these high-place fear neurons were only activated under height threats, but not looming, acoustic startle, predatory odor, or mild anxiogenic conditions. Furthermore, after a fear-conditioning procedure, these high-place fear neurons developed conditioned responses to the context, but not the cue, indicating a convergence in processing of dangerous/risky contextual information. Our results provide insights into the neuronal representation of the fear of heights and may have implications for the treatment of excessive fear disorders.SIGNIFICANCE STATEMENT Fear can be innate or learned, as innate fear does not require any associative learning or experiences. Previous research mainly focused on studying the neural mechanism of learned fear, often using an associative conditioning procedure such as pairing a tone with a footshock. Only recently scientists started to investigate the neural circuits of innate fear, including the fear of predator odors and looming visual threats; however, how the brain processes the innate fear of heights is unclear. Here we provide direct evidence that the basolateral amygdala (BLA) is involved in representing the fear of heights. A subpopulation of BLA neurons exhibits a selective response to height and contextual threats, but not to other fear-related sensory or anxiogenic stimuli.