Researchers have identified a cluster of neurons in mouse brains that encourage fear response to perceived threats. When an adjacent cluster of neurons is activated, boldness and courage behaviors are exhibited.
Salay, L. D., Ishiko, N., & Huberman, A. D. (2018). A midline thalamic circuit determines reactions to visual threat. Nature. doi.org/10.1038/s41586-018-0078-2