signals from the brain to body organs (efferent fibers), and some
carrying signals from the interior of the body to the brain (afferent
fibers). More than 50 percent of the axons in the vagus nerve are affer-
ent fibers. This robust communication in both directions between the
viscera and the brain may contribute to what we call “gut feelings”—
our emotional experience involves awareness of the physiological
state of the internal core of our body. Activity of the vagus nerve (as
captured by a concept called vagal tone) has been associated with
amore relaxed emotional style (equanimity), resilience when en-
countering negative emotions, more frequent experience of positive
emotions, greater prosocial expression (including empathy and social
connection), and improvements in measures of physical health.As for most things, many brain regions are involved in emotions and
their expression. While there is much research, lots of data, and a fair
amount of theorizing, there is yet little consensus as to exactly what is
going on and where. Some general themes may be stated.
The amygdala—a group of nuclei at the base of the temporal lobes
and heavily interconnected with sensory areas of the cerebral cortex,
as well as with numerous groups of neurons in the brainstem—is
involved in the perception of emotional expressions. There is some ev-
idence that sensory cues related to fear and anger may be of particular
salience. The amygdala is also involved in signaling the hypothalamus
to initiate a cascade of events that forms part of the body’s response to
stressful events.
The hypothalamus produces neuropeptides that regulate the
release of systemic hormones from the adjacent pituitary gland. One
such hypothalamic-pituitary neural connection regulates release
of adrenocorticotropic hormone from the pituitary gland into the
blood circulation. This hormone triggers the adrenal gland to release