Interoception, stress and stress-associated diseases

The brain and peripheral bodily organs continuously exchange information. Interoception refers
to the processing of afferent signals from the body to the brain. Stress activates peripheral
bodily organs via neural and endocrine pathways and can thus be seen as an example of efferent
signal transmission between the brain and the body. The interaction of interoception and stress,
therefore, implies bi-directional communication on the brain-body axis. Ten studies are presented
to address the following objectives: To reveal ‘normal’ bi-directional communication on the
brain-body axis (i.e. interoception and stress) in healthy individuals and mechanisms of potentially
altered brain-body communication in stress-associated diseases. With regard to interoception,
the studies focus on different interoceptive facets, including early stages of CNS representation
of visceral-afferent signals, attention focused on visceral sensations and their interpretation.
Concerning stress, both physiological stress axes, the sympatho-adreno-medullary (SAM) axis
and the hypothalamic-pituitary-adrenocortical axis, are addressed. An activation of the SAM axis
does not only stimulate the cardiovascular system, but it also enhances attention focused on
bodily sensations. Cortisol seems to selectively amplify the brain-body communication at cortical
level, without affecting peripheral cardiovascular activation. Stress-associated disorders, such as
depersonalization/derealization, somatic symptom, post-traumatic stress, major depression or
borderline personality disorder, are characterized by a highly-specific patterns of alterations of
interoceptive signal transmission and physiological stress axis dysregulations. In conclusion, new
intervention methods should be developed that enhance the communication between the brain and
the body to improve mental health. These may be based on nerve or brain stimulation, perceptual
learning or neurofeedback.