192 Self and the Phenomenon of Life
b2726 Self and the Phenomenon of Life: A Biologist Examines Life from Molecules to Humanity “9x6”The ventromedial prefrontal cortex is also involved in aesthetic experi-
ence. It is activated not only during music and visual art appreciation,
but also by mathematical equations, when these equations are perceived
as “beautiful” by test subjects who are mathematicians.^27
9.5.7 Periaqueductal gray
The periaqueductal gray is the gray matter in the midbrain that per-
forms a “gating” function for incoming pain sensation reaching the brain
(Fig. 9.3). Its destruction leads to coma. Stimulation of this area elicits
defense response such as excitement and freezing. Through its connec-
tion with the hypothalamus, it enhances copulatory behavior (lordosis)
in female animals.^28
9.5.8 Parabrachial nucleus
Situated in the pons, the parabrachial nucleus (Fig. 9.3) is a major chan-
nel for visceral sensation to reach the brain. It receives sensory fibers
from the body after a relay in the nucleus tractus solitarius (NTS) in
the medulla, and sends fibers to the other emotional centers including
the periaqueductal gray, amygdala, hypothalamus, and thalamus. Fibers
passing through the thalamus reach the anterior insular cortex, produc-
ing conscious sensation of the internal organs and the subjective feeling
of emotional experience. As part of the reticular activating system it also
conveys alertness. Together with the thalamus, amygdala, and hypothal-
amus, it also plays a role in regulating cardio-respiratory function.
9.6 Interoception and the Sensation of Emotion
Charles Sherrington in 1907 coined the word “interoception” to denote
those sensations that refer to our own body, including the internal
organs (visceral sensation), as opposed to those that refer to the out-
side world.29,30 The latter, called exteroception, maps out the environ-
ment surrounding us through external sense organs like the eyes, ears,