188 Self and the Phenomenon of Life
b2726 Self and the Phenomenon of Life: A Biologist Examines Life from Molecules to Humanity “9x6”9.5.2 Nucleus accumbens and ventral pallidum
The role of the nucleus accumbens, also known as ventral striatum,
located deep in the basal forebrain, as a principal “pleasure center” is
well documented (Fig. 9.3). Its function has been correlated with sexual
activity, food intake, and even artistic enjoyment.^14 It was reported that
insertion of electrodes into the nucleus accumbens in humans allevi-
ates severe depression, and that the nucleus accumbens is central to the
mechanism of placebo effect. The major input to nucleus accumbens
is the dopaminergic pathway from ventral tegmental area (VTA) in the
midbrain. Injection of dopamine directly into the nucleus accumbens
in the rat has been observed to increase the motivation for reward.^15 In
the light of present knowledge, Olds and Milder’s initial observation of
Fig. 9.2. Human brain showing some areas involved in emotion. Top left: Right
hemisphere seen from the outside, with part of the frontal cortex carved away to expose
the insula. Top right: Right hemisphere seen from the inside, showing the anterior
cingulate cortex and the ventromedial prefrontal cortex. Bottom: Cross-section of both
hemispheres cut along the vertical line indicated in top pictures, showing the location of
the two amygdalas. Note that other deep brain structures concerned with emotion, such
as nucleus accumbens, are not shown in this figure. [See Note 22; permission Cell Press.]