FoundationalConceptsNeuroscience

these neuropeptides into extracellular space within the hypothala-
mus and into the cerebrospinal fluid, from which they may diffuse to
other sites in the central nervous system. Additionally, axons from
hypothalamic neurons release oxytocin and vasopressin into the
brainstem, hippocampus, amygdala, nucleus accumbens, and other
specific regions in the interior of the brain (Fig. 21.4).
Recent investigations suggest oxytocin and vasopressin play roles
in a variety of prosocial actions—mother-infant bonding (as assessed
by things like eye gaze, touch, and response to vocalizations) and
other parental care behaviors, as well as trust, generosity, and coop-
eration, have all been related to actions of these neuropeptides. There
has even been some exploration of these neuropeptides as drugs to
increase prosocial behaviors in individuals suffering from conditions
in which social connection is impaired—autistic spectrum disorders,
depression, and schizophrenia, for example.
“Feeling good” is often associated, especially in the popular media,
with the brain’s famous “reward pathways.” In the 1950s, James Olds
(1922-1976) discovered regions of the brain that, when electrically
stimulated, induced rats to execute behaviors that would garner them
more such electrical stimulation. That is, electrical stimulation of
these neural pathways was reinforcing, and interpreted as perhaps
being rewarding and even pleasurable for the animal. Originally these
brain regions were even called “pleasure centers.” One of Olds’s most
dramatic findings involved implanted electrodes that would electri-
cally stimulate these neurons when rats pressed a lever. Rats wired
up in this way would repeatedly push the lever to deliver stimulation,
thousands of lever presses per hour, until they collapsed from exhaus-
tion and took a break to eat and sleep. After resting, they resumed
their lever pressing. These neural pathways—reward circuits—have
been extensively investigated in the years since Olds’s discovery.