Front Matter

Connecting the Dots 15

prostate and breast cancers, as well as leukemia and lymphoma, has increased
dramatically since 1960, with no thanks to the endocrine disrupting synthetic
chemicals [63].
A fetus, and especially a fetal brain, can be a major target for any synthetic
chemical that can cause mutations and/or interrupt the well‐orchestrated
pattern of fetal brain development. A human brain contains over 100 billion
neurons, of which about one‐fifth are located in the cerebral cortex. Each
cortical neuron has on average of 7,000 synaptic connections to other neu­
rons, resulting in a total of 0.15 quadrillion synapses, or 1,500,000,000,000,0
00,000,000,000 connections between various neurons. If you measure the
distance that they cover, it translates to more than 150 km of nerve fibers.
This whole sophisticated human brain system is caged into a skull in which
the brain floats in a special fluid with a volume of 1,350 cm^3 and a total sur­
face area of 1,820 cm^2 [81].
The most conspicuous connective structure within the human brain is
known as the corpus callosum, a flat and wide bundle composed of over one‐
fifth of a billion contralateral axons, which play the crucial role of connecting
the brain’s right and left cerebral hemispheres (Figure 1.8). Corpus callosum
abnormality, a congenital disorder that is both severe and rare, a condition
in  which the corpus callosum is either completely or partially missing, is

Cerebrum

Hypothalamus

Corpus callosum

Thalamus

Amygdala

Pons

Cerebellum

Medulla

oblongata

Spinal

cord

Figure 1.8 An illustration of a typical adult human brain structure. Source: Adapted from
https://www.khemcorp.com/autism‐and‐social‐anxiety‐research‐summary‐and‐science/.
(See insert for color representation of this figure.)