Many Diseases That Were Considered Genetic are Being Reassessed 155neurotoxic agent that targets oxytocin or AVP receptors at later stages of fetal
development, the adverse effects would depend on at what stage the destruc-
tion occurred. For example, if this occurred at day 14 of gestation, the conse-
quences would be severe since there will be only a few neurons that would be
positive for oxytocin and AVP receptors. If exposure took place at week 8 of
gestation, there will be several hundred thousands of oxytocin‐ and AVP‐
receptor positive neurons and the damage may less significant (depending on
the amount of the specific neurotoxin that reaches the brain). If exposure to a
Figure 6.5 The hypothesis of why ASD is a “spectrum”. The brain of a fetus develops
throughout pregnancy. Starting out with a few cells, the cells grow and divide until the
brain contains billions of specialized cells (over 100 billion neurons, not including other
supporting cells). Once in place, each neuron sends out long fibers that connect with other
neurons. In this way, lines of communication are established between various
compartments and faculties of the brain and between the brain and the rest of the body.
As each neuron receives a signal it releases neurotransmitters, which pass the signal to the
next neuron. By birth, the brain has evolved into a complex organ with several distinct
compartments, faculties and foci (nuclei), each with a precise set of functions and
responsibilities. If a fetal brain is exposed to a harmful synthetic chemical (such as synthetic
fragrances, EDCs, insecticides or herbicides) at very early stages of pregnancy (i.e., day 25)
then it may harm a specific kind of progenitor neuron or neurons which were destined to
become a specific compartment, faculty or nuclei of an offspring, resulting in either
complete elimination of that region or subregion of the brain or malformation of that
particular faculty. Since at the early stages of brain development there are very few neurons,
each one is a progenitor neuron (or mother neuron) for a specific brain compartment and
elimination of that compartment would result in severe damage to the brain. In the case
where a fetus is exposed to the same type of neuron‐damaging synthetic chemical (at the
same dose) at later stages of development, the damage may be less severe and the result
may be less obvious. We believe that this is the cause of the “spectrum” in ASD. This
spectrum will never fit into a single “box”.