Autism, Viewpoint on the Brain Disorder

1 – Major points
The following chapters of this book are a review of
the mainstream medical literature in support of the
major points touched on in the preceding
paragraphs. In brief the data and concepts I think
merit exploration as relevant to autism are:

(1) All measures of cerebral metabolism indicate that
the inferior colliculus of the auditory system is
metabolically the most active center of the brain. This
suggests that biochemical processes within the
inferior colliculus serve some especially important
functions.

(2) The auditory sense serves as an alerting system
for visual attention and general awareness.
Heightened senses of touch and vision become
alternatives for people who are deaf, but the auditory
system has evolved as the primary alerting system for
higher vertebrate species. Impairment of alerting
functions is likely involved in the attention deficits of
children with autism.

(3) The inferior colliculus and other brainstem nuclei
of high metabolic rate may control signal multiplexing,
as in computer systems, to optimize use of neural
circuits and minimize the massive number of nerve
bundles that would otherwise be required for
processing of sensory information.

(4) Verbal auditory agnosia (as described by Rapin
1997) may be the primary disorder in autism, making
it difficult for the child with impaired auditory
processing to recognize syllable and word boundaries
in rapid streams of speech.

(5) Children normally learn to speak before the
language circuits of the cerebral cortex are fully
myelinated, thus early speech development must be
dependent upon intact functioning of the brainstem
auditory system.

(6) Early maturation of the auditory system is trophic
for synaptic growth, and development of the cerebral
cortex and its association pathways. There are
critical periods for expression of transient
neurotransmitters, and these critical periods can be
disrupted by exposure to toxic substances, infections,
or anoxia.

(7) Frontal lobe executive functions appear blunted
even in children with high-functioning autism and
Asperger Syndrome. A developmental cause
resulting from loss of trophic guidance, in turn due to
impairment of vulnerable brainstem nuclei of high
metabolic rate, would seem worthy of investigation.

(8) There is a critical period for learning a new
language by ear (within the first decade of life for
most people). Verbal auditory agnosia may be an
affliction we all develop with maturation and aging.
High metabolic rate in the auditory system may lead
to earlier aging than in less active regions of the
brain. There are also critical periods for superior
mastery of fine motor skills like learning to play the
piano (see Wernicke 1874) or figure skating. Aging
of brainstem motor nuclei may take place not much
later than in the auditory system.

(9) Among the multiple etiologies of autism are:
(a) prenatal exposure to alcohol, drugs, and other
toxic substances, (b) abnormal and toxic metabolites
produced in genetic metabolic disorders like
phenylketonuria (PKU), (c) perinatal infections, and
(d) asphyxia at birth.

(10) The auditory system is vulnerable to all of the
multiple etiologies of autism including prenatal
exposure to alcohol, drugs, toxic substances, and
toxic abnormal metabolites produced in genetic
metabolic disorders, plus perinatal infections and
anoxia at birth.

(11) The inferior colliculus can be spared by
protective biofeedback mechanisms that go into
action under adverse conditions. Then slightly less
active brainstem nuclei of high metabolic rate such as
the mammillary bodies and motor centers of the
cortex may sustain the major damage. This suggests
a basis for a spectrum of autistic disorders that
includes children with Asperger's syndrome and their
difficulties with fine motor coordination.

(12) A spectrum of auditory and motor system
impairments distinguishes autism from Asperger
syndrome. This spectrum is based on the different
vulnerabilities of auditory nuclei and less
metabolically active areas of the motor cortex to total
or partial disruption of metabolism.