2 -  Working Hypothesis
Evidence for the following seems clear:

1. The auditory system is vulnerable to many of
   the medical conditions associated with autism.
   
2. The auditory system is mature and functional
   before birth.
   
3. Trophic transmitters are produced in auditory
   nuclei during early development.  These trophic
   transmitters promote development of later
   maturing temporal and frontal lobes of the
   cerebral cortex.
   

Therefore, what I propose is:

If auditory nuclei like the inferior colliculus are
damaged around the time of birth, trophic
transmitters will not be produced to stimulate
normal growth of cortical systems; and this may
explain the blunting of higher cortical faculties in
individuals with autism.

Autistic disorder is observed in children with diverse
medical conditions.  Prenatal rubella, phenylketonuria,
tuberous sclerosis, and fragile X syndrome are among
the most well known [1-10].  However, the core
syndrome of autism defined by Kanner (1943, 1946) is
distinctive and cannot be simply dismissed as
evidence of widespread brain damage in a variety of
different disorders [11, 12].  Rather, these disorders
must all affect a particular brain system required for
development of social motivation and normal use of
language.

The difficulty in finding visible signs of damage by
traditional neuropathology or on MRI and PET scans
indicates that, in most cases, a metabolic rather than
structural anomaly within the brain is responsible for
the core syndrome of autism.  Preservation of islands
of intelligence in children with autism suggests further
that this metabolic anomaly is not an affliction of the
whole brain, but affects function in those areas
required for joint attention and other components of
human social interactions including language.

1. Chess S (1971) Autism in
   children with congenital
   rubella.
   
2. Chess S et al. (1978)
   Behavioral consequences of
   congenital rubella.
   
3. Williams RS et al. (1980)
   Autism and mental
   retardation: Neuropathologic
   studies performed in four
   retarded persons with
   autistic behavior.
   
4. Lowe TL et al. (1980).
   Detection of phenylketonuria
   in autistic and psychotic
   children.
   
5. Chen CH, Hsiao KJ (1989) A
   Chinese classic
   phenylketonuria manifested
   as autism.
   
6. Miladi N et al. (1992)
   Phenylketonuria: an
   underlying etiology of
   autistic syndrome. A case
   report.
   
7. Leuzzi V et al. (1995)
   Biochemical, clinical and
   neuroradiological (MRI)
   correlations in late-detected
   PKU patients.
   
8. Brown WT et al. (1982)
   Autism is associated with
   the fragile-X syndrome. .
   
9. Folstein SE, Rutter ML
   (1988) Autism: familial
   aggregation and genetic
   implications.
   
10. Budimirovic DB et al. (2006)
    Autism spectrum disorder in
    Fragile X syndrome:
    differential contribution of
    adaptive socialization and
    social withdrawal.
    
11. Kanner L (1943) Autistic
    disturbances of affective
    contact.
    
12. Kanner L (1946) Irrelevant
    and metaphorical language
    early infantile autism.
    

Full References

References

1. Chess S (1971) Autism in children with congenital rubella.  Journal of Autism and
   Childhood Schizophrenia 1:33-47.
   
2. Chess S, Fernandez P, Korn S. (1978) Behavioral consequences of congenital rubella.
   Journal of Pediatrics. 93:699-703.
   
3. Williams RS, Hauser S, Purpura DP, deLong GR, Swisher CN (1980) Autism and
   mental retardation: Neuropathologic studies performed in four retarded persons with
   autistic behavior.  Archives of Neurology 37:748-753..
   
4. Lowe TL, Tanaka K, Seashore MR, Young JG, Cohen DJ (1980). Detection of
   phenylketonuria in autistic and psychotic children. Journal of the American Medical
   Association 243:126-128.
   
5. Chen CH, Hsiao KJ (1989) A Chinese classic phenylketonuria manifested as autism.
   British Journal of Psychiatry 155:251-3
   
6. Miladi N, Larnaout A, Kaabachi N, Helayem M, Ben Hamida M (1992) Phenylketonuria:
   an underlying etiology of autistic syndrome. A case report. Journal of Child Neurology 7:
   22-23.
   
7. Leuzzi V, Trasimeni G, Gualdi GF, Antonozzi I (1995) Biochemical, clinical and
   neuroradiological (MRI) correlations in late-detected PKU patients. Journal of Inherited
   Metabolic Disease 18:624-634.
   
8. Brown WT, Jenkins EC, Friedman E, Brooks J, Wisniewski K, Raguthu S, French J.
   (1982) Autism is associated with the fragile-X syndrome. Journal of Autism and
   Developmental Disorders. 12:303-8.
   
9. Folstein SE, Rutter ML (1988) Autism: familial aggregation and genetic implications.
   Journal of  Autism and Developmental Disorders. 18:3-30.
   
10. Budimirovic DB, Bukelis I, Cox C, Gray RM, Tierney E, Kaufmann WE.Autism spectrum
    disorder in Fragile X syndrome: differential contribution of adaptive socialization and
    social withdrawal.  Am J Med Genet A. 2006 Sep 1;140(17):1814-26.
    
11. Kanner L (1943) Autistic disturbances of affective contact.  Nervous Child 2:217-250.
    
12. Kanner L (1946) Irrelevant and metaphorical language early infantile autism.  American
    Journal of Psychiatry 103:242-246.
    

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