AUTISM AND THE BASAL GANGLIA

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AUTISM AND THE BASAL GANGLIA
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INTRODUCTION

• Phenomenological similarity in repetitive
  behaviors in autism with developmental and
  neurological disorders validates shared basal
  ganglia abnormalities, neurotransmitter system
  abnormalities, and pharmacotherapy treatment

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In terms of Neuroanatomy..

• In a study, MRI (i. e magnetic resonance
  imaging) studies performed by Sears and
  colleagues have attributed repetitive behaviors
  in autistic individuals to abnormalities in the
  basal ganglia.

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From studies

• Sears study on Autistic individuals, ADI scores
• Caudate volume enlarged or too small? Conflicted
  findings
• Globus pallidus no change compared to controls
• Putamen no change compared to controls

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Abnormalities in Neurotransmitter Systems and
Pharmacological treatment
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Reduced Dopamine levels in Striatum and
Repetitive Behaviors

• Social deprivation study in rhesus monkeys,
  social deprived rhesus
• Monkeys suffered from repetitive or stereotyped
  behaviors
• Dopaminergic pathway nigostriatal
• Dopamine receptor super sensitivity, no change in
  Dopamine receptor density

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Cont..

• Decreased Dopamine innervation to striatum in
  nigostriatal pathway, decreased dopamine in
  synapses suggested by dopamine
• D2 antagonists are effective, D2 receptors?
• Antipsychotic treatment Haloperdiol, Pimozide,
  Clozapine, and Risperidine as potent D2 receptor
  antagonists that reduce some
  repetitive behaviors.

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Cont...

• However have some side effects i.etardive
  dyskinesia, akathisia).
• What about dopamine agonists? Necessary for Down
  regulation?

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Reduced Serotonin levels in Striatum and
Repetitive Behaviors

• effectiveness of SSRIs in OCD (similar to autism
  in repetitive behaviors).
• serotonin depletion in striatum or striatum
  pathway
• chronic administration of 5-HT reduces repetitive
  behaviors ex head weaving increased in lab rats.
  Suggests tryptophan depletion in Striatum.

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Cont...

• acute administration of 5-HT increases repetitive
  or stereotyped behaviors
• ex head weaving increased in lab rats
• suggests an interaction of dopamine and serotonin
  in pathway from raphe nuclei to striatum?
• SSRIs good for treating stereotypies, compulsions
  and self-injury

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Opiates

• Opiate antagonists effective in treatment of self
  injurious behaviors. Ex Nalxterone
• High concentration of Opioids in striatum?
  Terminal field system of Striatum?
• Interaction of dopamine and opioids?

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Conclusion

• The evidence that caudate volume changes, the
  effectiveness of pharmacological treatments in
  targeting the basal ganglia or pathways to basal
  ganglia, suggests repetitive behaviors in autism
  are due to both neuroanatomical and
  neurotransmitter dysfunction in the basal ganglia.