In the dopamine hypothesis of schizophrenia, which pathway's HYPERACTIVITY is specifically responsible for the positive symptoms?
- A Mesolimbic pathway ✓
- B Mesocortical pathway
- C Tuberoinfundibular pathway
- D Nigrostriatal pathway
Correct answer: A. Mesolimbic pathway
Explanation
The revised dopamine hypothesis attributes positive symptoms (hallucinations, delusions) to hyperactivity of the mesolimbic dopamine pathway (VTA to nucleus accumbens/limbic areas). The mesocortical pathway hypoactivity (to prefrontal cortex) underlies negative symptoms and cognitive deficits. Nigrostriatal pathway blockade causes extrapyramidal side effects; tuberoinfundibular pathway blockade causes hyperprolactinaemia. These distinctions are central to understanding why broad D2 blockade helps positive but not negative symptoms.
Reference: Kaplan & Sadock's Synopsis of Psychiatry, 11th ed.
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