Modeling operant behavior in the Parkinsonian rat

Irene Avila, Mark P. Reilly, Federico Sanabria, Diana Posadas-Sánchez, Claudia L. Chavez, Nikhil Banerjee, Peter Killeen, Eddie Castañeda

Research output: Contribution to journalArticlepeer-review

28 Scopus citations


Mathematical principles of reinforcement (MPR; Killeen, 1994) is a quantitative model of operant behavior that contains three parameters representing motor capacity (δ), motivation (a), and short term memory (λ). The present study applied MPR to characterize the effects of bilateral infusions of 6-OHDA into the substantia nigra pars compacta in the rat, a model of Parkinson's disease. Rats were trained to lever press under a 5-component fixed-ratio (5, 15, 30, 60, and 100) schedule of food reinforcement. Rats were tested for 15 days prior to dopamine lesions and again for 15 days post-lesion. To characterize functional loss relative to lesion size, rats were grouped according to the extent and the degree of lateralization of their dopamine loss. Response rates decreased as a function of dopamine depletion, primarily at intermediate ratios. MPR accounted for 98% of variance in pre- and post-lesion response rates. Consistent with reported disruptions in motor behavior induced by dopaminergic lesions, estimates of δ increased when dopamine was severely depleted. There was no support for different estimates of a based on pre- and post-lesion performance of any lesion group, suggesting that dopamine loss has negligible effects on incentive motivation. The present study demonstrates the usefulness of combining operant techniques with a theoretical model to better understand the effects of a neurochemical manipulation.

Original languageEnglish (US)
Pages (from-to)298-305
Number of pages8
JournalBehavioural Brain Research
Issue number2
StatePublished - Mar 17 2009


  • Dopamine
  • Fixed-ratio schedule
  • MPR
  • Memory
  • Motivation
  • Motor
  • Operant behavior
  • Parkinson's disease

ASJC Scopus subject areas

  • Behavioral Neuroscience


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