Excitotoxic lesions of the medial striatum delay extinction of a reinforcement color discrimination operant task in domestic chicks; A functional role of reward anticipation

Yoko Ichikawa, Ei Ichi Izawa, Toshiya Matsushima

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

To reveal the functional roles of the striatum, we examined the effects of excitotoxic lesions to the bilateral medial striatum (mSt) and nucleus accumbens (Ac) in a food reinforcement color discrimination operant task. With a food reward as reinforcement, 1-week-old domestic chicks were trained to peck selectively at red and yellow beads (S+) and not to peck at a blue bead (S-). Those chicks then received either lesions or sham operations and were tested in extinction training sessions, during which yellow turned out to be nonrewarding (S-), whereas red and blue remained unchanged. To further examine the effects on postoperant noninstrumental aspects of behavior, we also measured the "waiting time", during which chicks stayed at the empty feeder after pecking at yellow. Although the lesioned chicks showed significantly higher error rates in the nonrewarding yellow trials, their postoperant waiting time gradually decreased similarly to the sham controls. Furthermore, the lesioned chicks waited significantly longer than the controls, even from the first extinction block. In the blue trials, both lesioned and sham chicks consistently refrained from pecking, indicating that the delayed extinction was not due to a general disinhibition of pecking. Similarly, no effects were found in the novel training sessions, suggesting that the lesions had selective effects on the extinction of a learned operant. These results suggest that a neural representation of memory-based reward anticipation in the mSt/Ac could contribute to the anticipation error required for extinction.

Original languageEnglish
Pages (from-to)76-83
Number of pages8
JournalCognitive Brain Research
Volume22
Issue number1
DOIs
Publication statusPublished - 2004 Dec 1
Externally publishedYes

Keywords

  • Caudate
  • Lobus parolfactorius
  • Neostriatum
  • Nucleus accumbens
  • Putamen

ASJC Scopus subject areas

  • Experimental and Cognitive Psychology
  • Cognitive Neuroscience
  • Behavioral Neuroscience

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