Infusion of lidocaine into the dorsal hippocampus before or after the shock training phase impaired conditioned freezing in a two-phase training task of contextual fear conditioning

Shih Dar Chang, Der Yow Chen, K. C. Liang

Research output: Contribution to journalArticlepeer-review

23 Citations (Scopus)

Abstract

Learning in a contextual fear conditioning task involves forming a context representation and associating it with a shock. The dorsal hippocampus (DH) is implicated in representing the context, but whether it also has a role in associating the context and shock is unclear. To address this issue, male Wistar rats were trained on the task by a two-phase training paradigm, in which rats learned the context representation on day 1 and then reactivated it to associate with the shock on day 2; conditioned freezing was tested on day 3. Lidocaine was infused into the DH at various times in each of the two training sessions. Results showed that intra-DH infusion of lidocaine shortly before or after the context training session on day 1 impaired conditioned freezing, attesting to the DH involvement in context representation. Intra-DH infusion of lidocaine shortly before or after the shock training session on day 2 also impaired conditioned freezing. This deficit was reproduced by infusing lidocaine or APV (α-amino-5-phosphonovaleric acid) into the DH after activation of the context memory but before shock administration. The deficit was not due to drug-induced state-dependency, decreased shock sensitivity or reconsolidation failure of the contextual memory. These results suggest that in contextual fear conditioning integrity of the DH is required for memory processing of not only context representation but also context-shock association.

Original languageEnglish
Pages (from-to)95-105
Number of pages11
JournalNeurobiology of Learning and Memory
Volume89
Issue number2
DOIs
Publication statusPublished - 2008 Feb 1

All Science Journal Classification (ASJC) codes

  • Experimental and Cognitive Psychology
  • Cognitive Neuroscience
  • Behavioral Neuroscience

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