Reduced after-hyperpolarization in rat piriform cortex pyramidal neurons is associated with increased learning capability during operant conditioning

Edi Barkai

    Research output: Contribution to journalArticlepeer-review

    184 Scopus citations

    Abstract

    Learning-related cellular modifications were studied in the rat piriform cortex. Water-deprived rats were divided to three groups: 'trained' rats were trained in a four-arm maze to discriminate positive cues in pairs of odours, 'control' rats were 'pseudo-trained' by random water rewarding, and 'naive' rats were water-deprived only. In one experimental paradigm, the trained group was exposed to extensive training with rats learning to discriminate between 35 and 50 pairs of odours. Piriform cortex pyramidal neurons from 'trained','control' and 'naive' rats did not differ in their passive membrane properties and single spike characteristics. However, the after-hyperpolarizations (AHPs) that follow six-spike trains were reduced after 'extensive training' by 43% acid 35% compared with 'control' and 'naive', respectively. This effect was not observed in the piriform cortex of another group of rats, in which hyperexcitability was induced by chemical kindling. In another experimental paradigm rats were trained only until they demonstrated 'rule learning', usually after discriminating between one and two pairs of odours ('mild training'). In this experiment, a smaller, yet significant, reduction (20%) in AHPs was observed. AHP reduction was apparent in most of the sampled neurons. AHP remained reduced up to 3 days after the last training session. 5 days or more after the last training session, AHP amplitude recovered to pre-training value and did not differ between 'trained' rats and the others. Accordingly, training suspension for 5 days or more resulted in slower learning of novel odours. We suggest that increased neuronal excitability, manifested as reduced AHP, is related to the ability of the cortical network to enter a 'learning mode' which creates favourable conditions for enhanced learning capability.

    Original languageEnglish
    Pages (from-to)1518-1523
    Number of pages6
    JournalEuropean Journal of Neuroscience
    Volume10
    Issue number4
    DOIs
    StatePublished - 28 Jul 1998

    Keywords

    • AHP
    • Odour-learning
    • Piriform cortex
    • Pyramidal cells

    ASJC Scopus subject areas

    • General Neuroscience

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