Sandoz Jean-Christophe, Pham-Delègue Minh-Hà
Centre de Recherches sur la Cognition Animale, CNRS UMR 5169, Université Paul Sabatier, 31062 Toulouse cedex 04, France.
Learn Mem. 2004 Sep-Oct;11(5):586-97. doi: 10.1101/lm.81504.
In honeybees, the proboscis extension response (PER) can be conditioned by associating an odor stimulus (CS) to a sucrose reward (US). Conditioned responses to the CS, which are acquired by most bees after a single CS-US pairing, disappear after repeated unrewarded presentations of the CS, a process called extinction. Extinction is usually thought to be based either on (1) the disruption of the stored CS-US association, or (2) the formation of an inhibitory "CS-no US" association that is better retrieved than the initial CS-US association. The observation of spontaneous recovery, i.e., the reappearance of responses to the CS after time passes following extinction, is traditionally interpreted as a proof for the formation of a transient inhibitory association. To provide a better understanding of extinction in honeybees, we examined whether time intervals during training and extinction or the number of conditioning and extinction trials have an effect on the occurrence of spontaneous recovery. We found that spontaneous recovery mostly occurs when conditioning and testing took place in a massed fashion (1-min intertrial intervals). Moreover, spontaneous recovery depended on the time elapsed since extinction, 1 h being an optimum. Increasing the number of conditioning trials improved the spontaneous recovery level, whereas increasing the number of extinction trials reduced it. Lastly, we show that after single-trial conditioning, spontaneous recovery appears only once after extinction. These elements suggest that in honeybees extinction of the PER actually reflects the impairment of the CS-US association, but that depending on training parameters different memory substrates are affected.
在蜜蜂中，伸吻反射（PER）可以通过将气味刺激（条件刺激，CS）与蔗糖奖励（非条件刺激，US）相关联来进行条件反射。大多数蜜蜂在一次CS-US配对后就能获得对CS的条件反应，但在对CS进行多次无奖励呈现后，这种反应就会消失，这个过程称为消退。消退通常被认为是基于以下两种情况之一：（1）存储的CS-US关联被破坏；（2）形成了一种抑制性的“CS-无US”关联，这种关联比最初的CS-US关联更容易被检索到。自发恢复现象的观察，即消退后经过一段时间对CS的反应再次出现，传统上被解释为形成了一种短暂抑制性关联的证据。为了更好地理解蜜蜂的消退现象，我们研究了训练和消退过程中的时间间隔或条件反射和消退试验的次数是否会对自发恢复的发生产生影响。我们发现自发恢复大多发生在集中进行条件反射和测试时（每次试验间隔1分钟）。此外，自发恢复取决于自消退以来经过的时间，1小时是最佳时间。增加条件反射试验的次数会提高自发恢复水平，而增加消退试验的次数则会降低自发恢复水平。最后，我们表明在单次试验条件反射后，消退后自发恢复只出现一次。这些因素表明，在蜜蜂中，PER的消退实际上反映了CS-US关联的受损，但根据训练参数的不同，不同的记忆基质会受到影响。
