Clayton N S
Department of Zoology, Oxford University, United Kingdom.
J Neurosci. 1995 Apr;15(4):2796-807. doi: 10.1523/JNEUROSCI.15-04-02796.1995.
Food-storing birds, for example, marsh tits, Parus palustris, use memory to retrieve stored food and have a larger hippocampus relative to the rest of the telencephalon than do species that store little or no food such as the blue tit, P. caeruleus. The difference between food storers and nonstorers in relative hippocampal volume occurs after the young birds have fledged from the nest and is dependent upon some aspect of memory for retrieving caches of stored food. To test whether or not species differences in memory and volumetric changes in the hippocampus could be triggered by experience of memory tasks other than retrieval of stored food, groups of hand-raised marsh tits and blue tits were tested between days 35 and 192 posthatch on a one-trial associative memory task in which they were rewarded in phase II for returning to the feeder where they had eaten part of a peanut 20 min earlier. No species differences were found when the peanut was visible in phase I, but when the peanut was hidden in phase I, marsh tits performed better than blue tits, irrespective of whether or not they had had previous experience of storing and retrieving food. In dissociation trials (transformed array of feeders), marsh tits with food-storing experience responded preferentially to spatial cues, whereas blue tits responded equally to both spatial position and object-specific cues. These species differences are also found in wild-caught adults. However, marsh tits without food-storing experience responded equally to both spatial position and object-specific cues, which suggests that experience of storing and/or retrieving caches is required in order for marsh tits to develop the spatial preference seen in adult food storers. Both marsh tits with experience of the one-trial associative memory task and those that had also had food-storing experience had larger relative hippocampal volumes than did controls, independent of age. Of the marsh tits trained on the one-trial associative memory task, there was no difference between those that had had food-storing experience and those that had not. However, in blue tits, there was no effect of experience on relative hippocampal volume. No volumetric differences were observed in ectostriatum, which served as a control brain region. The results suggest that some aspect of memory for retrieving food (whether or not stored by the bird) directly influences growth of the hippocampal region in marsh tits, the food-storing species, but not in blue tits, the nonstoring species.
例如，储存食物的鸟类，如沼泽山雀（Parus palustris），会利用记忆来找回储存的食物，相对于端脑的其他部分，它们的海马体比很少储存或不储存食物的物种（如蓝山雀，P. caeruleus）更大。食物储存者和非储存者在海马体相对体积上的差异出现在幼鸟离巢之后，并且取决于找回储存食物缓存的记忆的某些方面。为了测试除了找回储存食物之外的记忆任务经验是否能引发记忆和海马体体积变化的物种差异，在孵化后第35天至192天之间，对人工饲养的沼泽山雀和蓝山雀群体进行了一项一次性联想记忆任务测试，在第二阶段，它们若回到20分钟前吃过一部分花生的喂食器处就会得到奖励。当第一阶段花生可见时，未发现物种差异，但当第一阶段花生被隐藏时，无论沼泽山雀是否有过储存和找回食物的经验，它们的表现都比蓝山雀好。在分离试验（变换排列的喂食器）中，有食物储存经验的沼泽山雀优先对空间线索做出反应，而蓝山雀对空间位置和物体特定线索的反应相同。这些物种差异在野生捕获的成年鸟中也有发现。然而，没有食物储存经验的沼泽山雀对空间位置和物体特定线索的反应相同，这表明为了让沼泽山雀形成成年食物储存者所表现出的空间偏好，需要有储存和/或找回缓存的经验。有一次性联想记忆任务经验的沼泽山雀和有食物储存经验的沼泽山雀的相对海马体体积都比对照组大，与年龄无关。在接受一次性联想记忆任务训练的沼泽山雀中，有食物储存经验的和没有食物储存经验的之间没有差异。然而，在蓝山雀中，经验对相对海马体体积没有影响。在作为对照脑区的外纹状体中未观察到体积差异。结果表明，找回食物（无论是否由鸟类储存）的记忆的某些方面直接影响储存食物的物种沼泽山雀海马区的生长，但不影响不储存食物的物种蓝山雀的海马区生长。
