Clayton N S
Section of Neurobiology, Physiology and Behavior, University of California Davis, 95616, USA.
Neuropharmacology. 1998 Apr-May;37(4-5):441-52. doi: 10.1016/s0028-3908(98)00037-9.
Comparative studies provide a unique source of evidence for the role of the hippocampus in learning and memory. Within birds and mammals, the hippocampal volume of scatter-hoarding species that cache food in many different locations is enlarged, relative to the remainder of the telencephalon, when compared with than that of species which cache food in one larder, or do not cache at all. Do food-storing species show enhanced memory function in association with the volumetric enlargement of the hippocampus? Comparative studies within the parids (titmice and chickadees) and corvids (jays, nutcrackers and magpies), two families of birds which show natural variation in food-storing behavior, suggest that there may be two kinds of memory specialization associated with scatter-hoarding. First, in terms of spatial memory, several scatter-hoarding species have a more accurate and enduring spatial memory, and a preference to rely more heavily upon spatial cues, than that of closely related species which store less food, or none at all. Second, some scatter-hoarding parids and corvids are also more resistant to memory interference. While the most critical component about a cache site may be its spatial location, there is mounting evidence that food-storing birds remember additional information about the contents and status of cache sites. What is the underlying neural mechanism by which the hippocampus learns and remembers cache sites? The current mammalian dogma is that the neural mechanisms of learning and memory are achieved primarily by variations in synaptic number and efficacy. Recent work on the concomitant development of food-storing, memory and the avian hippocampus illustrates that the avian hippocampus may swell or shrivel by as much as 30% in response to presence or absence of food-storing experience. Memory for food caches triggers a dramatic increase in the total number of number of neurons within the avian hippocampus by altering the rate at which these cells are born and die.
比较研究为海马体在学习和记忆中的作用提供了独特的证据来源。在鸟类和哺乳动物中，与那些将食物储存在一个贮藏处或根本不贮藏食物的物种相比，在许多不同地点贮藏食物的分散贮藏物种的海马体体积相对于端脑的其余部分有所增大。贮藏食物的物种是否会随着海马体体积的增大而表现出增强的记忆功能？在山雀科（山雀和五子雀）和鸦科（松鸦、坚果雀和喜鹊）这两个鸟类家族中进行的比较研究表明，食物贮藏行为存在自然差异，这可能与分散贮藏有关的两种记忆特化有关。首先，在空间记忆方面，与贮藏食物较少或根本不贮藏食物的近缘物种相比，一些分散贮藏物种具有更准确和持久的空间记忆，并且更倾向于更依赖空间线索。其次，一些分散贮藏的山雀科和鸦科鸟类对记忆干扰也更具抵抗力。虽然关于贮藏地点最关键的因素可能是其空间位置，但越来越多的证据表明，贮藏食物的鸟类会记住关于贮藏地点内容和状态的其他信息。海马体学习和记忆贮藏地点的潜在神经机制是什么？当前哺乳动物的观点是，学习和记忆的神经机制主要通过突触数量和效能的变化来实现。最近关于食物贮藏、记忆和鸟类海马体同步发育的研究表明，鸟类海马体可能会因有无食物贮藏经验而膨胀或萎缩多达30%。对食物贮藏的记忆通过改变这些细胞的生死速率，引发鸟类海马体内神经元总数的急剧增加。
