Hippocampal Plasticity Induced by Patterned Stimulation

行为神经科学研究的一个主要目标是识别构成学习和记忆基础的神经生物学过程。检验基于经验的神经元活动变化的一个重要模型系统是长时程增强，或称LTP。这是突触效率的一个相对持久的变化，这是由短暂的高频弱电脉冲刺激引起的。这种形式的“神经元可塑性”最早是在海马体结构中发现的，海马体结构是已知的与记忆形成有关的大脑区域。罗斯博士最近的工作表明，通过使用一种模仿海马体两种显著电生理活动模式(复杂的尖峰放电和theta节律)的电刺激模式，他可以显著降低诱导LTP的阈值。这种效应被称为“预激脉冲”(PB)增强，只需五个适当模式的刺激就能相当可靠地被调用。由于其阈值低，并且与众所周知的电活动模式相似，因此有人认为，在新记忆的形成过程中，海马体内可能发生了一个类似PB的过程。罗斯博士正在记录正常清醒大鼠海马区的电生理活动，以评估这一假说。这项工作正在澄清促进PB增强的生理和行为条件，从而暗示它们在学习过程中的作用。他还通过检测压力和衰老(两种已知会损害记忆功能的条件)对海马突触能力的影响来检验PB增强和记忆之间的相关性，以显示这种PB效应。

A major goal of behavioral neuroscience research is the identification of the neurobiological processes which underlie learning and memory. One important model system for examining experience-based changes in neuronal activity is long-term potentiation, or LTP. This is a relatively long-lasting change in the efficiency of synapses, which results from stimulation with a brief, high frequency train of weak electrical pulses. This form of "neuronal plasticity" was first discovered in the hippocampal formation, a brain region known to be involved in memory formation. Dr. Rose' recent work has shown that by using a pattern of electrical stimulation which mimics either of two prominent electrophysiological activity patterns of the hippocampus (complex spike discharge and theta rhythm), he could markedly reduce the threshold for inducing LTP. This effect, termed "primed burst" (PB) potentiation, is invoked quite reliably by as few as five appropriately patterned stimuli. Because of its low threshold, and of its similarity to well-known electrical activity patterns, it is proposed that a PB-like process may occur within the hippocampus during the formation of new memories. Dr. Rose is recording electrophysiological activity from the hippocampi of normal, awake rats to evaluate this hypothesis. This work is clarifying both the physiological and behavioral conditions which promote PB potentiation, thus suggesting their role in the learning process. He is also examining the correlation between PB potentiation and memory by examining the effects of stress and aging (two conditions known to impair mnemonic function) upon the capacity of hippocampal synapses to show this PB effect.