Desimone R
Laboratory of Neuropsychology, National Institute of Mental Health, Bethesda, MD 20892-4415, USA.
Proc Natl Acad Sci U S A. 1996 Nov 26;93(24):13494-9. doi: 10.1073/pnas.93.24.13494.
Recent studies show that neuronal mechanisms for learning and memory both dynamically modulate and permanently alter the representations of visual stimuli in the adult monkey cortex. Three commonly observed neuronal effects in memory-demanding tasks are repetition suppression, enhancement, and delay activity. In repetition suppression, repeated experience with the same visual stimulus leads to both short- and long-term suppression of neuronal responses in subpopulations of visual neurons. Enhancement works in an opposite fashion, in that neuronal responses are enhanced for objects with learned behavioral relevance. Delay activity is found in tasks in which animals are required to actively hold specific information "on-line" for short periods. Repetition suppression appears to be an intrinsic property of visual cortical areas such as inferior temporal cortex and is thought to be important for perceptual learning and priming. By contrast, enhancement and delay activity may depend on feedback to temporal cortex from prefrontal cortex and are thought to be important for working memory. All of these mnemonic effects on neuronal responses bias the competitive interactions that take place between stimulus representations in the cortex when there is more than one stimulus in the visual field. As a result, memory will often determine the winner of these competitions and, thus, will determine which stimulus is attended.
近期研究表明，学习和记忆的神经元机制既能动态调节，也能永久性改变成年猴子皮层中视觉刺激的表征。在需要记忆的任务中，三种常见的神经元效应是重复抑制、增强和延迟活动。在重复抑制中，对相同视觉刺激的反复体验会导致视觉神经元亚群中神经元反应的短期和长期抑制。增强作用则相反，即对于具有习得行为相关性的物体，神经元反应会增强。延迟活动出现在要求动物在短时间内“在线”积极保持特定信息的任务中。重复抑制似乎是颞下皮层等视觉皮层区域的固有特性，被认为对知觉学习和启动很重要。相比之下，增强和延迟活动可能依赖于前额叶皮层向颞叶皮层的反馈，被认为对工作记忆很重要。当视野中有多个刺激时，所有这些对神经元反应的记忆效应都会使皮层中刺激表征之间发生的竞争性相互作用产生偏差。因此，记忆通常会决定这些竞争的胜者，从而决定关注哪个刺激。
