The Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Proc Natl Acad Sci U S A. 2009 Dec 15;106(50):21341-6. doi: 10.1073/pnas.0908193106. Epub 2009 Nov 19.
The ability to hold multiple objects in memory is fundamental to intelligent behavior, but its neural basis remains poorly understood. It has been suggested that multiple items may be held in memory by oscillatory activity across neuronal populations, but yet there is little direct evidence. Here, we show that neuronal information about two objects held in short-term memory is enhanced at specific phases of underlying oscillatory population activity. We recorded neuronal activity from the prefrontal cortices of monkeys remembering two visual objects over a brief interval. We found that during this memory interval prefrontal population activity was rhythmically synchronized at frequencies around 32 and 3 Hz and that spikes carried the most information about the memorized objects at specific phases. Further, according to their order of presentation, optimal encoding of the first presented object was significantly earlier in the 32 Hz cycle than that for the second object. Our results suggest that oscillatory neuronal synchronization mediates a phase-dependent coding of memorized objects in the prefrontal cortex. Encoding at distinct phases may play a role for disambiguating information about multiple objects in short-term memory.
同时记住多个物体的能力是智能行为的基础，但它的神经基础仍未被很好地理解。有人认为，多个项目可以通过神经元群体的振荡活动来保持在记忆中，但目前几乎没有直接的证据。在这里，我们表明，在短期记忆中记住的两个物体的神经元信息在基础振荡群体活动的特定相位得到增强。我们记录了猕猴在短暂间隔内记住两个视觉物体时的前额叶皮质的神经元活动。我们发现，在这段记忆期间，前额叶群体活动以约 32 和 3 Hz 的频率有节奏地同步，并且在特定相位，尖峰携带关于记忆物体的最多信息。此外，根据它们的呈现顺序，第一个呈现的物体的最佳编码明显早于第二个物体的 32 Hz 周期。我们的结果表明，振荡神经元同步介导了前额叶皮层中记忆物体的相位依赖编码。在不同相位的编码可能在短期记忆中对多个物体的信息进行去模糊化方面发挥作用。
