Does Neuronal Activity in Auditory Cortex Support Auditory Short Term Memory? Causal Interrogations using Intracranial Direct Current Stimulation

听觉感知、认知和语言主要依赖于通过时间连接连续的声音。这是因为许多声音只有在之前和之后的其他声音的背景下才有意义。演讲就是一个最好的例子。为了连接声音，听觉系统需要能够记住几秒钟的声音，以便将它们与即将到来的声音进行比较和整合。最近的研究表明，这种短期听觉信息记忆所需的过程涉及听觉系统的最高层次——听觉皮层。研究发现，当受试者需要在记忆中保存听觉信息以执行听觉记忆任务时，听觉皮层的不同子区（包括初级听觉皮层）出现了持续的神经元活动。然而，由于短期记忆和听觉皮层之间的这些联系只是一种相关性，我们的项目打算解决因果关系的更基本的神经科学问题，并将测试听觉皮层是否对短期记忆至关重要。为了测试因果关系，我们将通过颅内直流电刺激来改变猴子听觉皮层的活动，并期望这种干预会改变它们执行听觉记忆任务的能力。我们的项目将加深对听觉皮层（也许还有一般的感觉皮层）在短期记忆中的作用的理解。我们的项目也将促进对直流电刺激对单个神经元放电和皮层局部场电位的影响的认识。总之，目前的项目将产生关于直流电刺激如何调节大脑活动和大脑功能的新知识。

Auditory perception, cognition, and language critically depend on linking sequential sounds through time. This is because many sounds make sense only when perceived in the context of other sounds before and after. Speech is a prime example. To link sounds the auditory system needs to be capable of memorizing sounds for several seconds in order to compare and integrate them with upcoming sounds. Recent studies suggest that processes required for such short term memory of auditory information involve the highest level of the auditory system, the auditory cortex. Here, it was found that persistent neuronal activity emerged in different subfields of auditory cortex, including the primary auditory cortex, during time periods when subjects needed to hold auditory information in memory in order to perform an auditory memory task. However, because these associations between short term memory and auditory cortex are only of a correlational nature, our project intends to address the more fundamental neuroscientific question of causality, and will test whether auditory cortex is essential for short term memory. In order to test causality we will modify activity in the auditory cortex of monkeys by means of intracranial direct current stimulation and expect that this intervention will change their ability to perform auditory memory tasks. Our project will deepen the understanding of the role of auditory cortex (and perhaps of sensory cortex in general) in short term memory. Our project will also advance the knowledge of the effects of direct current stimulation on the firing of single neurons and local field potentials in cortex. In summary, the present project will generate new knowledge on how direct current stimulation modulates brain activity and brain functions.