Information in Limited-Capacity Neural Codes

描述（由申请人提供）：许多事情同时发生-总是有大量的刺激要感知，要记住的项目，以及要计划的行动方案。关于注意力的大量研究已经探索了我们有限的大脑是如何屏蔽这些冲击的。这个问题的另一面是，尽管处理能力有限，但有时必须保留有关多个刺激的信息。这项提议探索了能够同时保存多个听觉信息的潜在大脑机制。 我们试图了解不同类型的神经代码如何完成这一壮举。我们专注于声音定位，这对于在复杂场景中进行沟通和避免危险至关重要。定位多个声音涉及两种类型的代码在听觉脑区：一个发射率代码的水平声音位置，这是叠加在地图上的声音频率。然而，用于定位的放电率代码的一个关键限制是，多个IEM的表示似乎是不可能的，因为神经元不能同时以一个以上的放电率放电。 因此，我们将研究两种可能性：代码保留多个项 通过相关频率图提供的不同活动丘的分离（目标1），并且代码通过某种形式的切换行为保留多个项目，其中单个神经元一次仅编码一个刺激，但在群体水平和/或跨时间表示多个声音（目标2）。这些实验将在下丘（IC）进行，下丘是听觉通路的一个重要处理阶段：几乎所有到达更高听觉区域的信息都必须通过这个结构。因此，IC可以编码的内容对后续处理阶段可用的信息施加了边界条件。我们将进行单电极和多电极记录的尖峰和局部场电位活动在执行任务，涉及眼睛运动到多种声音。 这些实验将对正常感知和认知以及相关疾病的许多方面产生重要的见解。记住多个项目的能力是沟通、工作记忆、注意力和感觉运动技能的核心，并且它可能在诸如注意力缺陷障碍、自闭症、中枢听觉处理障碍和年龄相关性听力损失的障碍中受到不利影响。

DESCRIPTION (provided by applicant): Many things happen at once - there are always abundant stimuli to be perceived, items to be remembered, and courses of action to be planned. Considerable research on attention has explored how our limited-capacity brains screen out the onslaught. The flip side of this problem is that sometimes information about multiple stimuli must be preserved despite limitations in processing capacity. This proposal explores potential brain mechanisms capable of preserving multiple auditory items of information simultaneously. We seek to understand how different types of neural codes accomplish this feat. We focus on sound location, which is critical for communicating and avoiding hazards in complex scenes. Localizing multiple sounds involves two types of codes in auditory brain areas: a firing-rate code for horizontal sound location which is superimposed on a map for sound frequency. A critical limitation of the firing- rate code for location, however, is that the representation of multiple iems would appear to be impossible because neurons cannot discharge at more than one firing rate at a time. We will therefore investigate two possibilities: that the code preserves multiple items via segregation into different hills of activity as afforded by the associated frequency map (aim 1), and that the code preserves multiple items by some form of switching behavior, in which individual neurons encode only one stimulus at a time but multiple sounds are represented at the population level and/or across time (aim 2). These experiments will be carried out in the inferior colliculus (IC), an essential processing stage of the auditory pathway: nearly all information reaching higher auditory areas must pass through this structure. Thus, what the IC can encode places boundary conditions on the information that is available to subsequent stages of processing. We will conduct single and multiple electrode recordings of spiking and local field potential activity during performance of a task involving eye movements to multiple sounds. These experiments will yield important insights into many aspects of normal perception and cognition as well as related disorders. The ability to keep multiple items in mind is central t communication, working memory, attention, and sensory-motor skills, and it may be adversely affected in disorders such as attention-deficit disorder, autism, central auditory processing disorder, and age- related hearing loss.