Negative BOLD in Sensory Cortices During Verbal Memory: A Component in Generating Internal Representations?
Negative BOLD in Sensory Cortices During Verbal Memory: A Component in Generating Internal Representations?
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DOI：
10.1007/s10548-009-0089-2
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发表时间：
2009-05-01
期刊：
影响因子：
2.7
通讯作者：
Amedi, Amir
中科院分区：
文献类型：
--
作者：
Azulay, Haim;Striem, Ella;Amedi, Amir
当试图从记忆中检索一个事件或视觉图像时，人们倾向于闭上眼睛。然而，这种现象背后的大脑机制仍然知之甚少。最近，我们发现在视觉心理意象中，听觉区域比视觉感知表现出更强的失活。在这里，我们想知道这是否是一种更普遍的现象的特例，这种现象涉及到内在的、内部存储的信息的检索，这将导致与手头任务无关的其他感觉皮层的跨模失活。为了验证这一假设，研究人员对9名视力正常的人进行了扫描，同时对高度抽象的单词（即想象力得分较低的单词）进行了记忆检索。我们还扫描了一组先天失明的10人，根据定义，他们本身没有任何视觉图像。在有视力的受试者中，听觉和视觉区域在记忆检索过程中都被强烈地失活，而在盲人中，听觉皮层被失活，而视觉区域（先前显示与该任务相关）呈现出积极的BOLD信号。这些结果表明，当需要检索或操作内部存储的表征时，失活可能在与任务无关的感觉皮质中最为突出。因此，激活和停用之间存在一种任务相关的平衡，这可能允许资源最大化，并过滤掉不相关的信息，从而能够将注意力分配到所需的任务上。此外，这些结果表明，积极和消极BOLD之间的平衡可能对我们理解包括高级认知功能、感觉加工和多感觉整合在内的各种内在和外在任务至关重要。
People tend to close their eyes when trying to retrieve an event or a visual image from memory. However the brain mechanisms behind this phenomenon remain poorly understood. Recently, we showed that during visual mental imagery, auditory areas show a much more robust deactivation than during visual perception. Here we ask whether this is a special case of a more general phenomenon involving retrieval of intrinsic, internally stored information, which would result in crossmodal deactivations in other sensory cortices which are irrelevant to the task at hand. To test this hypothesis, a group of 9 sighted individuals were scanned while performing a memory retrieval task for highly abstract words (i.e., with low imaginability scores). We also scanned a group of 10 congenitally blind, which by definition do not have any visual imagery per se. In sighted subjects, both auditory and visual areas were robustly deactivated during memory retrieval, whereas in the blind the auditory cortex was deactivated while visual areas, shown previously to be relevant for this task, presented a positive BOLD signal. These results suggest that deactivation may be most prominent in task-irrelevant sensory cortices whenever there is a need for retrieval or manipulation of internally stored representations. Thus, there is a task-dependent balance of activation and deactivation that might allow maximization of resources and filtering out of non relevant information to enable allocation of attention to the required task. Furthermore, these results suggest that the balance between positive and negative BOLD might be crucial to our understanding of a large variety of intrinsic and extrinsic tasks including high-level cognitive functions, sensory processing and multisensory integration.