Department of Physiology and Neuroscience Graduate Program, University of California, San Francisco, San Francisco, California 94143-0444, USA.
J Neurosci. 2011 May 4;31(18):6661-73. doi: 10.1523/JNEUROSCI.2921-10.2011.
The planning and control of sensory-guided movements requires the integration of multiple sensory streams. Although the information conveyed by different sensory modalities is often overlapping, the shared information is represented differently across modalities during the early stages of cortical processing. We ask how these diverse sensory signals are represented in multimodal sensorimotor areas of cortex in macaque monkeys. Although a common modality-independent representation might facilitate downstream readout, previous studies have found that modality-specific representations in multimodal cortex reflect upstream spatial representations. For example, visual signals have a more eye-centered representation. We recorded neural activity from two parietal areas involved in reach planning, area 5 and the medial intraparietal area (MIP), as animals reached to visual, combined visual and proprioceptive, and proprioceptive targets while fixing their gaze on another location. In contrast to other multimodal cortical areas, the same spatial representations are used to represent visual and proprioceptive signals in both area 5 and MIP. However, these representations are heterogeneous. Although we observed a posterior-to-anterior gradient in population responses in parietal cortex, from more eye-centered to more hand- or body-centered representations, we do not observe the simple and discrete reference frame representations suggested by studies that focused on identifying the "best-match" reference frame for a given cortical area. In summary, we find modality-independent representations of spatial information in parietal cortex, although these representations are complex and heterogeneous.
感觉引导运动的规划和控制需要整合多个感觉流。尽管不同感觉模式所传达的信息通常是重叠的,但在皮质处理的早期阶段,不同模式之间的共享信息的表示方式不同。我们想知道这些不同的感觉信号在猕猴的多感觉运动区皮层中是如何被表示的。虽然共同的模态无关表示可能有助于下游的读出,但以前的研究发现,多模态皮质中的模态特定表示反映了上游的空间表示。例如,视觉信号具有更以眼为中心的表示。当动物注视另一个位置时,我们记录了参与到达计划的两个顶叶区域(5 区和内侧顶内区(MIP))的神经活动,这些区域到达视觉、视觉和本体感觉的组合以及本体感觉的目标。与其他多模态皮质区域不同,相同的空间表示用于在 5 区和 MIP 中表示视觉和本体感觉信号。然而,这些表示是异构的。尽管我们在顶叶皮层中观察到群体反应从更以眼为中心到更以手或身体为中心的表示存在后向前梯度,但我们没有观察到那些专注于为给定的皮质区域识别“最佳匹配”参考框架的研究中所提出的简单而离散的参考框架表示。总之,我们发现顶叶皮层中存在空间信息的模态无关表示,尽管这些表示复杂且异构。