Engagement of posterior parietal cortex (PPC) in visuospatial attention and arithmetic processing has been extensively documented using neuroimaging methods. Numerous studies have suggested a close connection between visuospatial attention and arithmetic processing. However, the extant evidence in humans stems from neuroimaging methods that have relied on group analyses without much knowledge about the profile of neurophysiological engagement within localized neuronal populations at the individual brain level. Hence, it has remained unclear if the overlap of two functions in the PPC is the product of averaging, or they truly stem from a common profile of activity within the same neuronal populations in the human PPC. In the current study, we leveraged the anatomical precision and high signal-to-noise ratio of intracranial electrocorticography and probed the engagement of discrete PPC neuronal populations in seven neurosurgical patients (n = 179 total PPC sites covered; 26 sites on average per individual participant). We aimed to study the extent of parietal activations within each individual brain during visuospatial attention versus arithmetic tasks and the profile of electrophysiological responses within a given recording site during these tasks. Our findings indicated that about 40% of PPC sites did not respond to either visuospatial attention or arithmetic stimuli—or episodic memory conditions that were used as an adjunct control condition. Of those that were activated during either visuospatial attention or arithmetic conditions, a large majority showed overlapping responses during both visuospatial attention and arithmetic conditions. Most interestingly, responses during arithmetic processing were greatest in sites along the intraparietal sulcus region showing preference to contralateral, instead of ipsilateral, visual probes in the visuospatial attention task. Our results provide novel data about the relationship between numerical and spatial orientation at the neuronal population level and shed light on the complex functional organization of the PPC that could not be attained with noninvasive methods.

使用神经影像学方法广泛记录了后顶叶皮层 (PPC) 在视觉空间注意和算术处理中的参与。许多研究表明视觉空间注意力和算术处理之间存在密切联系。然而，人类现存的证据源于依赖于群体分析的神经影像学方法，而对个体大脑水平的局部神经元群中的神经生理学参与情况没有太多了解。因此，目前尚不清楚 PPC 中两种功能的重叠是否是平均的产物，或者它们确实源于人类 PPC 中相同神经元群中的共同活动特征。在目前的研究中，n= 涵盖 179 个 PPC 站点；每个参与者平均有 26 个站点）。我们旨在研究在视觉空间注意与算术任务期间每个个体大脑内顶叶激活的程度，以及在这些任务期间给定记录部位内的电生理反应概况。我们的研究结果表明，大约 40% 的 PPC 站点对视觉空间注意力或算术刺激或用作辅助控制条件的情景记忆条件没有反应。在视觉空间注意或算术条件下被激活的那些中，绝大多数在视觉空间注意和算术条件下表现出重叠的反应。最有趣的是，算术处理过程中的反应在沿顶内沟区域的位置最大，在视觉空间注意任务中表现出对对侧而不是同侧的视觉探测的偏好。我们的结果提供了关于神经元群体水平上数值和空间方向之间关系的新数据，并阐明了 PPC 的复杂功能组织，这是非侵入性方法无法实现的。