Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA.
Proc Natl Acad Sci U S A. 2010 Apr 27;107(17):7933-8. doi: 10.1073/pnas.1002825107. Epub 2010 Apr 12.
Contralateral hemispheric representation of sensory inputs (the right visual hemifield in the left hemisphere and vice versa) is a fundamental feature of primate sensorimotor organization, in particular the visuomotor system. However, many higher-order cognitive functions in humans show an asymmetric hemispheric lateralization--e.g., right brain specialization for spatial processing--necessitating a convergence of information from both hemifields. Electrophysiological studies in monkeys and functional imaging in humans have investigated space and action representations at different stages of visuospatial processing, but the transition from contralateral to unified global spatial encoding and the relationship between these encoding schemes and functional lateralization are not fully understood. Moreover, the integration of data across monkeys and humans and elucidation of interspecies homologies is hindered, because divergent findings may reflect actual species differences or arise from discrepancies in techniques and measured signals (electrophysiology vs. imaging). Here, we directly compared spatial cue and memory representations for action planning in monkeys and humans using event-related functional MRI during a working-memory oculomotor task. In monkeys, cue and memory-delay period activity in the frontal, parietal, and temporal regions was strongly contralateral. In putative human functional homologs, the contralaterality was significantly weaker, and the asymmetry between the hemispheres was stronger. These results suggest an inverse relationship between contralaterality and lateralization and elucidate similarities and differences in human and macaque cortical circuits subserving spatial awareness and oculomotor goal-directed actions.
感觉输入的对侧半球表示（左半球的右视野和右半球的左视野）是灵长类动物感觉运动组织的基本特征，特别是视觉运动系统。然而，人类的许多高级认知功能表现出不对称的半球侧化，例如，右半球专门用于空间处理，这需要来自两个半球的信息融合。猴子的电生理研究和人类的功能成像已经研究了视觉空间处理的不同阶段的空间和动作表示，但从对侧到统一的全局空间编码的转变，以及这些编码方案与功能侧化之间的关系，尚未完全了解。此外，由于不同的发现可能反映了实际的物种差异，也可能源于技术和测量信号（电生理学与成像）的差异，因此，跨猴子和人类的数据整合以及物种间同源性的阐明受到阻碍。在这里，我们使用工作记忆眼球追踪任务期间的事件相关功能 MRI，直接比较了猴子和人类的动作规划的空间线索和记忆表示。在猴子中，额叶、顶叶和颞叶区域的线索和记忆延迟期活动强烈地对侧。在假定的人类功能同源物中，对侧性显著减弱，并且半球之间的不对称性更强。这些结果表明，对侧性与侧化之间存在反比关系，并阐明了空间意识和眼球运动目标导向动作的人类和猕猴皮质回路的相似性和差异。
