Department of Psychology, Bournemouth University, Poole House, Talbot Campus, Fern Barrow, Poole, Dorset BH12 5BB, UK.
Exp Brain Res. 2011 Jan;208(1):61-71. doi: 10.1007/s00221-010-2460-7. Epub 2010 Oct 24.
Path integration is a fundamental mechanism of spatial navigation. In non-human species, it is assumed to be an online process in which a homing vector is updated continuously during an outward journey. In contrast, human path integration has been conceptualized as a configural process in which travelers store working memory representations of path segments, with the computation of a homing vector only occurring when required. To resolve this apparent discrepancy, we tested whether humans can employ different path integration strategies in the same task. Using a triangle completion paradigm, participants were instructed either to continuously update the start position during locomotion (continuous strategy) or to remember the shape of the outbound path and to calculate home vectors on basis of this representation (configural strategy). While overall homing accuracy was superior in the configural condition, participants were quicker to respond during continuous updating, strongly suggesting that homing vectors were computed online. Corroborating these findings, we observed reliable differences in head orientation during the outbound path: when participants applied the continuous updating strategy, the head deviated significantly from straight ahead in direction of the start place, which can be interpreted as a continuous motor expression of the homing vector. Head orientation-a novel online measure for path integration-can thus inform about the underlying updating mechanism already during locomotion. In addition to demonstrating that humans can employ different cognitive strategies during path integration, our two-systems view helps to resolve recent controversies regarding the role of the medial temporal lobe in human path integration.
路径整合是空间导航的基本机制。在非人类物种中，它被认为是一个在线过程，在向外的旅程中不断更新归巢向量。相比之下，人类的路径整合被概念化为一种构形过程，旅行者存储路径段的工作记忆表示，只有在需要时才计算归巢向量。为了解决这一明显的差异，我们测试了人类是否可以在相同的任务中使用不同的路径整合策略。使用三角形完成范式，参与者被指示要么在运动过程中不断更新起点位置（连续策略），要么记住外出路径的形状，并根据该表示计算归巢向量（构形策略）。虽然在构形条件下整体归巢准确性更高，但在连续更新时参与者的反应速度更快，这强烈表明归巢向量是在线计算的。这些发现得到了证实，我们观察到在外出路径期间头部方向有可靠的差异：当参与者应用连续更新策略时，头部明显偏离直线朝向起点方向，这可以解释为归巢向量的连续运动表达。头部方向——一种新的路径整合在线测量方法——因此可以在运动过程中提供有关基础更新机制的信息。除了证明人类可以在路径整合过程中使用不同的认知策略之外，我们的双系统观点还有助于解决最近关于内侧颞叶在人类路径整合中的作用的争议。
