空间导航:路标学习和路径整合的关系

路标学习是指加工获取路标信息的过程,路径整合是指导航者通过对自身运动信息(前庭觉、本体觉、视觉等)加以整合以不断更新自己位置表征的过程,两者都是人类空间导航研究的焦点问题。当前研究尝试探讨路标学习与路径整合的关系,并着重回答以下问题:在正常的空间导航中,导航者是否同时进行路标学习和路径整合?同时利用路标与自身运动信息是否优于利用单一信息?路标学习与路径整合相互干扰还是相互促进?未来研究应更多关注空间线索对导航行为的作用效果,并利用虚拟现实技术等手段深入探究相应的信息加工机制。     

预期对路径整合的影响

人们通过整合自身运动信息进行的空间巡航称为路径整合。本研究采用头盔式虚拟现实和分段式虚拟迷宫, 探究个体的预期如何影响其路径整合的准确性。任务要求被试从包含4个或8个路段的外出路径的起点出发, 行经所有路段后到达外出路径的终点, 再从终点直接返回起点。三组被试在实验前接受不同的指导语, 并因此对正确返航距离产生不同的预期。实验结果表明, 个体返回起点的行为反应受到外出路径特点的影响, 而且反应的准确性在实际情形违背预期时比符合预期时更低。这样的研究结果表明, 预期作为一种非感知觉因素而影响人们进行路径整合, 体现了人类路径整合的高度适应性和策略性。     

空间场景表征中的参照系选取

被试在矩形房间中从两个不同的观察点学习物体场景并在多个朝向上对物体形成的空间关系进行判断,通过控制场景中物体主要内在轴相对于环境结构（房间和地毯）的方向和被试的学习顺序,探讨被试在场景空间表征中采用何种参照系和参照系选取时的影响因素。两个实验结果发现：（1）内在参照系（intrinsic reference systems）和环境参照系均可以用于物体场景的表征,两类参照系之间的关系却是影响被试物体场景表征时参照系选取的重要因素,即当内在参照系与环境参照系方向一致时,被试无论从哪个朝向学习,都选择从垂直于内在参照系和环境参照系的朝向进行表征。反之,当二者方向不一致时,表征时参照系的选择取决于被试的学习经历;（2）无论内在参照系与环境参照系方向是否一致,物体场景本身内在结构的规则性都能够促进空间记忆,即内在结构的规则性既有助于准确编码物体的相对位置,也有助于提高空间关系判断的准确性。     

涉空对话中表征对齐的产生机制

人类如何处理并交换空间信息是现有空间认知领域的热点问题, 这一过程主要是通过涉空对话实现的。在涉空对话中存在着表征对齐现象, 互动双方在对话中会实现空间术语、空间参照系及空间视角等表征的对齐。空间场景物理特征和人与人的协作都会影响表征对齐的程度, 而实现表征对齐的生理基础是对话双方神经活动的一致性。未来可继续探究表征对齐的作用机制, 如与个体空间偏好的关系, 以及合作伙伴特征如何影响表征对齐的程度等。     

虚拟场景中的信息类型对路径整合效率的影响

空间巡航中常采用路径整合进行位置追踪及方向更新,本研究利用返回起点任务,通过对虚拟场景中不同信息类型的设置,探讨地标、纹理、双线索（地标+纹理）及纯色条件下路径整合效率的差异。结果发现,除角度误差外,双线索条件下路径整合效率显著较高,其次是地标条件,纹理条件次之,纯色条件下表现最差。结果表明,不同信息类型下路径整合效率存在显著差异,且双视觉信息较单一视觉信息条件下的整合效率更优。     

虚拟场景中的信息类型对路径整合效率的影响

空间巡航中常采用路径整合进行位置追踪及方向更新,本研究利用返回起点任务,通过对虚拟场景中不同信息类型的设置,探讨地标、纹理、双线索（地标+纹理）及纯色条件下路径整合效率的差异。结果发现,除角度误差外,双线索条件下路径整合效率显著较高,其次是地标条件,纹理条件次之,纯色条件下表现最差。结果表明,不同信息类型下路径整合效率存在显著差异,且双视觉信息较单一视觉信息条件下的整合效率更优。     

基于参数表征的数量空间关系加工

空间关系的理解是概念表征向知觉表征的转化, 而空间关系的表达则是知觉表征向概念表征的转化。两种表征的转化以参照系为中介。视觉数量空间关系加工属于知觉表征向概念表征转化的空间关系表达过程。本研究通过控制方向、朝向及距离在启动与探测中的匹配关系, 采用三个实验探讨了数量空间关系加工中参照系各参数的表征及其相互作用。结果发现：(1) 数量空间关系加工中存在方向表征, 一定任务情境下存在朝向表征。(2) 距离匹配的促进效果只在启动刺激和探测刺激的方位关系处于参照系同轴时发生。这些结果进而说明, 数量空间关系加工中内隐地包含类别空间关系表征, 一定任务情境下, 可能存在垂直/水平的类别空间关系表征; 数量空间关系加工中的距离是联系于参照系轴的表征。     

人类空间记忆和空间巡航

人类如何表征周围环境的空间结构信息,如何利用记忆中的空间表征来指导个体在环境中的空间活动,已成为认知心理学、神经科学、地理学以及人工智能研究的重要课题。文章综述了作者负责的实验室及其合作者近年来在视觉空间信息表征、基于运动的空间表征更新,以及认知系统中的不同空间信息处理模块等方面的研究工作,对以上问题及其内在的认知机制问题进行了初步的探讨     

飞行员动态空间表征建构的策略研究

运用动态视觉空间工作记忆任务探讨了飞行员和对照组的动态空间表征的建构特征。从两个方面考察策略运用:(1)在客体运动轨迹表征反应选择项上,根据客体运动轨迹的几何特征将选择项设置为整体型策略和局部型策略;(2)有关策略运用的问卷测试。结果发现,在完成运动轨迹的动态工作记忆时,飞行员更多采用整体策略,控制组更多采用局部。结果提示具有较高空间能力的飞行员在合并运动刺激元素、整合客体表征转化为整体表征时具有优势。最后提出延时动态空间表征表达运动客体运动轨迹表征,其空间构型依赖于一段时间的客体运动特性的积累。     

序列本体感觉学习获得稳定的自我中心空间表征*

通过同步视觉或者序列本体感觉,被试学习不规则场景。学习完毕之后,在面对学习方向、自主旋转240°、和持续旋转直至迷向3种运动条件下,被试随机指出各个物体的位置。迷向导致同步视觉学习组指向的内部一致性显著变差,而序列本体感觉学习组不受迷向影响。离线的相对位置判断任务表明两组被试的环境中心空间表征没有差异。这证明通过序列本体感觉学习被试也可以形成稳定的自我中心空间表征,支持了空间快照理论的扩展和空间认知的功能等价假说。     

Spatial memory: how egocentric and allocentric combine

Recent experiments indicate the need for revision of a model of spatial memory consisting of viewpoint-specific representations, egocentric spatial updating and a geometric module for reorientation. Instead, it appears that both egocentric and allocentric representations exist in parallel, and combine to support behavior according to the task. Current research indicates complementary roles for these representations, with increasing dependence on allocentric representations with the amount of movement between presentation and retrieval, the number of objects remembered, and the size, familiarity and intrinsic structure of the environment. Identifying the neuronal mechanisms and functional roles of each type of representation, and of their interactions, promises to provide a framework for investigation of the organization of human memory more generally.     

The human parahippocampal cortex subserves egocentric spatial learning during navigation in a virtual maze

BackgroundPresent evidence suggests that the hippocampus (HC) and the parahippocampal cortex (PHC) are involved in allocentric (world-centered) spatial memory. However, the putative role of the PHC in egocentric (body-centered) spatial learning has received only limited systematic investigation.MethodsTo examine the role of the PHC in egocentric learning, 19 healthy volunteers learned to find their way in a virtual maze during functional magnetic resonance imaging (fMRI). The virtual maze presented a first-person view, lacked any topographical landmarks and could be learned only using egocentric navigation strategies.ResultsDuring learning, increased medial temporal lobe activity was observed in the PHC bilaterally. Activity was also observed in cortical areas known to project to the PHC and proposed to contribute to egocentric spatial navigation and memory.ConclusionsOur results point to a role of the PHC for the representation and storage of egocentric information. It seems possible that the PHC contributes to egocentric memory by its feedback projections to the posterior parietal cortex. Moreover, access to allocentric and egocentric streams of spatial information may enable the PHC to construct a global and comprehensive representation of spatial environments and to promote the construction of stable cognitive maps by translating between egocentric and allocentric frames of memory.     

Emergence of an egocentric cue guiding and allocentric inferring strategy that mirrors hippocampal brain-derived neurotrophic factor (BDNF) expression in the Morris water maze

From insects to humans, successful navigation relies on retained representations of spatial relations. These representations are thought to depend on the hippocampal formation, particularly those that are independent of the navigator (allocentric representations). The Morris water maze is a simple and popular task often used to assess spatial navigation. But how animals navigate toward and retain information regarding the location of the goal in this task remains unclear. We provide a comprehensive account of how the water maze is accomplished behaviourally. Our findings suggest that animals solve the task using distal cues via an initial view-matching strategy that is supported by egocentric guidance. Through increased training, however, an emergence of an egocentric-guiding strategy combined with the animal’s greater ability to infer the hidden platform’s location (via allocentric extrapolation) emerges. We also demonstrate that behavioural changes, towards a more allocentric strategy, are reflected in increases in hippocampal brain-derived neurotrophic factor.     

Remembering the past and imagining the future: a neural model of spatial memory and imagery

The authors model the neural mechanisms underlying spatial cognition, integrating neuronal systems and behavioral data, and address the relationships between long-term memory, short-term memory, and imagery, and between egocentric and allocentric and visual and ideothetic representations. Long-term spatial memory is modeled as attractor dynamics within medial-temporal allocentric representations, and short-term memory is modeled as egocentric parietal representations driven by perception, retrieval, and imagery and modulated by directed attention. Both encoding and retrieval/imagery require translation between egocentric and allocentric representations, which are mediated by posterior parietal and retrosplenial areas and the use of head direction representations in Papez's circuit. Thus, the hippocampus effectively indexes information by real or imagined location, whereas Papez's circuit translates to imagery or from perception according to the direction of view. Modulation of this translation by motor efference allows spatial updating of representations, whereas prefrontal simulated motor efference allows mental exploration. The alternating temporal-parietal flows of information are organized by the theta rhythm. Simulations demonstrate the retrieval and updating of familiar spatial scenes, hemispatial neglect in memory, and the effects on hippocampal place cell firing of lesioned head direction representations and of conflicting visual and ideothetic inputs.     

Theories of spatial representations and reference frames: What can configuration errors tell us?

The issue of reference frame is central to theories of spatial representations. Various classifications have been made for different types of reference frames, along with prototypical research paradigms to distinguish between them. This article focuses on the configuration error paradigm proposed by Wang and Spelke (Cognition 77:215-250, 2000) that has been used to examine the nature of the spatial representations underlying object localization during self-movement. Three basic models of spatial memory and spatial updating are discussed, as well as the assumptions behind the configuration error paradigm, to distinguish between static representations, such as the traditional allocentric cognitive map and the egocentric snapshots, and dynamic representations, such as the egocentric updating system. Recent experimental findings are reexamined and shown to be consistent with multiple models, among which the egocentric-updating-and-reload model with an enduring egocentric component provides the simplest interpretations.     

旋转任务中3～5岁儿童空间物体位置编码的研究

本实验探讨3~5岁儿童在对空间物体位置进行编码时,能否有效采用心理旋转策略或根据物体"位置关系"来判断物体方位。实验采用3×4混合设计,在旋转条件下研究上述问题。结果表明:(1)在策略方面,儿童对心理旋转的使用要显著优于利用位置关系进行判断;(2)随着年龄增长,心理旋转的能力不断提高,5岁时进步尤其明显;(3)3~5岁儿童均不能自动利用位置关系对物体位置进行编码,但5岁儿童经提示后可采用此策略。     

Evidence of separable spatial representations in a virtual navigation task

Three experiments investigated spatial orientation in a virtual navigation task. Subjects had to adjust a homing vector indicating their end position relative to the origin of the path. It was demonstrated that sparse visual flow was sufficient for accurate path integration. Moreover, subjects were found to prefer a distinct egocentric or allocentric reference frame to solve the task. "Turners" reacted as if they had taken on the new orientation during turns of the path by mentally rotating their sagittal axis (egocentric frame). "Nonturners," by contrast, tracked the new orientation without adopting it (allocentric frame). When instructed to use their nonpreferred reference frame, both groups displayed no decline in response accuracy relative to their preferred frame; even when presented with reaction formats based on either ego or allocentric coordinates, with format unpredictable on a trial, both groups responded highly accurately. These findings support the assumption of coexisting spatial representations during navigation.     

How different spatial representations interact in virtual environments: the role of mental frame syncing

This experiment is aimed at understanding how egocentric experiences, allocentric viewpoint-dependent representations, and allocentric viewpoint-independent representations interact when encoding and retrieving a spatial environment. Although several cognitive theories have highlighted the interaction between reference frames, it is less clear about the role of a real-time presentation of allocentric viewpoint-dependent representation on the spatial organization of information. Sixty participants were asked to navigate in two virtual cities to memorize the position of one hidden object. Half of the participants had the possibility to visualize the virtual city with an interactive aerial view. Then, they were required to find the position of the object in three different experimental conditions (“retrieval with an interactive aerial view” vs. “retrieval on a map” vs. “retrieval without an interactive aerial view”). Results revealed that participants were significantly more precise in retrieving the position of the object when immersed in an egocentric experience with the interactive aerial view. The retrieval of spatial information is facilitated by the presence of the interactive aerial view of the city, since it provides a real-time allocentric viewpoint-dependent representation. More participants with high preference for using cardinal points tend to be more accurate when they were asked to retrieve the position of the object on the map. As suggested by the mental frame syncing hypothesis, the presence of an allocentric viewpoint-dependent representation during the retrieval seems to ease the imposition on a specific viewpoint on the stored abstract allocentric viewpoint-independent representation. Our findings represent another significant step toward the comprehension of the organization of spatial representations of our environment.     

To point a finger: attentional and motor consequences of observing pointing movements

Recent studies showed that action observation activates neural circuits used in performing the same action and facilitates execution of a similar motor program. This system for direct mapping of observed actions onto observer’s own motor representation is considered critical for human imitation capabilities. The present study shows that observing a pointing action activates a representation of that action in anatomical space, irrespectively of whether the action is shown in allocentric or egocentric perspective. This finding is at odds with the studies on imitation which showed that humans tend to imitate in a spatially compatible (specular) way, as if looking in a mirror. Our results suggest that shared representations for actions are organized in the same spatial coordinates; however, a transformation of this representation might be required for imitation tasks in order to accommodate the goals of imitative action.