Self-organizing continuous attractor network models of hippocampal spatial view cells

Single neuron recording studies have demonstrated the existence of hippocampal spatial view neurons which encode information about the spatial location at which a primate is looking in the environment. These neurons are able to maintain their firing even in the absence of visual input. The standard neuronal network approach to model networks with memory that represent continuous spaces is that of continuous attractor networks. It has recently been shown how idiothetic (self-motion) inputs could update the activity packet of neuronal firing for a one-dimensional case (head direction cells), and for a two-dimensional case (place cells which represent the place where a rat is located). In this paper, we describe three models of primate hippocampal spatial view cells, which not only maintain their spatial firing in the absence of visual input, but can also be updated in the dark by idiothetic input. The three models presented in this paper represent different ways in which a continuous attractor network could integrate a number of different kinds of velocity signal (e.g., head rotation and eye movement) simultaneously. The first two models use velocity information from head angular velocity and from eye velocity cells, and make use of a continuous attractor network to integrate this information. A fundamental feature of the first two models is their use of a 'memory trace' learning rule which incorporates a form of temporal average of recent cell activity. Rules of this type are able to build associations between different patterns of neural activities that tend to occur in temporal proximity, and are incorporated in the model to enable the recent change in the continuous attractor to be associated with the contemporaneous idiothetic input. The third model uses positional information from head direction cells and eye position cells to update the representation of where the agent is looking in the dark. In this case the integration of idiothetic velocity signals is performed in the earlier layer of head direction cells.     

空间-时间关联的中介共同表征结构:来自反转STEARC效应的证据

通过3个双任务实验(诱导任务和特征任务)探讨空间-时间联合编码(STEARC)效应的加工机制。实验1采用时间信息作为诱导任务材料,实验2采用空间信息作为诱导任务材料,在特征任务中都发现映射不一致组被试(看到过去/左侧刺激时按右键反应,看到未来/右侧刺激时按左键反应)出现反转STEARC效应,映射一致组被试表现出常规的STEARC效应,表明从时间信息加工到空间反应过程符合中介共同表征结构。实验3分离两种任务的反应方式(手动和眼动),发现不一致映射规则下,被试仍然表现出常规的STEARC效应,表明这种中介共同表征结构存在特定联结效应,即在不同反应器中出现时间和空间相互独立的表征结构。总体而言,研究支持空间-时间关联符合中介共同表征结构,并且这种关联中存在反应器特定联结效应。     

计算机虚拟技术训练辅助盲人构建空间表征之研究

摘要 由于视觉经验的缺乏,盲人的空间认知存在一定的缺陷,尤其表现在对现实环境的空间布局认识存在困难。本研究欲探究计算机虚拟技术手段辅助盲人建构表征的成效,并在此基础上探究盲人定向行走的效果。本研究是一个现场实验,采用随机分配的方式将全盲被试分为三组,之后让被试接受三种不同的实验处理,即计算机虚拟技术、触觉地图和人导处理,最后接受空间任务测试,测试不仅考察被试对环境空间布局的认识,而且还测量了被试在现实环境的行走探路效率。结果发现,虚拟技术组的被试不仅能够对整个实验环境形成清晰整体的认识,而且还能借助形成的空间表征在测验场地有效地实施定向行走。从研究结果得知,计算机虚拟技术这一手段对应用于改善盲人空间表征系统及提高盲人定向行走训练效率具有一定的积极意义。     

The relationship between the field-shifting phenomenon and representational coherence of place cells in CA1 and CA3 in a cue-altered environment

Subfields of the hippocampus display differential dynamics in processing a spatial environment, especially when changes are introduced to the environment. Specifically, when familiar cues in the environment are spatially rearranged, place cells in the CA3 subfield tend to rotate with a particular set of cues (e.g., proximal cues), maintaining a coherent spatial representation. Place cells in CA1, in contrast, display discordant behaviors (e.g., rotating with different sets of cues or remapping) in the same condition. In addition, on average, CA3 place cells shift their firing locations (measured by the center of mass, or COM) backward over time when the animal encounters the changed environment for the first time, but not after that first experience. However, CA1 displays an opposite pattern, in which place cells exhibit the backward COM-shift only from the second day of experience, but not on the first day. Here, we examined the relationship between the environment-representing behavior (i.e., rotation vs. remapping) and the COM-shift of place fields in CA1 and CA3. Both in CA1 and CA3, the backward (as well as forward) COM-shift phenomena occurred regardless of the rotating versus remapping of the place cell. The differential, daily time course of the onset/offset of backward COM-shift in the cue-altered environment in CA1 and CA3 (on day 1 in CA1 and from day 2 onward in CA3) stems from different population dynamics between the subfields. The results suggest that heterogeneous, complex plasticity mechanisms underlie the environment-representating behavior (i.e., rotate/remap) and the COM-shifting behavior of the place cell.     

Toddlers' representations of space: the role of viewer perspective

In the present study, we examined how people code object location when an object is hidden in an enclosed space. On object location tasks involving disorientation, viewers must code the location of an object in relation to the spatial environment because they cannot directly track their changing relation to the object. Recently, we showed that viewers also code their perspective relative to the entire space (inside vs. outside) in such tasks. To determine whether viewers code perspective whenever they must locate an object, we examined young children's performance on a task in which coding perspective would be difficult. Our task involved both disorientation and translation (i.e., movement from inside to outside the space or vice versa). When translation preceded disorientation, performance was comparable to performance on tasks with no translation. However, when disorientation preceded translation, performance was at chance. The implications of these findings for location coding are discussed.     

道德概念的垂直空间隐喻及其对认知的影响

采用不同的研究方法考察道德概念的垂直空间隐喻表征, 及其对于人的认知的影响。实验1采用迫选法, 在明确要求被试把道德词放在垂直空间位置的上方或下方时, 发现在意识层面, 被试倾向于把道德词放在垂直空间的上部, 把不道德词放在垂直空间的下部。实验2采用无关任务法, 对实验词语作褒贬义判断, 实验结果发现, 道德词出现在空间的上方(相对于下方)时, 被试对道德词作褒贬义判断的时间短; 不道德词出现在空间的下方(相对于上方)时, 被试作褒贬义判断的时间则短。实验3通过记忆任务发现, 道德概念的启动使得个体高估了相继出现的客体的高度和长度, 不道德概念的启动使得个体低估了其高度和长度。三个实验的结果表明, 汉语道德概念的垂直空间隐喻具有心理现实性; 汉语道德概念的垂直空间隐喻既存在于无意识层面又可以在意识的层面显现; 汉语道德概念的垂直空间隐喻表征会影响对物体的高度和长度的估计, 表现为汉语道德概念隐喻表征的“认知偏移效应”。     

Systematic angular biases in the representation of visual space

Representing spatial information is one of our most foundational abilities. Yet in the present work we find that even the simplest possible spatial tasks reveal surprising, systematic misrepresentations of space—such as biases wherein objects are perceived and remembered as being nearer to the centers of their surrounding quadrants. We employed both a placement task (in which observers see two differently sized shapes, one of which has a dot in it, and then must place a second dot in the other shape so that their relative locations are equated) and a matching task (in which observers see two dots, each inside a separate shape, and must simply report whether their relative locations are matched). Some of the resulting biases were shape specific. For example, when dots appeared in a triangle during the placement task, the dots placed by observers were biased away from certain parts of the symmetry axes. But other systematic biases were not shape specific, and seemed instead to reflect differences in the grain of resolution for different regions of space. For example, with both a circle and even a shapeless configuration (with only a central landmark) in the matching task, observers were better at discriminating angular differences (when a dot changed positions around the circle, as opposed to inward/outward changes) in cardinal versus oblique sectors. These data reveal a powerful angular spatial bias, and highlight how the resolution of spatial representation differs for different regions and dimensions of space itself.

     

Enhancing the mental representations of space used by blind pedestrians, based on an image schemata model

The configuration of mental representation of space plays a major role in successful navigational activities. Therefore, navigational assistance for pedestrians who are blind should help them to better configure their mental representation of the environment. In this paper, we propose and exploit a computational model for the mental representation of urban areas as an aid to orientation and navigation for visually impaired pedestrians. Our model uses image schemata to capture the spatial semantics and configural elements of urban space necessary for this purpose. These image schemata are schematic structures that are continually requested by individuals in their perception, bodily movement and interaction with surrounding objects. Our proposed model also incorporates a hierarchical structure to provide different levels of detail tied to appropriate spatial perspectives at each scale. We presume that such computational model will help us to develop an appropriate structure of spatial data used to assist the target population. At the end of the paper, we illustrate the utility of our configural model by developing a typical scenario for the navigation of a blind pedestrian in an urban area.     

Three-dimensional spatiotemporal imaging of movement patterns: Another step toward analyzing the continuity of behavior

Computer-aided spatiotemporal imaging techniques, like those that are proving to be important in many other scientific fields, are being used to represent and study movement patterns of animals exposed to basic reinforcement contingencies. Data from a video-tracking system that provides real-time tracking of the position of an experimental animal as it moves about in a three-dimensional space can be plotted in up to three dimensions. When the data are plotted in two spatial dimensions and the time dimension, behavior is captured as continuous patterns or structures in space-time. Spatiotemporal imaging of movement patterns permits regularities to be observed that are not seen as readily in other ways such as watching videotapes of the experimental sessions or simply examining rate of responding. By providing a concise spatiotemporal representation of the movement patterns that occurred in a given experimental preparation, the imaging techniques described here represent an advancement in the scientific study of continuously flowing behavior. Although we concentrate here on movement patterns produced by basic reinforcement contingencies, the spatiotemporal imaging technology is applicable to any research topic in which movement patterns are of interest, such as foraging, place learning, sign language, and limb movement.     

A visual representation and the control of manual aiming movements

Three experiments were conducted to determine if a representation of the movement environment is functional in the organization and control of limb movements, when direct visual contact with the environment is prevented. In Experiment 1, a visual rearrangement procedure was employed to show that a representation of the environment that provides inaccurate information about the spatial location of a target can disrupt manual target aiming. In Experiment 2, we demonstrated that spatial information about the position of a target can be destroyed by a visual pattern mask, supporting our claim that the representation is visual. A target-cuing procedure was used in Experiment 3 to show that representation of target position can be useful for premovement organization in a target-aiming task. Together our findings suggest that a short-lived visual representation of the movement environment may serve a useful role in the organization and control of limb movements.     

A Visual Representation and the Control of Manual Aiming Movements

Three experiments were conducted to determine if a representation of the movement environment is functional in the organization and control of limb movements, when direct visual contact with the environment is prevented. In Experiment 1, a visual rearrangement procedure was employed to show that a representation of the environment that provides inaccurate information about the spatial location of a target can disrupt manual target aiming. In Experiment 2, we demonstrated that spatial information about the position of a target can be destroyed by a visual pattern mask, supporting our claim that the representation is visual. A target-cuing procedure was used in Experiment 3 to show that representation of target position can be useful for premovement organization in a targetaiming task. Together our findings suggest that a short-lived visual representation of the movement environment may serve a useful role in the organization and control of limb movements.     

Position of code and code for position: From isomorphism to a sensorimotor account of space perception

The paper starts with a discussion of the assumption that positions of the outer world are coded by the anatomical locations of firing neurons within retinotopic maps (“coding position by position”). This “code position theory” explains space perception by some kind of structural isomorphism since it implies that the perceptual space is based on a spatial structure within the brain. The axiom of structural isomorphism is rejected. Subsequently, a sensorimotor account of space perception is outlined according to which the spatial structure of the outer world is coded by the temporal structure of cortical processing. The basis is that action changes the perceiver's relationship to the outer world and, therefore, changes the representation of the outer world coded by the sensory responses of the brain. According to this view the code for position is not a spatial but a temporal structure resulting from action (“coding position by action”). The sensorimotor account offers a possible solution to the binding problem. The paper ends with some remarks on the possible origin and function of retinotopic representations.     

Representing auditory space

Ontario Institute for Studtes tn Education, University of Toronto, Toronto, Canada M5S 1 V6 Auditory space has been characterized as an entity without bound or dimension, as opposed to visual space which is limited in three dimensions. While there is evidence that visual space may be represented mentally in terms of contrastive values on these dimensions, no evidence exists concerning the representation of auditory space. Two experiments used an auditory Stroop-like task to investigate (1) whether the linguistic code for auditory space is comprised of component dimensions as in vision or whether it is unitary, and (2) whether auditory space can also be encoded in a nonlinguistic fashion. Subjects were required to respond to the spatial location of a locative term whose meaning could be congruent, incongruent, or neutral with respect to its location. The findings pointed to the conclusion that when subjects are encouraged to code auditory space linguistically, the code is an undifferentiated symbol or name. Furthermore, some tentative evidence existed that auditory space may also be encoded in a nonlinguistic manner.     

The dreamer's use of space

The dreamer often portrays wishes, conflicts, or current problems in terms of visual-spatial representations and metaphors.The spatial dimensions of dreams frequently signify important affective themes of the dream. In doing so, they serve to continue or reflect processes of self-recognition in relation to the environment, processes that began in early childhood, when the developing child's experience of movement through space played a central role in organizing affect and motivation systems that contribute to emerging schemata of the self. Representations of that movement through space gradually grow to serve a broader symbolic function, as may be seen in the spatial dimensions of both play and dreaming. Spatial relations then become building blocks for aspects of metaphoric and abstract thinking. The resultant personal "geography," a constellation of physical imagery of a body moving through space, retains an important place in mental life as development unfolds. It is complemented and enhanced by the achievement of language, but it never recedes as a core aspect of self. Developmental and neurobiological observations suggest the clinical usefulness of heightened attention to this spatial aspect of dreams. Clinical examples illustrate how attention to the spatial arrangements of a dream and the dreamer's movement through space can enhance access to the affective tone and meaning of the dream.     

On routes and routines: The early development of spatial and temporal representations

Despite apparently fundamental differences, time and space pose similar challenges for representational development. In both cases, children must code relationships between elements that are experienced one at a time. Two influential models of spatial and temporal knowledge in early childhood place considerable emphasis on the coding of sequential relations. These parallels led us to compare the operations that a group of preschool children (M age = 4, 7) could perform on their representations of their nursery school routine and a novel unidirectional route that we taught them. We found that for both contents, the children could describe the order of elements, arrange cards depicting the elements in forward order, and place the cards in backward order. When groups were equated on the basis of their forward-order competence on the route and routine tasks, similar levels of accuracy were shown on the two backward-order tasks. These findings support the existence of representational similarities, but additional research will be required to determine the extent of the overlap. Such research should also help us evaluate the adequacy of existing models of early spatial and temporal representation.     

空间再定向任务中心理表征的多样性——来自虚拟现实实验的证据

成人和儿童完成空间再定向的具体过程与内在机制一直是研究者们关注的问题,在空间中是否形成了关于环境的整体表征是其中的一个关键。研究者们的观点并不一致,研究结果也提供了不同的证据。使用传统的空间再定向任务在此问题上难以得到明确的结论。本研究采用虚拟现实技术,让被试在虚拟现实环境中观察所在空间,然后直接向被试呈现空间的俯视视角并要求完成位置再认。通过对正确率和反应时的模式分析,发现被试反应可以划分为三种类型：整体的、独立于视角的心理表征（各方向均为高正确率低反应时）;整体的、依赖于方向的心理表征（正确率和反应时在不同方向上差异显著）和视角匹配的心理表征（各方向上均为低正确率）。三种不同的表征形式在人群中同时存在,并且在同一个体身上表现出不稳定性。     

Numerical-spatial representation affects spatial coding: binding errors across the numerical distance effect

Does numerical-spatial representation affect feature binding? Studies of visual attention show that poor spatial coding leads to illusory conjunctions (ICs). In numerical cognition, it has been shown that numbers and space are not totally dissociated. This association underlies the numerical distance effect (DE): faster responses as the distance between the compared digits becomes larger (2 7 vs. 2 4). We used the DE to test whether numerical-spatial representation is available to visual processes that rely on spatial coding, such as feature binding. Participants reported the larger of two colored numbers. Both numerical distance (distances 2 and 5) and number–space congruity (e.g., congruent pair, 1 3; incongruent pair, 3 1) were analyzed. Results showed a higher proportion of ICs for distance 2 than for distance 5, providing strong evidence that numerical-spatial representation (1) entails a strong location code and (2) is available to visual processes that rely on location information.     

Independent coding of target distance and direction in visuo-spatial working memory

The organization of manual reaching movements suggests considerable independence in the initial programming with respect to the direction and the distance of the intended movement. It was hypothesized that short-term memory for a visually-presented location within reaching space, in the absence of other allocentric reference points, might also be represented in a motoric code, showing similar independence in the encoding of direction and distance. This hypothesis was tested in two experiments, using adult human subjects who were required to remember the location of a briefly presented luminous spot. Stimuli were presented in the dark, thus providing purely egocentric spatial information. After the specified delay, subjects were instructed to point to the remembered location. In Exp. 1, temporal decay of location memory was studied, over a range of 4–30 s. The results showed that (a) memory for both the direction and the distance of the visual target location declined over time, at about the same rate for both parameters; however, (b) errors of distance were much greater in the left than in the right hemispace, whereas direction errors showed no such effect; (c) the distance and direction errors were essentially uncorrelated, at all delays. These findings suggest independent representation of these two parameters in working memory. In Exp. 2 the subjects were required to remember the locations of two visual stimuli presented sequentially, one after the other. Only after both stimuli had been presented did the subject receive a signal from the experimenter as to which one was to be pointed to. The results showed that the encoding of a second location selectively interfered with memory for the direction but not for the distance of the to-be-remembered target location. As in Exp. 1, direction and distance errors were again uncorrelated. The results of both experiments indicate that memory for egocentrically-specified visual locations can encode the direction and distance of the target independently. Use of motor-related representation in spatial working memory is thus strongly suggested. The findings are discussed in the context of multiple representations of space in visuo-spatial short-term memory.     

The Correlational Structure of Natural Images and the Calibration of Spatial Representations

Physiologists have long proposed that correlated input activity is important in normal sensory development. Here it is postulated that the visual system is sensitive to the correlation in image intensity across the visual field, and that these correlations are used to help calibrate spatial representations. Since measurements made near to each other in the visual field are more correlated than measurements made at a distance, the degree of correlation can be used as an estimate of the distance between two measurements and can therefore be used to calibrate a roughly organized spatial representation. We therefore explored the hypothesis that low level spatial representations are calibrated using a signal based on image intensity correlation. If the visual system uses input statistics to calibrate its spatial representation, then any distortions and anisotropies in these input statistics should be mirrored by distortions in the representation of space. To test the psychological implications of this hypothesis, a collection of 81 images of open and urban landscapes were used to estimate the degree of correlation between image intensity measurement pairs as a function of both distance and orientation. Doing this we show that a system that used the statistics measured to calibrate its representation would show: (1) a horizontal-vertical illusion;(2) the magnitude of this illusion would depend on the amount of open and urban landscapes in the environment;(3) there would be a nontrivial relationship between line orientation and judged length. Analogues of all these distortions and regularities can be found in the psychophysical literature on distance estimation. This gives strength to the proposal that spatial representations are calibrated using input statistics.     

Do you see what I’m singing? Visuospatial movement biases pitch perception

The nature of the connection between musical and spatial processing is controversial. While pitch may be described in spatial terms such as “high” or “low”, it is unclear whether pitch and space are associated but separate dimensions or whether they share representational and processing resources. In the present study, we asked participants to judge whether a target vocal note was the same as (or different from) a preceding cue note. Importantly, target trials were presented as video clips where a singer sometimes gestured upward or downward while singing that target note, thus providing an alternative, concurrent source of spatial information. Our results show that pitch discrimination was significantly biased by the spatial movement in gesture, such that downward gestures made notes seem lower in pitch than they really were, and upward gestures made notes seem higher in pitch. These effects were eliminated by spatial memory load but preserved under verbal memory load conditions. Together, our findings suggest that pitch and space have a shared representation such that the mental representation of pitch is audiospatial in nature.