Visual and proprioceptive representations in spatial memory

It has been shown that spatial information can be acquired from both visual and nonvisual modalities. The present study explored how spatial information from vision and proprioception was represented in memory, investigating orientation dependence of spatial memories acquired through visual and proprioceptive spatial learning. Experiment 1 examined whether visual learning alone and proprioceptive learning alone yielded orientation-dependent spatial memory. Results showed that spatial memories from both types of learning were orientation dependent. Experiment 2 explored how different orientations of the same environment were represented when they were learned visually and proprioceptively. Results showed that both visually and proprioceptively learned orientations were represented in spatial memory, suggesting that participants established two different reference systems based on each type of learning experience and interpreted the environment in terms of these two reference systems. The results provide some initial clues to how different modalities make unique contributions to spatial representations.     

Neural representations in human spatial memory

Ekstrom et al. report the responses of single neurons recorded from the brains of human subjects performing a spatial navigation task in virtual reality. They found cells encoding the subject's current location, view and destination. These data, and related findings in animals, directly reveal some of the representations underlying spatial cognition. They highlight the potential for cognitive psychology and systems neuroscience to combine to provide a neuronal-level understanding of human behaviour.     

Extrapolating spatial layout in scene representations

Can the visual system extrapolate spatial layout of a scene to new viewpoints after a single view? In the present study, we examined this question by investigating the priming of spatial layout across depth rotations of the same scene (Sanocki &; Epstein, 1997). Participants had to indicate which of two dots superimposed on objects in the target scene appeared closer to them in space. There was as much priming from a prime with a viewpoint that was 10° different from the test image as from a prime that was identical to the target; however, there was no reliable priming from larger differences in viewpoint. These results suggest that a scene’s spatial layout can be extrapolated, but only to a limited extent.     

Configural representations in spatial working memory

Two studies investigate the nature of representations in spatial working memory, directly addressing the question of whether people represent the configuration information above and beyond independent positional information when representing multiple sequentially presented locations. In Experiment 1, participants performed a location memory task in which they recalled the location of objects that were presented sequentially on a screen. Comparison of participants' data with simulated data modelled to represent independent positional representation of spatial locations revealed that participants represented the configural properties of shorter sequences (3 and 4 locations) but not of longer ones (5 and 7 locations). Experiment 2 employed a sequential recognition task in which participants were asked to judge whether two consequently presented spatial sequences were identical. These experiments confirmed sensitivity to configural properties of spatial sequences.     

Active navigation and orientation-free spatial representations

In this study, we examined the orientation dependency of spatial representations following various learning conditions. We assessed the spatial representations of human participants after they had learned a complex spatial layout via map learning, via navigating within a real environment, or via navigating through a virtual simulation of that environment. Performances were compared between conditions involving (1) multiple- versus single-body orientation, (2) active versus passive learning, and (3) high versus low levels of proprioceptive information. Following learning, the participants were required to produce directional judgments to target landmarks. Results showed that the participants developed orientation-specific spatial representations following map learning and passive learning, as indicated by better performance when tested from the initial learning orientation. These results suggest that neither the number of vantage points nor the level of proprioceptive information experienced are determining factors; rather, it is the active aspect of direct navigation that leads to the development of orientation-free representations.     

Body-specific representations of spatial location

The body specificity hypothesis (Casasanto, 2009) posits that the way in which people interact with the world affects their mental representation of information. For instance, right- versus left-handedness affects the mental representation of affective valence, with right-handers categorically associating good with rightward areas and bad with leftward areas, and left-handers doing the opposite. In two experiments we test whether this hypothesis can: extend to spatial memory, be measured in a continuous manner, be predicted by extent of handedness, and how the application of such a heuristic might vary as a function of informational specificity. Experiment 1 demonstrates systematic and continuous spatial location memory biases as a function of associated affective information; right-handed individuals misremembered positively- and negatively-valenced locations as further right and left, respectively, relative to their original locations. Left-handed individuals did the opposite, and in general those with stronger right- or left-handedness showed greater spatial memory biases. Experiment 2 tested whether participants would show similar effects when studying a map with high visual specificity (i.e., zoomed in); they did not. Overall we support the hypothesis that handedness affects the coding of affective information, and better specify the scope and nature of body-specific effects on spatial memory.     

Determining the dimensionality in spatial representations of semantic concepts

When multidimensional scaling solutions are used to study semantic concepts, the dimensionality of the optimal configuration has to be determined. Several strategies have been proposed to choose the appropriate dimensionality. In the present paper, the traditional dimensionality choice criteria were evaluated and compared to a method based on the prediction of an external criterion. Two studies were conducted in which typicality of an exemplar within a semantic concept was predicted from its distance to the concept centroid. In contrast to the low-dimensional solutions selected by the traditional methods, predictions of an external criterion improved with additional dimensions up till dimensionalities that were much higher than what is common in the literature. This suggests that traditional methods underestimate the richness of semantic concepts as revealed in spatial representations derived from similarity measures.     

Mental representations of spatial and nonspatial relations

Four experiments investigated the representation and integration in memory of spatial and nonspatial relations. Subjects learned two-dimensional spatial arrays in which critical pairs of object names were semantically related (Experiment 1), semantically and episodically related (Experiment 2), or just episodically related (Experiments 3a and 3b). Episodic relatedness was established in a paired-associate learning task that preceded array learning. After learning an array, subjects participated in two tasks: item recognition, in which the measure of interest was priming; and distance estimation. Priming in item recognition was sensitive to the Euclidean distance between object names and, for neighbouring locations, to nonspatial relations. Errors in distance estimations varied as a function of distance but were unaffected by nonspatial relations. These and other results indicated that nonspatial relations influenced the probability of encoding spatial relations between locations but did not lead to distorted spatial memories.     

Retrieving enduring spatial representations after disorientation

Four experiments tested whether there are enduring spatial representations of objects' locations in memory. Previous studies have shown that under certain conditions the internal consistency of pointing to objects using memory is disrupted by disorientation. This disorientation effect has been attributed to an absence of or to imprecise enduring spatial representations of objects' locations. Experiment 1 replicated the standard disorientation effect. Participants learned locations of objects in an irregular layout and then pointed to objects after physically turning to face an object and after disorientation. The expected disorientation was observed. In Experiment 2, after disorientation, participants were asked to imagine they were facing the original learning direction and then physically turned to adopt the test orientation. In Experiment 3, after disorientation, participants turned to adopt the test orientation and then were informed of the original viewing direction by the experimenter. A disorientation effect was not observed in Experiment 2 or 3. In Experiment 4, after disorientation, participants turned to face the test orientation but were not told the original learning orientation. As in Experiment 1, a disorientation effect was observed. These results suggest that there are enduring spatial representations of objects' locations specified in terms of a spatial reference direction parallel to the learning view, and that the disorientation effect is caused by uncertainty in recovering the spatial reference direction relative to the testing orientation following disorientation.     

Object representations maintain attentional control settings across space and time

Previous research has revealed that we create and maintain mental representations for perceived objects on the basis of their spatiotemporal continuity. An important question is what type of information can be maintained within these so-called object files. We provide evidence that object files retain specific attentional control settings for items presented inside the object, even when it disappears from vision. The objects were entire visual search displays consisting of multiple items moving into and out of view. It was demonstrated that search was speeded when the search target position was repeated from trial to trial, but especially so when spatiotemporal continuity suggested that the entire display was the same object. We conclude that complete spatial attentional biases can be stored in an object file.     

Multisensory spatial representations in eye-centered coordinates for reaching

Humans can reach for objects with their hands whether the objects are seen, heard or touched. Thus, the position of objects is recoded in a joint-centered frame of reference regardless of the sensory modality involved. Our study indicates that this frame of reference is not the only one shared across sensory modalities. The location of reaching targets is also encoded in eye-centered coordinates, whether the targets are visual, auditory, proprioceptive or imaginary. Furthermore, the remembered eye-centered location is updated after each eye and head movement. This is quite surprising since, in principle, a reaching motor command can be computed from any non-visual modality without ever recovering the eye-centered location of the stimulus. This finding may reflect the predominant role of vision in human spatial perception.     

Object location memory: The interplay of multiple representations

This article reports three experiments in which the representational nature of human object location memory was studied. The results show that multiple frames of reference can be used to encode the spatial relationships among objects. Depending on their dominancy, availability, and validity, these multiple representations interact to determine memory performance. Specifically, representations that are automatically encoded and extensively practiced are more dominant, and their availability improves performance when they are valid. On the other hand, when the dominant representations are available but invalid, people may have to resort to the less dominant representations. As a result, the availability of these dominant but invalid representations can actually hurt performance, due to interference. If these interfering representations are eliminated, the performance is again improved. The implications of these findings for general human spatial cognition are discussed.     

Biased representations of the spatial structure of navigable environments

Recent studies (e.g., Shelton & McNamara in Cognitive Psychology, 43(4), 274–310, 2001; Valiquette, McNamara, & Smith in Memory and Cognition, 31(3), 479–489, 2003) have demonstrated that judgments of relative direction (JRD) access a single enduring orientation-dependent allocentric representation of the layout of objects in an environment, regardless of whether the space is viewed from one or multiple vantage points. Two experiments tested the limits of this phenomenon. In both experiments participants learned the locations of objects in a large room from two views: one view was aligned with salient environmental frames of reference (edges of the mat on which objects were placed and walls of the enclosing room) and expected to be preserved in long-term memory; the other view was misaligned and not expected to be preserved in long-term memory. The first experiment demonstrated that performing JRD between studying the misaligned view and studying the aligned view did not result in the misaligned view being maintained in long-term memory. The second experiment demonstrated that after studying the layout extensively from the misaligned view, 30 s of exposure to the aligned view (with no instructions to learn the layout from that view) resulted in the aligned but not the misaligned view being preserved in long-term memory. These findings indicate that the human spatial memory and navigation system is strongly biased to represent the spatial structure of navigable environments with reference directions or axes that are aligned with salient environmental frames of reference.     

Transient and enduring spatial representations under disorientation and self-rotation

Current theories of environmental cognition typically differentiate between an online, transient, and dynamic system of spatial representation and an offline and enduring system of memory representation. Here the authors present additional evidence for such 2-system theories in the context of the disorientation paradigm introduced by R. F. Wang and E. S. Spelke (2000). Several experiments replicate the finding that disorientation results in a decrease in the precision of people's estimates of relative directions. In contrast to the typical interpretation of this effect as indicating the primacy of a transient spatial system, the present results are generally more consistent with an interpretation of it as indicating a switch from a relatively precise online representation to a relatively coarse enduring one. Further experiments examine the relative precision of transient and enduring representations and show that switching between them does not require disorientation, but can also be produced by self-rotations as small as 135 degrees .     

Object updating and the flash-lag effect

Flash lag is a misperception of spatial relations between a moving object and a briefly flashed stationary one. This study began with the observation that the illusion occurs when the moving object continues following the flash, but is eliminated if the object's motion path ends with the flash. The data show that disrupting the continuity of the moving object, via a transient change in size or color, also eliminates the illusion. We propose that this is because a large feature change leads to the formation of a second object representation. Direct evidence for this proposal is provided by the results for a corollary perceptual feature of the disruption in object continuity: the perception of two objects, rather than only one, on the motion path.     

Roles of egocentric and allocentric spatial representations in locomotion and reorientation

Four experiments investigated the nature of spatial representations used in locomotion. Participants learned the layout of several objects and then pointed to the objects while blindfolded in 3 conditions: before turning (baseline), after turning to a new heading (updating), and after disorientation (disorientation). The internal consistency of pointing in the disorientation condition was relatively high and equivalent to that in the baseline and updating conditions, when the layout had salient intrinsic axes and the participants learned the locations of the objects on the periphery of the layout. The internal consistency of pointing was disrupted by disorientation when participants learned the locations of objects while standing amid them and the layout did not have salient intrinsic axes. It was also observed that many participants retrieved spatial relations after disorientation from the original learning heading. These results indicate that people form an allocentric representation of object-to-object spatial relations when they learn the layout of a novel environment and use that representation to locate objects around them. Egocentric representations may be used to locate objects when allocentric representations are not of high fidelity.     

The effect of spatial competition between object-level representations of target and mask on object substitution masking

One of the processes determining object substitution masking (OSM) is thought to be the spatial competition between independent object file representations of the target and mask (e.g., Kahan & Lichtman, 2006). In a series of experiments, we further examined how OSM is influenced by this spatial competition by manipulating the overlap between the surfaces created by the modal completion of the target (an outline square with a gap in one of its sides) and the mask (a four-dot mask). The results of these experiments demonstrate that increasing the spatial overlap between the surfaces of the target and mask increases OSM. Importantly, this effect is not caused by the mask interfering with the processing of the target features it overlaps. Overall, the data indicate, consistent with Kahan and Lichtman, that OSM can arise through competition between independent target and mask representations.