Steven A. Marchette

Anchoring the neural compass: coding of local spatial reference frames in human medial parietal lobe.

The neural systems that code for location and facing direction during spatial navigation have been investigated extensively; however, the mechanisms by which these quantities are referenced to external features of the world are not well understood. To address this issue, we examined behavioral priming and functional magnetic resonance imaging activity patterns while human subjects recalled spatial views from a recently learned virtual environment. Behavioral results indicated that imagined location and facing direction were represented during this task, and multivoxel pattern analyses indicated that the retrosplenial complex (RSC) was the anatomical locus of these spatial codes. Critically, in both cases, location and direction were defined on the basis of fixed elements of the local environment and generalized across geometrically similar local environments. These results suggest that RSC anchors internal spatial representations to local topographical features, thus allowing us to stay oriented while we navigate and retrieve from memory the experience of being in a particular place.

Cognitive Mappers to Creatures of Habit: Differential Engagement of Place and Response Learning Mechanisms Predicts Human Navigational Behavior

Learning to navigate plays an integral role in the survival of humans and other animals. Research on human navigation has largely focused on how we deliberately map out our world. However, many of us also have experiences of navigating on “autopilot” or out of habit. Animal models have identified this cognitive mapping versus habit learning as two dissociable systems for learning a space—a hippocampal place-learning system and a striatal response-learning system. Here, we use this dichotomy in humans to understand variability in navigational style by demonstrating that brain activation during spatial encoding can predict where a persons behavior falls on a continuum from a more flexible cognitive map-like strategy to a more rigid creature-of-habit approach. These findings bridge the wealth of knowledge gained from animal models and the study of human behavior, opening the door to a more comprehensive understanding of variability in human spatial learning and navigation.

Outside Looking In: Landmark Generalization in the Human Navigational System

The use of landmarks is central to many navigational strategies. Here we use multivoxel pattern analysis of fMRI data to understand how landmarks are coded in the human brain. Subjects were scanned while viewing the interiors and exteriors of campus buildings. Despite their visual dissimilarity, interiors and exteriors corresponding to the same building elicited similar activity patterns in the parahippocampal place area (PPA), retrosplenial complex (RSC), and occipital place area (OPA), three regions known to respond strongly to scenes and buildings. Generalization across stimuli depended on knowing the correspondences among them in the PPA but not in the other two regions, suggesting that the PPA is the key region involved in learning the different perceptual instantiations of a landmark. In contrast, generalization depended on the ability to freely retrieve information from memory in RSC, and it did not depend on familiarity or cognitive task in OPA. Together, these results suggest a tripartite division of labor, whereby PPA codes landmark identity, RSC retrieves spatial or conceptual information associated with landmarks, and OPA processes visual features that are important for landmark recognition. SIGNIFICANCE STATEMENT A central element of spatial navigation is the ability to recognize the landmarks that mark different places in the world. However, little is known about how the brain performs this function. Here we show that the parahippocampal place area (PPA), a region in human occipitotemporal cortex, exhibits key features of a landmark recognition mechanism. Specifically, the PPA treats different perceptual instantiations of the same landmark as representationally similar, but only when subjects have enough experience to know the correspondences among the stimuli. We also identify two other brain regions that exhibit landmark generalization, but with less sensitivity to familiarity. These results elucidate the brain networks involved in the learning and recognition of navigational landmarks.

Spatial memory in the real world: long-term representations of everyday environments

When people learn an environment, they appear to establish a principle orientation just as they would determine the “top” of a novel object. Evidence for reference orientations has largely come from observations of orientation dependence in pointing judgments: Participants are most accurate when asked to recall the space from a particular orientation. However, these investigations have used highly constrained encoding in both time-scale and navigational goals, leaving open the possibility that larger spaces experienced during navigational learning depend on a different organizational scheme. To test this possibility, we asked undergraduates to perform judgments of relative direction on familiar landmarks around their well-learned campus. Participants showed clear evidence for a single reference orientation, generally aligned along salient axes defined by the buildings and paths. This result argues that representing space involves the establishment of a reference orientation, a requirement that endures over repeated exposures and extensive experience.

Object properties and frame of reference in spatial memory representations

Abstract Considerable evidence suggests that humans flexibly select reference frames for spatial memory based on qualities such as the shape of the environment, the configuration of elements, and ones own egocentric experience of the space. We propose that the elements, or objects themselves, may also convey useful information about salient reference orientations. In Experiment 1, participants viewed objects elongated along their front-back axis that were either all oriented in the same direction or oriented at 10 different randomly selected directions. Participants in the random orientation condition were most accurate at the orientation they visually experienced at learning, whereas participants in the shared orientation condition were most accurate at an orientation consistent with or orthogonal to the coincident object orientations. Experiment 2 replicated these effects using animals that were less elongated but had clear conceptual orientations. These results suggest that the principles governing spatial memory capitalize on a wide range of properties that likely interact to support an enduring representation.

Persistent and Stable Biases in Spatial Learning Mechanisms Predict Navigational Style

A wealth of evidence in rodents and humans supports the central roles of two learning systems—hippocampal place learning and striatal response learning—in the formation of spatial representations to support navigation. Individual differences in the ways that these mechanisms are engaged during initial encoding and subsequent navigation may provide a powerful framework for explaining the wide range of variability found in the strategies and solutions that make up human navigational styles. Previous work has revealed that activation in the hippocampal and striatal networks during learning could predict navigational style. Here, we used functional magnetic resonance imaging to investigate the relative activations in these systems during both initial encoding and the act of dynamic navigation in a learned environment. Participants learned a virtual environment and were tested on subsequent navigation to targets within the environment. We observed that a given individual had a consistent balance of memory system engagement across both initial encoding and subsequent navigation, a balance that successfully predicted the participants’ tendencies to use novel shortcuts versus familiar paths during dynamic navigation. This was further supported by the observation that the activation during subsequent retrieval was not dependent on the type of solution used on a given trial. Taken together, our results suggest a model in which the place- and response-learning systems are present in parallel to support a variety of navigational behaviors, but stable biases in the engagement of these systems influence what solutions might be available for any given individual.

Object Working Memory Performance Depends on Microstructure of the Frontal-Occipital Fasciculus

Re-entrant circuits involving communication between the frontal cortex and other brain areas have been hypothesized to be necessary for maintaining the sustained patterns of neural activity that represent information in working memory, but evidence has so far been indirect. If working memory maintenance indeed depends on such temporally precise and robust long-distance communication, then performance on a delayed recognition task should be highly dependent on the microstructural integrity of white-matter tracts connecting sensory areas with prefrontal cortex. This study explored the effect of variations in white-matter microstructure on working memory performance in two separate groups of participants: patients with multiple sclerosis and age- and sex-matched healthy adults. Functional magnetic resonance imaging was performed to reveal cortical regions involved in spatial and object working memory, which, in turn, were used to define specific frontal to extrastriate white-matter tracts of interest via diffusion tensor tractography. After factoring out variance due to age and the microstructure of a control tract (the corticospinal tract), the number of errors produced in the object working memory task was specifically related to the microstructure of the inferior frontal-occipital fasciculus. This result held for both groups, independently, providing a within-study replication with two different types of white-matter structural variability: multiple sclerosis-related damage and normal variation. The results demonstrate the importance of interactions between specific regions of the prefrontal cortex and sensory cortices for a nonspatial working memory task that preferentially activates those regions.

A Mechanistic Approach to Individual Differences in Spatial Learning, Memory, and Navigation

Abstract Navigation is a complex task that depends on the processes of perception, learning, memory, and reasoning to be successful. Given this complexity, it is not surprising that humans (and other species) vary dramatically in their approach and success at navigation. This wide range of abilities has been of great interest to the field of human spatial cognition. In addition, spatial navigation is a cross-species phenomenon that can speak to a variety of learning and memory processes. Therefore, understanding individual differences in this domain can offer a wide range of insights that affect many behaviors in the real world. A cognitive framework that gives precedent to the flexible use of spatial information and explicit or declarative learning processes has driven much of the work on individual differences in navigation in humans. However, animal models of basic learning mechanisms may also offer substantial insight into individual differences in both how well people navigate their surroundings and in the strategies or styles that they bring to bear on the navigational problems. This mechanistic approach may offer a stronger foundation for not only how individual differences might emerge but also how they interact with differences in the environments and goals that drive our need to learn, remember, and navigate in the world.

Multiple Views of Space: Continuous Visual Flow Enhances Small-Scale Spatial Learning.

In the real word, we perceive our environment as a series of static and dynamic views, with viewpoint transitions providing a natural link from one static view to the next. The current research examined if experiencing such transitions is fundamental to learning the spatial layout of small-scale displays. In Experiment 1, participants viewed a tabletop array from 4 orientations in 1 of 3 conditions. The control condition presented the array sequentially, as a series of static views. In the remaining conditions, participants experienced the transition between viewpoints by rotating the array or moving around it. Both transitions improved spatial performance. Experiment 2 added a passive rotation condition to examine the effect of watching the transition without actively generating it. Spatial performance was equivalent across active and passive rotation conditions, with both outperforming static views. Together, these findings suggest that continuous visual flow is key to small-scale spatial learning.

Why people get lost in the Seattle central library

This book evaluates how we perceive buildings in different ways depending upon our academic and professional background. With reference to the Seattle Central Library, it illustrates a range of different methods available through its application. By seeing such a variety of different methods applied to one setting, it allows the opportunity for researchers to understand how tools can highlight various aspects of a building and how those different methods can augment, or complement each other. Unique to this book are contributions from internationally renowned academics from fields including architecture, ethnography, architectural criticism, phenomenology, sociology, environmental psychology and cognitive science, all of which are united by a single, real-world application, the Seattle Central Library. This book will be of interest to architects and students of architecture as well as disciplines such as ethnography, sociology, environmental psychology, and cognitive science that have an interest in applying research methods to the built environment.