Talk Abstracts
1. Grid-cell contributions to the emergence of place tuning in the hippocampus: Implications for representational drift and artificial place field induction
Author: Francesco Savelli, Department of Neuroscience, Developmental and Regenerative Biology, University of Texas at San Antonio
Abstract: A consensus appears to have consolidated around the notion that grid-cell inputs are dispensable in generating hippocampal place fields. Theoretically, this idea has informed discussion on the nature of the cognitive map well beyond rodent neurophysiology and into human neuroscience. Experimentally, it motivates intracellular, synaptic, and circuit analysis focused on intrahippocampal interactions among place cells that have already acquired the ability to fire spatially. In contrast, the problem of how place tuning first emerges in the hippocampus has received less attention. Careful consideration of the available data does not justify such a limited appreciation of the role of grid-cell inputs. On the contrary, these inputs seem critical for place fields developing in unfamiliar environments larger than traditionally employed in place-cell studies (e.g., large enough for grid cells to express their grid patterns.) Computational modeling has identified the characteristics of a “postsynaptically-gated” synaptic plasticity rule that enables the grid-to-place transformation on a behaviorally realistic spatial and temporal scale. More recent studies building on this model have explored (i) its mechanistic implications for the “representational drift” of the place-cell code as increasingly documented in longitudinal studies and (ii) factors possibly involved in the variable success of experimental protocols attempting the inception of artificial place fields.
2. How Our Internal And External Environment Shape Navigation
Presenter: Thackery I. Brown
Georgia Institute of Technology, School of Psychology and Neuroscience Program
Abstract: Recent neuroscience and psychology work has underscored the importance of tracking internal and external conditions in navigation for understanding the mechanisms behind observed navigation strategies and performance. Two interrelated factors are (externally) environmental “complexity” and (internally) psychological stress. Especially in complex environments, the act of navigating itself can be stressful, and a growing body of work demonstrates that acute psychological stress can disrupt memory processes as well as risk/reward computations necessary for flexibility in navigation. In this talk, I will briefly discuss a series of recent studies from the MAP Lab at Georgia Tech demonstrating the influences of these two interrelated factors on spatial mapping and navigation behavior, and illustrating current and future directions we are involved in as part of the Center for Research and Education in Navigation (CRaNE) organization. Specific data presented will demonstrate how the manipulation of barriers in virtual environments shapes direction-sensitive neural coding in the brain and behavior, and how psychological stress manipulations interact with prior knowledge to shape how humans approach choices between different navigation strategies in an environment. Collectively, these data highlight points of leverage from which future interdisciplinary research can further advance our understanding of the basic science of navigation, but also potential interventions for improving human navigation performance in health and disease.
3. The cognitive constraining of architectural morphology
Author: Sonit Bafna, Associate Professor, School of Architecture, Georgia Tech
Abstract:
My talk will touch upon the relationship between the spatial layout of built forms and our cognitive capacity to map the physical environment. The thrust of the argument is that, in large part, built forms (at the scale of both buildings and cities) are spatially organized to conform to our natural cognitive mapping capacities. This match of the spatial morphology of built forms and our mental capacities is an evolutionary phenomenon—wherever it occurs, it is achieved through institutional processes that shape built forms, not though knowledge that designers, builders, or planners possess about our cognitive mapping capacity. But in deliberately designed complex spatial environments such as large institutional buildings or planned cities, this match often fails to arise. The reason is that the practical knowledge required to create navigable and intelligible layouts requires not just an understanding of our cognitive mapping capacities, but also of the way these capacities constrain the morphological structure of buildings and cities. This, in short, defines the problem of wayfinding design guidance.
I will describe findings from architectural morphology and environmental psychology that support this argument, discuss why efforts to find markers of good wayfinding design have not succeeded, and, using examples of some recent studies at Georgia Tech, describe a line of inquiry through which the environmental qualities that serve our cognitive wayfinding capacities can be learned.
4. Metacognition is initially an online process, but it does not continuously monitor decisional evidence
Lead Author: Marshall L. Green, Georgia Institute of Technology
Abstract: Metacognition is the ability to evaluate the success of internal cognitive processes, such as assigning confidence to whether a visual stimulus was correctly identified or not given the available sensory information. Confidence is often and intuitively thought of as a post-decision process in that a confidence judgment is made after the decision. However, most models assume that confidence is computed from the internal decisional evidence, suggesting that confidence can be an online process. Here we tested whether metacognition is a post-decision process or an online process by examining the time- courses of perceptual and metacognitive sensitivity in a motion estimation task. Participants estimated the direction of a motion stimulus by centering a confidence interval on the perceived motion direction, and they provided confidence by adjusting the width of the confidence interval until they were maximally confident that it contained the true motion direction. The motion stimulus was presented for an average of 3.5s. Angular error and confidence were recorded every 16ms and used to estimate the time courses of decisional and metacognitive sensitivity. The results showed that both decisional and metacognitive sensitivity began to increase at the same time. However, whereas metacognitive sensitivity peaked and plateaued after an average of 1s, decisional sensitivity continued to rise until an average of 2s, suggesting that decisional evidence continued to accumulate after the final confidence judgment was computed. This overall pattern of results suggests that metacognition is initially an online process, but it does not continuously monitor decisional evidence indefinitely.
5. Age-related and disease-related differences object-in-location memory using immersive virtual reality
Authors: Tammy Tran, Elizabeth Johnson, Daniel Tadeo, Lauren Dacorro, Hadi Hosseini
Stanford University
Abstract:
Misplacing objects is a commonly reported clinical symptom that scales with disease severity in Alzheimer’s disease. In both aging and Alzheimer’s disease, patients report losing common household items, suggesting a potential role of object misplacement as both a digital biomarker and early indicator of Alzheimer’s disease clinical symptoms. However, tracking object misplacement clinically has proven to be challenging. Tracking object location misplacement typically involve self-report and questionnaire-based approaches or 2D screen-based learning approaches where participants recall the location of an object on a screen. However, these approaches do not encompass the complexity of real-world naturalistic behaviors.
In the current study, we used immersive virtual reality to investigate object misplacement in a naturalistic interactive environment in young adults, older adults and patients with mild cognitive impairment, a transitional stage between healthy aging and Alzheimer’s disease dementia. Participants encoded and retrieved the location of objects within the environment and were tested on the precision of their object location memory. In a second task, participants were tested in their allocentric object location memory and mnemonic object discrimination to examine object location binding and object memory specificity. Preliminary findings reveal clear age-related differences in allocentric and egocentric object location memory. Older adults also demonstrate decreased precision for object location memory compared to young adults, as well as decreased mnemonic object discrimination. Together, these findings indicate that examining real-world behaviors in an immersive virtual reality can reveal clear age-related differences in memory performance.
6. Utricular Dysfunction and Hearing Impairment Affect Spatial Navigation in Adults
Authors:
Colin R. Grove (Presenting Author)
Emory University, Atlanta, GA
Eric R. Anson
University of Rochester, Rochester, NY
Yuri Agrawal
University of Colorado, Aurora, CO
Eleanor M. Simonsick
National Institutes of Health, Bethesda, MD
Michael C. Schubert
Johns Hopkins University, Baltimore, MD
Abstract:
Introduction: Spatial navigation, the ability to move through one’s environment, is a complex skill utilized in everyday life. The effects of specific vestibular end-organ deficits and hearing impairments on spatial navigation have received little to no attention. We hypothesized that hearing impairment adversely affects spatial navigation and that bi-modal impairments (vestibular and hearing) further impair navigation ability.
Methods: Data from 182 participants in the Baltimore Longitudinal Study of Aging who had interpretable results for the video head impulse test (vHIT), cervical (cVEMP) and ocular (oVEMP) vestibular evoked myogenic potentials, audiometric testing, and the triangle completion test (TCT) were retrospectively analyzed. Multiple linear regression, controlling for age, sex, and cognition, was employed to identify predictors of TCT performance in terms of end-point error, angle deviation, and distance walked.
Results: oVEMP abnormalities were associated with larger end-point error (p=0.008) and larger angle deviation (p=0.002) but were not associated with distance walked (p=0.392). Abnormalities on cVEMP and vHIT were not associated with distance walked (p=0.835, p=0.300), end-point error (p=0.256, p=0.808), or angle deviation (p=0.192, p=0.966). Compared with normal hearing adults, hearing impaired adults walked a shorter distance during the TCT (p=0.049) but had similar end-point error (p=0.302) and angle deviation (p=0.466). There was no interaction between vestibular and hearing function for predicting spatial navigation ability.
Conclusion: In this cohort analysis, utricular dysfunction and hearing impairment were associated with poorer spatial navigation performance. We postulate that hearing impairment negatively affects one’s ability to use real-time, intrinsic auditory cues and/or prior experience to guide navigation.