Iowa State University Capstones, Theses and Graduate Theses and Dissertations Dissertations 2019 Effect of spatial and non-spatial changes on perceived self-location Lucia Annaleigh Cherep Iowa State University Follow this and additional works at: https://lib.edu/etd Part of the Neuroscience and Neurobiology Commons, and the Psychology Commons Recommended Citation Cherep, Lucia Annaleigh, "Effect of spatial and non-spatial changes on perceived self-location" (2019). Graduate Theses and Dissertations.edu/etd/16988 This Thesis is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Graduate Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact digirep@iastate.
Effect of spatial and non-spatial changes on perceived self-location by Lucia Cherep A thesis submitted to the graduate faculty in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Major: Psychology Program of Study Committee: Jonathan Kelly, Major Professor Eric Cooper Christian Meissner The student author, whose presentation of the scholarship herein was approved by the program of study committee, is solely responsible for the content of this thesis. The Graduate College will ensure this thesis is globally accessible and will not permit alterations after a degree is conferred. Iowa State University Ames, Iowa 2019 Copyright © Lucia Cherep, 2019. All rights reserved.
ii TABLE OF CONTENTS Page NOMENCLATURE. 1 Animal Research on Place Cells. 2 Human Research on Place Cells. 56 iii NOMENCLATURE VR Virtual Reality VE Virtual Environment SAE Sensorimotor Alignment Effect JRD(s) Judgement(s) of Relative Direction iv ACKNOWLEDGMENTS I would like to thank my major professor, Dr.
Jonathan Kelly, and my committee members, Dr. Eric Cooper and Dr. Christian Meissner, for their guidance and support throughout the course of this research. In addition, I would also like to thank my friends, colleagues, the department faculty and staff for making my time at Iowa State University a wonderful experience.
I want to also offer my appreciation to those who were willing to participate in my experiments, without whom, this thesis would not have been possible. v ABSTRACT Place cell activity is measured through single-cell recording in animals, though place- responsive cells and related properties have been identified in the human hippocampus. Human behavioral studies would strengthen these findings, especially given the challenge of conducting neuroscientific research on human place-responsive cells. The current study was based on the finding (Lenck-Santini et al., 2005) that rodent place cells partially remap after spatial environmental changes (rotating objects relative to enclosure) but are unaffected by non-spatial changes (object substitution).
In two completed studies, human perceived self-location was evaluated in response to spatial and non-spatial changes in a virtual environment (VE). Participants studied object locations in a learning VE with three orienting cues: two landmarks and a featural cue (blue stripe on the wall of the surrounding circular room). Participants then performed judgments of relative direction (JRD) in which they imagined various perspectives using the learned object locations. The JRD task was performed while standing in one of four test VEs which varied in spatial and non-spatial changes relative to the learning VE.
Perceived self- location was inferred from the presence/absence of a sensorimotor alignment effect (SAE), indicated by facilitation for imagined perspectives aligned with the body at retrieval. It was expected that the SAE would be present in non-spatial change VEs and absent in spatial change VEs. As predicted, results indicated that non-spatial changes did not disrupt perceived self-location (SAE present). Spatial changes did disrupt perceived self-location (SAE absent), but this effect appeared to depend on participant view at test.
INTRODUCTION The majority of species effectively navigate across vast environments by relying on strategies that take advantage of available sources of information. External information, such as visual cues (e., proximal and distal landmarks) and the geometric structure of the environment is one source. Another source originates from self- movement cues, which include optic flow (visually experienced movement through the environment), proprioception (sense of body position and effort in movements), and vestibular cues (Wolbers & Hegarty, 2010). For example, the desert ant (Cataglyphis) can travel several meters in a curvilinear, outward path and then return in a linear, homeward path.
This feat utilizes by path integration, a process which integrates body- based self-motion cues over time and polarized light from the sun to sense direction (Wehner, 2003). These multiple sensory signals input to various cellular networks and combine to form an internal spatial representation or cognitive map of the environment. An animal’s self-localization, or understanding of its position in space relative to the surrounding environment, was based on Tolman’s (1948) theory that mammals use spatial information as if it was stored in a map-like fashion. This theory, which was subsumed to be an integration of spatial knowledge and personal experiences, was elucidated in rodent behavior.
A rat was trained to follow a path in a maze to a specified location where the rat was rewarded with food. After four days, the maze was altered. The original path was blocked and 12 arms radiated from the central arena. Prevented from using the original path, the rat explored the environment until it selected a new arm and traversed the entire length.
Nineteen of the 53 rats (36%) chose the arm closest in distance to the original path (i., the selected arm had a location about four inches from 2 the original location). This result suggests that the rats acquired knowledge of the direction of the original location, and selected a new path with a location spatially close to the original location (Tolman, Ritchie, & Kalish, 1946). The rodent brain appeared to form a representation of the rat’s current position while simultaneously integrating the rat’s previous experience with the original location into a “shortcut” the rat had never experienced (i., the entire length of the new radial arm). This combination of spatial information and personal experiences encouraged Tolman (1948) to refer to a theory of how we represent our surrounding environment as a metaphorical cognitive map.
Humans are also quite adept at representing shortcuts in familiar environments. A conceptually similar paradigm is the triangle completion task, which requires participants to traverse two path legs then indicate the origin, usually by walking or pointing. Performance is typically accurate, with an average heading error of about 10˚ when participants physically walk and turn to complete the task (Klatzky, Loomis, Beall, Chance, & Golledge, 1998). Animal Research on Place Cells The theory of a cognitive map was further specified by work which suggested that the hippocampus serves as a map-like representation of space (O’Keefe & Dostrovsky, 1971; O’Keefe & Nadel, 1978).
The mammalian hippocampus consists of two “C- shaped” parts, the cornu ammonis (CA) fields, and it is currently suggested that around 11-25% of neurons in the human hippocampus and parahippocampal regions respond purely to spatial locations (Ekstrom et al., 2003; Miller et al. To characterize the role of the hippocampus as a representation of space, O’Keefe, and Dostrovsky (1971) used electrophysiology, a process which measures electrical activity associated with activity in the body, to access single pyramidal cells in the dorsal hippocampus (CA1 and 3 4). By inserting microelectrodes into a rat brain, they were able to record action potentials extracellularly. Wires from a preamplifier were attached to recording equipment and displayed firing in real-time, while postmortem histology confirmed the location of recording sites.
Out of 76 recorded units, eight cells were of interest due to their preferential firing in a specific location relative to non-existent firing, or silence, across other locations., placing a hand on the rodent), visual (e., rotating the platform, dimming light sources), and olfactory stimuli were either introduced or removed in an attempt to alter cell firing, but these unique variations in sensory information did not produce a differential firing response in those cells. Thus, these cells appeared to not rely preferentially on any single sensory input but instead weighted them equally as evidenced by the inability to disrupt firing through single cue alteration. Only the manipulation of several items in the environment, such as varying the size and shape of the animal’s environment, elicited altered firing responses of recorded cells. From these results, O’Keefe and Dostrovsky (1971) proposed that the hippocampus functions as a spatial map.
The cells of interest in O’Keefe and Dostrovsky’s (1971) experiment that fire preferentially based off of an animal’s occupied location in an environment were first referred to as “spatial cells” (see Figure 1). This name would later be refined to the current concept of “place cells.” The discovery of place cells in the hippocampus was regarded as a prime example for the role of the hippocampus in the formation of a cognitive map and the beginning of several investigations into elucidating single cell responses from the hippocampus and surrounding regions (Eichenbaum, 2017; O’Keefe & Nadel, 1978). Additional evidence for the hippocampus serving as a neural 4 representation of space came from discoveries of a class of cells that respond to the direction that an animal is facing at a given time, aptly named “head direction cells” (Muller, Ranck Jr., & Taube, 1996; Taube et al. More recently “grid cells” have also been found in regions within the hippocampal system (e., the medial entorhinal cortex (MEC) and in the pre- and parasubiculum) (Boccara et al., 2010; Moser, Rowland, & Moser, 2015; Hartley, Lever, Burgess, & O’Keefe, 2014).
Grid cells fire in a hexagonal pattern when an animal navigates a given space and are presumed to support place cell formation through additive firing (McNaughton, Battaglia, Jensen, Moser, & Moser, 2006; Solstad, Moser, & Einevoll, 2006). The importance of refining the role of the hippocampus was recognized in 2014 when the Nobel Prize in Physiology or Medicine was awarded to John O’Keefe and May-Britt and Edvard Moser for their discoveries of cells that constitute a “positioning system” in the brain. These findings have led to the view that the hippocampus and surrounding structures represent an internal system that supports spatial navigation. For this paper, the focus will be primarily on experiments that have investigated properties of place cells.
Place cells denote a location in the environment by combining several sensory inputs (O’Keefe, 1979), and though place cells are typically recorded from the hippocampus, these cells have also been found in additional regions, such as the dentate gyrus and MEC (Grieves & Jeffrey, 2017; O’Keefe, 1979; Park, Dvorak, & Fenton, 2011). One property of place cells is stability over time. For example, Thompson and Best (1990) recorded a single place cell that fired in the same location during 14 independent sessions over 153 days (about five months). However, if the environment 5 changed (e., altered geometric shape) place cells can change the location of their firing, or cease entirely, and represent the space uniquely (Anderson & Jeffrey, 2003; O’Keefe & Conway, 1978; Wills, Lever, Cacucci, Burgess, & O’Keefe, 2005) (see Figure 2).
This process of differential firing based on altered environments is referred to as “remapping” (Muller & Kubie, 1987). This phenomenon of remapping appears to be unpredictable, since researchers cannot reliably predict where (or if) a particular place cell will fire in a novel environment. Remapping in place cells is unique, and this is especially evident when compared to firing properties from head direction cells. For example, if the geometric configuration of space is altered (e., change from a circular environment to a rectangular environment), head direction cells will not cease firing or change location (Taube et al.
Instead, head-direction cells have been shown to rotate along with the environment to preserve the cell’s preferred firing direction. For example, the rotation of a cue card produced almost near-equal rotation in the preferred firing direction of head- direction cells (Taube et al. Conversely, two place cells that represent adjacent locations in one enclosure may not represent adjacent locations in a different enclosure. In fact, place cells might not even respond at all.