Restoring an allocentric reference frame in blind individuals through echolocation

It is not clear to date how visual deprivation affects auditory spatial perception. Recent psychophysical evidences described a spatial auditory deficit in congenitally blind individuals while some others found a spatial auditory improvement. Particularly, Gori, Sandini, Martinoli, & Burr (2014) and Vercillo, Milne, Gori, & Goodale (2015) reported that people who were born blind were less efficient in localizing sound sources with respect to auditory landmarks than sighted individuals. On the other side, blind people performed similarly or even better than sighted participants during the localization of single sound sources. We investigated auditory spatial perception in early blind using different auditory spatial tasks and found that blind individuals did not succeed in localizing sound sources in an external frame of reference. The performance of early blind was severely impaired during the localization of brief auditory stimuli with respect to acoustic landmarks (allocentric frame of reference) but was comparable to that one of sighted participants when they had to localize sounds with respect to their own body (egocentric reference frame). Our results suggest that, after early visual deprivation, auditory spatial perception is centered on an egocentric reference system.

Research in spatial navigation revealed the existence of discrete strategies defined by the use of distinct reference frames during virtual path integration. The present study investigated the distribution of these navigation strategies as a function of gender, video gaming experience, and self-estimates of spatial navigation abilities in a population of 300 subjects. Participants watched videos of virtual passages through a star-field with one turn in either the horizontal (yaw) or the vertical (pitch) axis. At the end of a passage they selected one out of four homing arrows to indicate the initial starting location. To solve the task, participants could employ two discrete strategies, navigating within either an egocentric or an allocentric reference frame. The majority of valid subjects (232/260) consistently used the same strategy in more than 75% of all trials. With that approach 33.1% of all participants were classified as Turners (using an egocentric reference frame on both axes) and 46.5% as Non-turners (using an allocentric reference frame on both axes). 9.2% of all participants consistently used an egocentric reference frame in the yaw plane but an allocentric reference frame in the pitch plane (Switcher). Investigating the influence of gender on navigation strategies revealed that females predominantly used the Non-turner strategy while males used both the Turner and the Non-turner strategy with comparable probabilities. Other than expected, video gaming experience did not influence strategy use. Based on a strong quantitative basis with the sample size about an order of magnitude larger than in typical psychophysical studies these results demonstrate that most people reliably use one out of three possible navigation strategies (Turners, Non-turners, Switchers) for spatial updating and provides a sound estimate of how those strategies are distributed within the general population.

Previous studies have shown increased sensitivity to auditory motion in early blind (EB) individuals. However, the mechanisms underlying this enhanced performance remains unknown. We estimated auditory motion filters in EB using a psychophysical reverse correlation paradigm-the auditory analogue of Neri (2014).Participants (8 EB and 8 sighted controls (SC)) discriminated the direction of a signal motion (left/right) embedded in broadband noise bursts (500-14,000 Hz) presented over a 10x10 grid (space: -/+30 °; time: 0-800 ms). Amplitude of signal motion was adjusted using staircases to maintain performance at 65%. We made two independent measurements: tuning of auditory motion filters (how noise bursts influence the probability of hearing motion direction), and amplitude threshold for hearing the signal.The estimated filters for both EB and SC were predominantly responsive to sound onsets/offsets, different from the non-separable spatiotemporal selectivity previously observed for visual motion. Also, the filters for EB were more accurate in detecting signal onsets/offsets across both space and time. This more refined tuning successfully predicted the greater sensitivity to hear signal motion in EB, as measured by the amplitude threshold (t(14) = -5.59, p < .001). Thus, EB individuals show subtle qualitative rather than quantitative differences in auditory motion processing that nonetheless result in significant improvements in perception.

A Study of Object-Location Memory Hongbin Wang (Hongbin.Wang@uth.tmc.edu) Todd R. Johnson (Todd.R.Johnson@uth.tmc.edu) Jiajie Zhang (Jiajie.Zhang@uth.tmc.edu) Yue Wang (Yue.Wang@uth.tmc.edu) School of Health Information Sciences, University of Texas Health Science Center at Houston 7000 Fannin, Suite 600, Houston, TX 77030 USA Abstract This paper aims to study the representational nature of human object-location memory. Two experiments are reported, including both performance data and eye movement data. The results show that multiple allocentric frames of reference are used to encode spatial relationships among objects and late computation in object-location memory retrieval in object- cued conditions is often inevitable. The implications on developing a general model of human spatial cognition are discussed. Introduction One important aspect of human spatial memory has to do with remembering the location of objects relative to each other. For example, you might recall that the book you read last night is on your office desk between your computer and the desk lamp. This type of memory for spatial relationships is an essential component of a more general type of memory for spatial layout and is obviously critical for many spatial tasks including locating and navigation (see Tversky, 2000, for a review). It is not clear, however, how spatial relationships among objects are encoded in memory. While it seems apparent that allocentric frames of reference (i.e., locations defined relative to external objects) rather than egocentric frames of reference (i.e., locations relative to the observer self) are often used to describe these spatial relationships, the representational and computational nature of this description is controversial (see Hunt & Waller, 1999; Klatzky, 1998). For example, are object-based spatial relationships encoded and stored directly (early computation)? Or do they have to be inferred much later at the retrieval stage (late computation)? What factors determine which representational scheme is used? In this paper we report two experiments we conducted to directly address these issues. The results show that multiple allocentric frames of reference are used to encode spatial relationships among objects and late computation in object- location memory retrieval in object-cued conditions is often inevitable. This paper consists of three major parts. In the first section, the experimental paradigm is briefly introduced. In the second section, the experiments are reported, including both performance data and eye movement data. In the final section, we briefly discuss our ongoing work of developing a computational model of the object-location memory and its implications on modeling human spatial cognition in general. The Experimental Paradigm We adopted an experimental paradigm developed by Milner and colleagues in the 1990s, which we call the Milner paradigm (e.g., Johnsrude, Owen, Crane, Milner, & Evans, 1999; Milner, Johnsrude, & Crane, 1997; Owen, Milner, Petrides, & Evans, 1996). Though their focus was on neuroimaging studies of the brain foundations of object- location memory, the Milner paradigm offers an elegant experimental design that allows a systematic evaluation of multiple schema for representing spatial relationships. In addition, the availability of neuroimaging data provides invaluable constraints on both understanding behavioral results and developing computational models (e.g., Wang, Johnson, & Zhang, 2001). There are two phases in the Milner paradigm. In the encoding phase (Figure 1A), eight drawings (objects) are individually presented on a computer screen to subjects, with each drawing accompanied by two landmarks (solid squares). Subjects are asked to remember the locations of drawings, relative to the landmarks. In the retrieval phase, subjects are presented some cues plus two identical drawings. One of the two identical drawings (target) is presented in its original location, and the other one (noise) is presented in a different location (or more accurately, it occupies the original location of another object). Subjects are required to perform a forced-choice recognition of the target, relative to the cues. Milner and colleagues originally used four retrieval conditions: 1. In the fixed-landmark condition (Figure 1C), the two landmarks were presented as cues, along with the target-noise pair. The absolute location of landmarks and objects on the screen was unchanged from their original encoding positions. 2. In the shifted-landmark condition (Figure 1D), the two landmarks were presented as cues, along with the target-noise pair. Though the spatial relationships among the landmarks/drawings remained unchanged, the absolute locations of the landmarks/drawings on the screen were shifted. 3. In the fixed-object condition (Figure 1E), two encoded drawings instead the two landmarks were

Sex differences in navigation have often been attributed to the use of different navigation strategies in men and women. However, no study so far has investigated sex differences in the brain networks supporting different navigation strategies. To address this issue, we employed a 3D-navigation task during functional MRI in 36 men and 36 women, all scanned thrice, and modeled navigation strategies by instructions requiring an allocentric vs. egocentric reference frame on the one hand, as well as landmark-based vs. Euclidian strategies on the other hand. We found distinct brain networks supporting different perspectives/strategies. Men showed stronger activation of frontal areas, whereas women showed stronger activation of posterior brain regions. The left inferior frontal gyrus was more strongly recruited during landmark-based navigation in men. The hippocampus showed stronger connectivity with left-lateralized frontal areas in women and stronger connectivity with superior parietal areas in men. We discuss these findings in the light of a stronger recruitment of verbal networks supporting a more verbal strategy in women compared to a stronger recruitment of spatial networks supporting a more spatial strategy use in men. In summary, this study provides evidence that different navigation strategies activate different brain areas in men and women.

The spatial location of objects is processed in egocentric and allocentric reference frames, the early temporal dynamics of which have remained relatively unexplored. Previous experiments focused on ERP components related only to egocentric navigation. Thus, we designed a virtual reality experiment to see whether allocentric reference frame-related ERP modulations can also be registered. Participants collected reward objects at the end of the west and east alleys of a cross maze, and their ERPs to the feedback objects were measured. Participants made turn choices from either the south or the north alley randomly in each trial. In this way, we were able to discern place and response coding of object location. Behavioral results indicated a strong preference for using the allocentric reference frame and a preference for choosing the rewarded place in the next trial, suggesting that participants developed probabilistic expectations between places and rewards. We also found that the amplitude of the P1 was sensitive to the allocentric place of the reward object, independent of its value. We did not find evidence for egocentric response learning. These results show that early ERPs are sensitive to the location of objects during navigation in an allocentric reference frame.

How robust are the deviations in haptic parallelity?

The activity of head direction cells signals the direction of an animal's head relative to landmarks in the world. Although driven by internal estimates of head movements, head direction cells must be kept aligned to the external world by sensory inputs, which arrive in the reference frame of the sensory receptors. We present a computational model, which proposes that sensory inputs are correctly associated to head directions by virtue of a conjunctive representation of place and head directions in the retrosplenial cortex. The model allows for a stable head direction signal, even when the sensory input from nearby cues changes dramatically whenever the animal moves to a different location, and enables stable representations of head direction across connected environments.

This study proposes a scale-based interaction framework for multidimensional data exploration in three-dimensional immersive analytic environments. Grounded in egocentric and allocentric reference frames, the framework integrates four variables—distance, sensitivity, visual density, and information display—that adapt to data scale. Two VR experiments examined interaction and visualization effects across four scale levels (Small Allo, Large Allo, Small Ego, Large Ego). Results showed that performance and exploration strategies varied by reference frame: allocentric conditions supported higher accuracy, while egocentric conditions enabled faster task completion. Cognitive load was lowest under fixed distance and density, and immersion was strongest in structurally stable settings. Spatial ability and prior VR experience also influenced performance and user experience. These findings provide empirical support for scale-aware interaction design and offer a foundation for developing adaptive principles in immersive data interfaces.

The classic Simon effect refers to the phenomenon that responses are faster when the task-irrelevant egocentric stimulus location is on the same side as the response hand than when not. However, the spatial location of an object often varies according to which reference frame the object location was represented in, e.g., egocentric versus allocentric reference frame. It has been unknown, however, whether and how the Simon effect based on the egocentric and the allocentric reference interact, and whether the potential interaction between them is affected by task demands. To investigate these questions, we orthogonally crossed the stimulus-response compatibility induced by the egocentric and the allocentric positions during the Simon effect. Moreover, the irrelevant egocentric and allocentric positions were either explicitly represented via interleaving spatial and non-spatial tasks in Experiment 1 or not in Experiment 2. The results suggested that the Simon effect based on the egocentric locations occurred irrespective of whether the egocentric representations were explicitly coded based on current task demands or not. The Simon effect based on allocentric locations, however, seemed to occur only when the allocentric representations were explicitly induced. Moreover, the egocentric and allocentric Simon effect interacted in a similar way irrespective of task demands, with significantly delayed responses when both the egocentric and the allocentric locations were incongruent with the response code.

Navigating in a virtual three-dimensional maze: how do egocentric and allocentric reference frames interact?

Early-blind Individuals Show Impaired Performance in Wine Odor Categorization

It has been well documented, and fairly well known, that concomitant with an increase in chronological age is a corresponding increase in sensory impairment. As most people realize, our hearing suffers as we get older; hence, the increased need for hearing aids. The first portion of the present paper is how the change in age apparently affects auditory judgments of sound source position. A summary of the literature evaluating the changes in the perception of sound source location and the perception of sound source motion as a function of chronological age is presented. The review is limited to empirical studies with behavioral findings involving humans. It is the view of the author that we have an immensely limited understanding of how chronological age affects perception of space when based on sound. In the latter part of the paper, discussion is given to how auditory spatial perception is traditionally conducted in the laboratory. Theoretically, beneficial reasons exist for conducting research in the manner it has been. Nonetheless, from an ecological perspective, the vast majority of previous research can be considered unnatural and greatly lacking in ecological validity. Suggestions for an alternative and more ecologically valid approach to the investigation of auditory spatial perception are proposed. It is believed an ecological approach to auditory spatial perception will enhance our understanding of the extent to which individuals perceive sound source location and how those perceptual judgments change with an increase in chronological age.

EEG correlates of spatial orientation in the human retrosplenial complex

Cognitive scientists increasingly use virtual reality scenarios to address spatial perception, orientation, and navigation. If based on desktops rather than mobile immersive environments, this involves a discrepancy between the physically experienced static position and the visually perceived dynamic scene, leading to cognitive challenges that users of virtual worlds may or may not be aware of. The frequently reported loss of orientation and worse performance in point-to-origin tasks relate to the difficulty of establishing a consistent reference system on an allocentric or egocentric basis. We address the verbalizability of spatial concepts relevant in this regard, along with the conscious strategies reported by participants. Behavioral and verbal data were collected using a perceptually sparse virtual tunnel scenario that has frequently been used to differentiate between humans' preferred reference systems. Surprisingly, the linguistic data we collected relate to reference system verbalizations known from the earlier literature only to a limited extent, but instead reveal complex cognitive mechanisms and strategies. Orientation in desktop virtual reality appears to pose considerable challenges, which participants react to by conceptualizing the task in individual ways that do not systematically relate to the generic concepts of egocentric and allocentric reference frames.