Perception of 3-D location based on vision, touch, and extended touch

Are tools truly incorporated as an extension of the body representation?: Assessing the evidence for tool embodiment

The predominant view on human tool-use suggests that an action-oriented body representation, the body schema, is altered to fit the tool being wielded, a phenomenon termed tool embodiment. While observations of perceptual change after tool-use purport to support this hypothesis, several issues undermine their validity in this context, discussed at length in this critical review. The primary measures used as indicators of tool embodiment each face unique challenges to their construct validity. Further, the perceptual changes taken as indicating extension of the body representation only appear to account for a fraction of the tool's size in any given experiment, and do not demonstrate the covariance with tool length that the embodiment hypothesis would predict. The expression of tool embodiment also appears limited to a narrow range of tool-use tasks, as deviations from a simple reaching paradigm can mollify or eliminate embodiment effects altogether. The shortcomings identified here generate important avenues for future research. Until the source of the kinematic and perceptual effects that have substantiated tool embodiment is disambiguated, the hypothesis that the body representation changes to fit tools during tool-use should not be favored over other possibilities such as the formation of separable internal tool models, which seem to offer a more complete account of human tool-use behaviors. Indeed, studies of motor learning have observed analogous perceptual changes as aftereffects to adaptation despite the absence of handheld tool-use, offering a compelling alternative explanation, though more work is needed to confirm this possibility.

Voice Navigation Created by VIP Improves Spatial Performance in People with Impaired Vision

The difficulty associated with spatial navigation is one of the main obstacles to independent living for visually impaired people. With a lack of visual feedback, visually impaired people must identify information from the external environment through other sense organs. This study employed an observational survey to assess voice navigation version A, created by visually impaired people, and voice navigation version B, created by non-visually impaired people. Thirty-two simulated visually impaired people were assigned to conduct task assessments of voice navigation version A and version B. For mission 1, the mean completion rate is 0.988 ± 0.049 (version A); the mean error rate is 0.125 ± 0.182 (version A). For mission 2, the mean completion rate is 0.953 ± 0.148 (version A); the mean error rate is 0.094 ± 0.198 (version A). The assessment results concluded that version A has a higher completion rate (p = 0.001) and a lower error rate (p = 0.001). In the assessment of subjective satisfaction, all the indicators regarding the impression of navigation directives in version A were significantly superior to those indicators in version B. It appears that version A has a different logic of framing than version B. In future applications, a voice navigation version shall be built, according to the way visually impaired people think, because it will facilitate the direction guide when there is a lack of visual feedback.

Alpha Oscillations Are Involved in Localizing Touch on Handheld Tools

The sense of touch is not restricted to the body but can also extend to external objects. When we use a handheld tool to contact an object, we feel the touch on the tool and not in the hand holding the tool. The ability to perceive touch on a tool actually extends along its entire surface, allowing the user to accurately localize where it is touched similarly as they would on their body. Although the neural mechanisms underlying the ability to localize touch on the body have been largely investigated, those allowing to localize touch on a tool are still unknown. We aimed to fill this gap by recording the electroencephalography signal of participants while they localized tactile stimuli on a handheld rod. We focused on oscillatory activity in the alpha (7–14 Hz) and beta (15–30 Hz) ranges, as they have been previously linked to distinct spatial codes used to localize touch on the body. Beta activity reflects the mapping of touch in skin-based coordinates, whereas alpha activity reflects the mapping of touch in external space. We found that alpha activity was solely modulated by the location of tactile stimuli applied on a handheld rod. Source reconstruction suggested that this alpha power modulation was localized in a network of fronto-parietal regions previously implicated in higher-order tactile and spatial processing. These findings are the first to implicate alpha oscillations in tool-extended sensing and suggest an important role for processing touch in external space when localizing touch on a tool.

Perturbation of cortical activity elicits regional and age-dependent effects on unconstrained reaching behavior: a pilot study

Contributions from premotor and supplementary motor areas to reaching behavior in aging humans are not well understood. The objective of these experiments was to examine effects of perturbations to specific cortical areas on the control of unconstrained reaches against gravity by younger and older adults. Double-pulse transcranial magnetic stimulation (TMS) was applied to scalp locations targeting primary motor cortex (M1), dorsal premotor area (PMA), supplementary motor area (SMA), or dorsolateral prefrontal cortex (DLPFC). Stimulation was intended to perturb ongoing activity in the targeted cortical region before or after a visual cue to initiate moderately paced reaches to one of three vertical target locations. Regional effects were observed in movement amplitude both early and late in the reach. Perturbation of PMA increased reach distance before the time of peak velocity to a greater extent than all other regions. Reaches showed greater deviation from a straight-line path around the time of peak velocity and greater overall curvature with perturbation of PMA and M1 relative to SMA and DLPFC. The perturbation increased positional variability of the reach path at the time of peak velocity and the time elapsing after peak velocity. Although perturbations had stronger effects on reaches by younger subjects, this group exhibited less reach path variability at the time of peak velocity and required less time to adjust the movement trajectory thereafter. These findings support the role of PMA in visually guided reaching and suggest an age-related change in sensorimotor processing, possibly due to a loss of cortical inhibitory control.

VES: A Mixed-Reality Development Platform of Navigation Systems for Blind and Visually Impaired

Herein, we describe the Virtually Enhanced Senses (VES) system, a novel and highly configurable wireless sensor-actuator network conceived as a development and test-bench platform of navigation systems adapted for blind and visually impaired people. It allows to immerse its users into “walkable” purely virtual or mixed environments with simulated sensors and validate navigation system designs prior to prototype development. The haptic, acoustic, and proprioceptive feedback supports state-of-art sensory substitution devices (SSD). In this regard, three SSD were integrated in VES as examples, including the well-known “The vOICe”. Additionally, the data throughput, latency and packet loss of the wireless communication can be controlled to observe its impact in the provided spatial knowledge and resulting mobility and orientation performance. Finally, the system has been validated by testing a combination of two previous visual-acoustic and visual-haptic sensory substitution schemas with 23 normal-sighted subjects. The recorded data includes the output of a “gaze-tracking” utility adapted for SSD.

Navigation Systems for the Blind and Visually Impaired: Past Work, Challenges, and Open Problems

Over the last decades, the development of navigation devices capable of guiding the blind through indoor and/or outdoor scenarios has remained a challenge. In this context, this paper’s objective is to provide an updated, holistic view of this research, in order to enable developers to exploit the different aspects of its multidisciplinary nature. To that end, previous solutions will be briefly described and analyzed from a historical perspective, from the first “Electronic Travel Aids” and early research on sensory substitution or indoor/outdoor positioning, to recent systems based on artificial vision. Thereafter, user-centered design fundamentals are addressed, including the main points of criticism of previous approaches. Finally, several technological achievements are highlighted as they could underpin future feasible designs. In line with this, smartphones and wearables with built-in cameras will then be indicated as potentially feasible options with which to support state-of-art computer vision solutions, thus allowing for both the positioning and monitoring of the user’s surrounding area. These functionalities could then be further boosted by means of remote resources, leading to cloud computing schemas or even remote sensing via urban infrastructure.

Embodied pain in fibromyalgia: Disturbed somatorepresentations and increased plasticity of the body schema

Fibromyalgia syndrome (FMS) is a highly prevalent, chronic musculoskeletal condition characterized by widespread pain and evoked pain at tender points. This study evaluated various aspects of body awareness in a sample of 14 women with FMS and 13 healthy controls, such as plasticity of the body schema, body esteem, and interoceptive awareness. To this end, the Rubber Hand Illusion (RHI), the Body Esteem Scale (BES), and the Body Perception Questionnaire (BPQ) were used, respectively. Consistent with increased plasticity of the body schema, FMS patients scored higher, with large or very large effect sizes, across all three domains evaluated in the RHI paradigm, namely proprioceptive drift and perceived ownership and motor control over the rubber hand. Scores on all items addressed by the BES were consistently lower among FMS subjects (2.52, SEM .19 vs 3.89, SEM .16, respectively, p < .01, Cohen’s d = .38-.66). In the FMS sample, BES scores assigned to most painful regions also were lower than those assigned to the remaining body sites (1.58, SEM .19 vs 2.87, SEM .18, respectively, p < .01). Significantly higher scores (p < .01, Cohen’s d = .51-.87) were found in the FMS sample across awareness (3.57 SEM .15 vs 1.87 SEM .11), stress response (3.76 SEM .11 vs 1.78 SEM .11), autonomic nervous system reactivity (2.59 SEM .17 vs 1.35 SEM .07), and stress style 2 (2.73 SEM .27 vs 1.13 SEM .04) subscales of the BPQ. Intensity of ongoing clinical pain was found to be strongly correlated with interoceptive awareness (r = .75, p = .002). The results suggest a disturbed embodiment in FMS, characterized by instability of the body schema, negatively biased cognitions regarding one’s own body, and increased vigilance to internal bodily cues. These manifestations may be interpreted as related with the inability of incoming sensory inputs to adequately update negatively biased off-line somatorepresentations stored as long-term memory.

SPATIAL UPDATING OF HAPTIC ARRAYS ACROSS THE LIFE SPAN

Background/Study Context: Aging research addressing spatial learning, representation, and action is almost exclusively based on vision as the input source. Much less is known about how spatial abilities from nonvisual inputs, particularly from haptic information, may change during life-span spatial development. This research studied whether learning and updating of haptic target configurations differs as a function of age.

METHODS

Three groups of participants, ranging from 20 to 80 years old, felt four-target table-top circular arrays and then performed several tasks to assess life-span haptic spatial cognition. Measures evaluated included egocentric pointing, allocentric pointing, and array reconstruction after physical or imagined spatial updating.

RESULTS

All measures revealed reliable differences between the oldest and youngest participant groups. The age effect for egocentric pointing contrasts with previous findings showing preserved egocentric spatial abilities. Error performance on allocentric pointing and map reconstruction tasks showing a clear age effect, with the oldest participants exhibiting the greatest error, is in line with other studies in the visual domain. Postupdating performance sharply declined with age but did not reliably differ between physical and imagined updating.

CONCLUSION

Results suggest that there is a general trend for age-related degradation of spatial abilities after haptic learning, with the greatest declines manifesting in all measures in people over 60 years of age. Results are interpreted in terms of a spatial aging effect on mental transformations of three-dimensional representations of space in working memory.

Intrinsic spatial knowledge about terrestrial ecology favors the tall for judging distance

Our sense of vision reliably directs and guides our everyday actions, such as reaching and walking. This ability is especially fascinating because the optical images of natural scenes that project into our eyes are insufficient to adequately form a perceptual space. It has been proposed that the brain makes up for this inadequacy by using its intrinsic spatial knowledge. However, it is unclear what constitutes intrinsic spatial knowledge and how it is acquired. We investigated this question and showed evidence of an ecological basis, which uses the statistical spatial relationship between the observer and the terrestrial environment, namely, the ground surface. We found that in dark and reduced-cue environments where intrinsic knowledge has a greater contribution, perceived target location is more accurate when referenced to the ground than to the ceiling. Furthermore, taller observers more accurately localized the target. Superior performance was also observed in the full-cue environment, even when we compensated for the observers' heights by having the taller observer sit on a chair and the shorter observers stand on a box. Although fascinating, this finding dovetails with the prediction of the ecological hypothesis for intrinsic spatial knowledge. It suggests that an individual's accumulated lifetime experiences of being tall and his or her constant interactions with ground-based objects not only determine intrinsic spatial knowledge but also endow him or her with an advantage in spatial ability in the intermediate distance range.

Navigation using sensory substitution in real and virtual mazes

Under certain specific conditions people who are blind have a perception of space that is equivalent to that of sighted individuals. However, in most cases their spatial perception is impaired. Is this simply due to their current lack of access to visual information or does the lack of visual information throughout development prevent the proper integration of the neural systems underlying spatial cognition? Sensory Substitution devices (SSDs) can transfer visual information via other senses and provide a unique tool to examine this question. We hypothesize that the use of our SSD (The EyeCane: a device that translates distance information into sounds and vibrations) can enable blind people to attain a similar performance level as the sighted in a spatial navigation task. We gave fifty-six participants training with the EyeCane. They navigated in real life-size mazes using the EyeCane SSD and in virtual renditions of the same mazes using a virtual-EyeCane. The participants were divided into four groups according to visual experience: congenitally blind, low vision & late blind, blindfolded sighted and sighted visual controls. We found that with the EyeCane participants made fewer errors in the maze, had fewer collisions, and completed the maze in less time on the last session compared to the first. By the third session, participants improved to the point where individual trials were no longer significantly different from the initial performance of the sighted visual group in terms of errors, time and collision.

The visible ground surface as a reference frame for scaling binocular depth of a target in midair

The natural ground surface carries texture information that extends continuously from one's feet to the horizon, providing a rich depth resource for accurately locating an object resting on it. Here, we showed that the ground surface's role as a reference frame also aids in locating a target suspended in midair based on relative binocular disparity. Using real world setup in our experiments, we first found that a suspended target is more accurately localized when the ground surface is visible and the observer views the scene binocularly. In addition, the increased accuracy occurs only when the scene is viewed for 5 s rather than 0.15 s, suggesting that the binocular depth process takes time. Second, we found that manipulation of the configurations of the texture-gradient and/or linear-perspective cues on the visible ground surface affects the perceived distance of the suspended target in midair. Third, we found that a suspended target is more accurately localized against a ground texture surface than a ceiling texture surface. This suggests that our visual system uses the ground surface as the preferred reference frame to scale the distance of a suspended target according to its relative binocular disparity.

The planar mosaic fails to account for spatially directed action

Humans' spatial representations enable navigation and reaching to targets above the ground plane, even without direct perceptual support. Such abilities are inconsistent with an impoverished representation of the third dimension. Features that differentiate humans from most terrestrial animals, including raised eye height and arms dedicated to manipulation rather than locomotion, have led to robust metric representations of volumetric space.

The visual system's intrinsic bias and knowledge of size mediate perceived size and location in the dark

Dimly lit targets in the dark are perceived as located about an implicit slanted surface that delineates the visual system's intrinsic bias (Ooi, Wu, & He, 2001). If the intrinsic bias reflects the internal model of visual space-as proposed here-its influence should extend beyond target localization. Our first 2 experiments demonstrated that the intrinsic bias also influences perceived target size. We employed a size-matching task and an action task to measure the perceived size of a dimly lit target at various locations in the dark. Then using the size distance invariance hypothesis along with the accurately perceived target angular declination, we converted the perceived sizes to locations. We found that the derived locations from the size judgment tasks can be fitted by slanted curves that resemble the intrinsic bias profile from judged target locations. Our third experiment revealed that armed with the explicit knowledge of target size, an observer perceives target locations in the dark following an intrinsic bias-like profile that is shifted slightly farther from the observer than the profile obtained without knowledge of target size (i.e., slightly more veridical). Altogether, we showed that the intrinsic bias serves as an internal model, or memory, of ground surface layouts when the visual system cannot rely on external depth information. This memory/model can also be weakly influenced by top-down knowledge.

Elevation easier than plan for sighted and early-blind adults in a perspective-taking task

Plans show shapes of objects from above, and represent both their left-right order and their order in the z-dimension (the distance of the objects). Elevations show only the vertical shapes of objects arranged from left to right. Plans, having more spatial information, may be more difficult for participants to construct. Results from a study with sighted, sighted-blindfolded, and early-blind participants on Piaget's perspective-taking three-mountain task support this hypothesis. The plan task was judged more difficult than the elevation task even when participants performed with the same level of accuracy on both tasks. In visual and tactile tasks, amount of spatial-order information may determine difficulty, rather than plan versus elevation per se.