Transformations of Visuospatial Images

Age effects on processing spatial relations within different reference frames: The role of executive functions

Mental representations of space can be generated and communicated with respect to different reference frames and perspectives. The present study investigated the effects of age and individual differences in domain-general executive functions on people's ability to process spatial relations as expressed in language within different spatial reference frames (SRFs). Healthy adults aged between 18 and 85 completed a novel task involving self-, third-person-, object-, and environment-centered judgements of spatial relations between two objects, as well as standard tests of working memory, inhibition, and mental flexibility. A psychometric evaluation confirmed the test-retest reliability and the convergent and divergent validity of the new task. Results showed that the lifespan trajectories varied depending on the SRF. Processing from a self-centered perspective or an object-centered frame remained intact throughout the adult-lifespan. By contrast, spatial processing from a third-person-centered perspective or within an environment-centered frame declined in late adulthood. Mediation regression models showed that mental flexibility accounted for a significant part of the age-related variance in spatial processing across all allocentric SRFs. The age effects on environment-centered processing were also partially mediated by age-related changes in visuospatial working memory capacity. These findings suggest that at least partially distinct systems are involved in mentally representing space under different SRFs, which are differentially affected by typical aging. Our results also highlight that people's ability to process spatial relations across different SRFs depends on their capacity to employ domain-general effortful cognitive resources.

Learning Internal Representations of 3D Transformations From 2D Projected Inputs

We describe a computational model for inferring 3D structure from the motion of projected 2D points in an image, with the aim of understanding how biological vision systems learn and internally represent 3D transformations from the statistics of their input. The model uses manifold transport operators to describe the action of 3D points in a scene as they undergo transformation. We show that the model can learn the generator of the Lie group for these transformations from purely 2D input, providing a proof-of-concept demonstration for how biological systems could adapt their internal representations based on sensory input. Focusing on a rotational model, we evaluate the ability of the model to infer depth from moving 2D projected points and to learn rotational transformations from 2D training stimuli. Finally, we compare the model performance to psychophysical performance on structure-from-motion tasks.

Dynamic spatial representation of self and others' actions in the macaque frontal cortex

Modulation of neuronal firing rates by the spatial locations of physical objects is a widespread phenomenon in the brain. However, little is known about how neuronal responses to the actions of biological entities are spatially tuned and whether such spatially tuned responses are affected by social contexts. These issues are of key importance for understanding the neural basis of embodied social cognition, such as imitation and perspective-taking. Here, we show that spatial representation of actions can be dynamically changed depending on others' social relevance and agents of action. Monkeys performed a turn-taking choice task with a real monkey partner sitting face-to-face or a filmed partner in prerecorded videos. Three rectangular buttons (left, center, and right) were positioned in front of the subject and partner as their choice targets. We recorded from single neurons in two frontal nodes in the social brain, the ventral premotor cortex (PMv) and the medial prefrontal cortex (MPFC). When the partner was filmed rather than real, spatial preference for partner-actions was markedly diminished in MPFC, but not PMv, neurons. This social context-dependent modulation in the MPFC was also evident for self-actions. Strikingly, a subset of neurons in both areas switched their spatial preference between self-actions and partner-actions in a diametrically opposite manner. This observation suggests that these cortical areas are associated with coordinate transformation in ways consistent with an actor-centered perspective-taking coding scheme. The PMv may subserve such functions in context-independent manners, whereas the MPFC may do so primarily in social contexts.

Visuospatial perspective-taking of a protagonist during narrative comprehension: the effects of task load and individual differences in visuospatial working memory

Introduction

This study examined whether visuospatial perspective uses the character perspective during narrative comprehension.

Method

Participants read narrative stimuli depicting the spatial positional relationships between characters and objects and judged whether the objects were on the left or right from the character's perspective. We manipulated whether the spatial positional relationships between characters depicted in the narrative stimuli resulted in a visuospatial perspective. We hypothesized that the high-load perspective-taking condition would indicate longer reaction times compared to the low-load perspective-taking condition, as shifting perspectives between characters in the high-load condition require more time for visuospatial perspective-taking.

Results

As predicted, the reaction time was longer for high-load perspective-taking than for low-load perspective-taking.

Discussion

During narrative comprehension, the reaction time for visuospatial perspective-taking must move virtually within the representation from the main character's perspective to that of another character. Visuospatial perspective-taking is involved in narrative comprehension.

The influence of another's actions and presence on perspective taking

The ability to take each other's visuospatial perspective has been linked to people's capacity to perceive another's action possibilities and to predict their actions. Research has also shown that visuospatial perspective taking is supported by one's own mental own-body transformation. However, how these two processes of action perception and visuospatial perspective taking might interact remains largely unknown. By introducing seven angular disparities between participants and the model in the stimuli pictures across "Action" and "No Action" conditions, we investigated whether the observation of a goal-directed action facilitates perspective taking and whether this facilitation depends on the level of mental own-body transformation required to take perspective. The results showed that action observation facilitated performance independently of the level of mental-own body transformation. The processes behind this facilitation could involve anatomical mapping that is independent of the congruency between the participants' and the model's perspectives. Further, we replicated previous research findings, showing that participants were more accurate and faster when taking the perspective of a person compared to an inanimate object (a chair). The strongest facilitation effects were seen at the highest angular disparities between participants and the model in the stimuli pictures. Together, these findings enhance our knowledge of the mechanisms behind visuospatial perspective taking.

The brain dynamics of visuospatial perspective-taking captured by intracranial EEG

Visuospatial perspective-taking (VPT) is the ability to imagine a scene from a position different from the one used in self-perspective judgments (SPJ). We typically use VPT to understand how others see the environment. VPT requires overcoming the self-perspective, and impairments in this process are implicated in various brain disorders, such as schizophrenia and autism. However, the underlying brain areas of VPT are not well distinguished from SPJ-related ones and from domain-general responses to both perspectives. In addition, hierarchical processing theory suggests that domain-specific processes emerge over time from domain-general ones. It mainly focuses on the sensory system, but outside of it, support for this hypothesis is lacking. Therefore, we aimed to spatiotemporally distinguish brain responses domain-specific to VPT from the specific ones to self-perspective, and domain-general responses to both perspectives. In particular, we intended to test whether VPT- and SPJ specific responses begin later than the general ones. We recorded intracranial EEG data from 30 patients with epilepsy who performed a task requiring laterality judgments during VPT and SPJ, and analyzed the spatiotemporal features of responses in the broad gamma band (50-150 Hz). We found VPT-specific processing in a more extensive brain network than SPJ-specific processing. Their dynamics were similar, but both differed from the general responses, which began earlier and lasted longer. Our results anatomically distinguish VPT-specific from SPJ-specific processing. Furthermore, we temporally differentiate between domain-specific and domain-general processes both inside and outside the sensory system, which serves as a novel example of hierarchical processing.

No effects of different perturbations on the performance in a mental body-rotation task (MBRT) with egocentric perspective transformations and object-based transformations

The present study investigates participants' performance in two different mental body-rotation tasks (MBRTs) under conditions in which dynamic stability is challenged in two different balancing conditions: active balance control (Experiment 1), where participants actively maneuver, and re-active balance control (Experiment 2), where participants react to an external perturbation. The two MBRTs induced either an object-based spatial transformation (based on a same-different judgment) or an egocentric transformation (based on a left-right judgment). In Experiment 1, 48 participants were tested while standing on an even ground (low balancing requirements) or on a balance board (high balancing requirements). In Experiment 2, 32 participants performed while either standing still on a vibration plate or with the vibration plate moving in a low (20 Hz) or high (180 Hz) frequency. In both experiments, the results for response time and response error revealed effects of rotation angle and type of task. An effect of balancing condition was only observed for response error in Experiment 1. More precisely, response times and response errors increased for higher rotation angles. Also, performance was better for egocentric than for object-based spatial transformations. However, the different challenges to dynamic stability in Experiments 1 and 2 did not influence performance in the two MBRTs (except for response errors in Experiment 1) nor in a control condition (Experiment 1) without mental rotation.

Exploring the neural basis and modulating factors of implicit altercentric spatial perspective-taking with fNIRS

Humans spontaneously take the perspective of others when encoding spatial information in a scene, especially with agentive action cues present. This functional near-infrared spectroscopy (fNIRS) study explored how action observation influences implicit spatial perspective-taking (SPT) by adapting a left-right spatial judgment task to investigate whether transformation strategies underlying altercentric SPT can be predicted on the basis of cortical activation. Strategies associated with two opposing neurocognitive accounts (embodied versus disembodied) and their proposed neural correlates (human mirror neuron system; hMNS versus cognitive control network; CCN) are hypothesized. Exploratory analyses with 117 subjects uncover an interplay between perspective-taking and post-hoc factor, consistency of selection, in regions alluding to involvement of the CCN. Descriptively, inconsistent altercentric SPT elicited greater activation than consistent altercentric SPT and/or inconsistent egocentric SPT in the left inferior frontal gyrus (IFG), left dorsolateral prefrontal cortex (DLPFC) and left motor cortex (MC), but not the inferior parietal lobules (IPL). Despite the presence of grasping cues, spontaneous embodied strategies were not evident during implicit altercentric SPT. Instead, neural trends in the inconsistent subgroups (22 subjects; 13 altercentric; 9 egocentric) suggest that inconsistency in selection modulates the decision-making process and plausibly taps on deliberate and effortful disembodied strategies driven by the CCN. Implications for future research are discussed.

Embodied perspective-taking enhances interpersonal synchronization: A body-swap study

Humans exhibit a strong tendency to synchronize movements with each other, with visual perspective potentially influencing interpersonal synchronization. By manipulating the visual scenes of participants engaged in a joint finger-tapping task, we examined the effects of 1st person and 2nd person visual perspectives on their coordination dynamics. We hypothesized that perceiving the partner's movements from their 1st person perspective would enhance spontaneous interpersonal synchronization, potentially mediated by the embodiment of the partner's hand. We observed significant differences in attractor dynamics across visual perspectives. Specifically, participants in 1st person coupling were unable to maintain de-coupled trajectories as effectively as in 2nd person coupling. Our findings suggest that visual perspective influences coordination dynamics in dyadic interactions, engaging error-correction mechanisms in individual brains as they integrate the partner's hand into their body representation. Our results have the potential to inform the development of applications for motor training and rehabilitation.

Left or right, that is the question: use of egocentric frame of reference and the right-eye advantage for understanding gestural signs in bottlenose dolphins (Tursiops truncatus)

How do bottlenose dolphins visually perceive the space around them? In particular, what cues do they use as a frame of reference for left-right perception? To address this question, we examined the dolphin's responses to various manipulations of the spatial relationship between the dolphin and the trainer by using gestural signs for actions given by the trainer, which have different meanings in the left and right hands. When the dolphins were tested with their backs to the trainer (Experiment 1) or in an inverted position underwater (Experiments 2 and 3), correct responses from the trainer's perspective were maintained for signs related to movement direction instructions. In contrast, reversed responses were frequently observed for signs that required different sounds for the left and right hands. When the movement direction instructions were presented with symmetrical graphic signs such as " × " and "●", accuracy decreased in the inverted posture (Experiment 3). Furthermore, when the signs for sounds were presented from either the left or right side of the dolphin's body, performance was better when the side of the sign movement coincided with the body side on which it was presented than when it was mismatched (Experiment 4). In the final experiment, when one eye was covered with an eyecup, the results showed that, as in the case of body-side presentation, performance was better when the open eye coincided with the side on which the sign movement was presented. These results indicate that dolphins used the egocentric frame for visuospatial cognition. In addition, they showed better performances when the gestural signs were presented to the right eye, suggesting the possibility of a left-hemispheric advantage in the dolphin's visuospatial cognition.

Measuring Spatial Abilities in Children: A Comparison of Mental-Rotation and Perspective-Taking Tasks

Mental rotation (MR) and perspective taking (PT) are important spatial abilities and predictive of performance in other cognitive domains. Yet, age-appropriate measures to assess these spatial abilities in children are still rare. This study examined psychometric properties of four MR tasks in 6- to 9-year-olds (N = 96). Two were developed specifically for children and two were based on established assessments for adults; one of each was a computerized and one was a paper-pencil task. Furthermore, spatial perspective taking (PT)-a different but closely related ability-was assessed to determine discriminant validity. Factor analyses showed that all MR tasks loaded on one single factor, with PT only loading weakly on the same factor, suggesting high construct validity. The computerized task for adults showed moderate factor loadings, constituted its own (but correlated) factor when a two-factor solution was forced, and showed the lowest reliabilities, suggesting that it was very difficult for children. On average, the new MR tasks had good to excellent reliabilities, differentiated well between age groups, and proved to be well-suited to assess MR in this age range. The PT task also showed good reliability and a steep developmental progression. Relations to verbal skills, gaming experience, and TV consumption are discussed.

Dissociating visual perspective taking and belief reasoning using a novel integrated paradigm: A preregistered online study

There is considerable conceptual overlap between Level-2 Visual Perspective Taking (VPT-2) and Belief Reasoning; both cognitive processes require us to represent another's viewpoint and experience of reality while inhibiting our own egocentric representations. This study investigated if these facets of mentalising are distinct from one another in the general adult population. To do so, we developed a novel "Seeing-Believing Task" with which to compare VPT-2 and true belief (TB) reasoning directly - one in which both judgement types refer to the same state of reality, requiring identical responses, and where self and other perspectives can be dissociated. Across three preregistered online experiments, this task demonstrated consistent differences between these two cognitive processes; specifically, TB judgements were associated with slower response times than VPT-2. This suggests that VPT-2 and TB reasoning are at least partly distinct psychological processes. Further, the greater cognitive effort required for TB reasoning is unlikely to be explained by differences in mnemonic processing. We suggest, therefore, that VPT-2 and TB reasoning differ in the complexity of social processing involved and we discuss theoretical implications based on minimal vs. full-blown Theory of Mind. Future research must attempt to test these conjectures.

It's Not You, It's Me: A Review of Individual Differences in Visuospatial Perspective Taking

Visuospatial perspective taking (VSPT) concerns the ability to understand something about the visual relationship between an agent or observation point on the one hand and a target or scene on the other. Despite its importance to a wide variety of other abilities, from communication to navigation, and decades of research, there is as yet no theory of VSPT. Indeed, the heterogeneity of results from different (and sometimes the same) VSPT tasks point to a complex picture suggestive of multiple VSPT strategies, individual differences in performance, and context-specific factors that together have a bearing on both the efficiency and accuracy of outcomes. In this article, we review the evidence in search of patterns in the data. We found a number of predictors of VSPT performance but also a number of gaps in understanding that suggest useful pathways for future research and, possibly, a theory (or theories) of VSPT. Overall, this review makes the case for understanding VSPT by better understanding the perspective taker rather than the target agents or their perception.

Embodied Mental Rotation - Does It Affect Postural Stability?

The effect of different human body part stimuli in mental rotation tasks (MRTs) on postural stability was investigated in two dual-task experiments. There were significant differences within egocentric MRTs (Experiment 1, N = 46): Hand and foot stimuli tended to cause more body sway than whole-body figures and showed increased body sway for higher rotation angles in the MRTs. In object-based MRTs (Experiment 2, N = 109) different stimuli did not evoke different levels of body sway, but higher rotation angles led to higher body sway. Both experiments showed a stabilizing effect of MRTs compared to the control condition. Exploratorily analyses identified reaction time in MRTs as a significant predictor of body sway. The results suggest a heterogeneous impact of mental rotation on postural stability.

A Smart Model of Imaginal Perspective Taking

The ability to judge spatial relations from perspectives that differ from one's current body orientation and location is important for many everyday activities. Despite considerable research on imaginal perspective taking, however, detailed computational accounts of the processes involved in this ability are missing. In this contribution, I introduce Smart (Spatial Memory Access by Reference Frame SelecTion) as a computational cognitive model of imaginal perspective taking processes. In assuming that imaginal perspective taking is governed by reference frame selection for memory access and subsequent motor activation, Smart is able to explain and simulate key findings on human imaginal perspective taking. In addition to providing novel insight into the mechanisms underlying imaginal perspective taking, Smart also has several implications for our view on spatial memory, more generally. In particular, Smart supports the idea that enduring spatial representations are essentially orientation-free and that spatial representations are best viewed as flexible combinations of representation structures and reference frames.

Advanced aging effects on implicit motor imagery and its links to motor performance: An investigation via mental rotation of letters, hands, and feet

This study focuses on changes in implicit motor imagery during advanced aging and these changes’ co-occurrences with physical motor deficits. We administered a mental rotation (MR) task with letters, hands, and feet to 28 young adults (20–27 years) and to 71 older adults (60–87 years), and assessed motor skills (gait mobility and hand dexterity) and neuropsychological performance. Compared to young adults, older adults showed lower MR performance for all stimuli and stronger biomechanical constraint effects on both hand and foot rotation. Moreover, the foot biomechanical constraint effect continued to increase during late adulthood, and declines in hand and foot motor imagery emerged at earlier old ages than declines in visual imagery. These results first demonstrated distinct aging trajectories of hand motor imagery, foot motor imagery, and visual imagery. Exploratory partial correlation analysis for older adults showed positive associations of low-level perceptual-motor skills (Trail Making Test-A performance) with hand and foot MR performance and positive associations of mobility (Timed Up and Go test performance) with foot and letter MR performance. These associations exhibited somewhat different patterns from those of young adults and raised the possibility that age-related declines in motor (and visual) imagery co-occur with declines in motor functioning.

Visuospatial perspective-taking in social-emotional development: enhancing young children’s mind and emotion understanding via block building training

Background

Theory of Mind (ToM) refers to the ability to represent one's own and others' mental states, and emotion understanding involves appropriately comprehending and responding to others' emotional cues in social interactions. Individual differences in mind and emotion understanding have been associated strongly with verbal ability and interaction and, as such, existing training for children's ToM and emotion understanding is mostly language-based. Building on the literature on embodied cognition, this study proposes that mind and emotion understanding could be facilitated by one's visuospatial experience in simulating other's frames of reference.

Methods

This protocol consists of two training studies. Study 1 will examine if visuospatial perspective-taking training promotes ToM and emotion understanding. Participants will consist of 96 4.5-year-olds and will be randomly assigned to one of two training groups: the altercentric block building group (trained to be visuospatial perspective-takers), or the egocentric block building group (no visuospatial perspective-taking is involved). Study 2 will compare the engagement of visuospatial perspective-taking and verbal interaction in the development of mind and emotion understanding. Participants will consist of 120 4.5-year-olds. They will be randomly assigned to one of three training groups: the socialized altercentric block building (both visuospatial perspective-taking and verbal interaction), the parallel altercentric block building (visuospatial perspective-taking only), or the paired dialogic reading (verbal interaction only).

Conclusions

In terms of theoretical implications, the potential causal relationship between visuospatial perspective-taking and ToM and emotion understanding may shed new insights on what underlies the development of mental state understanding. The findings of this study also have practical implications: researchers and educators may popularize visuospatial perspective-taking training in the form of block-building games if it is found to be effective in complementing conventional language-based theory-of-mind training.

Hand and Foot Selection in Mental Body Rotations Involves Motor-Cognitive Interactions

Action imagery involves the mental representation of an action without overt execution, and can contribute to perspective taking, such as that required for left-right judgments in mental body rotation tasks. It has been shown that perspective (back view, front view), rotational angle (head-up, head-down), and abstractness (abstract, realistic) of the stimulus material influences speed and correctness of the judgement. The present studies investigated whether left-right judgements are more difficult on legs than on arms and whether the type of limb interacts with the other factors. Furthermore, a combined score for speed and accuracy was explored to eliminate possible tradeoffs and to obtain the best possible measure of subjects' individual ability. Study 1 revealed that the front view is more difficult than the back view because it involves a vertical rotation in perspective taking. Head-down rotations are more difficult than head-up rotations because they involve a horizontal rotation in perspective taking. Furthermore, leg stimuli are more difficult than hand stimuli, particularly in head-down rotations. In Study 2, these findings were replicated in abstract stimuli as well as in realistic stimuli. In addition, perspective taking for realistic stimuli in the back view is easier than realistic stimuli in the front view or abstract stimuli (in both perspectives). We conclude that realistic stimulus material facilitates task comprehension and amplifies the effects of perspective. By replicating previous findings, the linear speed-accuracy score was shown to be a valid measure to capture performance in mental body rotations.

The role of spatial ability in mixed reality learning with the HoloLens

The use of mixed reality in science education has been increasing and as such it has become more important to understand how information is learned in these virtual environments. Spatial ability is important in many learning contexts, but especially in neuroanatomy education where learning the locations and spatial relationships between brain regions is paramount. It is currently unclear what role spatial ability plays in mixed reality learning environments, and whether it is different compared to traditional physical environments. To test this, a learning experiment was conducted where students learned neuroanatomy using both mixed reality and a physical plastic model of a brain (N = 27). Spatial ability was assessed and analyzed to determine its effect on performance across the two learning modalities. The results showed that spatial ability facilitated learning in mixed reality (β = 0.21, P = 0.003), but not when using a plastic model (β = 0.08, P = 0.318). A non-significant difference was observed between the modalities in terms of knowledge test performance (d = 0.39, P = 0.052); however, mixed reality was more engaging (d = 0.59, P = 0.005) and learners were more confident in the information they learned compared to using a physical model (d = 0.56, P = 0.007). Overall, these findings suggest that spatial ability is more relevant in virtual learning environments, where the ability to manipulate and interact with an object is diminished or abstracted through a virtual user interface.

Virtual navigation in healthy aging: Activation during learning and deactivation during retrieval predicts successful memory for spatial locations

Spatial navigation and spatial memory are two important skills for independent living, and are known to be compromised with age. Here, we investigate the neural correlates of successful spatial memory in healthy older adults in order to learn more about the neural underpinnings of maintenance of navigation skill into old age. Healthy older adults watched a video shot by a person navigating a route and were asked to remember objects along the route and then attempted to remember object locations by virtually pointing to the location of hidden objects from several locations along the route. Brain activity during watching and pointing was recorded with functional MRI. Larger activations in temporal and frontal regions during watching, and larger deactivations in superior parietal cortex and intraparietal sulcus during pointing, were associated with smaller location errors. These findings suggest that larger evoked responses during learning of spatial information coupled with larger deactivation of canonical spatial memory regions at retrieval are important for effective spatial memory in late life.

Different Profiles of Spatial Navigation Deficits In Alzheimer’s Disease Biomarker-Positive Versus Biomarker-Negative Older Adults With Amnestic Mild Cognitive Impairment

Background

Spatial navigation impairment is a promising cognitive marker of Alzheimer’s disease (AD) that can reflect the underlying pathology.

Objectives

We assessed spatial navigation performance in AD biomarker positive older adults with amnestic mild cognitive impairment (AD aMCI) vs. those AD biomarker negative (non-AD aMCI), and examined associations between navigation performance, MRI measures of brain atrophy, and cerebrospinal fluid (CSF) biomarkers.

Methods

A total of 122 participants with AD aMCI (n = 33), non-AD aMCI (n = 31), mild AD dementia (n = 28), and 30 cognitively normal older adults (CN) underwent cognitive assessment, brain MRI (n = 100 had high-quality images for volumetric analysis) and three virtual navigation tasks focused on route learning (body-centered navigation), wayfinding (world-centered navigation) and perspective taking/wayfinding. Cognitively impaired participants underwent CSF biomarker assessment [amyloid-β1–42, total tau, and phosphorylated tau181 (p-tau181)] and amyloid PET imaging (n = 47 and n = 45, respectively), with a subset having both (n = 19).

Results

In route learning, AD aMCI performed worse than non-AD aMCI (p < 0.001), who performed similarly to CN. In wayfinding, aMCI participants performed worse than CN (both p ≤ 0.009) and AD aMCI performed worse than non-AD aMCI in the second task session (p = 0.032). In perspective taking/wayfinding, aMCI participants performed worse than CN (both p ≤ 0.001). AD aMCI and non-AD aMCI did not differ in conventional cognitive tests. Route learning was associated with parietal thickness and amyloid-β1–42, wayfinding was associated with posterior medial temporal lobe (MTL) volume and p-tau181 and perspective taking/wayfinding was correlated with MRI measures of several brain regions and all CSF biomarkers.

Conclusion

AD biomarker positive and negative older adults with aMCI had different profiles of spatial navigation deficits that were associated with posterior MTL and parietal atrophy and reflected AD pathology.

Perspective Taking and Avatar-Self Merging

Today, avatars often represent users in digital worlds such as in video games or workplace applications. Avatars embody the user and perform their actions in these artificial environments. As a result, users sometimes develop the feeling that their self merges with their avatar. The user realizes that they are the avatar, but the avatar is also the user-meaning that avatar's appearance, character, and actions also affect their self. In the present paper, we first introduce the event-coding approach of the self and then argue based on the reviewed literature on human-avatar interaction that a self-controlled avatar can lead to avatar-self merging: the user sets their own goals in the virtual environment, plans and executes the avatar's actions, and compares the predicted with the actual motion outcomes of the avatar. This makes the user feel body ownership and agency over the avatar's action. Following the event-coding account, avatar-self merging should not be seen as an all-or-nothing process, but rather as a continuous process to which various factors contribute, including successfully taking the perspective of the avatar. Against this background, we discuss affective, cognitive, and visuo-spatial perspective taking of the avatar. As evidence for avatar-self merging, we present findings showing that when users take the avatar's perspective, they can show spontaneous behavioral tendencies that run counter to their own.

Seeing through the cat's eyes: evidence of a spontaneous perspective taking process using a non-human avatar

In many daily face-to-face interactions, people are able to take the perspective of others, for example, coding right and left based on point-of-view of others. In the present study, we investigated whether observers are able to take the perspective of a non-human figure such as a cat, observing the same effects obtained with human or robot avatars. In both experiments, we used a centrally presented stimulus (i.e. a cat), with its tail lateralized to the left or to the right. Participants had to respond to the side of the tail with a lateralized keypress. In Experiment 1 (spatial perspective taking task), participants were required to explicitly adopt the cat's perspective to respond, whereas in Experiment 2 (SR compatibility task), this was not explicitly required. In both experiments, faster RTs are obtained when the cat is presented back, with a greater difference between front and back views when the tail is on the right; furthermore, there is no temporal modulation of the back-front effect. These common results between the two experiments are interpreted on the basis of the spatial perspective taking processes, elicited voluntarily (Experiment 1) or spontaneously (Experiment 2).

Autistic Adults Show Similar Performance and Sensitivity to Social Cues on a Visual Perspective Taking Task as Non-autistic Adults

Autistic and non-autistic adults completed a visual perspective taking (VPT) task, reporting an object’s location from an actor’s perspective, or their own. On half the trials the actor looked at and reached for the object, and on half did not. Accuracy and reaction time were measured. In Experiment 1, both groups (N = 34, mean age = 24 years) responded slower when reporting the actor’s perspective, with no group differences in this effect. Experiment 2 included “other” VPT trials only. Both groups (N = 30, mean age = 25 years) showed sensitivity to the actor’s behaviour, more accurately reporting his perspective when he acted upon the object. No group differences were observed. In contrast to developmental studies, these experiments suggest similar VPT abilities in autistic and non-autistic adults.

Viewer and object mental rotation in young adults with psychotic disorders

Schizophrenia patients have difficulty with processing visuo-spatial information, which may explain their deficits with considering other people's point-of-view. Processing visuo-spatial information operates on egocentric and allocentric frames of reference. Here, we tested the ability of individuals at different stages of psychotic disorders, specifically ultra-high-risk for psychosis individuals, as well as first-episode psychosis, and chronic schizophrenia patients, to perform a viewer mental rotation task and an object mental rotation task. The two tasks were differentiated only by the instruction given. Healthy individuals and patients with a diagnosis of anxiety/depressive mood disorder served as non-patient and patient controls, respectively. The results show that first-episode psychosis and chronic schizophrenia patients, but not ultra-high-risk individuals, had more errors and longer response times with both mental rotation tasks than the two control groups. In addition, chronic schizophrenia patients had additional difficulty with the object rotation task. The difference in performance between groups and tasks remained significant even after controlling for age, IQ, and antipsychotic medication dose. The results indicate that patients with psychotic disorders have a deficit of mental spatial imagery that include both egocentric and allocentric representations. This deficit may explain the difficulty of these patients with perspective-taking, and inferring other people's point of view, thoughts or intentions which is at the core of the pathogenesis of schizophrenia.

Cortical Activation in Mental Rotation and the Role of the Corpus Callosum: Observations in Healthy Subjects and Split-Brain Patients

The mental rotation (MR) is an abstract mental operation thanks to which a person imagines rotating an object or a body part to place it in an other position. The ability to perform MR was belived to belong to the right hemisphere for objects, and to the left for one’s ownbody images. Mental rotation is considered to be basic for imitation with the anatomical perspective, which in turn is needed for social interactions and learning. Altered imitative performances have been reported in patients with resections or microstructure alterations of the corpus callosum (CC). These patients also display a reduced MR ability compared to control subjects, as shown in a recent behavioral study. The difference was statistically significant, leading us to hypothesize a role of the CC to integrate the two hemispheres’ asymmetric functions. The present study was designed to detect, by means of a functional MRI, the cortical activation evoked during an MR task in healthy control subjects and callosotomized patients. The results suggest that performing MR requires activation of opercular cortex and inferior parietal lobule in either hemispheres, and likely the integrity of the CC, thus confirming that the main brain commissure is involved in cognitive functions.

Does the presence of more features in a bound representation in working memory require extra object-based attention?

Recent studies have examined the role of attention in retaining bound representations in working memory (WM) and found that object-based attention plays a pivotal role. However, no study has investigated whether maintaining bound representations with more features in WM requires extra object-based attention. We investigated this by examining whether a secondary task consuming object-based attention was more disruptive to the maintenance of bindings in WM when more features were stored per object. We instructed participants to memorize three bound representations in a WM task while manipulating the number of features (two vs. three features) contained in each representation. Moreover, we manipulated whether a secondary task consuming object-based attention was interpolated into the maintenance phase of WM. If extra object-based attention was required after the addition of an extra feature in the bound representation, the secondary task would result in a greater disruption of the three- rather than two-featured binding. In two experiments, we found that the added secondary task significantly impaired the binding performance, but the performance of the two- and three-featured bindings was disrupted to the same extent. These results suggest that the presence of more features in a bound representation in WM does not require extra object-based attention.

Correlational Evidence for the Role of Spatial Perspective-Taking Ability in the Mental Rotation of Human-Like Objects

People can mentally rotate objects that resemble human bodies more efficiently than nonsense objects in the same/different judgment task. Previous studies proposed that this human-body advantage in mental rotation is mediated by one's projections of body axes onto a human-like object, implying that human-like objects elicit a strategy shift, from an object-based to an egocentric mental rotation. To test this idea, we investigated whether mental rotation performance involving a human-like object had a stronger association with spatial perspective-taking, which entails egocentric mental rotation, than a nonsense object. In the present study, female participants completed a chronometric mental rotation task with nonsense and human-like objects. Their spatial perspective-taking ability was then assessed using the Road Map Test and the Spatial Orientation Test. Mental rotation response times (RTs) were shorter for human-like than for nonsense objects, replicating previous research. More importantly, spatial perspective-taking had a stronger negative correlation with RTs for human-like than for nonsense objects. These findings suggest that human-like stimuli in the same/different mental rotation task induce a strategy shift toward efficient egocentric mental rotation.

Counterexample Search in Diagram-Based Geometric Reasoning

Topological relations such as inside, outside, or intersection are ubiquitous to our spatial thinking. Here, we examined how people reason deductively with topological relations between points, lines, and circles in geometric diagrams. We hypothesized in particular that a counterexample search generally underlies this type of reasoning. We first verified that educated adults without specific math training were able to produce correct diagrammatic representations contained in the premisses of an inference. Our first experiment then revealed that subjects who correctly judged an inference as invalid almost always produced a counterexample to support their answer. Noticeably, even if the counterexample always bore a certain level of similarity to the initial diagram, we observed that an object was more likely to be varied between the two drawings if it was present in the conclusion of the inference. Experiments 2 and 3 then directly probed counterexample search. While participants were asked to evaluate a conclusion on the basis of a given diagram and some premisses, we modulated the difficulty of reaching a counterexample from the diagram. Our results indicate that both decreasing the counterexample density and increasing the counterexample distance impaired reasoning performance. Taken together, our results suggest that a search procedure for counterexamples, which proceeds object-wise, could underlie diagram-based geometric reasoning. Transposing points, lines, and circles to our spatial environment, the present study may ultimately provide insights on how humans reason about topological relations between positions, paths, and regions.

Directionality eclipses agency: How both directional and social cues improve spatial perspective taking

Research on spatial perspective taking has suggested that including an agent in the display benefits performance. However, little research has examined the mechanisms underlying this benefit. Here, we examine how an agent benefits performance by examining its effects on three mental steps in a perspective-taking task: (1) imagining oneself at a location (station point) within in the array, (2) adopting a different perspective (heading), and (3) pointing to an object from that perspective. We also examine whether a non-agentive directional cue (an arrow) is sufficient to improve performance in an abstract map-like display. We compared a non-directional cue to two cues for position and orientation: a human figure (agentive, directional) and an arrow (non-agentive, directional). To examine the effects of cues on steps 2 and 3 of the perspective-taking process, magnitude of the initial perspective shift and pointing direction were varied across trials. Response time and error increased with the magnitude of the imagined perspective shift and pointing to the front was more accurate than pointing to the side, or back, but these effects were independent of directional cue. A directional cue alone was sufficient to improve performance relative to control, and agency did not provide additional benefit. The results overall indicate that most people adopt an embodied cognition strategy to perform this task and directional cues facilitate the first step of the perspective-taking process, imagining oneself at a location within in the array.

Brain mechanisms of visuospatial perspective-taking in relation to object mental rotation and the theory of mind

Visuospatial perspective-taking (VPT) is a process of imagining what can be seen and how a scene looks from a location and orientation in space that differs from one's own. It comprises two levels that are underpinned by distinct neurocognitive processes. Level-2 VPT is often studied in relation to two other cognitive phenomena, object mental rotation (oMR) and theory of mind (ToM). With the aim to describe the broad picture of neurocognitive processes underlying level-2 VPT, here we give an overview of the recent behavioral and neuroscientific findings of level-2 VPT. We discuss its relation to level-1 VPT, which is also referred to as perspective-tracking, and the neighboring topics, oMR and ToM. Neuroscientific research shows that level-2 VPT is a diverse cognitive process, encompassing functionally distinct neural circuits. It shares brain substrates with oMR, especially those parietal brain areas that are specialized in spatial reasoning. However, compared to oMR, level-2 VPT involves additional activations in brain structures that are typically involved in ToM tasks and deal with self/other distinctions. In addition, level-2 VPT has been suggested to engage brain areas coding for internal representations of the body. Thus, the neurocognitive model underpinning level-2 VPT can be understood as a combination of visuospatial processing with social cognition and body schema representations.

The interaction of the visuo-spatial and the vestibular system depends on sensory experience in development

In hearing individuals, vestibular and visuo-spatial functions seem to be functionally linked. Previous studies have suggested that congenitally deaf individuals are at a higher risk for vestibular problems, which in hearing adults have often been found to be associated with impairments in visuo-spatial processing. However, communicating in a sign language provides extensive practice in visuo-spatial processing, which might counteract negative effects of vestibular impairments. Here, we investigated whether the functional link between vestibular and visuo-spatial functions is mandatory, that is whether it is impenetrable to experience or context, or whether it is dependent on specific sensory and cognitive experiences. To this end, we tested a group of congenitally deaf native signers and a group of hearing nonsigners on mental rotation and balance tasks. Compared to hearing nonsigners, mental rotation was superior in the deaf signers in conditions crucial for sign language comprehension. By contrast, the balance performance of the group of deaf signers was impaired. While in the group of hearing nonsigners, balance skills correlated with mental rotation abilities, no such relationship was observed in the group of deaf signers. These results suggest that the link between vestibular and visuo-spatial functions is not fixed but can be altered or even cancelled out by certain sensory or cognitive experiences, such as the acquisition of a sign language.

Spatial reasoning, mathematics, and gender: Do spatial constructs differ in their contribution to performance?

BACKGROUND

The role of gender in both spatial and mathematics performance has been extensively studied separately, with a male advantage often found in spatial tasks and mathematics from adolescence. Spatial reasoning is consistently linked to mathematics proficiency, yet despite this, little research has investigated the role of spatial orientation and gender in the relationship between spatial reasoning and mathematics.

AIMS

In the present study, three spatial reasoning constructs (mental rotation, spatial visualization, and spatial orientation) were examined for their unique contributions to mathematics performance in two samples (Study 1: grade 5; Study 2: grade 8). In light of the emerging gender gap in mathematics as children develop, these relationships were explored as a function of gender.

SAMPLE

Eighty-four fifth-grade students participated in Study 1 (43 females, 41 males; mean age = 11.19 years). Nine hundred and three eighth-grade students participated in Study 2 (498 females, 405 males; mean age = 13.83 years).

METHODS

The three spatial reasoning constructs (mental rotation, spatial visualization, and spatial orientation) were examined for their unique contributions to mathematics performance for females and males in general and across different mathematical content (geometry-measurement and number sense).

RESULTS

Spatial factors accounted for 51% of the variance in math scores in Study 1 (grade 5) and 32% of the variance in math scores in Study 2 (grade 8). In both studies, spatial factors predicted a larger proportion of variance in geometry-measurement than for number sense. Spatial orientation was found to be a unique contributor in all mathematics models, object-based spatial skills (mental rotation and spatial visualization) varied in their contribution to math performance depending on mathematics content and gender.

CONCLUSIONS

The present work highlights the unique contribution of spatial orientation in the spatial-mathematics relationship and provides insights into the nature of gender differences in mathematical problem-solving as a function of spatial reasoning and mathematics content.

Mental Rotation Ability: Right or Left Hemisphere Competence? What We Can Learn from Callosotomized and Psychotic Patients

Mental rotation is an abstract operation whereby a person imagines rotating an object or a body part to place it in a different position. The ability to perform mental rotation was attributed to right hemisphere for objects, to the left for one’s own body images. Mental rotation seems to be basic for imitation in anatomical mode. Previous studies showed that control subjects, callosotomized and psychotic patients chose the mirror-mode when imitating without instructions; when asked to use the same or opposite limb as the model, controls chose the anatomical mode, callosotomized patients mainly used mirror mode, psychotic patients were in between. The preference of callosotomized subjects is likely due to defective mental rotation, because of the lack of the corpus callosum (CC), thus suggesting an asymmetry in the hemispheric competence for mental rotation. Present research investigated the mental rotation ability in control subjects, callosotomized and psychotic patients. All subjects were shown pictures of a model, in first or third person perspective, with a cup in her right or left hand. They had to indicate which model’s hand held the cup, by answering with a verbal or motor modality in separate experimental sessions. In both sessions, control subjects produced 99% of correct responses, callosotomy patients 62%, and psychotic patients 91%. The difference was statistically significant, suggesting a role of the CC in the integration of the two hemispheres’ asymmetric functions in mental rotation.

The role of attention in retaining the binding of integral features in working memory

Previous studies have suggested that retaining bindings in working memory (WM) requires more object-based attention than retaining constituent features. However, we still need to address the object-based attention hypothesis to determine both the generality (Does the object-based attention hypothesis of binding apply to feature bindings other than those tested?) and the reality (Was the observed effect in previous studies an artifact of the testing process?). We addressed these two issues by focusing on the binding of integral features, which was ignored in previous studies. Integral features can be manipulated independently but cannot be attended to or processed independently of each other, and they are primarily perceived in a more unitary fashion. Consequently, integral-feature bindings should be processed as integrated units without the help of extra object-based attention. We examined whether or not the object-based attention hypothesis applied to integral-feature bindings (generality), and these results enabled us to check the reality of the hypothesis. In line with our prediction, we found that a secondary task consuming object-based attention did not selectively impair the binding performance (Experiments 1, 2, 3, 5, and 7). The absence of selective binding impairment was not attributable to the use of an invalid secondary task (Experiment 4), failure to memorize the binding between length and width (Experiment 6), tapping the incorrect type of attention (Experiment 6), the feasibility of feature categorization (Experiment 7), or poor task performance (Experiment 7). Overall, these results suggest that the object-based attention hypothesis does not fit for the integral-feature bindings, and that the pivotal role of object-based attention reported by previous studies was reliable.

Spatial Perspective-Taking in Children With Autism Spectrum Disorders: The Predictive Role of Visuospatial and Motor Abilities

Despite its impact on everyday functioning, spatial perspective-taking has rarely been investigated in autism spectrum disorders (ASD), and previous findings are surprisingly sparse and inconsistent. In the present study, we aimed to investigate spatial perspective-taking abilities in children and adolescents with ASD without intellectual disabilities, comparing them with a group of typically developing (TD) peers. Our objectives were: (i) to test similarities and differences between these groups in a spatial perspective-taking task; and (ii) to see whether similar or different underlying processes (i.e., fine and gross motor skills, and visuospatial abilities) might account for the groups’ performance in the spatial perspective-taking task. A group of children with ASD (N = 36) was compared with a TD group (N = 39), aged from 8 to 16 years. Participants were administered tasks assessing spatial perspective-taking, fine and gross motor skills, visuo-constructive abilities, visuospatial working memory, visual imagery, and mental rotation. Our results revealed that the ASD group had more difficulty with the spatial perspective-taking task than the TD group. The two groups also had some shared and some different processes that predicted their perspective-taking performance: a significant predictive effect of fine motor skills and visuospatial working memory emerged for both groups, while gross motor skills (i.e., walking heel-to-toe) and visuospatial imagery only revealed a role in the TD group. These findings suggest that different abilities might account for the two groups’ performance in the spatial perspective-taking task. Gross motor skills and complex visuospatial abilities seem to be more important in sustaining spatial perspective-taking ability in typical development than in the event of ASD. Some of the clinical and educational implications of these findings are discussed.

Electrical stimulation of cranial nerves in cognition and disease

The cranial nerves are the pathways through which environmental information (sensation) is directly communicated to the brain, leading to perception, and giving rise to higher cognition. Because cranial nerves determine and modulate brain function, invasive and non-invasive cranial nerve electrical stimulation methods have applications in the clinical, behavioral, and cognitive domains. Among other neuromodulation approaches such as peripheral, transcranial and deep brain stimulation, cranial nerve stimulation is unique in allowing axon pathway-specific engagement of brain circuits, including thalamo-cortical networks. In this review we amalgamate relevant knowledge of 1) cranial nerve anatomy and biophysics; 2) evidence of the modulatory effects of cranial nerves on cognition; 3) clinical and behavioral outcomes of cranial nerve stimulation; and 4) biomarkers of nerve target engagement including physiology, electroencephalography, neuroimaging, and behavioral metrics. Existing non-invasive stimulation methods cannot feasibly activate the axons of only individual cranial nerves. Even with invasive stimulation methods, selective targeting of one nerve fiber type requires nuance since each nerve is composed of functionally distinct axon-types that differentially branch and can anastomose onto other nerves. None-the-less, precisely controlling stimulation parameters can aid in affecting distinct sets of axons, thus supporting specific actions on cognition and behavior. To this end, a rubric for reproducible dose-response stimulation parameters is defined here. Given that afferent cranial nerve axons project directly to the brain, targeting structures (e.g. thalamus, cortex) that are critical nodes in higher order brain networks, potent effects on cognition are plausible. We propose an intervention design framework based on driving cranial nerve pathways in targeted brain circuits, which are in turn linked to specific higher cognitive processes. State-of-the-art current flow models that are used to explain and design cranial-nerve-activating stimulation technology require multi-scale detail that includes: gross anatomy; skull foramina and superficial tissue layers; and precise nerve morphology. Detailed simulations also predict that some non-invasive electrical or magnetic stimulation approaches that do not intend to modulate cranial nerves per se, such as transcranial direct current stimulation (tDCS) and transcranial magnetic stimulation (TMS), may also modulate activity of specific cranial nerves. Much prior cranial nerve stimulation work was conceptually limited to the production of sensory perception, with individual titration of intensity based on the level of perception and tolerability. However, disregarding sensory emulation allows consideration of temporal stimulation patterns (axon recruitment) that modulate the tone of cortical networks independent of sensory cortices, without necessarily titrating perception. For example, leveraging the role of the thalamus as a gatekeeper for information to the cerebral cortex, preventing or enhancing the passage of specific information depending on the behavioral state. We show that properly parameterized computational models at multiple scales are needed to rationally optimize neuromodulation that target sets of cranial nerves, determining which and how specific brain circuitries are modulated, which can in turn influence cognition in a designed manner.

Perspective taking in judgment of relative direction tasks

Mental rotation and visual-spatial perspective taking (VSPT) are two visual-spatial abilities that are highly correlated. Judgment of relative direction (JRD) tasks are commonly used to examine VSPT in conjunction with mental rotation. Moreover, in many studies the task involves switching from an imagined perspective to a sensorimotor perspective at the response phase. The current study employed a JRD task that enabled examination of mental rotation, perspective taking, and perspective switching, separately. In two experiments we found that both perspective taking and perspective switching affected accuracy and response time (RT). Namely, trials with a perspective change larger than 90° (that required perspective taking) were harder than trials with a change smaller than 90° (that required mental rotation), and so were trials that required switching from an imagined perspective to a sensorimotor perspective. Importantly, we suggest that VSPT and mental rotation are dissociable.

A letter on a hand: Rotating together or separately?

The motor system plays a role in some object mental rotation tasks, and researchers have reported that people may use a strategy of motor simulation to mentally rotate objects. In this study, we used images of a hand with a letter printed on the palm to directly determine whether a hand image can be automatically rotated during the deliberate mental rotation of an object and whether the hand and object are rotated in the same trajectory. A total of 41 participants were shown the stimuli and asked to decide whether the letters, which were upright or tilted at specific degrees, were normal or mirrored. The hand images in the background showed either a left or a right hand in the palm view, with fingers pointing upwards, medial, downwards, or lateral. Reaction times and error rates were measured to determine the speed and accuracy of mental rotation. A complex interaction between the hand posture and letter orientation revealed that the hand image was mentally rotated automatically, together with the deliberate mental rotation of the letter. The biomechanical constraints of the hand also influenced reaction times, suggesting the involvement of the motor system in the concomitant mental rotation of the hand image. Consistent with the motor simulation theory, the participants seemed to imagine the hand carrying the object in its movement. These behavioural data support the motor simulation theory and elucidate specific processes of mental rotation that have not been addressed by neuroimaging studies.

Visuospatial imagery in healthy individuals with different hypnotizability levels

Hypnotizability is a psychophysiological trait associated with morpho-functional brain differences. Since also cerebellar peculiarities have been reported in individuals with different hypnotizability levels and the cerebellar function is relevant to spatial imagery, the present study was aimed at investigating possible hypnotizability-related differences in the ability of spatial imagery. Highly (highs, N = 31), low (lows, N = 17) and medium (mediums, N = 16) hypnotizable participants (classified by Stanford Hypnotic Susceptibility Scale, form A) of both genders were submitted to a test of mental rotation, which requires the integrity of both executive and cerebellar structures. In order to disentangle the role of the cerebellum from that of executive circuits as much as possible, visuospatial and verbal working memory tests, which mainly reflect executive processes, were also performed. Healthy highs exhibited higher scores of mental rotation ability compared to mediums in the absence of significant differences in visual-spatial and verbal working memory. Lows reported intermediate scores not significantly different from both highs' and mediums'. Different cognitive strategies were observed in the three groups as the correlations between mental rotation, visuospatial and verbal working memory were different in highs, mediums and lows. In conclusion, present findings represent the first report of hypnotizability-related differences in a mental rotation task, which is relevant to several cognitive functions.

Temporal and spectral profiles of conflict processing among multiple frames of reference

Individuals rely on various frames of reference (FORs), such as an egocentric FOR (EFOR) and intrinsic FOR (IFOR), to represent spatial information. Previous behavioral studies have shown different IFOR-IFOR (II) and EFOR-IFOR (EI) conflict effects and an effect of their interaction. However, the neural mechanism of conflict processing between two FOR-based conflicts is unclear. In the current ERP study, two FOR-based conflicts were manipulated using a two-cannon task to elucidate common and distinct brain mechanisms that underlie FOR-based conflict processing. The behavioral results showed that both conflicts exhibited longer reaction times and larger error rates in the II (180° cannon angle) and EI (target cannon pointed down) incongruent conditions than in the II (0° cannon angle) and EI (target cannon pointed up) congruent conditions and that an interaction existed between the two conflicts. The ERP results indicated that, for both conflicts, more negative N2 amplitudes and less positive P3 amplitudes occurred in the incongruent conditions than in the congruent conditions, and the interactions between the two conflicts during later P3 amplitudes were significant. Time-frequency analysis further indicated that, in the early time window, the II conflict and the EI conflict specifically modulated power in the theta bands and beta bands, respectively. In contrast, in the later time window, both conflicts modulated power in the alpha and beta bands. In summary, our findings provide insights into the potential existence of two specific early conflict monitoring systems and a general late executive control system for FOR-based conflicts.

Visual dependence and spatial orientation in benign paroxysmal positional vertigo

People with benign paroxysmal positional vertigo (BPPV) probably have otoconial particles displaced from the utricle into the posterior semicircular canal. This unilateral change in the inertial load distributions of the labyrinth may result in visual dependence and may affect balance control. The goal of this study was to explore the interaction between visual dependence and balance control. We compared 23 healthy controls to 17 people with unilateral BPPV on the Clinical Test of Sensory Interaction and Balance on compliant foam with feet together, the Rod-and-Frame Test and a Mental Rotation Test. In controls, but not BPPV subjects, subjects with poor balance scores had significantly greater visual dependence, indicating that reliance on visual cues can affect balance control. BPPV and control subjects did not differ on the mental rotation task overall but BPPV reaction time was greater at greater orietantions, suggesting that this cognitive function was affected by BPPV. The side of impairment was strongly related to the side of perceived bias in the Earth vertical determined by BPPV subjects, indicating the relationship between the effect of asymmetric otolith unloading with simultaneous canal loading on spatial orientation perception.