The tool effect is lower in older adults with or without cognitive impairments than in young adults.

Grabbing a phone from a table or stepping over an obstacle on the ground are daily activities that require the brain to take account of both object and the body's parameters. Research has shown that a person's estimated maximum reach is temporarily overestimated after using a tool, even when the tool is no longer in hand. This tool effect reflects the high plasticity of the perceptual-motor system (e.g., body schema updating)-at least in young individuals. The objective of the present study was to determine whether the tool effect is smaller in older adults. Forty-four young adults, 37 older adults without cognitive impairment and 30 older adults with cognitive impairment took part in the experiment. The task consisted in visually estimating the ability to reach (using the index finger) a target positioned at different locations on a table, both before and after using a rake. We observed a strong after-effect of tool use in the young adults only. Conversely, a tool effect was similarly absent in the older adults without and with cognitive impairment. Moreover, even before the tool was used, the maximum reach was overestimated in each of the three groups, although the overestimation was greatest in the two groups of older adults. In summary, we showed that the tool effect, observed in young adults, was absent in older adults; this finding suggests that with advancing age, the perceptual-motor system is less able to adapt to novel sensorimotor contexts. This lack of adaptation might explain (at least in part) the overestimation of motor skills often reported in the elderly.

Emotional exhaustion and fear of COVID-19 in geriatric facilities during the COVID-19 pandemic.

OBJECTIVE: Since the onset of the COVID-19 pandemic, healthcare workers, especially those employed in hospital settings, have been exposed to a variety of stressors in the workplace. The aim of this study was to explore the Emotional Exhaustion (EE) of workers in geriatric facilities during the COVID-19 crisis. We accordingly sought to investigate the short-term impact of the COVID-19 pandemic in terms of the EE experienced by workers in geriatric facilities, and to examine the manner in which psychosocial conditions and fear of COVID-19 in the workplace have affected EE. METHODS: Surveys were administered in the midst of the COVID-19 crisis (October to December 2020). The study included 118 French healthcare workers with a mean age of 35.61 ± 0.73 recruited in geriatric facilities. We assessed EE, psychosocial conditions (e.g., demands at work, health and well-being, etc.) and fear of COVID-19 in the workplace. RESULTS: The analysis yielded two main outcomes. First, 34.75% workers (41) reported severe levels of EE. Second, demands at work and the fear of COVD-19 increased EE. Health and well-being were, however, demonstrated to protect against EE. DISCUSSION: Furthermore, fear of COVID-19 was shown to contribute significantly to EE healthcare workers in geriatric facilities. It is likely that Covid-19 indirectly contributes to EE by influencing demands at work.

Gap affordance judgments in bumblebees: Same as humans?

When flying through narrow gaps, bumblebees of different body sizes fly either straightforward or sideways, depending on the relation between their wingspan and the width of the gap (Ravi et al., 2020). They thus behave like humans when walking through narrow passages, which raises the question of the mechanisms underlying their own-body perception.

Do Older People Accurately Estimate the Length of Their First Step during Gait Initiation?

Background/Study Context: Advancing age is associated with a decrease in step length. In line with previous studies showing that older adults often overestimate their motor abilities, we investigate whether older adults overestimate the length of their first step during gait initiation. The underlying effect could be a failure to update the internal model of motor action as a function of age-related motor decline. Methods: Without taking a step, community-dwelling older women (n = 22, age range: 68-87 years) and younger women (n = 19, age range: 19-33 years) estimated the length of their first step for both preferred step length and largest step length, which were performed without endangerment. Thereafter, the participants performed real gait initiation for both types of steps. The estimated step lengths were compared to the actual step lengths. Results: Older adults judged their first step as larger than it was (mean error: 30% for the preferred step and 9% for the largest step). A fine-grained analysis showed that this effect mainly concerned those for whom an increased risk of falling was suspected. These older adults were also among those who performed the shortest steps, and they presented with a slight decrease in cognitive functioning. Younger participants underestimated their preferred step length. Overall, the estimates were more accurate for the largest steps than for the preferred-length steps. Conclusion: Step length estimation revealed powerful evidence for overestimation in older adults. Those who overestimated step length presented with more signs of motor decline. While this result sustains the idea of an insufficient actualization of the motor-action model, the explanation also refers to more global appraisal processes. Further research should explore the relevance of this task as a clinical laboratory tool for assessing gait capacity and the risk of falling.

[Specificity of the neuropsychological assessment in geriatrics]. / Spécificité de l'évaluation neuropsychologique en gériatrie.

The demographic evolution of our society has increased the need to assess the cognitive functions of people aged over 80. These assessments are made difficult due to the specificities of this population. It is possible to clarify the issues relating to the neuropsychological assessment in geriatrics and to put forward areas for discussion.

Individuals with pronounced schizotypal traits are particularly successful in tickling themselves.

We assessed self-tickling sensations in a group of participants high in schizotypal traits (n=27) and group of participants low in schizotypal traits (n=27). The groups were formed by screening a pool of 397 students for extreme scores in the French version of the Schizotypal Personality Questionnaire. As observed in a previous study involving psychiatric people with auditory hallucinations and/or passivity experiences our results showed that self-applied tactile stimulations are felt to be more ticklish by healthy individuals high in schizotypal traits. In contrast, there were no significant intergroup differences in the mean tickle rating in the externally-produced tickling condition. Furthermore, more successful self-tickling was associated with more frequent self-reports of unusual perceptual experiences (such as supernatural experiences) and passivity experiences in particular (such as a feeling of being under the control of an outside force or power).

Kinaesthetic mirror illusion and spatial congruence.

Position sense and kinaesthesia are mainly derived from the integration of somaesthetic and visual afferents to form a single, coherent percept. However, visual information related to the body can play a dominant role in these perceptual processes in some circumstances, and notably in the mirror paradigm. The objective of the present study was to determine whether or not the kinaesthetic illusions experienced in the mirror paradigm obey one of the key rules of multisensory integration: spatial congruence. In the experiment, the participant's left arm (the image of which was reflected in a mirror) was either passively flexed/extended with a motorized manipulandum (to induce a kinaesthetic illusion in the right arm) or remained static. The right (unseen) arm remained static but was positioned parallel to the left arm's starting position or placed in extension (from 15° to 90°, in steps of 15°), relative to the left arm's flexed starting position. The results revealed that the frequency of the illusion decreased only slightly as the incongruence prior to movement onset between the reflected left arm and the hidden right arm grew and remained quite high even in the most incongruent settings. However, the greater the incongruence between the visually and somaesthetically specified positions of the right forearm (from 15° to 90°), the later the onset and the lower the perceived speed of the kinaesthetic illusion. Although vision dominates perception in a context of visuoproprioceptive conflict (as in the mirror paradigm), our results show that the relative weightings allocated to proprioceptive and visual signals vary according to the degree of spatial incongruence prior to movement onset.

Perception of affordances during long-term exposure to weightlessness in the International Space station.

On Earth, visual eye height (VEH)--the distance from the observer's line of gaze to the ground in the visual scene--constitutes an effective cue in perceiving affordance such as the passability through apertures, based on the assumption that one's feet are on the ground. In the present study, we questioned whether an observer continues to use VEH to estimate the width of apertures during long-term exposure to weightlessness, where contact with the floor is not required. Ten astronauts were tested in preflight, inflight in the International Space Station, and postflight sessions. They were asked to adjust the opening of a virtual doorway displayed on a laptop device until it was perceived to be just wide enough to pass through (i.e., the critical aperture). We manipulated VEH by raising and lowering the level of the floor in the visual scene. We observed an effect of VEH manipulation on the critical aperture. When VEH decreased, the critical aperture decreased too, suggesting that widths relative to the body were perceived to be larger when VEH was smaller. There was no overall significant session effect, but the analysis of between-subjects variability revealed two participant profile groups. The effect of weightlessness was different for these two groups even though the VEH strategy remained operational during spaceflight. This study shows that the VEH strategy appears to be very robust and can be used, if necessary, in inappropriate circumstances such as free-floating, perhaps promoted by the nature of the visual scene.

Burden of family caregivers in Alzheimer's disease: The role of caregivers' perception of cognitive impairment.

OBJECTIVES: This study examined the role of caregivers' perception of cognitive impairment in burden of family caregivers in Alzheimer's disease (AD). We hypothesized that the evaluation of cognitive impairment by family caregivers plays a pivotal role in burden. METHODS: The study included 110 dyads (person with AD and their caregiver) recruited from a Memory Unit in France. The cognitive impairment and depressive symptoms of person with AD were evaluated by a geriatrician using the Mini Mental State Examination (MMSE) and the Geriatric Depression Scale (GDS-15). Caregivers provided self-reports on the perception of cognitive impairment (IQCODE) of the care recipient, the caregiving burden (ZBI), depressive symptoms (GDS-15), and self-esteem (RSE). Descriptive analyses, comparison of different caregiver burden groups, and multinomial logistic regression analyses to understand correlates of caregiver burden were conducted with SPSS®, version 20. RESULTS: The findings show that the caregivers are on average 60 years old and the majority are women. They care for persons with AD, who are on average 82 years old and most of whom are women. Our results show that the duration of caregiving, depression of the caregiver, and caregivers' perception of cognitive impairment contribute significantly to burden of caregiver. DISCUSSION: This study shows that it is necessary to adopt the caregiver-centered approach to support the dyad. The role of the caregivers' perception of cognitive impairment in AD should be developed when supporting caregivers in suffering.

Gender and line size factors modulate the deviations of the subjective visual vertical induced by head tilt.

BACKGROUND: The subjective visual vertical (SVV, the visual estimation of gravitational direction) is commonly considered as an indicator of the sense of orientation. The present study examined the impact of two methodological factors (the angle size of the stimulus and the participant's gender) on deviations of the SVV caused by head tilt. Forty healthy participants (20 men and 20 women) were asked to make visual vertical adjustments of a light bar with their head held vertically or roll-tilted by 30° to the left or to the right. Line angle sizes of 0.95° and 18.92° were presented. RESULTS: The SVV tended to move in the direction of head tilt in women but away from the direction of head tilt in men. Moreover, the head-tilt effect was also modulated by the stimulus' angle size. The large angle size led to deviations in the direction of head-tilt, whereas the small angle size had the opposite effect. CONCLUSIONS: Our results showed that gender and line angle size have an impact on the evaluation of the SVV. These findings must be taken into account in the growing body of research that uses the SVV paradigm in disease settings. Moreover, this methodological issue may explain (at least in part) the discrepancies found in the literature on the head-tilt effect.

Spatial orientation constancy is impaired in anorexia nervosa.

In anorexia nervosa (AN), body distortions have been associated with parietal cortex (PC) dysfunction. The PC is also the anatomical substrate of a supramodal reference framework involved in spatial orientation constancy. Given the impaired spatial orientation constancy found in hemineglect, we sought to determine whether similar disturbances could be observed in anorexic patients. We investigated the effect of passive lateral body inclination on the tactile subjective vertical (SV). Fifty participants (25 AN patients and 25 healthy controls) were asked to manually set a rod into the vertical position under three postural conditions. For tilted conditions, we observed a significant deviation of the tactile SV towards the body. This effect was abnormally accentuated in AN patients and might be caused by higher weighting with respect to the egocentric frame of reference. Our findings reinforce the role of the PC in AN and suggest that this dysfunction affects spatial orientation constancy as well as body boundaries.

[Force platforms, a technological innovation]. / Les plates-formes de force, une innovation technologique.

Falls in the elderly constitute a public health issue due to the seriousness of the physical and psychological consequences as well as the resulting financial cost. Static posturography with the help of a force platform helps to guide therapeutic decisions and to rehabilitate patients who have fallen.

Fear of COVID-19, emotional exhaustion, and care quality experience in nursing home staff during the COVID-19 pandemic.

BACKGROUND: Nursing home staff have been adversely impacted throughout the COVID-19 pandemic, facing difficulties in providing patient care. The aim of this study was to explore health workers' perception regarding their own care quality experience in nursing homes during the COVID-19 pandemic. Amidst the second wave of the pandemic, we investigated the relationships between fear of COVID-19 and care quality experiences in nursing homes with emotional exhaustion (EE) as a mediating role. We hypothesized that EE is associated with fear of COVID-19 and care quality experience among nursing home staff. Furthermore, we predicted that EE would mediate the relationships between fear of COVID-19 and care quality experience. METHODS: During the second wave of COVID-19 (October to December 2020), we administered surveys to a large sample of 129 French nursing home staff with a mean age of 38.47 ± 10.31 who were directly and repeatedly exposed to COVID-19. We assessed their emotional exhaustion (EE) and care quality experience in the workplace via subjective indicators using self-reported scales. RESULTS: In the context of COVID-19, low to severe emotional exhaustion levels were found among nursing home staff, and these levels were associated with care quality experience as well as fear of COVID-19. The groups with low and severe levels of EE reported the highest levels of fear of COVID-19. The groups with moderate and severe levels of EE reported the lowest levels of care quality experience. Lastly, the relationships between fear of COVID-19 and care quality experience were mediated by EE. CONCLUSIONS: The findings made by the present study focused on the role of emotional coping responses to COVID-19. EE was associated positively with fear of COVID-19 and negatively with care quality experience. Furthermore, EE was found to mediate the relationship between fear of COVID-19 and care quality experience. We discuss these findings as they relate to palliative care issues in nursing homes and the manner in which emotional exhaustion ought to be addressed among nursing home staff.

Functional properties of extended body representations in the context of kinesthesia.

A person's internal representation of his/her body is not fixed. It can be substantially modified by neurological injuries and can also be extended (in healthy participants) to incorporate objects that have a corporeal appearance (such as fake body segments, e.g. a rubber hand), virtual whole bodies (e.g. avatars), and even objects that do not have a corporeal appearance (e.g. tools). Here, we report data from patients and healthy participants that emphasize the flexible nature of body representation and question the extent to which incorporated objects have the same functional properties as biological body parts. Our data shed new light by highlighting the involvement of visual motion information from incorporated objects (rubber hands, full body avatars and hand-held tools) in the perception of one's own movement (kinesthesia). On the basis of these findings, we argue that incorporated objects can be treated as body parts, especially when kinesthesia is involved.

Asymmetry of visuo-vestibular mechanisms contributes to reversal of optokinetic after-nystagmus.

When the visual background is moving while subject fixate a visual target, optokinetic eye movements (OKN) are suppressed and the after response, called optokinetic after nystagmus (OKAN), occurring at the stimuli offset is often inverted as compared to the situation when the OKN movements are allowed. In this study, we investigated whether this reversal of OKAN results from a perceptual or extra-retinal feedback in relation with the pursuit system and/or the vestibular indirect system. Optokinesis performance was studied in normal subjects in four experiments always using the same background motion (1) to characterize the OKN and OKAN performance elicited by the whole visual field motion while fixating or not a central visual target, (2) to investigate the 3D characteristics of the OKAN reversal by using different orientations of the visual stimulation, (3) to correlate the occurrence of an inverted OKAN with functional asymmetry of the visuo-vestibular system, by studying the effects of ocular fixation deviations and finally (4) to examine the effects of the depth plane of gaze fixation on the OKAN characteristics. In Experiments 1 and 2, we observed that the visual fixation during full-field motion induced either a dumping effect or an inversion of the OKAN response that could occur in the different planes of eye movements. The time constant was significantly increased in the inverted after-responses as compared to the not inverted ones. In Experiment 3, we found that the occurrence of an OKAN reversal after eye movement inhibition was significantly related to the presence of right/left asymmetrical OKAN responses. Moreover, the OKAN time constant was strikingly dependent on the eye fixation position during the visual stimulation and this time constant/eye position relation diverged between OKAN responses with and without inversion. Finally, Experiment 4 showed that the OKAN inversion tended to disappear when the visual target to fixate was in the near space as compared to the far space included in the background. These results argue in favor of an extraretinal influence in relation to the dynamics of the vestibulo-motor system, rather than for a perceptual influence on the inverted OKAN mechanisms. More precisely, we postulate that the reversal of OKAN could be linked to an inhibition issued from pursuit signals combined with an asymmetrical activity in the VSM vestibular complex.

The haptic perception of spatial orientations.

This review examines the isotropy of the perception of spatial orientations in the haptic system. It shows the existence of an oblique effect (i.e., a better perception of vertical and horizontal orientations than oblique orientations) in a spatial plane intrinsic to the haptic system, determined by the gravitational cues and the cognitive resources and defined in a subjective frame of reference. Similar results are observed from infancy to adulthood. In 3D space, the haptic processing of orientations is also anisotropic and seems to use both egocentric and allocentric cues. Taken together, these results revealed that the haptic oblique effect occurs when the sensory motor traces associated with exploratory movement are represented more abstractly at a cognitive level.

[Can overestimating one's own capacities of action lead to fall? A study on the perception of affordance in the elderly]. / Surestimer ses capacités peut-il conduire à la chute? Une étude sur la perception des affordances posturales chez la personne âgée.

Falls are frequent in the elderly and account for medical complications and loss of autonomy. Affordance, a concept proposed by Gibson, can help to understand a possible cause of falls. An affordance is defined as a potentiality of action offered by the environment in relation with both the properties of this environment and the properties of the organism. Most of our daily activities reflect a perfect adjustment between the perception of these potentialities of action and our actual action abilities. In other words, we correctly perceive affordances. However, in the elderly, postural abilities are reduced and equilibration is more unstable. Thus, some falls could result from a misperception of the affordances of posturability. The aim of our study was to test the hypothesis that cognitive overestimation of real postural abilities in the elderly may cause falls. There would be a gap between what the old subjects believe to be able to do and what they actually can do. Fifteen young adults (mean age = 24 years) and fifteen older adults (mean age = 72 years) had to judge if they were able to stand upright on an inclined surface. The exploration of the inclined surface was made in two conditions: visually and also by haptics (without vision with a cane). In a second part, we measured their real postural stance on the inclined surface. The results show that the perceptual judgments were not different among old and young people. However, as expected, the old subjects had lower postural boundaries than the younger. They could stand on lower inclinations of the surface. These results show an involution of the perception of the affordances in aging. They support the hypothesis of a cognitive overestimation of action abilities in the elderly, possibly due to a difficulty to actualize the new limits for action.

Contribution of Visual Motion Cues from a Held Tool to Kinesthesia.

Incorporation of a tool into the body schema is well established. Here, we assessed whether visual signals originating from the tool provide relevant cues for the perception of arm movements, as would signals originating from the arm holding it. Kinesthetic illusions were investigated by passively moving one arm (via a robotized manipulandum) and therefore the tool (a rake), using the mirror paradigm, with the reflected part being limited to the tool, the arm, or both. Illusory movements concerned the other arm, remaining static and hidden behind the mirror. In Experiments 1 and 3, participants held the same tools in their hands. Results showed that seeing the displacement of the reflected tool in the mirror induced kinesthetic mirror illusions in the hidden arm, similarly to seeing the reflected arm itself, though slightly reduced in terms of strength and occurrence frequency. In Experiment 2, participants held either the same objects in their hands (the rakes) or different ones (a rake, the image of which was reflected in the mirror, and a ball in the other hand). Results showed that mirror vision of the moving tool was not sufficient for mirror illusions to occur, the same tool in the two hands being an essential condition. Finally, in Experiment 3, we showed that neither prior practice nor active tool use was necessary for the tool mirror illusion to occur. Altogether, these results demonstrate that the visual cues originating from the held-tool are integrated for sensing arm movement.

Body Schema Illusions: A Study of the Link between the Rubber Hand and Kinesthetic Mirror Illusions through Individual Differences.

BACKGROUND: The well-known rubber hand paradigm induces an illusion by having participants feel the touch applied to a fake hand. In parallel, the kinesthetic mirror illusion elicits illusions of movement by moving the reflection of a participant's arm. Experimental manipulation of sensory inputs leads to emergence of these multisensory illusions. There are strong conceptual similarities between these two illusions, suggesting that they rely on the same neurophysiological mechanisms, but this relationship has never been investigated. Studies indicate that participants differ in their sensitivity to these illusions, which provides a possibility for studying the relationship between these two illusions. METHOD: We tested 36 healthy participants to confirm that there exist reliable individual differences in sensitivity to the two illusions and that participants sensitive to one illusion are also sensitive to the other. RESULTS: The results revealed that illusion sensitivity was very stable across trials and that individual differences in sensitivity to the kinesthetic mirror illusion were highly related to individual differences in sensitivity to the rubber hand illusion. CONCLUSIONS: Overall, these results support the idea that these two illusions may be both linked to a transitory modification of body schema, wherein the most sensitive people have the most malleable body schema.

Perception of Affordance during Short-Term Exposure to Weightlessness in Parabolic Flight.

We investigated the role of the visual eye-height (VEH) in the perception of affordance during short-term exposure to weightlessness. Sixteen participants were tested during parabolic flight (0g) and on the ground (1g). Participants looked at a laptop showing a room in which a doorway-like aperture was presented. They were asked to adjust the opening of the virtual doorway until it was perceived to be just wide enough to pass through (i.e., the critical aperture). We manipulated VEH by raising the level of the floor in the visual room by 25 cm. The results showed effects of VEH and of gravity on the perceived critical aperture. When VEH was reduced (i.e., when the floor was raised), the critical aperture diminished, suggesting that widths relative to the body were perceived to be larger. The critical aperture was also lower in 0g, for a given VEH, suggesting that participants perceived apertures to be wider or themselves to be smaller in weightlessness, as compared to normal gravity. However, weightlessness also had an effect on the subjective level of the eyes projected into the visual scene. Thus, setting the critical aperture as a fixed percentage of the subjective visual eye-height remains a viable hypothesis to explain how human observers judge visual scenes in terms of potential for action or "affordances".