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.

[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.

Relationships Between Confabulations and Mental Time Travel in Alzheimer's Disease.

The authors assessed the relationship between confabulations in Alzheimer's disease and the ability to mentally travel in time to reexperience memories. Twenty-seven patients with Alzheimer's disease were administered evaluations of provoked confabulations, spontaneous confabulations, and mental time travel. Provoked and spontaneous confabulations were evaluated with questions probing personal and general knowledge and with a scale rated by nursing and medical staff. Mental time travel was assessed by asking patients to retrieve personal memories. After each memory, participants had to provide a "remember" response if they were able to retrieve the event with their encoding context or a "know" response if they knew that the event had occurred but were unable to recall any contextual details. Results showed significant negative correlations between confabulations and "remember" responses. These findings reflect a relationship between the occurrence of confabulations in patients with Alzheimer's disease and impairments in their ability to mentally project themselves in time when retrieving the context in which confabulated memories were originally encoded.

Self-perceived and actual ability in the functional reach test in patients with Parkinson's disease.

Falls frequently occur during daily activities such as reaching for an object in patients with Parkinson's disease (PD). Misjudgment is also reported to be one of the circumstances that lead to falls. The functional reach test is an indicator of dynamic balance. The primary objective was to establish whether there is a difference between self-perceived and actual ability to perform the functional reach test in patients with PD who have never fallen. Three groups of participants (all with no history of falls) were studied: young adults, elderly adults and PD patients. The participants first estimated their maximum reaching distance (but without performing the action, i.e. as a motor imagery task) and then actually performed the functional reach test (i.e. as a motor task). No significant overestimation or underestimation was observed. The reaching distance was lower in PD than in the two other groups. There were no differences between PD patients and elderly adults in terms of the forward centre of pressure displacement. Seven PD patients reported a fall in the year following the experiment. The fallers had a longer history of disease. Finally, PD patients adequately estimated their ability in the functional reach test and did not adopt an "at risk" strategy and appeared to be quite conservative (as were healthy elderly adults) in their postural control behavior. Ability to estimate self-performance is preserved in PD patients with no clinical impairments of postural control although they are at risk of future falls.

[Assessment of verbal episodic memory by a new memory test with self-initiated items (MAI test)]. / Évaluation de la mémoire épisodique des personnes âgées : normalisation d'une nouvelle épreuve de mémoire avec items auto-initiés (MAI).

The assessment of episodic memory is a critical aspect of psychometric assessment in elderly people, particularly for the diagnosis of dementia. However, evaluation of episodic memory in these subjects is not easy in subjects with non-native language, different culture, visual impairment or fatigability. To overcome these difficulties, a rapid assessment of episodic memory, the Auto-initiated memory test (MAI test) has been developed. The goal of our research is to validate and standardize this test. To achieve the standards, we included 84 non-demented older participants (74.24±6.9 years). Moreover, we included 171 older participants with cognitive impairment and 33 older participants with Mild cognitive impairment. The results showed that the MAI test (phase 2 of the test) has good psychometric properties in MCI patients (sensitivity=76%, specificity=100%). Thus it appears to be an useful screening tool for detection of pre-dementia in subjects who are not able to pass usual standard tests of episodic memory.

In the elderly, failure to update internal models leads to over-optimistic predictions about upcoming actions.

Before an action is performed, the brain simulates the body's dynamic behavior in relation to the environment, estimates the possible outcomes and assesses the feasibility of potential actions. Here, we tested a hypothesis whereby age-related changes in sensorimotor abilities result in failure to update internal models of action in the elderly. Young and older adults were required to judge in advance whether or not they could stand on an inclined plane (Experiment 1). Relative to young adults, elderly adults overestimated their postural capabilities: although the two groups made similar feasibility judgments, elderly participants showed significantly worse postural performance levels. This tendency to overestimate their own ability persisted when elderly adults had to not only estimate the feasibility of an action but also endanger themselves by walking towards an obstacle that was too high for them to clear (Experiment 2). An age-related failure to update internal models may prompt the elderly to make over-optimistic predictions about upcoming actions. In turn, this may favor risky motor decision-making and promote falls.

[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.

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.

[The overestimation of performance: a specific bias of aging?]. / La surestimation de ses performances : un biais spécifique du vieillissement ?

The decline of postural abilities with age leads to increased falls. In this study, we suggest that a disturbance in the perception of postural affordances, characterized by an overestimation of performance, could be a major risk of falls specifically in the elderly. In addition, we test the possible link between the overestimation of capabilities and postural balance as we know degraded in the elderly. A group of 10 young subjects (M = 24.2 years ± 2.04) and a group of 10 elderly subjects (M = 75.9 years ± 5.7) must evaluate, without action, the maximum height of an obstacle that they can stride over. Then their postural performances are measured. The results show that, contrary to young people who correctly evaluate their performance (difference of 1.75 cm between estimated performance and real performance), older participants overestimate their maximum height of crossing over (12.5 cm difference between performance and estimated real performance). Moreover, the overestimation of performance is associated with poor postural stability. The bias of overestimation may stem from a lack of updating of motor programs caused by a functional brain change with age and/or lack of exercise who reduces updating by trial and error.

[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.