Knowing "what for," but not "where": Dissociation between functional and contextual tool knowledge in healthy individuals and patients with dementia.

OBJECTIVE: Semantic tool knowledge underlies the ability to perform activities of daily living. Models of apraxia have emphasized the role of functional knowledge about the action performed with tools (e.g., a hammer and a mallet allow a "hammering" action), and contextual knowledge informing individuals about where to find tools in the social space (e.g., a hammer and a mallet can be found in a workshop). The goal of this study was to test whether contextual or functional knowledge, would be central in the organization of tool knowledge. It was assumed that contextual knowledge would be more salient than functional knowledge for healthy controls and that patients with dementia would show impaired contextual knowledge. METHODS: We created an original, open-ended categorization task with ambiguity, in which the same familiar tools could be matched on either contextual or functional criteria. RESULTS: In our findings, healthy controls prioritized a contextual, over a functional criterion. Patients with dementia had normal visual categorization skills (as demonstrated by an original picture categorization task), yet they made less contextual, but more functional associations than healthy controls. CONCLUSION: The findings support a dissociation between functional knowledge ("what for") on the one hand, and contextual knowledge ("where") on the other hand. While functional knowledge may be distributed across semantic and action-related factors, contextual knowledge may actually be the name of higher-order social norms applied to tool knowledge. These findings may encourage researchers to test both functional and contextual knowledge to diagnose semantic deficits and to use open-ended categorization tests.

Sensory Integration Deficits in Neurodegenerative Diseases: Implications for Apraxia.

OBJECTIVE: Apraxia is the inability to perform voluntary, skilled movements following brain lesions, in the absence of sensory integration deficits. Yet, patients with neurodegenerative diseases (ND) may have sensory integration deficits, so we tested the associations and dissociations between apraxia and sensory integration. METHODS: A total of 44 patients with ND and 20 healthy controls underwent extensive testing of sensory integration (i.e., localization of tactile, visual, and proprioceptive stimuli; agraphesthesia; astereognosis) and apraxia (i.e., finger dexterity, imitation, tool use). RESULTS: The results showed (i) that patients with Alzheimer's disease, corticobasal syndrome, or posterior cortical atrophy were impaired on both dimensions; (ii) An association between both dimensions; (iii) that when sensory integration was controlled for, the frequency of apraxia decreased dramatically in some clinical subgroups. CONCLUSION: In a non-negligible portion of patients, the hypothesis of a disruption of sensory integration can be more parsimonious than the hypothesis of apraxia in case of impaired skilled gestures. Clinicians and researchers are advised to integrate sensory integration measures along with their evaluation of apraxia.

Imitation of meaningless gestures in the Alzheimer's disease: influence of egocentric and allocentric spatial reference frames / Imitation de gestes non significatifs dans la maladie d'Alzheimer : l'influence des cadres de référence spatiale égocentrique et allocentrique

Imitation of meaningless gestures is a frequently used task to assess praxis skills in Alzheimer's disease (AD). The visuospatial analysis is considered to be one of the cognitive mechanisms most involved in perceiving the gestures of the other (i.e. model to imitate) in the imitation of meaningless gestures. However, in order to perform a classic gesture imitation task (i.e. face model), it is also necessary to transpose the representation of the other's gestures to better represent one's own gestures. This transposition can be superimposed on the dichotomy of egocentric spatial reference frames (i.e. self-gestures) and allocentric spatial reference frames (i.e. gestures of the other). Given previous researches on the relation between hippocampus and allocentric performance, we predicted that AD patients could have imitation difficulties specifically for the allocentric imitation. We thus propose a specific methodology to evaluate the imitation of meaningless gestures in both egocentric and allocentric conditions using unimanual ( i.e. one hand gestures) as well bimanual (i.e. two hand gestures) gest modalities for each condition. Our results show significant differences between the AD group and control group, except under the bimanualallocentric condition. Moreover, correlation analyses with visuospatial assessments do not validate the essential role of visuospatial abilities in our gestural imitation tasks. The comparison of the within-group results shows a significant difference between egocentric and allocentric conditions only for the elderly control group suggesting that the impact of spatial reference frames in gestural imitation would not be specific to AD. However, one should also be alert to within-pathological variability in AD, which would require a future study with several subgroups of AD patients.

L'imitation de gestes non significatifs est une tâche fréquemment utilisée pour évaluer les aptitudes praxiques de la maladie d'Alzheimer (MA). L'analyse visuospatiale est considérée comme un des mécanismes cognitifs les plus impliqués dans l'imitation de gestes non significatifs pour percevoir les gestes de l'autre (i.e., modèle à imiter). Cependant pour réaliser une tâche d'imitation de gestes en forme classique (i.e., modèle situé de face), il est également nécessaire de transposer la représentation des gestes de l'autre pour mieux se représenter ses propres gestes. Cette transposition peut être superposée à la dichotomie de l'espace égocentrique (cf. gestes de soi) et l'espace allocentrique (cf. gestes de l'autre). Nous proposons ainsi une méthodologie spécifique afin d'évaluer l'imitation de gestes à la fois en condition égocentrique et en condition allocentrique. Nos résultats montrent des différences significatives entre le groupe MA et le groupe contrôle dans toutes les conditions sauf en condition allocentrique de la modalité bimanuelle (i.e., en deux mains). De plus, les analyses de corrélation avec des évaluations visuo-spatiales ne valident pas le rôle essentiel des capacités visuo-spatiales dans nos tâches d'imitation de gestes non significatifs. La comparaison des résultats en intragroupe montrent une différence significative entre les conditions égocentrique et allocentrique uniquement pour le groupe contrôle âgé, laissant supposer que l'impact des cadres de référence spatiale dans l'imitation de gestes ne serait pas spécifique à la MA. Toutefois, il faudrait également être attentif à une variabilité intrapathologique de la MA, ce qui requerrait une future étude avec plusieurs sous-groupes des patients MA.

Examining frustration intolerance beliefs among adults with dyslexia or developmental coordination disorder.

BACKGROUND: Research suggests that adults diagnosed with specific learning disorders, such as dyslexia or developmental coordination disorder (DCD), are at greater risk of emotional problems related to frustration and anger. AIMS: The purpose of this study was to investigate patterns of frustration intolerance beliefs among two groups of adults with a specific learning disorder (dyslexia or DCD), compared with typical adults. METHODS AND PROCEDURES: Participants were 235 French adults (students or in employment) with dyslexia (Mage = 35.8 years, SD = 13.3; females = 63 %), DCD (Mage = 32.9 years, SD = 11.8; females = 58 %) or typical development (Mage = 33.2 years, SD = 12.7; females = 65 %), who completed an online self-report questionnaire. OUTCOMES AND RESULTS: Analysis of variance revealed a significant between-groups difference, as both learning disorder groups had higher frustration intolerance beliefs than the typical adults. Post hoc analysis showed that participants with DCD scored higher than those with dyslexia on each type of frustration intolerance belief, while participants with dyslexia scored higher than typical adults on achievement frustration and discomfort intolerance. CONCLUSIONS AND IMPLICATIONS: These results underline the usefulness of distinguishing between frustration intolerance dimensions, and of using rational emotive behavior therapy to reduce the irrational beliefs of people with DCD or dyslexia.

Neuropsychological Profile of Intellectually Gifted Children: A Systematic Review.

OBJECTIVE: The term intellectually gifted (IG) refers to children of high intelligence, which is classically measured by the intelligence quotient (IQ). Some researchers assume that the cognitive profiles of these children are characterized by both strengths and weaknesses, compared with those of their typically developing (TD) peers of average IQ. The aim of the present systematic review was to verify this assumption, by compiling data from empirical studies of cognitive functions (language, motor skills, visuospatial processing, memory, attention and executive functions, social and emotional cognition) and academic performances. METHOD: The literature search yielded 658 articles, 15 of which met the selection criteria taken from the Preferred Reporting Items for Systematic Reviews and Meta-Analyses model. We undertook a qualitative summary, to highlight any discrepancies between cognitive functions. RESULTS: IG children exhibited better skills than TD children in a number of domains, including attention, language, mathematics, verbal working memory, shifting, and social problem solving. However, the two groups had comparable skills in visuospatial processing, memory, planning, inhibition, and visual working memory, or facial recognition. CONCLUSION: Although IG children may have some strengths, many studies have failed to find differences between this population and their TD peers on many other cognitive measures. Just like any other children, they can display learning disabilities, which can be responsible for academic underachievement. Further studies are needed to better understand this heterogeneity. The present review provides pointers for overcoming methodological problems and opens up new avenues for giftedness research.

Meaningless imitation in neurodegenerative diseases: Effects of body part, bimanual imitation, asymmetry, and body midline crossing.

Visuo-imitative apraxia has been consistently reported in patients with dementia, yet there have been substantial methodological differences between studies, while multiple, sometimes competing hypotheses have been put forward to explain this syndrome. Our goals were to study specific imitation deficits in groups of patients who have been selected and assigned to a group solely based on clinical criteria. We tested the effects of body part, bimanual imitation, asymmetry of the model, and body midline crossing, in patients with cortical atrophy of the temporal lobes (semantic dementia, SD), frontal-parietal networks (FPN, i.e., posterior cortical atrophy and corticobasal syndrome) or both (Alzheimer's disease, AD). Sixty-three patients and 32 healthy controls were asked to imitate 45 meaningless finger/hand, uni-/bimanual, asymmetrical/symmetrical, and crossed/uncrossed postures. SD patients had subnormal imitation scores. FPN patients showed frequent and marked deficits in most conditions, better performance with hand than finger postures (probably because of visuo-constructive deficits), and better performance with uncrossed than crossed configurations (probably because of body schema disorganization). Bimanual configurations were difficult for AD patients, not because of bimanual activity in itself, but rather because of the complexity of the model. The finding of dissociations in 34/63 cases (54%) suggests that some patients, even within the same clinical category, can have variable performance in imitation tests as a function of the abovementioned factors. Clinicians are advised to use tests with a large array of items to properly capture patients' imitation skills. This provides a new basis for future research to unpack which neurocognitive mechanisms are disrupted to cause specific patterns of impaired imitation.

Daily life activities in patients with Alzheimer's disease or semantic dementia: Multitasking assessment.

The aim of the present study was to compare patients with mild to moderate Alzheimer's disease (AD) or semantic dementia (SD) on their cognitive processes and the severity of their daily life activity impairments. Three types of tasks were administered to patients (SD = 15; AD = 31) and 30 healthy controls (HC): 1) informant-based scales and questionnaires, 2) a neuropsychological assessment exploring executive functions, episodic and semantic memory, and 3) a new original test featuring multi-step naturalistic actions and multitasking: the Sequential Daily Life Multitasking (SDLM). We predicted that patients with AD would mainly exhibit task perplexity, associated with episodic and executive deficits on the SDLM, while the behavior of patients with SD would mostly be characterized by object perplexity, associated with semantic memory deficits. Results showed that patients with AD or SD were impaired across all neuropsychological tests, particularly episodic memory in AD and semantic memory in SD. General performance on the SDLM also appeared dramatically impaired in both patient groups, and correlated with results of questionnaires about instrumental activities and memory impairments. However, specific qualitative measurements on the SDLM did not allow us to pinpoint different patterns of errors and behavior in patients with AD versus SD. We suggest that the inability of patients in both groups to perform the SDLM may derive from a constellation of disorders or else from more subtle impairment of cognitive and conative processes that requires further exploration.

Imitation of meaningless gestures in normal aging.

While imitation of meaningless gestures is a gold standard in the assessment of apraxia in patients with either stroke or neurodegenerative diseases, little is known about potential age-related effects on this measure. A significant body of literature has indicated that different mechanisms (i.e., executive functioning, visuospatial skills, sensory integration, body knowledge, categorical apprehension) may underlie the performance depending on imitation conditions (i.e., finger/hand, uni-/bimanual, symmetric/asymmetric, crossed/uncrossed configurations). However, neither the effects of these conditions on performance, nor the contribution of the abovementioned mechanisms to imitation have been explored in normal aging. The aim of the present study was to fill this gap. To do so, healthy adults (n = 103) aged 50 to 89 were asked to imitate 45 meaningless gestures. The authors controlled for general cognitive function, motor function, visual-spatial skills, executive function, sensory integration, body knowledge, and mechanical problem-solving skills. The results showed that asymmetry, body-midline crossing and, to a lesser extent, bimanual activity added an additional layer of difficulty to imitation tasks. After controlling for motor speed and cognitive function, age had an effect on imitation skills after 70 years old. This may reflect a decline in body knowledge, sensory integration, and executive functions. In contrast, the visuospatial and mechanical problem-solving hypotheses were ruled out. An additional motor simulation hypothesis is proposed. These findings may prove useful for clinicians working in memory clinics by providing insights on how to interpret imitation deficits. Lower performance after 70 years old should not be considered abnormal in a systematic manner.

The - weak - role of memory in tool use: Evidence from neurodegenerative diseases.

OBJECTIVE: Although tool use disorders are frequent in neurodegenerative diseases, the question of which cognitive mechanisms are at stake is still under debate. Memory-based hypotheses (i.e., the semantic knowledge hypothesis and the manipulation knowledge hypothesis) posit that tool use relies solely on stored information about either tools or gestures whereas a reasoning-based hypothesis (i.e., the technical-semantic hypothesis) suggests that loss of semantic knowledge can be partially compensated by technical reasoning about the physical properties of tools and objects. METHOD: These three hypotheses were tested by comparing performance of 30 healthy controls, 30 patients with Alzheimer's disease and 13 patients with semantic dementia in gesture production tasks (i.e., pantomime of tool use, single tool use, real tool use) and tool or gesture recognition tasks (i.e., functional and contextual matching, recognition of tool manipulation). Individual, item-based patterns of performance were analyzed to answer the following question: Could participants demonstrate the use of tools about which they had lost knowledge? With this aim in mind, "validation" and "rebuttal" frequencies were calculated based on each prediction. RESULTS: Predictions from the technical-semantic hypothesis were more frequently observed than memory-based predictions. A number of patients were able to use and demonstrate the use of tools for which they had lost either semantic or manipulation knowledge (or both). CONCLUSIONS: These data lead to question the role of different types of memory in tool use. The hypothesis of stored, tool-specific knowledge does not predict accurately clinical performances at the individual level. This may lead to explore the influence of either additional memory systems (e.g., personal/impersonal memory) or other modes of reasoning (e.g., theory of mind) on tool use skills.

Tool use in neurodegenerative diseases: Planning or technical reasoning?

Recent works showed that tool use can be impaired in stroke patients because of either planning or technical reasoning deficits, but these two hypotheses have not yet been compared in the field of neurodegenerative diseases. The aim of this study was to address the relationships between real tool use, mechanical problem-solving, and planning skills in patients with Alzheimer's disease (AD, n = 32), semantic dementia (SD, n = 16), and corticobasal syndrome (CBS, n = 9). Patients were asked to select and use ten common tools, to solve three mechanical problems, and to complete the Tower of London test. Motor function and episodic memory were controlled using the Purdue Pegboard Test and the BEC96 questionnaire, respectively. A data-transformation method was applied to avoid ceiling effects, and single-case analysis was performed based on raw scores and completion time. All groups demonstrated either impaired or slowed tool use. Planning deficits were found only in the AD group. Mechanical problem-solving deficits were observed only in the AD and CBS groups. Performance in the Tower of London test was the best predictor of tool use skills in the AD group, suggesting these patients had general rather than mechanical problem-solving deficits. Episodic memory seemed to play little role in performance. Motor dysfunction tended to be associated with tool use skills in CBS patients, while tool use disorders are interpreted as a consequence of the semantic loss in SD in line with previous works. These findings may encourage caregivers to set up disease-centred interventions.

Rethinking the Cognitive Mechanisms Underlying Pantomime of Tool Use: Evidence from Alzheimer's Disease and Semantic Dementia.

OBJECTIVES: Pantomiming the use of familiar tools is a central test in the assessment of apraxia. However, surprisingly, the nature of the underlying cognitive mechanisms remains an unresolved issue. The aim of this study is to shed a new light on this issue by exploring the role of functional, mechanical, and manipulation knowledge in patients with Alzheimer's disease and semantic dementia and apraxia of tool use. METHODS: We performed multiple regression analyses with the global performance and the nature of errors (i.e., production and conception) made during a pantomime of tool use task in patients and control participants as dependent variables and tasks investigating functional, mechanical, and manipulation knowledge as predictors. RESULTS: We found that mechanical problem solving, assessing mechanical knowledge, was a good predictor of the global performance of pantomime of tool use. We also found that occurrence of conception errors was robustly predicted by the task assessing functional knowledge whereas that of production errors was not explained by only one predictor. CONCLUSIONS: Our results suggest that both functional and mechanical knowledge are important to pantomime the use of tools. To our knowledge, this is the first demonstration that mechanical knowledge plays a role in pantomime of tool use. Although impairment in pantomime of tool use tasks (i.e., apraxia) is widely explained by the disruption of manipulation knowledge, we propose that pantomime of tool use is a complex problem-solving task. (JINS, 2017, 23, 128-138).

Imitation and matching of meaningless gestures: distinct involvement from motor and visual imagery.

The aim of the present study was to understand the underlying cognitive processes of imitation and matching of meaningless gestures. Neuropsychological evidence obtained in brain damaged patients, has shown that distinct cognitive processes supported imitation and matching of meaningless gestures. Left-brain damaged (LBD) patients failed to imitate while right-brain damaged (RBD) patients failed to match meaningless gestures. Moreover, other studies with brain damaged patients showed that LBD patients were impaired in motor imagery while RBD patients were impaired in visual imagery. Thus, we hypothesize that imitation of meaningless gestures might rely on motor imagery, whereas matching of meaningless gestures might be based on visual imagery. In a first experiment, using a correlational design, we demonstrated that posture imitation relies on motor imagery but not on visual imagery (Experiment 1a) and that posture matching relies on visual imagery but not on motor imagery (Experiment 1b). In a second experiment, by manipulating directly the body posture of the participants, we demonstrated that such manipulation evokes a difference only in imitation task but not in matching task. In conclusion, the present study provides direct evidence that the way we imitate or we have to compare postures depends on motor imagery or visual imagery, respectively. Our results are discussed in the light of recent findings about underlying mechanisms of meaningful and meaningless gestures.

A cognitive-based model of tool use in normal aging.

While several cognitive domains have been widely investigated in the field of aging, the age-related effects on tool use are still an open issue and hardly any studies on tool use and aging is available. A significant body of literature has indicated that tool use skills might be supported by at least two different types of knowledge, namely, mechanical knowledge and semantic knowledge. However, neither the contribution of these kinds of knowledge to familiar tool use, nor the effects of aging on mechanical and semantic knowledge have been explored in normal aging. The aim of the present study was to fill this gap. To do so, 98 healthy elderly adults were presented with three tasks: a classical, familiar tool use task, a novel tool use task assessing mechanical knowledge, and a picture matching task assessing semantic knowledge. The results showed that aging has a negative impact on tool use tasks and on knowledge supporting tool use skills. We also found that aging did not impact mechanical and semantic knowledge in the same way, confirming the distinct nature of those forms of knowledge. Finally, our results stressed that mechanical and semantic knowledge are both involved in the ability to use familiar tools.

Involvement of Technical Reasoning More Than Functional Knowledge in Development of Tool Use in Childhood.

It is well-known that even toddlers are able to manipulate tools in an appropriate manner according to their physical properties. The ability of children to make novel tools in order to solve problems is, however, surprisingly limited. In adults, mechanical problem solving (MPS) has been proposed to be supported by "technical reasoning skills," which are thought to be involved in every situation requiring the use of a tool (whether conventional or unusual). The aim of this study was to investigate the typical development of real tool use (RTU) skills and its link with technical reasoning abilities in healthy children. Three experimental tasks were adapted from those used with adults: MPS (three different apparatus), RTU (10 familiar tool-object pairs), and functional knowledge (FK; 10 functional picture matching with familiar tools previously used). The tasks were administered to 85 healthy children divided into six age groups (from 6 to 14 years of age). The results revealed that RTU (p = 0.01) and MPS skills improve with age, even if this improvement differs according to the apparatus for the latter (p < 0.01 for the Hook task and p < 0.05 for the Sloping task). Results also showed that MPS is a better predictor of RTU than FK, with a significant and greater weight (importance weight: 0.65; Estimate ± Standard Error: 0.27 ± 0.08). Ours findings suggest that RTU and technical reasoning develop jointly in children, independently from development of FK. In addition, technical reasoning appears partially operative from the age of six onward, even though the outcome of these skills depends of the context in which they are applied (i.e., the type of apparatus).

Tool use disorders in neurodegenerative diseases: Roles of semantic memory and technical reasoning.

In the field of apraxia, it has been suggested that the ability to use tools and objects in daily life depends not only on semantic knowledge about tool function and context of use but also on technical reasoning about mechanical properties of tools and objects. The aim of the present work was to assess tool use abilities regarding these hypotheses in patients with neurodegenerative diseases and reduced autonomy. Performance of patients with Alzheimer's disease (AD) (n = 31), semantic dementia (SD) (n = 16) and corticobasal syndrome (CBS) (n = 7) was compared to that of healthy control participants (n = 31) in familiar tool use tasks, functional/contextual associations and mechanical problem solving (MPS). A conversion method was applied to data in order to avoid ceiling effects. Tool use disorders were found in all patient groups but the underlying reasons were different. Patients with SD had difficulties in imagining and selecting familiar tools due to the semantic loss but they performed in normal range in MPS tasks. Interestingly, they performed better with only one tool and its corresponding object, which is interpreted as a partial compensation of semantic loss by spared technical reasoning. Patients with CBS exhibited the reverse pattern, that is, MPS deficits without semantic loss. However, additional qualitative research is needed to disentangle the relative contributions of motor and technical reasoning deficits to this pattern. Both of these profiles were found in patients with AD. For all that, these patients did not commit the same errors as stroke patients with left brain-damage documented in previous works. Several hypotheses are proposed to account for the specificity of tool use disorders in neurodegenerative diseases, and recommendations are provided to caregivers.

Tool use in left brain damage and Alzheimer's disease: What about function and manipulation knowledge?

Tool use disorders are usually associated with difficulties in retrieving function and manipulation knowledge. Here, we investigate tool use (Real Tool Use, RTU), function (Functional Association, FA) and manipulation knowledge (Gesture Recognition, GR) in 17 left-brain-damaged (LBD) patients and 14 AD patients (Alzheimer disease). LBD group exhibited predicted deficit on RTU but not on FA and GR while AD patients showed deficits on GR and FA with preserved tool use skills. These findings question the role played by function and manipulation knowledge in actual tool use.

Mechanical problem-solving strategies in Alzheimer's disease and semantic dementia.

OBJECTIVE: The goal of this study was to explore whether the tool-use disorders observed in Alzheimer's disease (AD) and semantic dementia (SD) are of the same nature as those observed in left brain-damaged (LBD) patients. Recent evidence indicates that LBD patients with apraxia of tool use encounter difficulties in solving mechanical problems, characterized by the absence of specific strategies. This pattern may show the presence of impaired mechanical knowledge, critical for both familiar and novel tool use. So, we explored the strategies followed by AD and SD patients in mechanical problem-solving tasks in order to determine whether mechanical knowledge is also impaired in these patients. METHOD: We used a mechanical problem-solving task in both choice (i.e., several tools were proposed) and no-choice (i.e., only 1 tool was proposed) conditions. We analyzed quantitative data and strategy profiles. RESULTS: AD patients but not SD patients met difficulties in solving mechanical problem-solving tasks. However, the key finding is that AD patients, despite their difficulties, showed strategy profiles that are similar to that of SD patients or controls. Moreover, AD patients exhibited a strategy profile distinct from the one previously observed in LBD patients. CONCLUSIONS: Those observations lead us to consider that difficulties met by AD patients to solve mechanical problems or even to use familiar tools may not be caused by mechanical knowledge impairment per se. In broad terms, what we call apraxia of tool use in AD is certainly not the same as apraxia of tool use observed in LBD patients. (PsycINFO Database Record

Apraxia and Alzheimer's disease: review and perspectives.

Apraxia is one of the cognitive deficits that characterizes Alzheimer's disease. Despite its prevalence and relevance to diagnosing Alzheimer's disease, this topic has received little attention and is without comprehensive review. The review herein is aimed to fill this gap by first presenting an overview of the impairment caused in different clinical situations: pantomime of tool use, single tool use, real tool use, mechanical problem solving, function and manipulation knowledge tasks, and symbolic/meaningless gestures. On the basis of these results, we then propose alternative interpretations regarding the nature of the underlying mechanisms impaired by the disease. Also presented are principal methodological issues precluding firm conclusions from being drawn.

Mechanical problem-solving strategies in left-brain damaged patients and apraxia of tool use.

Left brain damage (LBD) can impair the ability to use familiar tools (apraxia of tool use) as well as novel tools to solve mechanical problems. Thus far, the emphasis has been placed on quantitative analyses of patients' performance. Nevertheless, the question still to be answered is, what are the strategies employed by those patients when confronted with tool use situations? To answer it, we asked 16 LBD patients and 43 healthy controls to solve mechanical problems by means of several potential tools. To specify the strategies, we recorded the time spent in performing four kinds of action (no manipulation, tool manipulation, box manipulation, and tool-box manipulation) as well as the number of relevant and irrelevant tools grasped. We compared LBD patients' performance with that of controls who encountered difficulties with the task (controls-) or not (controls+). Our results indicated that LBD patients grasped a higher number of irrelevant tools than controls+ and controls-. Concerning time allocation, controls+ and controls- spent significantly more time in performing tool-box manipulation than LBD patients. These results are inconsistent with the possibility that LBD patients could engage in trial-and-error strategies and, rather, suggest that they tend to be perplexed. These findings seem to indicate that the inability to reason about the objects' physical properties might prevent LBD patients from following any problem-solving strategy.