A model‐based approach to limb apraxia in Alzheimer's disease

Limb apraxia is a neurological deficit characterized by an inability to pantomime and/or imitate gestures, which can result from neurodegenerative disorders such as Alzheimer's disease (AD). The major goal of the study was to describe comprehensively the apraxia deficits observed in AD patients and to relate those deficits to general cognitive status, measures of daily activity, and other neuropsychological measures. Limb apraxia was assessed on a variety of conceptual and gesture production tasks in 30 AD patients. As a group, AD patients were impaired across gesture production tasks: of note was the greater impairment in imitation, as opposed to pantomime, which was especially pronounced when patients were imitating with a delay. Imitation performance was best predicted by measures of visuospatial processing, while imitation with delay was best predicted by measures of working memory. In addition, pantomime in response to pictures of tools was less accurate than Pantomime to Verbal Command and holding the tool during performance did not decrease the participants' impairment, while introducing a verbal cue during imitation increased the severity of deficits. Furthermore, investigation into patterns of deficits clearly demonstrated that the nature of limb apraxia deficits observed in AD can be quite heterogeneous and that dissociations between the conceptual and the production system exist. Finally, we also report on significant correlations between general cognitive status and limb apraxia.     

Pantomime, praxis, and aphasia.

The production and comprehension of pantomimed movements by asphasic subjects were studied with respect to their relationship to the aphasic deficit on one hand and apraxia on the other. At issue was whether impaired use of pantomime is a manifestation of reduced symbolic capacity or purely a manifestation of an apraxic impairment of purposeful movement or both. Tests of pantomime included a Pantomime Recognition Test, a nonverbal Transitive Pantomime Production Test, and an Intransitive Pantomime Production Test (to oral command). Imitation of Nonmeaningful Movements served as a measure of apraxia, uncontaminated by symbolic or linguistic factors. Imitation of Meaningful Movements taken from the pantomime tasks was also tested. Independent measures of auditory comprehension, picture naming, and reading comprehension were used as indices of language impairment. Intellectual function was measured by the Performance scale of the WAIS. Thirty aphasic subjects were examined. Twenty healthy age-matched normals served to establish scoring standards for the pantomime tests. Multiple regression analysis revealed significant, independent contributions from both auditory comprehension and imitation of Nonmeaningful Movements to all of the tests of pantomime production and pantomime recognition. All measures of pantomime production and pantomime recognition were strongly intercorrelated. While the three language measures were strongly correlated with each other, auditory comprehension was the only one of them that was significantly and consistently related to the pantomime tests. None was related to the imitation of nonmeaningful movement. The results are taken as indicating (1) that pantomime production and imitation share common factors with both praxis and auditory comprehension; (2) apraxia entails impairment of both production and interpretation of purposeful movements. Possible theoretical accounts for these results are offered.     

Getting a Grasp on Children’s Representational Capacities in Pantomime of Object Use

This study examined how 5- and 9-year-old children (N = 40) produce pantomimes of object use on verbal request. The task required participants to enact an action with an imagined object. Results showed that with age, children (a) proceeded from body part as object to imaginary object and (b) incorporated into their pantomimes more distinctive features of the object and its use. While the first result replicated previous findings with more items and a more sophisticated coding procedure, the latter result revealed new insights. Children’s selection of distinctive features in pantomime was related to their performance on a semantic odd-one-out task that requires the abstraction of specific features without situational support. The discussion focuses on the cognitive requirements of the task and the potential of pantomime being a reflection of children’s representational development. We suggest an explanation of the findings within the more general developmental model of Karmiloff-Smith.     

Pantomime recognition defect in aphasia: implications for the concept of asymbolia

This study investigated the relationship of impaired pantomime recognition to reading comprehension, sound recognition, letter recognition, and nonverbal abstract reasoning among aphasic patients. Defects in pantomime recognition were closely associated with defects in reading comprehension, but some with impaired pantomime recognition performed well on some or all of the remaining tests. Implications of the findings for the theory of asymbolia, and for reading comprehension are discussed.     

Mechanical knowledge does matter to tool use even when assessed with a non-production task: Evidence from left brain-damaged patients

In the literature on apraxia of tool use, it is now accepted that using familiar tools requires semantic and mechanical knowledge. However, mechanical knowledge is nearly always assessed with production tasks, so one may assume that mechanical knowledge and familiar tool use are associated only because of their common motor mechanisms. This notion may be challenged by demonstrating that familiar tool use depends on an alternative tool selection task assessing mechanical knowledge, where alternative uses of tools are assumed according to their physical properties but where actual use of tools is not needed. We tested 21 left brain-damaged patients and 21 matched controls with familiar tool use tasks (pantomime and single tool use), semantic tasks and an alternative tool selection task. The alternative tool selection task accounted for a large amount of variance in the single tool use task and was the best predictor among all the semantic tasks. Concerning the pantomime of tool use task, group and individual results suggested that the integrity of the semantic system and preserved mechanical knowledge are neither necessary nor sufficient to produce pantomimes. These results corroborate the idea that mechanical knowledge is essential when we use tools, even when tasks assessing mechanical knowledge do not require the production of any motor action. Our results also confirm the value of pantomime of tool use, which can be considered as a complex activity involving several cognitive abilities (e.g., communicative skills) rather than the activation of gesture engrams.     

Experimenter's Pantomimes Influence Children's Use of Body Part as Object and Imaginary Object Pantomimes: A Replication

Young children asked to pretend to use a series of absent objects typically pantomime by using a body part as the object (BPO) rather than by acting as if using an imaginary object (IO). This replication of Lyons's work (1983, 1986) examines whether different pretend contexts when requesting pantomimes influence children's use of IO and BPO pantomimes. Forty-three children aged 3;6 to 6;6 were asked to pretend to use 8 objects in 1 of 3 contexts: request, request after participating in an experimenter-provided imaginary context, and request after seeing the adult model the requested pretend action. The experimenter used IO pantomimes in the last 2 contexts. Children produced, on average, the most IO pantomimes in the modeling context, fewer in the imaginary context, and the fewest in the request context. Older children overall produced more IO pantomimes than did younger children; however, when pretend contexts were examined separately, ontogenetic differences in IO pantomimes were present for the request condition only. Externally directed actions resulted in more IO pantomiming than self-directed actions for only the youngest children.     

Patterns of limb apraxia in primary progressive aphasia

Primary progressive aphasia (PPA) is a syndrome characterized by a progressive language deficit without other dementia features for at least two years (). Other deficits that are likely to co-exist with aphasia, such as apraxia, have only been investigated in a few case studies and only at a rudimentary level for the most part. In this study we investigate the frequency and severity of apraxic deficits in PPA patients. Ten PPA patients and twelve aged-matched healthy adults performed eight transitive gestures to pantomime and to imitation. Gesture performance was measured along five movement dimensions and a composite score based on the arithmetic mean of the five dimensions was calculated. Overall, PPA patients performed worse than controls with both pantomime and imitation. Furthermore, individual comparisons revealed that out of the three apraxia patterns described by (pantomime alone, imitation alone, or apraxia in both conditions), the most frequent pattern in PPA patients was apraxia in both conditions. This result corresponds with previous findings in populations of stroke and Alzheimer's patients. Considering the occurrence of apraxia in this population, this study supports the idea that a comprehensive apraxia assessment should be administered in cases of PPA.     

Cognitive and affective Theory of Mind in mild to moderate Alzheimer's disease

Theory of Mind (ToM) allows one's own and others' cognitive and emotional mental states to be inferred. Although many patients with Alzheimer's disease (AD) display impaired social functioning as their disease progresses, very few studies have investigated ToM in AD. Those that have done so suggest that patients' ToM deficits are the consequence of other cognitive impairments. The aim of this study was thus to investigate changes in both the cognitive and the affective dimensions of ToM in AD, using tasks designed to circumvent the patients' comprehension difficulties. Sixteen mild to moderate AD patients and 15 healthy controls matched on age, sex and education level underwent cognitive (preference judgment and first‐ and second‐order false belief) and affective (Reading the Mind in the Eyes) ToM assessments. Comprehension of false belief stories was verified and an additional neuropsychological examination was undergone. We observed impaired performances by AD patients on all the ToM tasks. While working memory and executive functioning impairments contributed to the deterioration in the more complex aspects of cognitive ToM abilities as highlighted by a correlation analysis, we failed to observe any comprehension difficulties in patients who performed poorly on simple cognitive ToM tasks, which suggests that AD truly affects cognitive ToM.     

Pantomime and imitation of limb gestures in relation to the severity of Alzheimer's disease

The present study was designed to investigate the relationship between performance of limb gestures and the severity of Alzheimer's disease (A.D.). Apraxia tends to occur at later stages of A.D., and the severity of apraxia has been shown to vary with the severity of A.D. dementia. Participants were 19 mild (including 9 with no cognitive impairment and 10 with mild impairment) and 18 moderate A.D. patients as well as 25 controls and they were asked to pantomime (P) or imitate (both concurrent (CI) and delayed (DI)), eight transitive gestures to assess praxis performance. Results indicated that the moderate patients performed less accurately than mild and non-impaired patients, and that across all groups, the imitation conditions were performed less accurately than pantomime, relative to controls. Correlational analyses revealed that MMSE scores were correlated with all three performance conditions suggesting that impaired praxis performance may relate to more global impairment. Finally, a frequency analysis was conducted to examine whether A.D. patients showed patterns of apraxia as described in Roy's model (1996). Results indicated that A.D. patients showed greatest impairment on pattern 7 (deficits in P, DI, and CI), reflecting late-stage gesture production, with a greater frequency of moderate patients exhibiting each apraxic pattern.     

交流手势认知理论

手势是交流互动中一种重要的非语言媒介, 手势不仅可以辅助语言交流而且具有独立的交流性; 作为和语言共同发生的非语言媒介, 手势交流有助于降低交流认知负荷。文章重点归纳和述评了基于手势和语言表达关系的交流手势理论、交流手势激活理论、交流手势的认知节省理论。未来研究需要进一步考虑交流手势实验研究情境自然性和控制严格性间的平衡, 交流手势和其他非语言因素间的关系, 交流手势认知研究的现实意义。     

On the nature of the verbal memory deficit in Alzheimer''s disease

Verbal memory was investigated in patients with Alzheimer's disease (AD) with previously documented deficits in word production and comprehension. Procedures were employed to evaluate word recall and recognition within the context of both "multistore" and "levels of processing" models of memory. In addition, memory abilities were evaluated with respect to performance on measures of verbal fluency and language comprehension. As expected, the AD patients performed significantly worse than normal individuals on all tasks. However, in each experiment their pattern of recall across conditions was found to be qualitatively similar to that produced by normal subjects. It was argued that the memory impairment associated with Alzheimer's disease may be largely due to an inability to encode a sufficient number of stimulus features or attributes. Furthermore, this encoding deficit includes, but is not limited to, semantic attributes. Similarities between the performance of the AD patients and reported findings with Korsakoff patients and normal subjects with "weak" memory were discussed.     

Gestural impairment and gestural ability in aphasia: A review

Studies of gestural ability in aphasic subjects have found impairment of gestural expression and comprehension, with a close relationship between severity of aphasia and degree of gestural impairment. A few investigators have correlated gestural ability with specific language functions or subcategories of aphasia. Reading appears to correlate better with gestural recognition than does auditory comprehension. Despite the general findings of gestural impairment in aphasia, successes have been reported with gestural training including artificial language techniques, pantomime, Amerind, and American Sign Language. Future studies of gestural therapy in aphasia should examine specific language deficits in order to identify those aphasic individuals who can benefit from gestural training.     

Alzheimer's Disease Patients' Cognitive Status and Course Years Prior to Symptom Recognition

This is a prospective examination of the cognitive performance and cognitive course of persons in an asymptomatic “preclinical” phase who eventually developed Alzheimer's disease (AD). We compared performances on the Mayo Cognitive Factor Scales (MCFS) of 20 persons in a neurologically normal cohort who subsequently developed AD to the performances of 60 persons who remained free of dementia symptoms. For the AD patients, exams occurred prior to the appearance of dementia symptoms (an average of 4.2 and 1.5 years prior to symptom onset). Results reveal strong group differences on learning and retention, with eventual AD patients scoring lower than controls years prior to reporting symptoms of the disease. There was no significant interaction effect (group × testing session) for memory retention, suggesting that memory decline in this preclinical period may be too slow to be a useful indicator of future AD. A significant interaction (but no group effect) was seen for verbal comprehension.     

Alzheimer's disease patients' cognitive status and course years prior to symptom recognition

This is a prospective examination of the cognitive performance and cognitive course of persons in an asymptomatic "preclinical" phase who eventually developed Alzheimer's disease (AD). We compared performances on the Mayo Cognitive Factor Scales (MCFS) of 20 persons in a neurologically normal cohort who subsequently developed AD to the performances of 60 persons who remained free of dementia symptoms. For the AD patients, exams occurred prior to the appearance of dementia symptoms (an average of 4.2 and 1.5 years prior to symptom onset). Results reveal strong group differences on learning and retention, with eventual AD patients scoring lower than controls years prior to reporting symptoms of the disease. There was no significant interaction effect (group x testing session) for memory retention, suggesting that memory decline in this preclinical period may be too slow to be a useful indicator of future AD. A significant interaction (but no group effect) was seen for verbal comprehension.     

Metaphor comprehension in Alzheimer's disease: novelty matters

The comprehension of non-literal language was investigated in 20 probable Alzheimer's disease (pAD) patients by comparing their performance to that of 20 matched control subjects. pAD patients were unimpaired in the comprehension of conventional metaphors and idioms. However, their performance was significantly lower in the case of non-conventional (novel) metaphor comprehension. This ability was not related to global cognitive deterioration or to deficits in the cognitive domains of attention, memory and language comprehension. On the other hand, the impairment in verbal reasoning appeared to be relevant for both novel and conventional metaphor comprehension. The relationship between novel metaphor comprehension and performance in the visual-spatial planning task of the Behavioral Assessment of the Dysexecutive Syndrome (BADS) suggests that executive impairment, possibly related to prefrontal dysfunction, may be responsible for the pAD patients' poor performance in novel metaphor comprehension. The present findings suggest a role of the prefrontal cortex in novel metaphor comprehension.     

Cognitive procedural learning in early Alzheimer's disease: impaired processes and compensatory mechanisms

Introduction. The aim of this study was to study cognitive procedural learning in early Alzheimer's disease (AD). Methods. Cognitive procedural learning was assessed using the Tower of Hanoi (TH) task. In order to take account of possible interactions between different systems during cognitive procedural learning, we also measured non‐verbal intellectual functions, working memory, and declarative memory. Results. Our results showed an apparent preservation of cognitive procedural learning in AD and a deleterious effect of the disease on verbal intelligence and declarative memory. Correlational analyses revealed a difference between AD patients and control participants in the type of processing they applied to the task. Conclusion. The non‐involvement of declarative memory would appear to be partly responsible for a slowdown in the cognitive procedural dynamics of AD patients. As the AD patients were unable to use their declarative memory, they were still in a problem‐solving mode at the end of the learning protocol and had to implement higher order cognitive processes (i.e., compensatory mechanisms) to perform the procedural task.     

The Development of Symbolic Coordination: Representation of Imagined Objects,Executive Function,and Theory of Mind

Children's developing competence with symbolic representations was assessed in 3 studies. Study 1 examined the hypothesis that the production of imaginary symbolic objects in pantomime requires the simultaneous coordination of the dual representations of a dynamic action and a symbolic object. We explored this coordination of symbolic representations in 3- to 5-year-olds with a modified action pantomime task that employed both a "dynamic action + object" condition and a "hold + object" condition. Consistent with earlier research, production of imaginary symbolic objects rather than body-part-as-objects increased with age, although, even at age 5, children did not perform at adult levels. As hypothesized, children produced fewer body-part-as-object anchors when they were simply asked to hold an object, rather than perform a dynamic action with the object. Study 2 repeated the conditions of Study 1 and examined these conditions in relation to performance on the Dimensional Change Card Sort (DCCS) task. This study replicated the developmental findings of the earlier study and indicated a modest relation between pantomime and the DCCS, which disappeared with age partialled out. Study 3 examined the action pantomime task in relation to the DCCS, false belief, and appearance-reality with 3- to 5-year-olds. Though performance on the DCCS was related to theory of mind, production of imaginary symbolic objects in pantomime was not strongly related to theory of mind or the DCCS. Results are discussed in terms of children's developing reflective competence in coordinating symbolic representations.     

An investigation of body part as object (BPO) responses in normal and brain-damaged adults

A test of simple pantomime was administered to three groups of adults and comparisons were made across groups of the incidence of subjects who exhibited body part as object (BPO) responses and of the mean frequency of occurrence of BPO in each group. The three groups were left-hemisphere-damaged aphasics (N = 28), right-hemisphere-damaged (N = 24), and normal controls (N = 28). The results indicated no significant differences among groups on the BPO measures. Also, to test the strength of association between the frequency of occurrence of BPO and measures of limb apraxia and severity of aphasia for the left-hemisphere-damaged aphasic group, correlation coefficients were obtained. The correlations were low and nonsignificant. The results of this investigation do not support the common clinical assumption that the occurrence of BPO during the performance of simple pantomimes is pathognomic for left-hemisphere pathology or associated with limb apraxia.     

Relationship between object-related gestures and the fractionated object knowledge system

The praxic semantic system comprises a conceptual knowledge system, which stores functional information about objects, and an action knowledge system, which stores information about the correct manipulation of objects. Moreover, mechanical problem solving abilities permit to take advantages from objects structure to use unfamiliar tools or discover alternative ways of using familiar tools. This study aims at investigating whether conceptual knowledge, action knowledge and mechanical problem solving abilities intervene in the production of gestures with objects (i.e. pantomimes and object use) by testing a group of brain damaged patients. Results showed that the mechanical problem solving abilities are not sufficient to produce pantomimes and that only severe deficits in the praxic semantic system would affect the production of these gestures. Furthermore, a double dissociation was observed between mechanical problem solving abilities and the capacity to use multiple objects. Overall, the results indicate that the praxic semantic system can be disrupted at different levels, suggesting that the semantic system for object has to be conceived as fractionated in different entities.     

语言能力的老化机制：语言特异性与非特异性因素的共同作用

语言能力的衰退是由于一般认知能力衰退引起的, 还是由于语言加工系统的衰退引起的, 抑或是两者的共同作用?研究中测量了青年组和老年组的一般认知能力(加工速度、工作记忆和抑制能力), 以及在词汇、句子和语篇三个水平上的语言理解能力和语言产生能力。结果发现, 一般认知能力、语言理解和语言产生能力都存在年老化现象。分层回归分析表明, 一般认知能力对语言能力的贡献, 以及语言理解能力和产生能力之间的相互贡献在青年组和老年组中是不同的, 且存在词汇、句子和语篇水平上的差异。在词汇水平上, 青年人的成绩能够被一般认知能力和另一种语言能力所显著预测, 而老年人的成绩却不受一般认知因素影响; 在句子水平上, 青年人的成绩仍能被一般认知能力或另一种语言能力所解释, 但这两类变量都无法预测老年人的任务成绩; 在语篇水平上, 青年人理解任务的成绩显著地受到产生能力影响, 而老年人的理解和产生任务成绩则分别可以被一般认知能力和语言理解能力所解释。对组间差异的回归分析表明, 一般认知能力和另一种语言能力对组间差异都有显著贡献, 且前者的贡献大于后者。上述研究结果表明, 语言能力的老化是语言特异性因素和非特异性因素共同作用的结果。