1/10. Dyspraxia in a patient with corticobasal degeneration: the role of visual and tactile inputs to action.OBJECTIVES: To investigate the roles of visual and tactile information in a dyspraxic patient with corticobasal degeneration (CBD) who showed dramatic facilitation in miming the use of a tool or object when he was given a tool to manipulate; and to study the nature of the praxic and neuropsychological deficits in CBD. methods: The subject had clinically diagnosed CBD, and exhibited alien limb behaviour and striking ideomotor dyspraxia. General neuropsychological evaluation focused on constructional and visuospatial abilities, calculation, verbal fluency, episodic and semantic memory, plus spelling and writing because impairments in this domain were presenting complaints. Four experiments assessed the roles of visual and tactile information in the facilitation of motor performance by tools. Experiment 1 evaluated the patient's performance of six limb transitive actions under six conditions: (1) after he described the relevant tool from memory, (2) after he was shown a line drawing of the tool, (3) after he was shown a real exemplar of the tool, (4) after he watched the experimenter perform the action, (5) while he was holding the tool, and (6) immediately after he had performed the action with the tool but with the tool removed from his grasp. Experiment 2 evaluated the use of the same six tools when the patient had tactile but no visual information (while he was blindfolded). Experiments 3 and 4 assessed performance of actions appropriate to the same six tools when the patient had either neutral or inappropriate tactile feedback-that is, while he was holding a non-tool object or a different tool. RESULTS: Miming of tool use was not facilitated by visual input; moreover, lack of visual information in the blindfolded condition did not reduce performance. The principal positive finding was a dramatic facilitation of the patient's ability to demonstrate object use when he was holding either the appropriate tool or a neutral object. Tools inappropriate to the requested action produced involuntary performance of the stimulus relevant action. CONCLUSIONS: Tactile stimulation was paramount in the facilitation of motor performance in tool use by this patient with CBD. This outcome suggests that tactile information should be included in models which hypothesise modality specific inputs to the action production system. Significant impairments in spelling and letter production that have not previously been reported in CBD have also been documented.- - - - - - - - - - ranking = 1keywords = nature (Clic here for more details about this article) |
2/10. gait apraxia after bilateral supplementary motor area lesion.OBJECTIVES: The study aimed at addressing the issue of the precise nature of gait apraxia and the cerebral dysfunction responsible for it. methods: The case of a patient, affected by a bilateral infarction limited to a portion of the anterior cerebral artery territory is reported. The patient's ability to walk was formally assessed by means of a new standardised test. RESULTS: Due to an anomaly within the anterior cerebral artery system, the patient's lesion was centred on the supplementary motor regions of both hemispheres. He presented with clear signs of gait apraxia that could not be accounted for by paresis or other neurological deficits. No signs of any other form of apraxia were detected. CONCLUSIONS: The clinical profile of the patient and the analysis of 49 cases from previous literature suggest that gait apraxia should be considered a clinical entity in its own right and lesions to the supplementary motor areas are responsible for it.- - - - - - - - - - ranking = 1keywords = nature (Clic here for more details about this article) |
3/10. Pantomimes are special gestures which rely on working memory.The case of a patient is reported who presented consistently with overt deficits in producing pantomimes in the absence of any other deficits in producing meaningful gestures. This pattern of spared and impaired abilities is difficult to reconcile with the current layout of cognitive models for praxis. This patient also showed clear impairment in a dual-task paradigm, a test taxing the co-ordination aspect of working memory, though performed normally in a series of other neuropsychological measures assessing language, visuo-spatial functions, reasoning function, and executive function. A specific working memory impairment associated with a deficit of pantomiming in the absence of any other disorders in the production of meaningful gestures suggested a way to modify the model to account for the data. Pantomimes are a particular category of gestures, meaningful, yet novel. We posit that by their very nature they call for the intervention of a mechanism to integrate and synthesise perceptual inputs together with information made available from the action semantics (knowledge about objects and functions) and the output lexicon (stored procedural programmes). This processing stage conceived as a temporary workspace where gesture information is actively manipulated, would generate new motor programmes to carry out pantomimes. The model of gesture production is refined to include this workspace.- - - - - - - - - - ranking = 1keywords = nature (Clic here for more details about this article) |
4/10. Crossed apraxia of speech: a case report.The present study reports on the first case of crossed apraxia of speech (CAS) in a 69-year-old right-handed female (SE). The possibility of occurrence of apraxia of speech (AOS) following right hemisphere lesion is discussed in the context of known occurrences of ideomotor apraxias and acquired neurogenic stuttering in several cases with right hemisphere lesion. A current hypothesis on AOS-the dual route speech encoding (DRSE) hypothesis-and predictions based on DRSE were utilized to explore the nature of CAS in SE. One prediction based on the DRSE hypothesis is that there should be no difference in the frequency of occurrence of apraxic errors on words and non-words. This prediction was tested using a repetition task. The experimental stimuli included a list of minimal pairs that signaled voice-voiceless contrasts in words and non-words. Minimal-pair stimuli were presented orally, one at a time. SE's responses were recorded using audio and videotapes. Results indicate that SE's responses were characterized by numerous voicing errors. Most importantly, production of real word minimal pairs was superior to that of non-word minimal pairs. Implications of these results for the DRSE hypothesis are discussed with regard to currently developing perspectives on AOS.- - - - - - - - - - ranking = 1keywords = nature (Clic here for more details about this article) |
5/10. Apraxia of speech: the effectiveness of a treatment regimen.This investigation describes a treatment program for an adult patient with apraxia of speech. The program was composed of a series of physiologic (nonspeech) and phonetic (articulatory) tasks that began with oroneuromotor control activities and progressed to consonant-vowel (CV) syllable, word, and sentence drills. All activities were paced by a metronome. Detailed descriptions are provided about the (a) nature of the specific treatment steps, (b) sequence of steps followed, (c) criteria used for progression within and between steps, (d) actual number of trials and time required to reach criteria for each step, and (e) steps that were especially easy or difficult to master. A multiple probe design employed to test program efficacy revealed that (a) all tasks in the treatment program were successfully acquired, (b) control of all treatment behaviors was maintained, and (c) carry-over from treated to nontreated behaviors did not occur. Results confirmed that the program positively affected the patient's performance. Suggestions are offered outlining possible modification of the treatment steps so as to yield similar results with greater clinical efficiency.- - - - - - - - - - ranking = 1keywords = nature (Clic here for more details about this article) |
6/10. Visuoimaginal constructional apraxia: on a case of selective deficit of imagery.We report a case of a patient with a left occipital lesion who presented a peculiar behavioral dissociation. He was able to copy pictures but not to draw a simple object without a visual model; the relationship among the component parts was altered in drawings produced under the guidance of his mental representations. We have called this disturbance "visuoimaginal constructional apraxia." The mechanisms underlying visuoimaginal constructional apraxia are investigated in an attempt to contribute to studies on the nature of mental imagery.- - - - - - - - - - ranking = 1keywords = nature (Clic here for more details about this article) |
7/10. Congenital ocular motor apraxia--familial occurrence.The occurrence of congenital oculomotor apraxia in two children of the same family is described. The improvement of the ocular dysfunction in the older sister gave some hints to the benign nature of the condition and its tendency to recover with age. The possible pathophysiological mechanism underlying this anomaly is discussed.- - - - - - - - - - ranking = 1keywords = nature (Clic here for more details about this article) |
8/10. Ideatory apraxia in a left-handed patient with right-sided brain lesion.A case is described of a left-handed patient with a circumscribed right-sided posterior brain lesion, who presented with a neuro-psychological syndrome of Wernicke's aphasia, ideomotor and ideatory apraxia. The aphasia and ideomotor apraxia cleared within 10 days, while ideatory apraxia persisted. Ideatory apraxia therefore was not dependent on the language disorder, nor was it related to ideomotor apraxia. On the basis of various neuropsychological examinations, the nature of the apraxic movement disorder in this case is discussed. To our knowledge, this is the first case of ideatory apraxia with right-sided brain damage described in the literature. A particular feature of this patient is that obviously language and the motor functions underlying performance in tests for ideomotor apraxia had a bilateral hemispheric representation whereas a unilateral lesion was sufficient to bring about persistent ideatory apraxia.- - - - - - - - - - ranking = 1keywords = nature (Clic here for more details about this article) |
9/10. Progressive ideomotor apraxia: evidence for a selective impairment of the action production system.We report a patient with slowly progressive bilateral limb apraxia associated with an asymmetrical focal degenerative process of the parietal lobes. Clinical assessment of praxis production suggested a striking deficit in controlling the spatiotemporal attributes of purposeful skilled limb movements, consistent with ideomotor apraxia. The precise nature of the action production impairment was further defined by objective three-dimensional computergraphic analysis of transitive movements which demonstrated significant kinematic deficits in spatial accuracy, timing, spatiotemporal coupling, and joint coordination. Gesture comprehension and discrimination were spared. Furthermore, detailed evaluation of the conceptual praxis system revealed that despite an almost complete inability to perform transitive movements accurately, abstract knowledge of tool function and action was remarkably well preserved. The critical dissociation between intact conceptual knowledge of action and impaired movement execution documented in this case points to a fundamental competence/performance dichotomy in apraxia and provides empirical support for cognitive models of praxis that divide the action system into distinct conceptual and production subcomponents. Within this theoretical framework, our patient's severe ideomotor apraxia is interpreted to represent a selective disruption of the action production system.- - - - - - - - - - ranking = 1keywords = nature (Clic here for more details about this article) |
10/10. Identification without manipulation: a study of the relations between object use and semantic memory.The role of semantic knowledge in object utilisation is a matter of debate. It is usually presumed that access to semantic knowledge is a necessary condition for manipulation, but a few reports challenged this view. The existence of a direct, pre-semantic route from vision to action has been proposed. We report the case of a patient with a disorder of object use in everyday life, in the context of probable Alzheimer's disease. This patient was also impaired when manipulating single objects. He showed a striking dissociation between impairment in object use and preserved capacity to perform symbolic and meaningless gestures. To elucidate the nature of the disorder, and to clarify the relations between semantic knowledge and object use, we systematically assessed his capacity to recognise, name, access semantic knowledge, and use 15 common objects. We found no general semantic impairment for the objects that were not correctly manipulated, and, more importantly, no difference between the semantic knowledge of objects correctly manipulated and objects incorrectly manipulated. These data, although not incompatible with the hypothesis of a direct route for action, are better accommodated by the idea of a distributed semantic memory, where different types of knowledge are represented, as proposed by Allport (Allport, D. A. Current perspectives in dysphasia, pp. 32-60. Churchill Livingstone, Edinburgh, 1985).- - - - - - - - - - ranking = 1keywords = nature (Clic here for more details about this article) |
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