Ideomotor apraxia in Alzheimer disease and left hemisphere stroke: limb transitive and intransitive movements.

OBJECTIVE: Ideomotor apraxia was studied in patients with Alzheimer disease (AD) and unilateral left hemispheric damaged (LHD) stroke to determine whether these groups differed. BACKGROUND: Given that the neuropathology of AD is bilateral and more diffuse than the localized involvement in patients after an LHD stroke, and given that the cognitive deficits in AD are more widespread than in LHD stroke, the authors predicted that patients with these disorders would differ in response to an auditory command task administered to evaluate ideomotor apraxia, and that the two patient groups would be significantly more impaired than healthy matched control subjects. METHODS: Twenty-one persons were studied, including equal numbers of patients with AD, patients with unilateral LHD stroke, and control subjects. An auditory command test of limb apraxia was administered and videotaped to score performance and to code spatial-temporal or content errors. RESULTS: The patients with AD and LHD stroke were significantly more impaired than healthy control subjects. Whereas the patients with AD and LHD stroke were equally apraxic and did not differ in their performance of transitive limb movements, the patients with AD were significantly more impaired than the patients with stroke when performing intransitive limb movements. A positive correlation was found between severity of dementia and severity of apraxia in the patients with AD. The patients with LHD stroke were as likely to make spatial-temporal as content errors when performing intransitive limb movements, whereas the patients with AD made content errors only. Error types produced with transitive limb movements did not differ between groups; spatial-temporal errors were the most common errors made both by patients with AD and patients with LHD stroke. CONCLUSIONS: As predicted, patients with AD and with LHD stroke were impaired when producing limb movements after auditory command, and both patient groups were significantly more impaired than the healthy adults. Patients with AD were significantly more impaired than patients with stroke when performing intransitive limb movements, and error types differed by group. Patients with AD and patients with stroke were equally impaired when performing transitive movements, and error types did not differ by group. Patients with ideomotor apraxia are often degraded in their production of transitive and intransitive movements, and the observation that performance may differ depending on the type of limb movement suggests that movement representations for transitive and intransitive movements may be at least partially independent.

Rehabilitation of a case of pure alexia: exploiting residual abilities.

We present a case study of a 43-year-old woman with chronic and stable pure alexia. Using a multiple baseline design we report the results of two different interventions to improve reading. First, a restitutive treatment approach using an implicit semantic access strategy was attempted. This approach was designed to exploit privileged access to lexical-semantic representations and met with little success. Treatment was then switched to a substitutive treatment strategy, which involved using the patient's finger to pretend to copy the letters in words and sentences. Reading using this motor cross-cuing strategy was 100% accurate and doubled in speed after 4 weeks of intervention. We propose that this patient's inability to benefit from the implicit semantic access treatment approach may be in part related to her inability to suppress the segmental letter identification process of word recognition.

Conceptual apraxia from lateralized lesions.

Models of praxis have posited two major components, production and conceptual. Conceptual praxis disorders may occur in two domains: associative knowledge (tool-action associations such as hammer pound; tool-object associations such as hammer nail) and mechanical knowledge such as knowing the advantage that tools afford. Patients with Alzheimer's disease not only have conceptual apraxia (CA) but can dissociate CA from language deficits and from praxis production deficits (ideomotor apraxia). These findings suggests that knowledge about tools (action semantics) is independent of verbal semantics as well as movement representations. To learn if conceptual praxis knowledge is stored in one hemisphere (right or left) and if associative and mechanical conceptual praxis knowledge can be dissociated, we studied 29 right-handed subjects with unilateral strokes. Ten had left-hemisphere damage with no ideomotor apraxia. Eleven had left-hemisphere damage with ideomotor apraxia. There were eight right-hemisphere-damaged controls and 10 normal controls. These subjects were given tests for conceptual apraxia. There was a significant difference between groups, the left-hemisphere group with ideomotor apraxia being most impaired on both the associative and mechanical CA tests. There was a trend for associative and mechanical knowledge to be dissociated. Although conceptual praxis representations are stored in the left hemisphere, analysis of lesion sites did not reveal where in the left hemisphere they may be stored.

Selective deficit of praxis imagery in ideomotor apraxia.

We studied imagery for learned, skilled movements (praxis imagery) in a patient with severe ideomotor apraxia and intact language abilities. This patient, who made predominantly spatial and movement errors when performing transitive movements demonstrating the use of tools (transitive gestures), was also impaired in her ability to answer imagery questions about joint movement or the spatial position of the hands during action. However, visual object imagery was spared. The finding of parallel praxis production and praxis imagery deficits in this patient suggests that the same representations used for gesture production are also activated during imagery of motor acts. Our findings also suggest that certain aspects of motor imagery may be dissociable from general object imagery.

The significance of body part as tool errors in limb apraxia.

When pantomiming to command, individuals with left hemisphere brain damage (LBD) often produce errors in which they use a body part as if it were the tool (BPT). Some clinicians question the significance of this type of error because subjects without brain damage at times also make BPT responses. We analyzed BPT errors in LBD and normal subjects who were reinstructed to modify the inappropriate BPT responses when they occurred. We also analyzed errors in normal subjects who were never reinstructed if a BPT occurred. Whereas LBD subjects who were reinstructed produced significantly more BPT errors than normals who were also reinstructed, LBD subjects were not different from normals who were not reinstructed. When reinstructed, normal control subjects correctly modified virtually all BPT errors, whereas LBD subjects did not modify BPT errors. These findings underscore the need for reinstruction when a BPT error occurs to determine whether it represents a true BPT error, a sign of limb apraxia.

Cognitive neuropsychological analysis and neuroanatomic correlates in a case of acute anomia.

We describe an analysis of lexical processing performed in a patient with the acute onset of an isolated anomia. Based on a model of lexical processing, we evaluated hypotheses as to the source of the naming deficit. We observed impairments in oral and written picture naming and oral naming to definition with relatively intact semantic processing across input modalities, suggesting that output from the semantic system was impaired. In contrast to previous reports, we propose that this pattern represents an impairment that arises late in semantic processing prior to accessing mode-specific verbal and graphemic output lexicons. These deficits were associated with a lesion in the posterior portion of the middle temporal gyrus or area 37, an area of supramodal association cortex that is uniquely suited as a substrate for the multimodal deficit in naming.

Praxis performance with left versus right hemisphere lesions.

Praxis is defined as skilled, purposive limb movement. While it has been a consistent finding that lesions of the left cerebral hemisphere result in significantly worse performance on praxis testing than lesions of the right cerebral hemisphere, recently some investigators have proposed that the right hemisphere may also play an important role in mediating praxis. To learn if the right hemisphere does have a role in praxis we studied right-handed patients with right or left hemisphere lesions, as well as right-handed normal controls who were matched for age and education. Two trained raters scored the transitive gesture performance of the forelimb ipsilateral to the injured hemisphere. For the normal controls, left and right hand performances were scored separately and used for statistical comparison. Independent comparisons were made on six dimensions that are important for accurate gesture performance and on an overall apraxia score. When compared to normal control subjects the patients with left hemisphere lesions (LHD) did demonstrate deficient praxis; that is, ideomotor apraxia. However, those with right hemisphere lesions (RHD) did not. Based on this study it would appear that the right hemisphere does not play a crucial role in praxis.

The role of visual imagery in spelling.

Current models of spelling posit that information from the orthographic output buffer can be translated into physical letter codes for written output or into name letter codes for spoken output. It is not known, at present, whether or not visualization of these codes is necessary to spell or recognize orally spelled words. We report a 73-year-old woman who could spell words better than she could image them and who demonstrated near flawless recognition of orally spelled words. We conclude that visual imagery is not necessary to either spell or recognize orally spelled words.

Gesture laterality in aphasic and apraxic stroke patients.

Limb preference during conversational gestures may be a reflection of functional hemispheric asymmetries. In right-handers, speech and praxis are usually mediated by the left hemisphere and in conversation, right-handers gesture more with their right than left hand. However, patients with left hemisphere brain damage, who are aphasic and apraxic but not hemiplegic, may use their right hemisphere to compensate for their left. Therefore, we investigated spontaneous lateralized gesture production during conversation in a group of left hemisphere-damaged stroke patients, who were aphasic and apraxic but not hemiparetic, and compared their performance to a group of matched controls. Whereas the control group had a strong right-hand preference, the nonparetic but apraxic and aphasic stroke patients were as likely to produce gestures with the right, left, or both hands.

Spatial characteristics of thematic role representation.

Humans use language to describe actions by mapping the thematic roles of agent (doer of actions) and patient (recipient of actions) on the grammatical categories of subject and object. The extent to which thematic roles can be conceptualized independent of language is not known. If nonlinguistic conceptualization of thematic roles is possible, then representation of these roles would evidence nonlinguistic characteristics. Motivated by observations in an aphasic man, we wished to learn if thematic roles are conceptualized spatially. Normally subjects were asked to draw stick figures depicting the thematic roles of agent and patient. They demonstrated a systematic spatial bias in locating agents to the left of where they located patients. This bias, somewhat mitigated by ordering effects of motor output and auditory input, was brought into clearest focus when subjects depicted thematic roles in a context stripped of surface sentential form. These data imply that, in their nascent form, the thematic roles of agent and patient are spatially represented prior to being projected on grammar.

Agrammatic sentence production: the use of a temporal--spatial strategy.

We report the sentence production of a left-handed man with a right-hemisphere infarct. He demonstrated an inability to correctly map grammatical categories (subject, object) onto thematic roles (agent, patient) even for simple active sentences. The patient's performance appears to be the result of selective damage to the functional level (Garrett, 1980) of sentence production. His failure could not be accounted for by theories of agrammatism that implicate memory deficits, phonologic processing impairments, or deficits in processing complex transformations. The patient's performance revealed the consistent application of a temporal-spatial strategy in sentence production, despite adequate lexical-semantic abilities.

Asyntactic thematic role assignment: the use of a temporal-spatial strategy.

We report syntactic comprehension performance of a left-handed man with a right-hemisphere infarct. He was unable to accurately map grammatical categories (subject, object) onto thematic roles (agent, patient), despite demonstrating intact conceptual knowledge of these thematic roles. He performed poorly on both active and passive reversible sentences. His asyntactic thematic role assignment cannot be accounted for by a short-term memory impairment or any hypothesis that predicts selective vulnerability to passive sentence constructions. Rather than performing randomly, our patient used a temporal or spatial strategy in assigning thematic roles. Because he also had a production-mapping deficit and used the same temporal-spatial strategy in production tasks, we hypothesize that the mapping of thematic roles onto grammatical categories and vice versa may be a specific aspect of sentence processing that is common to sentential production and comprehension. We also raise the possibility that thematic roles have underlying spatial representations prior to being elaborated by grammar.

Attention and anosognosia: the case of a jargonaphasic patient with unawareness of language deficit.

Some patients with aphasia lack awareness of the language errors they make. We describe a man with undifferentiated jargonaphasia and preserved auditory comprehension who was unaware of his speech production errors when he had to both speak and listen simultaneously. However, when listening to a recording of his speech, he could detect the speech errors he had made. We attribute this patient's unawareness of his speech production errors to a reduced attentional capacity for simultaneous linguistic tasks.

Ecological implications of limb apraxia: evidence from mealtime behavior.

Humans learn skilled acts in order to effectively interact with their environment. A loss of the ability to perform skilled acts is termed apraxia. Apraxia has been thought to be of theoretical interest, but the ecological implications of apraxia are controversial and have not been fully studied. We examined ten patients with unilateral left hemisphere cerebral infarctions (eight of whom were apraxic) and compared their mealtime eating behavior to a group of neurologically normal, age-matched controls. The stroke patients were less efficient in completing the meal. They made more action errors and were less organized in the sequencing of mealtime activities. Because the patients made more errors while using tools than when performing nontool actions, their deficit could not be accounted for by an elemental motor deficit. A positive relationship was found between mealtime action errors and the severity of apraxia. These findings suggest that limb apraxia may adversely influence activities of daily living.

Lack of error awareness in an aphasic patient with relatively preserved auditory comprehension.

The neuropsychological mechanisms underlying unawareness of speech/language deficits are unknown, but four possibilities have been suggested: impaired lexical-semantic representations associated with impaired speech comprehension, a failure of feedback, reduced attentional capacity, and psychological denial. We studied a patient who was unaware of his jargon aphasia despite only a mild auditory comprehension disturbance. Delaying auditory feedback altered his speech patterns. He recognized more of his errors in a recording of his voice than he did while speaking. He also recognized more errors in a recording of the examiner making errors than he did when listening to the recordings of his own speech. Based on these results, we suggest that none of the proposed mechanisms can exclusively account for this man's performance and that each may contribute to his failure to detect and correct errors in speech production.