L.M. Maher

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 Alzheimers 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.

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.

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.

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.

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 mans performance and that each may contribute to his failure to detect and correct errors in speech production.

Attention and anosognosia The case of a jargonaphasic patient with unawareness of language deficit

Article abstract—Some patients with aphasia lack awareness of the language errors they make. We describe a man with undifferentiated jargon-aphasia 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 patients unawareness of his speech production errors to a reduced attentional capacity for simultaneous linguistic tasks.

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 patients 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 patients 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. ( JINS , 1998, 4 , 636–647.)

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 patients 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 patients performance revealed the consistent application of a temporal-spatial strategy in sentence production, despite adequate lexical-semantic abilities.

Analysis of lexical recovery in an individual with acute anomia

Observing recovery of cognitive functions may provide converging evidence about the organization of systems that mediate cognitive functions. We analyzed recovery of lexical abilities in a patient, HH, with an acute onset of anomic aphasia following a cerebral infarction confined to the left temporo-occipital junction (area 37). His initial assessment, described in detail elsewhere (Raymer et al. 1997a), indicated a cross-modal anomia arising at a stage in lexical processing at which semantic information accesses phonological and orthographic lexical mechanisms for speech and writing. We also documented reading and spelling impairments that we attributed to developmental deficits. We now report our patients follow-up testing at 6 and 15 months post-stroke. Recovery testing demonstrated significant improvements in task performance across recovery phases: word retrieval in naming and spelling tasks recovered in the earlier recovery phase and reading improved at the later testing. Word frequency effects varied across observations. Over time, error patterns evolved from off-target and semantically related responses towards correct responses. The parallel recovery patterns in oral and written naming support our proposal that a common impairment was responsible for the cross-modal anomia. In contrast, recovery of reading and spelling skills contradicts our hypothesis that these problems were developmental in origin.