Anastasia M. Raymer

Functional MRI of Language in Aphasia: A Review of the Literature and the Methodological Challenges

Animal analogue studies show that damaged adult brains reorganize to accommodate compromised functions. In the human arena, functional magnetic resonance imaging (fMRI) and other functional neuroimaging techniques have been used to study reorganization of language substrates in aphasia. The resulting controversy regarding whether the right or the left hemisphere supports language recovery and treatment progress must be reframed. A more appropriate question is when left-hemisphere mechanisms and when right-hemisphere mechanisms support recovery of language functions. Small lesions generally lead to good recoveries supported by left-hemisphere mechanisms. However, when too much language eloquent cortex is damaged, right-hemisphere structures may provide the better substrate for recovery of language. Some studies suggest that recovery is particularly supported by homologues of damaged left-hemisphere structures. Evidence also suggests that under some circumstances, activity in both the left and right hemispheres can interfere with recovery of function. Further research will be needed to address these issues. However, daunting methodological problems must be managed to maximize the yield of future fMRI research in aphasia, especially in the area of language production. In this review, we cover six challenges for imaging language functions in aphasia with fMRI, with an emphasis on language production: (1) selection of a baseline task, (2) structure of language production trials, (3) mitigation of motion-related artifacts, (4) the use of stimulus onset versus response onset in fMRI analyses, (5) use of trials with correct responses and errors in analyses, and (6) reliability and stability of fMRI images across sessions. However, this list of methodological challenges is not exhaustive. Once methodology is advanced, knowledge from conceptually driven fMRI studies can be used to develop theoretically driven, mechanism-based treatments that will result in more effective therapy and to identify the best patient candidates for specific treatments. While the promise of fMRI in the study of aphasia is great, there is much work to be done before this technique will be a useful clinical tool.

Phonological treatment of naming deficits in aphasia: Model-based generalization analysis

Abstract A phonologically based treatment was implemented to train oral picture naming in four aphasic subjects with severe word-retrieval deficits. An initial assessment based on current cognitive neuropsychological models of naming indicated different levels of phonological and/or semantic deficits underlying naming failure across the subjects. Using a single-subject multiple baseline design across behaviours and subjects, the effects of treatment were evaluated by daily probing of both trained and untrained items across lexical tasks: oral naming, oral reading, and written naming. Results indicated successful acquisition of trained naming targets for the four subjects, and varied patterns of response generalization to naming of untrained phonologically and semantically related pictures, and to oral reading and written naming for the same words. Baseline levels of oral reading performance were noted to predict success in oral naming treatment. Differences in generalization patterns across tasks are disc...

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.

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.

Category-specific naming deficits for objects and actions: semantic attribute and grammatical role hypotheses

Research on category-specific naming deficits and on noun and verb naming has raised questions about how organization of knowledge in the brain impacts word retrieval. The semantic attribute hypothesis posits that lexical access is mediated by brain systems that process the most definitive attributes of specific concepts. For example, it has been suggested that the most definitive attribute of living things is their visual form, whereas the most definitive attribute of non-living things is their function. The competing grammatical role hypothesis posits that access to a word depends on the grammatical role it plays in a sentence. Since nouns and verbs have different roles, it is assumed that the brain uses different systems to process them. These two hypotheses were tested in experimental subjects who had undergone left anterior temporal lobectomy (LATL) or right anterior temporal lobectomy (RATL) by assessing confrontation naming of living things, tools/implements, non-human actions, and human actions. The names of living things and implements are nouns and the names of actions are verbs. Within each grammatical class, items were characterized either predominantly by visual attributes (living things and non-human actions) or by attributes related to human activity (implements and human actions). Our results support the semantic attribute hypothesis. Patients with LATL were worse at naming tools/implements and human actions than RATL patients. Dysfunction in or removal of the left anterior temporal lobe disrupts fronto-temporal connections from the uncinate fasciculus. These connections may mediate activation of action-related information (i.e. movement plan and/or motor use) that facilitates the retrieval of names for tools/implements and human actions.

Effects of gesture+verbal treatment for noun and verb retrieval in aphasia

Links between verbs and gesture knowledge suggest that verb retrieval may be particularly amenable to gesture+verbal training (GVT) in aphasia compared to noun retrieval. This study examines effects of GVT for noun and verb retrieval in nine individuals with aphasia subsequent to left hemisphere stroke. Participants presented an array of noun and verb retrieval deficits, including impairments of semantic and/or phonologic processing. In a single-participant experimental design, we investigated effects of GVT for noun and verb retrieval in two counterbalanced treatment phases. Effects were evaluated in spoken naming and gesture production to pictured objects and actions. Spoken naming improvements associated with large effect sizes were noted for trained nouns (5/9) and verbs (5/9); no improvements were evident for untrained words. Gesture production improved for trained nouns (8/9) and verbs (6/9), and for untrained nouns (2/9) and verbs (2/9). No significant differences were evident between nouns and verbs in spoken naming or gesture production. Improvements were evident across individuals with varied sources of word retrieval impairments. GVT has the potential to improve communication by increasing spoken word retrieval of trained nouns and verbs and by promoting use of gesture as a means to communicate when word retrieval fails.

Response to contrasting verb retrieval treatments: A case study

Verb retrieval treatments for individuals with aphasia that have led to greater improvements in sentence production typically have incorporated semantic as compared to repetition treatments. However, studies have not contrasted treatments within subjects to compare treatment effectiveness. We compared effects of sequential verb retrieval treatments in one participant and analysed effects on sentence production. We tested one woman, WR, with nonfluent aphasia and mild verb retrieval impairment related to semantic dysfunction. She participated in three phases of verb retrieval treatment, semantic, phonologic, and rehearsal, in a multiple baseline crossover design. We examined accuracy of picture naming and sentence production for trained and untrained verbs. All treatments resulted in significantly improved naming of trained verbs, some generalised sentence production, and no improvement for untrained verbs. No difference was evident in effects across treatments. Unlike earlier studies, the repetition and phonologic treatments were as effective as semantic treatment for improving sentence production. These positive findings for all three treatments may relate to semantic activation that occurs whenever a word is retrieved in the context of picture presentation, thereby fundamentally altering semantic activation patterns and making the word more easily accessible in subsequent retrieval attempts, whether in isolation or in sentences.

Effects of gesture+verbal and semantic‐phonologic treatments for verb retrieval in aphasia

Background: Reports have indicated that gesture+verbal treatments and semantic‐phonologic treatments are effective for improving lexical retrieval in aphasia. Most studies focus on noun production, with verb production less commonly reported. Because of links between verbs and gesture knowledge, verbs may be particularly amenable to gesture+verbal training. We extend our appreciation to our four participants who diligently completed this study. This project was supported by NIH (NIDCD) grant P50 DC03888‐01A1 to the University of Florida (subcontract to Old Dominion University), and by the Dept. of Veterans Affairs Rehabilitation Research & Development Center of Excellence Grant F2182C to the Brain Rehabilitation Research Center, Gainesville, Florida. Aims: The purpose of this investigation was to study the effects of gesture+verbal and semantic‐phonologic treatments on verb retrieval in patients with chronic aphasia. Methods & Procedures: We report treatment results for four individuals, three men and one woman, with aphasia and verb retrieval impairments subsequent to left hemisphere stroke more than 8 months earlier. Word retrieval impairment was semantically based in one participant, phonologically based in another, and mixed semantic+phonologic in two others. In a single‐participant experimental treatment design, we investigated the effects of gesture+verbal treatment and semantic‐phonologic treatment for verb retrieval in two 10‐session training phases. The effects of treatment were evaluated in a verb picture‐naming task in which spoken naming and gestured responses were coded. Outcomes & Results: Spoken naming improvements associated with large effect sizes were noted in one participant during both the semantic‐phonologic training and gesture+verbal training. Gesture production improved in two other participants with severe anomia during gesture+verbal training. No improvements were evident in untrained words during either training phase. Conclusions: Gesture+verbal training and semantic‐phonologic training led to similar patterns of treatment results for verb spoken naming. The individual with phonologically based anomia responded better in treatment than the other three whose naming impairments were associated with semantic dysfunction. The item‐specific improvement in spoken naming for trained verbs only suggests that both treatments may affect individual lexical representations engaged during word retrieval. Gesture+verbal treatment may encourage use of a viable means of gestural communication for those who do not improve verbal production, even in the presence of severe limb apraxia.

Intensity of Aphasia Therapy: Evidence and Efficacy

Determining the optimal amount and intensity of treatment is essential to the design and implementation of any treatment program for aphasia. A growing body of evidence, both behavioral and biological, suggests that intensive therapy positively impacts outcomes. We update a systematic review of treatment studies that directly compares conditions of higher and lower intensity treatment for aphasia. We identify five studies published since 2006, review them for methodologic quality, and synthesize their findings with previous ones. For both acute and chronic aphasia, results at the language impairment and communication activity/participation levels tend to be more equivocal than previously demonstrated, with no clear differences between intensive and nonintensive treatment emerging across studies. Future research directions are discussed including research design, definitions of treatment intensity, and behavioral and biological measurement of short- and long-term changes following implementation of an intensive treatment.

Crossed apraxia: implications for handedness.

Liepmann posited that right hand preference relates to left hemisphere dominance for learned skilled movements. Limb apraxia, impairment of skilled movement, typically occurs in individuals with left hemisphere (LH) lesions. The occurrence of apraxia in right-handed individuals following right-hemisphere lesions appears to refute Liepmanns hypothesis. We studied the apraxia of a right-handed man, RF, following a right frontal lesion to determine whether his apraxia paralleled the apraxia seen following LH lesions. Results of behavioral testing indicated that, like individuals with apraxia following left frontal lesions, RF was better at gesture recognition than gesture production which was significantly impaired across tasks. Kinematic motion analyses of movement linearity, planarity, and the coupling of temporospatial aspects of movements substantiated the parallel impairments in RF and patients with LH apraxia. The impairment seen in our patient with crossed apraxia provides evidence for the fractionation of systems underlying hand preference and skilled movement.