Dana Moser

Neural Correlates of Phonological and Semantic Based Anomia Treatment in Aphasia

Most naming treatments in aphasia either assume a phonological or semantic emphasis or a combination thereof. However, it is unclear whether semantic or phonological treatments recruit the same or different cortical areas in chronic aphasia. Employing three persons with aphasia, two of whom were non-fluent, the present study compared changes in neural recruitment associated with phonologic and semantic-based naming treatments. The participants with non-fluent aphasia were able to name more items following both treatment approaches. Although this was not the case for the participant who had fluent aphasia, her naming errors decreased considerably following treatment. Post-treatment fMRI revealed similar changes in neural activity bilaterally in the precuneus among the two non-fluent participants--increased activity was noted in the right entorhinal cortex and posterior thalamus on post-treatment scans for the third participant. These findings imply that cortical areas not traditionally related to language processing may support anomia recovery in some patients with chronic aphasia.

Activity in Preserved Left Hemisphere Regions Predicts Anomia Severity in Aphasia

Understanding the neural mechanism that supports preserved language processing in aphasia has implications for both basic and applied science. This study examined brain activation associated with correct picture naming in 15 patients with aphasia. We contrasted each patients activation to the activation observed in a neurologically healthy control group, allowing us to identify regions with unusual activity patterns. The results revealed that increased activation in preserved left hemisphere areas is associated with better naming performance in aphasia. This relationship was linear in nature; progressively less cortical activation was associated with greater severity of anomia. These findings are consistent with others who suggests that residual language function following stroke relies on preserved cortical areas in the left hemisphere.

Neural recruitment associated with anomia treatment in aphasia

The purpose of this study was to investigate changes in the spatial distribution of cortical activity associated with anomia treatment in three persons with aphasia. Participants underwent three fMRI sessions before and after a period of intensive language treatment focused on object naming. The results revealed bilateral hemispheric recruitment associated with improved ability to name items targeted in treatment. This is the first study to employ multiple pre- and post-treatment fMRI sessions in the study of treatment-induced recovery from aphasia and has implications for future studies of brain plasticity in stroke.

Neural recruitment for the production of native and novel speech sounds

Two primary areas of damage have been implicated in apraxia of speech (AOS) based on the time post-stroke: (1) the left inferior frontal gyrus (IFG) in acute patients, and (2) the left anterior insula (aIns) in chronic patients. While AOS is widely characterized as a disorder in motor speech planning, little is known about the specific contributions of each of these regions in speech. The purpose of this study was to investigate cortical activation during speech production with a specific focus on the aIns and the IFG in normal adults. While undergoing sparse fMRI, 30 normal adults completed a 30-minute speech-repetition task consisting of three-syllable nonwords that contained either (a) English (native) syllables or (b) non-English (novel) syllables. When the novel syllable productions were compared to the native syllable productions, greater neural activation was observed in the aIns and IFG, particularly during the first 10 min of the task when novelty was the greatest. Although activation in the aIns remained high throughout the task for novel productions, greater activation was clearly demonstrated when the initial 10 min was compared to the final 10 min of the task. These results suggest increased activity within an extensive neural network, including the aIns and IFG, when the motor speech system is taxed, such as during the production of novel speech. We speculate that the amount of left aIns recruitment during speech production may be related to the internal construction of the motor speech unit such that the degree of novelty/automaticity would result in more or less demands respectively. The role of the IFG as a storehouse and integrative processor for previously acquired routines is also discussed.

Treating Visual Speech Perception to Improve Speech Production in Nonfluent Aphasia

Background and Purpose— Several recent studies have revealed modulation of the left frontal lobe speech areas not only during speech production but also for speech perception. Crucially, the frontal lobe areas highlighted in these studies are the same ones that are involved in nonfluent aphasia. Based on these findings, this study examined the utility of targeting visual speech perception to improve speech production in nonfluent aphasia. Methods— Ten patients with chronic nonfluent aphasia underwent computerized language treatment utilizing picture-word matching. To examine the effect of visual speech perception on picture naming, 2 treatment phases were compared—one that included matching pictures to heard words and another in which pictures were matched to heard words accompanied by a video of the speaker’s mouth presented on the computer screen. Results— The results revealed significantly improved picture naming of both trained and untrained items after treatment when it included a visual speech component (ie, seeing the speaker’s mouth). In contrast, the treatment phase in which pictures were only matched to heard words did not result in statistically significant improvement of picture naming. Conclusions— The findings suggest that focusing on visual speech perception can significantly improve speech production in nonfluent aphasia and may provide an alternative approach to treat a disorder in which speech production seldom improves much in the chronic phase of stroke.

Cortical mapping of naming errors in aphasia.

Persons with aphasia vary greatly with regard to clinical profile; yet, they all share one common feature—anomia—an impairment in naming common objects. Previous research has demonstrated that particular naming errors are associated with specific left hemisphere lesions. However, we know very little about the cortical activity in the preserved brain areas that is associated with aphasic speech errors. Utilizing functional magnetic resonance imaging (fMRI), we show for the first time that specific speech errors are associated with common cortical activity in different types and severities of aphasia. Specifically, productions of phonemic errors recruited the left posterior perilesional occipital and temporal lobe areas. A similar pattern of activity was associated with semantic errors, albeit in the right hemisphere. This study does not discount variability in cortical activity following left hemisphere stroke; rather, it highlights commonalities in brain modulation in a population of patients with a common diagnosis but vastly different clinical profiles. Hum Brain Mapp 2009.

Patterns of Poststroke Brain Damage That Predict Speech Production Errors in Apraxia of Speech and Aphasia Dissociate

Background and Purpose— Acquired apraxia of speech (AOS) is a motor speech disorder caused by brain damage. AOS often co-occurs with aphasia, a language disorder in which patients may also demonstrate speech production errors. The overlap of speech production deficits in both disorders has raised questions on whether AOS emerges from a unique pattern of brain damage or as a subelement of the aphasic syndrome. The purpose of this study was to determine whether speech production errors in AOS and aphasia are associated with distinctive patterns of brain injury. Methods— Forty-three patients with history of a single left-hemisphere stroke underwent comprehensive speech and language testing. The AOS Rating Scale was used to rate speech errors specific to AOS versus speech errors that can also be associated with both AOS and aphasia. Localized brain damage was identified using structural magnetic resonance imaging, and voxel-based lesion-impairment mapping was used to evaluate the relationship between speech errors specific to AOS, those that can occur in AOS or aphasia, and brain damage. Results— The pattern of brain damage associated with AOS was most strongly associated with damage to cortical motor regions, with additional involvement of somatosensory areas. Speech production deficits that could be attributed to AOS or aphasia were associated with damage to the temporal lobe and the inferior precentral frontal regions. Conclusions— AOS likely occurs in conjunction with aphasia because of the proximity of the brain areas supporting speech and language, but the neurobiological substrate for each disorder differs.

Temporal Order Processing of Syllables in the Left Parietal Lobe

Speech processing requires the temporal parsing of syllable order. Individuals suffering from posterior left hemisphere brain injury often exhibit temporal processing deficits as well as language deficits. Although the right posterior inferior parietal lobe has been implicated in temporal order judgments (TOJs) of visual information, there is limited evidence to support the role of the left inferior parietal lobe (IPL) in processing syllable order. The purpose of this study was to examine whether the left inferior parietal lobe is recruited during temporal order judgments of speech stimuli. Functional magnetic resonance imaging data were collected on 14 normal participants while they completed the following forced-choice tasks: (1) syllable order of multisyllabic pseudowords, (2) syllable identification of single syllables, and (3) gender identification of both multisyllabic and monosyllabic speech stimuli. Results revealed increased neural recruitment in the left inferior parietal lobe when participants made judgments about syllable order compared with both syllable identification and gender identification. These findings suggest that the left inferior parietal lobe plays an important role in processing syllable order and support the hypothesized role of this region as an interface between auditory speech and the articulatory code. Furthermore, a breakdown in this interface may explain some components of the speech deficits observed after posterior damage to the left hemisphere.

Age-related relative volume preservation of the dominant hand cortical region

Aging is usually associated with a progressive difficulty in learning new skills. Similarly, the dexterity in the non-dominant hand is usually decreased with age, while the dominant hand maintains a relative preservation in agility. We investigated if age-related volume loss affects the hand areas asymmetrically by comparing structural measures of the dominant hand area versus the non-dominant area. We performed a region of interest analysis of T1-weighted images focusing on the sensorimotor cortex corresponding to the hand area. We evaluated images from young subjects (younger than 65 years of age, n=38, mean age=24+/-7 years) and senior subjects (65 years or older, n=61, mean age =73+/-6 years). We observed that older adults exhibited greater leftward gray matter asymmetry of sensorimotor cortex, due in large part to more pronounced age-related loss of gray matter in the right hemisphere. These results are consistent with evidence that disuse leads to atrophy and suggest that age-related declines in gray matter, and perhaps function, may be limited by increasing the use of the non-dominant hand.

Sentence comprehension and general working memory.

Although the role of working memory in sentence comprehension has received substantial attention, the nature of this relationship remains unclear. The purpose of this study was to examine the interaction between general, nonverbal working memory (WM) and sentence parsing (SP) in normal English‐speaking adults. Accuracy and reaction times were recorded for thirty‐one young adults during three on‐line tasks: nonverbal WM, SP plausibility, and lexical decision (LD). A significant positive correlation was observed between reaction times for WM and SP, but not between LD and SP. These results suggest that SP may be supported by a general WM capacity, and therefore, some sentence comprehension difficulties observed in the clinical population may potentially be related to impairment in general WM.