Functional MRI studies of normal and impaired language function

Language ability plays an important role when communicating with others. Before a-typical language activation can be detected in patient populations, normal language function has to be explored. In this project we intend to study the influence of performance and difficulty related language ability on cortical activation in healthy subjects and in patients with language disability.

• Staff:

Maria Engström , Assoc. Prof.		Project manager		CMIV/Radiological Sciences
Peter Lundberg , Prof.		Physics		CMIV/Radiological Sciences
Anne-Marie Landtblom , Assoc. Prof.		Neurology		CMIV/Neurology
Thomas Karlsson , Assoc. Prof.		Neuropsychology		CMIV/Behavioral Sciences
Anita McAllister , Assoc. Prof.		Logopedics		Logopedics
Helene Van Ettinger-Veenstra , Stud.		Cognitive neuroscience		CMIV/Radiological Sciences

• Former Staff:

• Project Description:
Lesion and imaging research have marked Broca's and Wernicke's areas as two of the most important regions for processing and understanding language. Lesions in these areas often result in transient or persistent aphasia. However, complex cognitive cerebral processes bring forth the production and understanding of language and the neural correlates of more subtle language disabilities are not sufficiently explored. In this project we intend to combine fMRI and neurolinguistic tests for language ability in normal language functioning and language impaired groups. The aims are to determine the neural correlates to language ability and effort in healthy subjects and to detect a-typical language activation in patients with language disabilities. Following subprojects are proposed: 1. Influence of performance-related language ability on cortical activation 2. The influence of the right hemisphere on language function 2. Language ability and effort 3. Language function in patients with epilepsia



References
• H.M. Van Ettinger-Veenstra, M. Ragnehed, M. Hällgren, T. Karlsson, A-M Landtblom, P. Lundberg, and M. Engström. Right-hemispheric brain activation correlates to language performance. NeuroImage, 49:3481–3488, 2009.
  
     Abstract: Language function in the right-hemispheric homologues of Broca's and Wernicke's areas does not only correlate     with left-handedness or pathology, but occurs naturally in right-handed healthy subjects as well. In the current study, two non-invasive methods of assessing language lateralization are correlated with behavioral results in order to link hemispheric dominance to language ability in healthy subjects. Functional magnetic resonance imaging (fMRI) together with a sentence-completion paradigm was used to determine region-specific lateralization indices in the left- and right-sided Broca's and Wernicke's areas, the frontal temporal lobe, the anterior cingulate cortex and the parietal lobe. In addition, dichotic listening results were used to determine overall language lateralization and to strengthen conclusions by correlating with fMRI indices. Results showed that fMRI lateralization in the superior parietal, the posterior temporal, and the anterior cingulate cortices correlated to dichotic listening. A decreased right ear advantage (REA), which indicates less left-hemispheric dominance in language, correlated with higher performance in most administered language tasks, including reading, language ability, fluency, and non-word discrimination. Furthermore, right hemispheric involvement in the posterior temporal lobe and the homologue of Broca's area suggests better performance in behavioral language tasks. This strongly indicates a supportive role of the right-hemispheric counterparts of Broca's and Wernicke's areas in language performance.


• M. Engström, M. Karlsson, M. Crone, M. Ragnehed, W. Antepohl, A-M Landtblom, and P. Lundberg. Clinical fMRI of language function in aphasic patients: Reading paradigm successful, while word generation paradigm fails. Acta Radiologica, 51:679-686, 2010
  
     Abstract: Background: In fMRI examinations, it is very important to select appropriate paradigms assessing the brain function of interest. In addition, the patients’ ability to perform the required cognitive tasks during fMRI must be taken into account.
Purpose: To evaluate two language paradigms, word generation and sentence reading for their usefulness in examinations of aphasic patients and to make suggestions for improvements of clinical fMRI.
Material and Methods: Five patients with aphasia after stroke or trauma sequelae were examined by fMRI. The patients’ language ability was screened by neurolinguistic tests and elementary pre-fMRI language tests.
Results: The sentence-reading paradigm succeeded to elicit adequate language-related activation in perilesional areas whereas the word generation paradigm failed. These fi ndings were consistent with results on the behavioral tests in that all patients showed very poor performance in phonemic fl uency, but scored well above mean at a reading comprehension task.
Conclusion: The sentence-reading paradigm is appropriate to assess language function in this patient group, while the word-generation paradigm seems to be inadequate. In addition, it is crucial to use elementary pre-fMRI language tests to guide the fMRI paradigm decision.