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Degree of language lateralization determines susceptibility to unilateral brain lesions

(Knecht et al., 2002) . Degree of language lateralization determines susceptibility to unilateral brain lesions. Ana Cecilia Ulloa April 03, 2012. Language. Left-hemisphere dominant. Plasticity.

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Degree of language lateralization determines susceptibility to unilateral brain lesions

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  1. (Knecht et al., 2002) Degree of language lateralization determines susceptibility to unilateral brain lesions Ana Cecilia Ulloa April 03, 2012

  2. Language • Left-hemisphere dominant

  3. Plasticity • Undamaged hemisphere or undamaged parts of the injured hemisphere take over language representation Thulborn, Carpenter, & Just (1999), Am Heart J, 30, 749-54

  4. Language Lateralization • Individual differences in language organization in the brain could make some people more able to recover function after unilateral brain damage • Graded continuum from left hemispheric to right hemispheric language lateralization

  5. Previous Research • Some individuals possess weak lateralization or bihemispheric activation • Studies done in epilepsy patients • Cannot be generalized • Abnormal brains due to medication-resistant epilepsy • Bilaterality of language may be due to disorganization resulting from longstanding lesion.

  6. Does bihemispheric representation of language occur in healthy subjects? Does it offer resistance to language deficits after unilateral brain lesion?

  7. Methods • 20 subjects from a cohort of 324 healthy volunteers • Functional transcranial Doppler sonogropahy (fTCD) • fMRI • TMS

  8. fMRI Results

  9. Picture-Word Verification Task • Measured reaction time (RT) after TMS on either side of the brain • TMS over areas CP5 or CP6 • CP 5: Wernicke’s Area • CP 6: counterpart on right hemisphere • 30 minute rest before each administration

  10. Results Subjects with left language dominance were significantly slower than subjects with right language dominance after TMS over CP5

  11. Results Subjects with right language dominance were significantly slower than subjects with left language dominance after TMS over CP6

  12. Discussion &Implications • After TMS on subjects lacking marked hemispheric lateralization, subjects showed almost no slowing of verbal processing • Individuals with a more bilateral language representation will remain relatively unaffected in verbal functioning after stroke to either the right or left hemisphere

  13. Pros and Cons Pros • Simple, straightforward • Detailed explanations for methods and results Cons • Not much background information • Not much discussion of limitations, confounds, or future research

  14. Future Directions • Finding ways in which we can apply this knowledge of hemispheric lateralization as a way of treating stroke patients that suffer language deficits Crosson et al. (2009), Brain Lang, 111(2), 73-85.

  15. References Crosson, B., Moore, A. B., McGregor, K. M., Chang, Y. L., Benjamin, M., Gopinath, K., Sherod, M. E., Wierenga, C. E., Peck, K. K., Briggs, R. W., Rothi, L. J. G., & White, K. D. Regional changes in word-production laterallity after a naming treatment designed to produce a rightward shift in frontal activity.B Brain and Language, 111, 73-85. Knecht, S., Floel, A., Drager, B., Breitenstein, C., Sommer, J., Henningsen, H., Ringelstein, E. B., & Pascual-Leone, A. (2002). Degree of language lateralization determines susceptibility to unilateral brain lesions. Nature Neuroscience, 5, 695-699. Thulborn, K. R., Carpenter, P. A., & Just, M. A. (1999). Plasticity of language-related brain function during recovery from stroke. Stroke, 30, 749-754.

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