(Knecht et al., 2002) Ana Cecilia Ulloa April 03, 2012

Language  Left-hemisphere dominant

Plasticity  Undamaged hemisphere or undamaged parts of the injured hemisphere take over language representation Thulborn, Carpenter, & Just (1999), Am Heart J, 30,

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

 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. Previous Research

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

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

fMRI Results

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

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

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

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

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

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),

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, 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, Thulborn, K. R., Carpenter, P. A., & Just, M. A. (1999). Plasticity of language-related brain function during recovery from stroke. Stroke, 30,