Degree of language lateralization determines susceptibility to unilateral brain lesions
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Transcript of Degree of language lateralization determines susceptibility to unilateral brain lesions
DEGREE OF LANGUAGE LATERALIZATION DETERMINES
SUSCEPTIBILITY TO UNILATERAL BRAIN LESIONS
(Knecht et al., 2002)
Ana Cecilia UlloaApril 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, 749-54
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 patientsCannot 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 CP6CP 5: Wernicke’s AreaCP 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 ConsPros 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), 73-85.
ReferencesCrosson, 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.