Semantic Cortical Activation in Dyslexic Readers

dc.contributorAalto Universityen
dc.contributor.authorHelenius, Päivi
dc.contributor.authorSalmelin, Riitta
dc.contributor.authorService, Elisabet
dc.contributor.authorConnolly, John F.
dc.contributor.departmentNeurotieteen ja lääketieteellisen tekniikan laitosfi
dc.contributor.departmentDepartment of Neuroscience and Biomedical Engineeringen
dc.contributor.schoolPerustieteiden korkeakoulufi
dc.contributor.schoolSchool of Scienceen
dc.description.abstractThe combined temporal and spatial resolution of MEG (magnetoencephalography) was used to study whether the same brain areas are similarly engaged in reading comprehension in normal and developmentally dyslexic adults. To extract a semantically sensitive stage of brain activation we manipulated the appropriateness of sentence-ending words to the preceding sentence context. Sentences, presented visually one word at a time, either ended with a word that was (1) expected, (2) semantically appropriate but unexpected, (3) semantically anomalous but sharing the initial letters with the expected word, or (4) both semantically and orthographically inappropriate to the sentence context. In both subject groups all but the highly expected sentence endings evoked strong cortical responses, localized most consistently in the left superior temporal cortex, although additional sources were occasionally found in more posterior parietal and temporal areas and in the right hemisphere. Thus, no significant differences were found in the spatial distribution of brain areas involved in semantic processing between fluent and dyslexic readers. However, both timing and strength of activation clearly differed between the two groups. First, activation sensitivity to word meaning within a sentence context began about 100 msec later in dyslexic than in control subjects. This is likely to result from affected presemantic processing stages in dyslexic readers. Second, the neural responses were significantly weaker in dyslexic than in control subjects, indicating involvement of a smaller or less-synchronous neural population in reading comprehension. Third, in contrast to control subjects, the dyslexic readers showed significantly weaker activation to semantically inappropriate words that began with the same letters as the most expected word than to both orthographically and semantically inappropriate sentence-ending words. Thus, word recognition by the dyslexic group seemed to be qualitatively different: Whereas control subjects perceived words as wholes, dyslexic subjects may have relied on sublexical word recognition and occasionally mistook a correctly beginning word for the one they had expected.en
dc.description.versionPeer revieweden
dc.identifier.citationHelenius, Päivi & Salmelin, Riitta & Service, Elisabet & Connolly, John F. 1999. Semantic Cortical Activation in Dyslexic Readers. Journal of Cognitive Neuroscience. Volume 11, Issue 5. P. 535-550. ISSN 0898-929X (printed). DOI: 10.1162/089892999563599.en
dc.identifier.issn0898-929X (printed)
dc.publisherMIT Pressen
dc.relation.ispartofseriesJournal of Cognitive Neuroscienceen
dc.relation.ispartofseriesVolume 11, Issue 5
dc.rights© 1999 MIT Press. This is the final version of the article: Helenius, Päivi ; Salmelin, Riitta ; Service, Elisabet ; Connolly, John F. 1999. Semantic Cortical Activation in Dyslexic Readers. Journal of Cognitive Neuroscience. Volume 11, Issue 5. P. 535-550. ISSN 0898-929X (printed). DOI: 10.1162/089892999563599, which has been published in final form at
dc.rights.holderMIT Press
dc.subject.keywordcortical activityen
dc.subject.otherMedical sciencesen
dc.titleSemantic Cortical Activation in Dyslexic Readersen
dc.typeA1 Alkuperäisartikkeli tieteellisessä aikakauslehdessäfi
dc.type.versionFinal published versionen
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