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Abstract:
Linguistic and visual word form effects on brain activation
during visual sentence processing were examined in 13 healthy
right-handed native English speakers. Systematic natural language
writing system variations were exploited to construct four
contrasting stimulus conditions: 1) English sentences presented in
Roman alphabet, 2) Swahili in Roman alphabet, 3) Hindi in Hindi
alphabet, 4) English in a Hindi-like Roman alphabet font
(Samarkan). Whole-brain EPI images were acquired during stimulus
presentation, and multiple regression analyses were employed to
evaluate the significance of BOLD signal changes. An effect for
alphabet/font type was demonstrated: Hindi and Hindi-like alphabets
elicited widespread activation of extrastriate and superior
parietal cortices bilaterally relative to Roman font. A linguistic
effect was found for English vs. non-English comparisons,
irrespective of font, substantiating previous reports that native
language processing elicits focal activations in Broca's area and
temporal-parietal cortex of the left hemisphere. Our results
further revealed significant differences in patterns of brain
activation in response to the two unknown languages: Swahili,
presented in Roman alphabet and providing accessible English-legal
phonological information, and Hindi, presented in Hindi and
providing no accessible linguistic information: Activations were
greater for Swahili than for Hindi and are similarly focally
distributed in Broca's area and left temporal-parietal cortex,
suggesting language cortex sensitivity to the phonological system
in isolation. Implications for theories of brain-language
relationships are discussed.
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