The relationship between orthography (spelling) and phonology
(speech sounds) varies across alphabetic languages. Consequently,
learning to read a second alphabetic language, that uses the same
letters as the first, increases the phonological associations that can
be linked to the same orthographic units. In subjects with English
as their first language, previous functional imaging studies have
reported increased left ventral prefrontal activation for reading
words with spellings that are inconsistent with their orthographic
neighbors (e.g., PINT) compared with words that are consistent
with their orthographic neighbors (e.g., SHIP). Here, using
functional magnetic resonance imaging (fMRI) in 17 Italian--English
and 13 English--Italian bilinguals, we demonstrate that left ventral
prefrontal activation for first language reading increases with
second language vocabulary knowledge. This suggests that
learning a second alphabetic language changes the way that
words are read in the first alphabetic language. Specifically, first
language reading is more reliant on both lexical/semantic and
nonlexical processing when new orthographic to phonological
mappings are introduced by second language learning. Our
observations were in a context that required participants to switch
between languages. They motivate future fMRI studies to test
whether first language reading is also altered in contexts when the
second language is not in use
