| |
Abstract:
According to the dual route reading hypothesis, there are two
distinct processes involved in visual word recognition - a
phonological route which is presumed to underlie our capacity to
read pseudowords (e.g.,
glimf
) and a lexical route, assumed to be critical in reading exception
words (e.g.,
yacht
). An apparent double dissociation between these two routes has
been observed in patients with acquired alexias. In this study, we
addressed whether such a processing distinction is honored in the
intact brain. Previous studies examining this issue have used PET
and consequently may have lacked the sensitivity necessary to
observe relevant neuroanatomical differences. We investigated the
dual route hypothesis using fMRI, a technique that allows for the
observation of significant neural activity at a high spatial
resolution within a single subject.
In our fMRI study, participants passively viewed blocks of stimuli
consisting of fixation points, regular words, exception words, and
pseudowords. It was revealed that in contrast to fixation,
processing of all three word types resulted in bilateral (though
primarily left) activation of inferior occipito-temporal cortex,
left middle temporal gyrus, and activations near Broca's area and
Wernicke's area. Despite these robust activations vs. fixation,
there was no significant activation in the comparison of greatest
interest - pseudowords vs. exception words. Thus, results of this
fMRI study are more consistent with theories of visual word
recognition that do not posit anatomically separate phonological
and lexical routes to reading.
|
