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Abstract:
The left hemisphere plays a major role in representing the
lexical aspects of objects, and the right hemisphere, their figural
features. To investigate how these two representations interact, we
performed a one-back fMRI study which consisted of three types of
30 sec blocks of visually presented items: (1) Pictures - black and
white schematic drawings of objects; (2) Words - 4-6 letter words
identifying these objects; (3) Cross - Pictures interleaved with
Words. Each stimulus was presented for 100 ms with 1200 ms ISIs.
Subjects were asked to press a right button if the stimulus was
identical to the previous one (Pictures and Words), or refers to
the same object (Cross condition); if not - press a left button. A
spiral gradient echo scanning sequence was employed to acquire 36
4mm axial slices in 2 sec. Cohort z-maps were obtained from 14
right handed normal volunteers. When Pictures were contrasted with
Words, activations for the former were greater in right ventral
occipitotemporal cortex (BA 37/19), whereas for the latter they
were larger in bilateral superior and middle temporal gyrus, and in
left inferior parietal cortex. Contrasting the Cross condition with
both Pictures and Words demonstrated bilateral (slightly more right
than left) activation of basal temporal cortex, and predominantly
left activation of inferior parietal and middle and inferior
frontal cortex.
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