fMRI was used to determine the frontal, basal ganglia, and thalamic
structures engaged by three facets of language generation: lexical
status of generated items, the use of semantic vs. phonological
information during language generation, and rate of generation. During
fMRI, 21 neurologically normal subjects performed four tasks:
generation of nonsense syllables given beginning and ending consonant
blends, generation of words given a rhyming word, generation of words
given a semantic category at a fast rate (matched to the rate of
nonsense syllable generation), and generation of words given a semantic
category at a slow rate (matched to the rate of generating of rhyming
words). Components of a left pre-SMA–dorsal caudate
nucleus–ventral anterior thalamic loop were active during word
generation from rhyming or category cues but not during nonsense
syllable generation. Findings indicate that this loop is involved in
retrieving words from pre-existing lexical stores. Relatively diffuse
activity in the right basal ganglia (caudate nucleus and putamen) also
was found during word-generation tasks but not during nonsense syllable
generation. Given the relative absence of right frontal activity during
the word generation tasks, we suggest that the right basal ganglia
activity serves to suppress right frontal activity, preventing right
frontal structures from interfering with language production. Current
findings establish roles for the left and the right basal ganglia in
word generation. Hypotheses are discussed for future research to help
refine our understanding of basal ganglia functions in language
generation. (JINS, 2003, 9, 1061–1077.)