Linguistics Research Today is a free monthly online journal that collates and summarizes the latest research about Linguistics, including details on human language, phonetics, syntax, phonology.

Effects of generation mode in fMRI adaptations of semantic fluency: paced production and overt speech.

Basho S, Palmer ED, Rubio MA, Wulfeck B, Müller RA

Brain Development Imaging Laboratory, Department of Psychology, San Diego State University, San Diego, CA 92120-1863, USA.

Verbal fluency is a widely used neuropsychological paradigm. In fMRI implementations, conventional unpaced (self-paced) versions are suboptimal due to uncontrolled timing of responses, and overt responses carry the risk of motion artifact. We investigated the behavioral and neurofunctional effects of response pacing and overt speech in semantic category-driven word generation. Twelve right-handed adults (8 females), ages 21-37 were scanned in four conditions each: paced-overt, paced-covert, unpaced-overt, and unpaced-covert. There was no significant difference in the number of exemplars generated between overt versions of the paced and unpaced conditions. Imaging results for category-driven word generation overall showed left-hemispheric activation in inferior frontal cortex, premotor cortex, cingulate gyrus, thalamus, and basal ganglia. Direct comparison of generation modes revealed significantly greater activation for the paced compared to unpaced conditions in right superior temporal, bilateral middle frontal, and bilateral anterior cingulate cortex, including regions associated with sustained attention, motor planning, and response inhibition. Covert (compared to overt) conditions showed significantly greater effects in right parietal and anterior cingulate, as well as left middle temporal and superior frontal regions. We conclude that paced overt paradigms are useful adaptations of conventional semantic fluency in fMRI, given their superiority with regard to control over and monitoring of behavioral responses. However, response pacing is associated with additional non-linguistic effects related to response inhibition, motor preparation, and sustained attention.

Published 16 March 2007 in Neuropsychologia, 45(8): 1697-706.
Full-text of this article is available online (may require subscription).

© 2005-2008 Linguistics Research Today. All Rights Reserved.