Poster B141, Sunday, March 26, 8:00 – 10:00 am, Pacific Concourse
Cognitive Control for Speech Production: Evidence for a rostro-caudal activation gradient in the frontal lobes
Nicolas Bourguignon1, Don Nguyen2, Vincent Gracco2,3; 1Ghent University, 2Centre for Research on Brain, Language & Music, McGill University, 3Haskins Laboratories
Speech production requires lateral prefrontal cortices (LPFC) for cognitive control (CC) – the goal-directed selection of actions from competing alternatives. Yet, the extent to which these systems entail neural-computational principles of CC similar to those in other adaptive-creative behaviors remains elusive. Addressing this issue we examined the extent to which speech production recruits separate modules along the antero-posterior axis of LPFC tasked with the selection of spoken words from conflicting alternatives at distinct levels of representation: We reasoned that low-level selection of names for contextually specified objects – i.e., the nominative level of speech – should engage posterior LPFC (pLPFC), while higher-level selection of verbs semantically associated with contextual objects – the predicative level – should engage anterior LPFC (aLPFC). Using information-theoretic measures of uncertainty (entropy) as predictors of LPFC activity and speech onset latencies (SOLs), we hypothesized that the degree of involvement of pLPFC and aLPFC should reflect variations in selection uncertainty during confrontation naming (CN) and verb generation (VG) tasks, respectively. We tested these hypotheses in an fMRI study of speech production using participants’ cue-specific SOLs and information-theoretic indices of response entropy as regressors of interest. SOL in both tasks were reliably predicted by cue-specific entropy variations, and fMRI results revealed that selection uncertainty during CN engaged pLPFC while predicative uncertainty during VG activated aLPFC, providing evidence for the hierarchical organization of LPFC areas in uncertainty resolution at the nominative and predicative levels of speech production suggesting deep homologies between the neural-computational systems of speech and action control.
Topic Area: EXECUTIVE PROCESSES: Other