Fig. 1.

fMRI analysis of interference effects on normal word production. (A and B) Naming latencies in semantic and phonological blocked naming paradigms (error bars are 1 SEM). Because naming latencies were not obtained during fMRI scanning, a separate group of 18 volunteers (8 males, 10 females; ages 19–34) participated in a behavioral session so that naming latencies could be used to verify the predicted effects of semantic and phonological blocking with these materials and design. (A) We observed a semantic blocking interference effect (F1 and F2 P < 0.0001) that increased across cycles (interaction F1 P < 0.05, F2 P < 0.0001). (B) In contrast, phonological blocking facilitated naming latencies (F1 and F2 P < 0.0001). (C) fMRI blocking effects (blocked − mixed) in semantic and phonological paradigms, in LIFG and left temporal ROI (y axis reflects activation differences indexed by β values; error bars are 95% confidence intervals). Anatomical regions were defined in each subject by sulcal boundaries. Within each of these anatomical regions, the ROI was further constrained to include only those voxels that were more activated during the first cycle (repetition) of both semantic/phonological and mixed blocks compared with baseline. We used the first cycle to create the functional picture naming ROIs because repetition has been shown to decrease activations in the LIFG and temporal cortex (23). Within each functional–anatomical ROI, we compared activation (indexed by β values) associated with the two naming conditions. (D) The relationship between the numbers of errors produced in semantic blocked naming (x axis) and the difference in signal between semantically blocked naming and the baseline task as indexed by β values (y axis). This relationship was significant in the LIFG ROI (y axis; r = 0.76, P < 0.0001), but not in the left temporal ROI (r = 0.20, P = 0.46).