Item Retrieval and Competition in Noun and Verb Generation: An fMRI Study

Abstract

Abstract■ Selection between competing responses and stimulus-response association strength is thought to affect performance during verb generation. However, the specific contribution of these two processes remains unclear. Here we used fMRI to investigate the role of selection and association within frontal and BG circuits that are known to be involved in verb production. Subjects were asked to generate verbs from nouns in conditions requiring either high or low selection, but with constant association strength, and in conditions of weak or strong association strength, now with constant selection demands. Furthermore, we examined the role of selection and association during noun generation from noun stimuli. We found that the midpart of the left inferior frontal gyrus was more active in conditions requiring high compared with low selection, with matched association strength. The same left inferior frontal region activated irrespective of verb or noun generation. Results of ROI analyses showed effects of association strength only for verb generation and specifically in the anterior/ventral part of the left inferior frontal gyrus. Moreover, the BG were more active when weakly associated verbs had to be produced relative to weakly associated nouns. These results highlight a functional segregation within the left inferior frontal gyrus for verb generation. More generally, the findings suggest that both factors of selection between competing responses and association strength are important during single-word production with the latter factor becoming particularly critical when task-irrelevant stimuli interfere with the current task (here nouns during verb production), triggering additional activation of the BG. ■

Executive control of retrieval in noun and verb generation

“…The authors found that patients with lesions involving the left posterior region of the inferior frontal gyrus (pIFG) were specifically impaired in the high selection demands condition relative to patients with lesions of other areas in the frontal lobe. The potential role of task-relevant competition would be also compatible with other recent behavioral findings (Snyder & Munakata, 2008) and with an fMRI study on noun/verb generation carried out on young adult participants (Crescentini, Shallice, & Macaluso, 2009). This fMRI study showed that the posterior part of the left IFG (left mid/posterior ventrolateral prefrontal cortex, VLPFC) was involved in the selection of task-relevant competing responses even when no effect of selection demands was detected in RT data (A+SÀ = A+S+).…”

“…On the other hand, in this study, neuroimaging data showed that the left basal ganglia are particularly active when task-irrelevant stimuli interfere with the current task (e.g., nouns during verb generation), particularly in the AÀSÀ verb generation condition (Crescentini et al, 2009). Additionally, the same study showed that the more anterior section of the left VLPFC was also selectively involved in the AÀSÀ condition of verb generation.…”

Neural correlates of verb and noun processing: An fMRI study of Persian

“…The larger activation of MTG, specifically LMTG, in verb processing is in line with several studies (Berlingeri et al, 2008;Crescentini, Shallice, & Macaluso, 2010;Damasio et al, 2001;Davis et al, 2004;Liljestr€ om et al, 2008;Perani et al, 1999;Thompson et al, 2007;Tranel et al, 2005;Tyler et al, 2008Tyler et al, , 2003Willms et al, 2011;Yokoyama et al, 2006). Two main interpretations have been offered to explain LMTG involvement during verb processing.…”

A rostro-caudal axis for language in the frontal lobe: The role of executive control in speech production

“…Verb generation Naming Crescentini et al (2010) fMRI 14 Verb production and Noun generation (HS-SA) Verb production & Noun generation (LS/SA) Moss et al (2005) fMRI 15 Word generation (Competition condition) Unrelated control condition cortex have been shown to cause articulatory deficits (Hillis et al, 2004), while widespread brain damage sparing Rolandic pre-motor and motor regions typically preserves it (Geschwind et al, 1968in MacNeilage, 1998. Evidence for a rostro-caudal cascade of processes underlying speech production also comes from ECoG studies of word production (Llorens et al, 2011): anterior frontal regions are consistently activated approximately 700-100 ms before the patient actually produces the target word, at which point the signal continues to motor-premotor areas (see Edwards et al, 2010 for illustrative example).…”