Temporal Dissociation of Early Lexical Access and Articulation Using a Delayed Naming Task — An fMRI Study

Abstract

Neuroimaging studies of overt speech hold an important practical advantage allowing monitoring of subject performance, particularly valuable in disorders like aphasia. However, speech production is not a monotonic process but a complex sequence of stages. Levelt and colleagues have described these as roughly corresponding to two originally independent systems--conceptual and sensorimotor--that are linked in the formulation and expression of spoken language. In the initial stages a word is chosen to match a concept (lexical selection); in the later stages the sound and motor patterns are encoded and the word is uttered (articulation). It has been difficult to discriminate these stages using conventional neuroimaging techniques. We designed a functional magnetic resonance imaging study in an attempt to do this, by introducing a latency into a conventional naming paradigm, delaying the articulated response. Our results showed that left hemisphere perisylvian areas were active throughout, interacting with visual and heteromodal areas during early lexical access and with motor and auditory areas during overt articulation. These results are consistent with the broadest version of the Levelt model and with that derived from Chomsky's minimalist program in which a core language system interacts with conceptual-intentional systems and articulatory-perceptual systems during the early and late stages of lexical access respectively.

Sound-sized segments are significant for Mandarin speakers

“…Further support comes from Damian and Dumay (23), who reported a delayed colored picture-naming task in which English participants were instructed to prepare their response fully but to begin articulation only after a cue appeared. This procedure is typically taken to allow speakers to complete all cognitive processes involved in identification and phonological encoding of the target before the onset of motor execution (46,47). In this study, the typical facilitation effect attributable to phoneme repetition between color and object name (as in "green goat") was eliminated, which confirms that the effect visible in nondelayed picture naming is not grounded in articulation and must be attributed to earlier stages of speech production, such as phonological encoding.…”

Movement related cortical potentials in a face naming task: Influence of the tip-of-the-tongue state

“…In addition, the greater activation in the lateral prefrontal region may reflect maintenance mechanisms associated with the name retrieved in the working memory and access to episodic information in KNOW (Tsukiura et al, 2002;Tulving et al, 1994). Activation of the right premotor region was observed by Kemeny et al (2006) during the articulation phase in a picture naming fMRI study. The lack of differences in areas of the left hemisphere probably reflects the fact that in the three categories the areas associated with phonetic coding and articulation can be activated in the same way because the three categories require similar mechanisms.…”

Neural correlates of covert and overt production of tense and agreement morphology: Evidence from fMRI

“…Involvement of motor areas together with extensive activation of the premotor cortex seem to be directly related to the processes of overt word generation (Barch et al, 1999; Kemeny et al, 2006; Palmer et al, 2001). These areas are most likely involved in the conversion of phoneme sequences into articulatory motor commands and formulation of the phonetic output (Zelkowicz et al, 1998).…”