The temporal characteristics of functional activation in Broca's area during overt picture naming

Abstract

Picture namingBroca's area Language production Speech production a b s t r a c tThe opercular and triangular sections of the inferior frontal gyrus, also known as Broca's area, have been shown to be involved in various language tasks. In the current study we investigated both the functional role, as well as the precise temporal involvement of Broca's area during picture naming. We applied online event-related transcranial magnetic stimulation (TMS) to Broca's area at five different time points after picture presentation, aiming to cover the complete language production process. Applying real TMS at 300 msec after picture presentation led to an increase in picture naming latency, whereas sham stimulation and real stimulation at earlier and later time windows did not result in any changes in reaction time (RT). Our methodological approach enabled us to get insight into the temporal characteristics of the involvement of this brain area during picture naming.Making use of this information and directly relating it to psycholinguistic models, we conclude that Broca's area may be involved in the process of syllabification during overt speech production. ª 2008 Elsevier Srl. All rights reserved. IntroductionOur ability to communicate and comprehend verbal language represents one of the most crucial and complex human cognitive skills. By employing single case lesion studies, Broca (1861) and Wernicke (1874) were pioneers in the attempt to directly relate different aspects of language processing to the proper functioning of distinct regions of the cerebral cortex. With the advent of modern functional brain imaging techniques, a systematic non-invasive investigation of the neural correlates of language also became available in healthy volunteers. Until today, a vast amount of studies have continued to reveal detailed insights into the exact functional neuroanatomy underlying speech production using electrophysiological [magnetoencephalography (MEG) (Salmelin, 2007) and electroencephalography (EEG) (Schiller et al., 2003;Schmitt et al., 2000)] and metabolic brain imaging techniques (see for example Gernsbacher and Kaschak, 2003;Binder et al., 1997). Other studies have utilised transcranial magnetic stimulation (TMS) to transiently disrupt neural processing, thereby effectuating a quantifiable change in behavioural performance when it is applied to an area functionally involved in the task at question (Pascual-Leone et al., 2000).

The neural substrates for atypical planning and execution of word production in stuttering

“…This discrepency may have resulted from the fact that previous studies did not separately examine planning and execution processes in which the left IFG may play different roles. Evidence on normal speech indicates that the left IFG is mainly involved in syllabification (Schuhmann et al, 2008) or phonetic encoding (Papoutsi et al, 2009), both of which are related to the internal construction of motor plan of speech acts (Moser et al, 2009;Schnur et al, 2009). Thus, our results not only confirmed the involvement of the left IFG in stuttering, but also strongly suggested a key role of the left IFG in atypical planning process in stuttering.…”

Independent Distractor Frequency and Age-of-Acquisition Effects in Picture–Word Interference: fMRI Evidence for Post-lexical and Lexical Accounts according to Distractor Type

“…This is because of the increasing realization that brain imaging data represents an additional dependent variable of relevance to spreading activation models (e.g., Goldrick, 2007;Dell & Sullivan, 2004). There is now a large literature relating brain activation data to stages of processing in models of spoken word production (e.g., Acheson, Hamidi, Binder, & Postle, 2011;Peeva et al, 2010;Schuhmann, Schiller, Goebel, & Sack, 2009;Alario, Chainay, Lehericy, & Cohen, 2006;Indefrey & Levelt, 2004). These studies have identified roles for the midsection of the left middle temporal gyrus in lexical semantic processing and the posterior section of the middle and superior temporal gyri ( Wernickeʼs area) in phonological word form retrieval, respectively, within a predominantly left hemisphere cerebral network.…”

“…These studies have identified roles for the midsection of the left middle temporal gyrus in lexical semantic processing and the posterior section of the middle and superior temporal gyri ( Wernickeʼs area) in phonological word form retrieval, respectively, within a predominantly left hemisphere cerebral network. During naming of depicted objects, the time course of activation in these two regions typically occurs between 150 and 300 msec following initial visual object recognition, with postlexical processes of syllabification and phonetic encoding followed by articulation occurring between 300 and 600 msec attributed to the posterior left inferior pFC (Brocaʼs area) and premotor cortical areas, respectively (e.g., Acheson et al, 2011;Schuhmann et al, 2009;Indefrey & Levelt, 2004). Consequently, these studies provide candidate brain regions for testing the "input" and "output" accounts.…”

Time course of word production in fast and slow speakers: A high density ERP topographic study

“…In other words, the question is whether all encoding processes from concept to articulation are stretched in slow speakers relative to fast speakers, or if processing speed is associated with variable encoding times for a particular process. Schuhmann et al (2009) had to deal with the interpretation of which encoding process was associated with a specific time period in subjects with very short production latencies (during the production of a limited number of monosyllabic words): They hypothesized that speed affects all the processes involved in speech production equally.…”

“…Taking advantage of topographic (spatio-temporal) ERP analyses (Murray, et al, 2008;Michel et al, 2009), we examined the duration of specific electrophysiological patterns (functional microstates, Lehmann, 1987;Michel et al, 2009) across slow and fast speakers and their correlation with production latencies. If speed of word production is distributed along all the speech encoding processes as hypothesised by Schuhmann et al (2009), then differences between slow and fast speakers should be observed in several time windows from the moment a picture appears on the screen to articulation. On the other hand, if differences in processing speed are linked to a specific encoding process, then ERP divergences between slow and fast speakers should be limited to a given time window, which can be associated to a specific encoding process.…”