The temporal characteristics of functional activation in Broca's area during overt picture naming (original) (raw)
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Brain Structure & Function, 2019
Functional imaging data suggest different regions for semantic, syntactic, and phonological processing in an anterior-toposterior direction along the inferior frontal gyrus. Language mapping by use of neuro-navigated transcranial magnetic stimulation (TMS) is frequently applied in clinical research to identify language-related cortical regions. Recently, we proposed a high spatial resolution approach for more detailed language mapping of cortical sub-areas such as Broca's region. Here, we employed a phonological picture-word interference paradigm in healthy subjects to reveal functional specialization in Broca's region for phonological processing. The behavioral phonological priming effect is characterized by accelerated naming responses to target pictures accompanied by phonologically related auditory distractor words. We hypothesized that the inhibitory effects of TMS on language processing would reduce phonological priming only at stimulation sites involved in phonological processing. In active as compared to sham TMS, we found reduced phonological facilitation specifically at sites overlapping with the probabilistic cytoarchitectonic area 44. Our findings complemented functional imaging data by revealing structure-function relationship in Broca's region. The introduction of a reaction time based interference paradigm into TMS language mapping increases the objectivity of the method and allows to explore functional specificity with high temporal resolution. Findings may help to interpret results in clinical applications.
Brain and language, 2012
a b s t r a c t Magnetoencephalography (MEG) has shown pseudohomophone priming effects at Broca's area (specifically pars opercularis of left inferior frontal gyrus and precentral gyrus; LIFGpo/PCG) within 100msofviewingaword.ThisisconsistentwithBroca′sareainvolvementinfastphonologicalaccessduringvisualwordrecognition.Hereweusedonlinetranscranialmagneticstimulation(TMS)toinvestigatewhetherLIFGpo/PCGisnecessaryfor(notjustcorrelatedwith)visualwordrecognitionby100 ms of viewing a word. This is consistent with Broca's area involvement in fast phonological access during visual word recognition. Here we used online transcranial magnetic stimulation (TMS) to investigate whether LIFGpo/PCG is necessary for (not just correlated with) visual word recognition by 100msofviewingaword.ThisisconsistentwithBroca′sareainvolvementinfastphonologicalaccessduringvisualwordrecognition.Hereweusedonlinetranscranialmagneticstimulation(TMS)toinvestigatewhetherLIFGpo/PCGisnecessaryfor(notjustcorrelatedwith)visualwordrecognitionby100 ms. Pulses were delivered to individually fMRI-defined LIFGpo/PCG in Dutch speakers 75-500 ms after stimulus onset during reading and picture naming. Reading and picture naming reactions times were significantly slower following pulses at 225-300 ms. Contrary to predictions, there was no disruption to reading for pulses before 225 ms. This does not provide evidence in favour of a functional role for LIFGpo/PCG in reading before 225 ms in this case, but does extend previous findings in picture stimuli to written Dutch words.
2012
This thesis explored a possible role of Broca's area (specifically the pars opercularis of left inferior frontal gyrus and neighbouring precentral gyrus; LIFGpo/PCG) in accessing sublexical phonology during visual word recognition. In Experiments 1 to 4, behavioural masked sublexical phonological priming effects were tested during lexical decision and reading aloud in English. No sublexical phonological effects were found during the lexical decision tasks, but significant sublexical phonological priming effects were found during reading aloud. In Experiment 5, masked sublexical phonological priming effects were then tested during a silent reading task using magnetoencephalography. Sublexical phonological priming effects were localised to LIFGpo/PCG within ~200 ms for real word targets and within ~75 ms for nonword targets. This indicates an early sensitivity to sublexical phonological information at LIFGpo/PCG during silent reading of English. In Experiment 6 chronometric functional magnetic resonance imaging guided transcranial magnetic stimulation was used to create focal and transient virtual lesions to LIFGpo/PCG in order to test the hypothesis that the putative early sublexical phonological representations seen at LIFGpo/PCG are functionally necessary for visual word recognition. Dutch participants underwent transcranial magnetic stimulation during reading aloud as compared to picture naming.
Speaking of which: Dissecting the neurocognitive network of language production
2012
The noninvasive methods of cognitive neuroscience offer new possibilities to study language. We used neuronavigated multisite transcranial magnetic stimulation (TMS) to determine the functional relevance of 1) the posterior part of left superior temporal gyrus (Wernicke's area), 2) a midportion of Broca's area (slightly posterior/superior to apex of vertical ascending ramus), and 3) the midsection of the left middle temporal gyrus (MTG), during overt picture naming. Our chronometric TMS design enabled us to chart the time points at which neural activity in each of these regions functionally contributes to overt speech production. Our findings demonstrate that the midsection of left MTG becomes functionally relevant at 225 ms after picture onset, followed by Broca's area at 300 ms and Wernicke's area at 400 ms. Interestingly, during this late time window, the left MTG shows a second peak of functional relevance. Each area thus contributed during the speech production process at different stages, suggesting distinct underlying functional roles within this complex multicomponential skill. These findings are discussed and framed in the context of psycholinguistic models of speech production according to which successful speaking relies on intact, spatiotemporally specific feed forward and recurrent feedback loops within a left-hemispheric frontotemporal brain connectivity network.
The relationship between naming reaction time and functional MRI parameters in Broca's area
Magnetic Resonance Imaging, 2008
We examined the correlation between behavioural reaction time and functional imaging parameters of the blood oxygenated level dependent (BOLD) response in Broca's Area during a word identification task, and whether the correlation [Magnetic Resonance Imaging 22 (2004) 451-455] varies as a function of four stimulus types: regular words (REGs) (e.g., hint), irregular words (IRRs) (e.g., pint), nonwords (NWs) (e.g., bint), and pseudohomophones (PHs) (e.g., pynt). Participants named letter strings aloud during a functional magnetic resonance imaging study. Naming reaction times were recorded during regular gaps in image acquisition, and BOLD parameters were extracted via a Tikhonov regularized BOLD analysis technique. The results revealed that only PH reaction times were correlated with BOLD width, providing evidence that Broca's area supports phonetic decoding accompanied with phonological lexical access. In addition, we advanced the development of equation-based models of cognitive behaviour and neurophysiology, whereby we showed that the relationship of mathematical independence that exists for predicting REG accuracy, given IRR and NW or PH naming accuracy, was present for naming reaction time, BOLD width, BOLD time to peak, and BOLD intensity. Therefore, we provide converging behavioural and neuroanatomical evidence for a mathematically independent relationship between sight vocabulary and phonetic decoding systems, consistent with a dualroute model of reading.
Facilitation of picture naming by focal transcranial magnetic stimulation of Wernicke's area
Experimental Brain Research, 1998
On the basis of an evolutionary concept of language it was postulated that activation of the motor systems for arm movements, which are phylogenetically older, should facilitate language processes. In aphasic subjects picture naming can be improved by a concomitant movement of the dominant arm. In the present study it was investigated whether a similar facilitation can be observed in normal subjects by studying the effects of transcranial magnetic stimulation (TMS) on picture naming latencies. Suprathreshold focal TMS was applied to the left motor cortex for proximal arm muscles in right-handed subjects. The effects were compared with TMS of Wernicke's area. While TMS of the motor cortex and the non-dominant temporal lobe had no facilitatory effects, TMS of Wernicke's area decreased picture naming latencies significantly when TMS preceded picture presentation by 500 or 1000 ms. The observed effects depended on the intensity of the stimulus used. While clearly present with intensities of 35% and 55% of maximum output the facilitation disappeared with higher stimulation intensities. It is concluded that focal magnetic stimulation is able to facilitate lexical processes due to a general preactivation of language-related neuronal networks when delivered over Wernicke's area.
Dynamic reconfiguration of the language network preceding onset of speech in picture naming
Human brain mapping, 2014
Language production is a complex neural process that requires the interplay between multiple specialized cortical regions. We investigated modulations in large-scale cortical networks underlying preparation for speech production by contrasting cortico-cortical coherence for overt and silent picture naming in an all-to-all connectivity analysis. To capture transient, frequency-specific changes in functional connectivity we analyzed the magnetoencephalography data in two consecutive 300-ms time windows. Within the first 300 ms following picture onset beta frequency coherence was increased for overt naming in a network of regions comprising the bilateral parieto-temporal junction and medial cortices, suggesting that overt articulation modifies selection processes involved in speech planning. In the late time window (300-600 ms after picture onset) beta-range coherence was enhanced in a network that included the ventral sensorimotor and temporal cortices. Coherence in the gamma band was...
NeuroImage, 2002
In the picture-word interference task, naming responses are facilitated when a distractor word is orthographically and phonologically related to the depicted object as compared to an unrelated word. We used event-related functional magnetic resonance imaging (fMRI) to investigate the cerebral hemodynamic responses associated with this priming effect. Serial (or independent-stage) and interactive models of word production that explicitly account for picture-word interference effects assume that the locus of the effect is at the level of retrieving phonological codes, a role attributed recently to the left posterior superior temporal cortex (Wernicke's area). This assumption was tested by randomly presenting participants with trials from orthographically related and unrelated distractor conditions and acquiring image volumes coincident with the estimated peak hemodynamic response for each trial. Overt naming responses occurred in the absence of scanner noise, allowing reaction time data to be recorded. Analysis of this data confirmed the priming effect. Analysis of the fMRI data revealed blood oxygen level-dependent signal decreases in Wernicke's area and the right anterior temporal cortex, whereas signal increases were observed in the anterior cingulate, the right orbitomedial prefrontal, somatosensory, and inferior parietal cortices, and the occipital lobe. The results are interpreted as supporting the locus for the facilitation effect as assumed by both classes of theoretical model of word production. In addition, our results raise the possibilities that, counterintuitively, picture-word interference might be increased by the presentation of orthographically related distractors, due to competition introduced by activation of phonologically related word forms, and that this competition requires inhibitory processes to be resolved. The priming effect is therefore viewed as being sufficient to offset the increased interference. We conclude that information from functional imaging studies might be useful for constraining theoretical models of word production.
Spatiotemporal imaging of cortical activation during verb generation and picture naming
NeuroImage, 2010
One hundred and fifty years of neurolinguistic research has identified the key structures in the human brain that support language. However, neither the classic neuropsychological approaches introduced by Broca (1861) and Wernicke (1874), nor modern neuroimaging employing PET and fMRI has been able to delineate the temporal flow of language processing in the human brain. We recorded the electrocorticogram (ECoG) from indwelling electrodes over left hemisphere language cortices during two common language tasks, verb generation and picture naming. We observed that the very high frequencies of the ECoG (high-gamma, 70-160 Hz) track language processing with spatial and temporal precision. Serial progression of activations is seen at a larger timescale, showing distinct stages of perception, semantic association/selection, and speech production. Within the areas supporting each of these larger processing stages, parallel (or "incremental") processing is observed. In addition to the traditional posterior vs. anterior localization for speech perception vs. production, we provide novel evidence for the role of premotor cortex in speech perception and of Wernicke's and surrounding cortex in speech production. The data are discussed with regards to current leading models of speech perception and production, and a "dual ventral stream" hybrid of leading speech perception models is given.
Brain Stimulation, 2014
Background: Cathodal transcranial direct current stimulation (tDCS) of the right frontal cortex improves language abilities in post-stroke aphasic patients. Yet little is known about the effects of right frontal cathodal tDCS on normal language function. Objective/hypothesis: To explore the cathodal tDCS effects of the right-hemispheric homologue of Broca's area on picture naming in healthy individuals. We hypothesized that cathodal tDCS improves picture naming and that this effect is determined by the anatomical and functional connectivity of the targeted region. Methods: Cathodal and sham tDCS were applied to the right inferior frontal gyrus in 24 healthy subjects before a picture-naming task. All participants were studied with magnetic resonance imaging at pre-interventional baseline. Probabilistic tractography and dynamic causal modeling of functional brain activity during a word repetition task were applied to characterize anatomical and functional connectivity. Results: Subjects named pictures faster after cathodal relative to sham tDCS. The accelerating effect of tDCS was explained by a reduced frequency of very slow responses. tDCS-induced acceleration of picture naming correlated with larger volumes of the tract connecting the right Broca's area and the supplementary motor area (SMA) and greater functional coupling from the right SMA to the right Broca's area. Conclusions: The results support the notion that the after-effects of tDCS on brain function are at least in part determined by the anatomical and functional connectivity of the targeted region.