Syllable congruency and word frequency effects on brain activation

This article investigates the neural representation of the processes involved in recognizing multisyllabic words in Spanish asking whether lexical and sublexical processes are reflected in a different neuronal activation pattern. High and low frequency words were presented for lexical decision in two different colors. In the congruent condition the color boundaries matched the limit of the first syllable, whereas in the incongruent condition color boundaries and syllable boundaries did not match. The results revealed robust and dissociable brain activations for lexical frequency and syllable‐color congruency, but no interaction between the two. We interpreted the greater activation for low relative to high frequency words in the left pre/SMA region, and in the insula/inferior frontal cortex bilaterally to reflect a differential recruitment of lexico‐phonological and/or semantic processes. In contrast, we considered two interpretations for the greater deactivation in the precuneus for both lexical frequency and syllable‐color congruency words, and in the thalami and a frontal area for syllable‐color congruency words only. The deactivations may reflect the differential engagement of semantic processing or may result from the differential allocation of attentional resources. Importantly, while a differential deactivation pattern was observed in the precuneus region for lexicality and syllable‐color congruency, BOLD deconvolution revealed a remarkable difference in timing of the two effects with a much earlier deactivation peak for the syllable‐color congruency factor. Thus, effects of lexical frequency and syllable‐color congruency on brain activation show an important dissociation between lexical and sublexical processes during visual word recognition of multisyllabic words. Hum Brain Mapp 2009. © 2009 Wiley‐Liss, Inc.     

Brain activation for lexical decision and reading aloud: two sides of the same coin?

This functional magnetic resonance imaging study compared the neuronal implementation of word and pseudoword processing during two commonly used word recognition tasks: lexical decision and reading aloud. In the lexical decision task, participants made a finger-press response to indicate whether a visually presented letter string is a word or a pseudoword (e.g., "paple"). In the reading-aloud task, participants read aloud visually presented words and pseudowords. The same sets of words and pseudowords were used for both tasks. This enabled us to look for the effects of task (lexical decision vs. reading aloud), lexicality (words vs. nonwords), and the interaction of lexicality with task. We found very similar patterns of activation for lexical decision and reading aloud in areas associated with word recognition and lexical retrieval (e.g., left fusiform gyrus, posterior temporal cortex, pars opercularis, and bilateral insulae), but task differences were observed bilaterally in sensorimotor areas. Lexical decision increased activation in areas associated with decision making and finger tapping (bilateral postcentral gyri, supplementary motor area, and right cerebellum), whereas reading aloud increased activation in areas associated with articulation and hearing the sound of the spoken response (bilateral precentral gyri, superior temporal gyri, and posterior cerebellum). The effect of lexicality (pseudoword vs. words) was also remarkably consistent across tasks. Nevertheless, increased activation for pseudowords relative to words was greater in the left precentral cortex for reading than lexical decision, and greater in the right inferior frontal cortex for lexical decision than reading. We attribute these effects to differences in the demands on speech production and decision-making processes, respectively.     

Syllable-frequency effects in visual word recognition: evidence from ERPs

A lexical decision experiment was conducted while event related potentials (ERPs) were recorded. The word frequency and the first syllable frequency of each word were manipulated. Results showed that, while high frequency words produced less negative amplitudes in the N400 time window than low frequency words, the inverse pattern was found for syllable frequency. Words containing high frequency syllables produced more negative amplitudes than words containing low frequency syllables. Importantly, a significant syllable frequency effect was also obtained at the P200 time window. The results are interpreted in the framework of an interactive activation model, in which high frequency syllables produce the initial activation of a larger number of lexical candidates during the analysis of orthographic or phonological representations, which have to be inhibited later to allow the identification of a unique word. These findings support the idea that, at least in languages with clear syllabic boundaries, syllables are functional sublexical units during visual word recognition.     

fMRI evidence for dual routes to the mental lexicon in visual word recognition.

Event-related fMRI was used to investigate lexical decisions to words of high and low frequency of occurrence and to pseudowords. The results obtained strongly support dual-route models of visual word processing. By contrasting words with pseudowords, bilateral occipito-temporal brain areas and posterior left middle temporal gyrus (MTG) were identified as contributing to the successful mapping of orthographic percepts onto visual word form representations. Low-frequency words and pseudowords elicited greater activations than high-frequency words in the superior pars opercularis [Brodmann's area (BA) 44] of the left inferior frontal gyrus (IFG), in the anterior insula, and in the thalamus and caudate nucleus. As processing of these stimuli during lexical search is known to rely on phonological information, it is concluded that these brain regions are involved in grapheme-to-phoneme conversion. Activation in the pars triangularis (BA 45) of the left IFG was observed only for low-frequency words. It is proposed that this region is involved in processes of lexical selection.     

An event-related fMRI investigation of phonological-lexical competition

This study explored the neural correlates of phonological-lexical competition and frequency on word recognition. An event-related fMRI experiment was conducted using an auditory lexical decision task in which word and nonword stimuli varied in terms of neighborhood density (high and low). Word stimuli also varied in terms of frequency (high and low). Behavioral results were similar to those of Luce and Pisoni [Luce, P. A., & Pisoni, D. B. (1998). Recognizing spoken words: The neighborhood activation model. Ear and Hearing, 19, 1-36], with the reaction time data showing a main effect of word frequency and density as well as a significant interaction effect between these two factors. fMRI results revealed an overall greater neural response for high-density compared to low-density words in the left supramarginal gyrus, consistent with the view that there are greater demands on phonological processing under conditions of increased phonological-lexical competition. The comparison between high and low frequency words revealed greater activation for high frequency words in both anterior and posterior left middle temporal gyrus. A significant interaction between density and frequency was found in lateral and medial frontal structures. This frontal activation may reflect the greater computational resources required in integrating frequency and density information in order to access a word. Overall, these findings demonstrate the sensitivity of neural structures to different properties of the lexicon.     

Auditory and visual word processing studied with fMRI

Brain activations associated with semantic processing of visual and auditory words were investigated using functional magnetic resonance imaging (fMRI). For each form of word presentation, subjects performed two tasks: one semantic, and one nonsemantic. The semantic task was identical for both auditory and visual presentation: single words were presented and subjects determined whether the word was concrete or abstract. In the nonsemantic task for auditory words, subjects determined whether the word had one syllable or multiple syllables. In the nonsemantic task for visual words, subjects determined whether the word was presented in lower case or upper case. There was considerable overlap in where auditory and visual word semantic processing occurred. Visual and auditory semantic tasks both activated the left inferior frontal (BA 45), bilateral anterior prefrontal (BA 10, 46), and left premotor regions (BA 6) and anterior SMA (BA 6, 8). Left posterior temporal (middle temporal and fusiform gyrus) and predominantly right‐sided cerebellar activations were observed during the auditory semantic task but were not above threshold during visual word presentation. The data, when averaged across subjects, did not show obligatory activation of left inferior frontal and temporal language areas during nonsemantic word tasks. Individual subjects showed differences in the activation of the inferior frontal region while performing the same task, even though they showed similar response latency and accuracy. Hum. Brain Mapping 7:15–28, 1999. © 1999 Wiley‐Liss, Inc.     

Neural pathways involved in the processing of concrete and abstract words.

The purpose of this study was to delineate the neural pathways involved in processing concrete and abstract words using functional magnetic resonance imaging (fMRI). Word and pseudoword stimuli were presented visually, one at a time, and the participant was required to make a lexical decision. Lexical decision epochs alternated with a resting baseline. In each lexical decision epoch, the stimuli were either concrete words and pseudowords, or abstract words and pseudowords. Behavioral data indicated that, as with previous research, concrete word stimuli were processed more efficiently than abstract word stimuli. Analysis of the fMRI data indicated that processing of word stimuli, compared to the baseline condition, was associated with neural activation in the bilateral fusiform gyrus, anterior cingulate, left middle temporal gyrus, right posterior superior temporal gyrus, and left and right inferior frontal gyrus. A direct comparison between the abstract and concrete stimuli epochs yielded a significant area of activation in the right anterior temporal cortex. The results are consistent with recent positron emission tomography work showing right hemisphere activation during processing of abstract representations of language. The results are interpreted as support for a right hemisphere neural pathway in the processing of abstract word representations.     

Early Top-Down Modulation in Visual Word Form Processing: Evidence From an Intracranial SEEG Study

Visual word recognition, at a minimum, involves the processing of word form and lexical information. Opinions diverge on the spatiotemporal distribution of and interaction between the two types of information. Feedforward theory argues that they are processed sequentially, whereas interactive theory advocates that lexical information is processed fast and modulates early word form processing. To distinguish between the two theories, we applied stereoelectroencephalography (SEEG) to 33 human adults with epilepsy (25 males and eight females) during visual lexical decisions. The stimuli included real words (RWs), pseudowords (PWs) with legal radical positions, nonwords (NWs) with illegal radical positions, and stroked-changed words (SWs) in Chinese. Word form and lexical processing were measured by the word form effect (PW versus NW) and lexical effect (RW versus PW), respectively. Gamma-band (60 ∼ 140 Hz) SEEG activity was treated as an electrophysiological measure. A word form effect was found in eight left brain regions (i.e., the inferior parietal lobe, insula, fusiform, inferior temporal, middle temporal, middle occipital, precentral and postcentral gyri) from 50 ms poststimulus onset, whereas a lexical effect was observed in five left brain regions (i.e., the calcarine, middle temporal, superior temporal, precentral, and postcentral gyri) from 100 ms poststimulus onset. The two effects overlapped in the precentral (300 ∼ 500 ms) and postcentral (100 ∼ 200 ms and 250 ∼ 600 ms) gyri. Moreover, high-level regions provide early feedback to word form regions. These results demonstrate that lexical processing occurs early and modulates word form recognition, providing vital supportive evidence for interactive theory.SIGNIFICANCE STATEMENT A pivotal unresolved dispute in the field of word processing is whether word form recognition is obligatorily modulated by high-level lexical top-down information. To address this issue, we applied intracranial SEEG to 33 adults with epilepsy to precisely delineate the spatiotemporal dynamics between processing word form and lexical information during visual word recognition. We observed that lexical processing occurred from 100 ms poststimulus presentation and even spatiotemporally overlapped with word form processing. Moreover, the high-order regions provided feedback to the word form regions in the early stage of word recognition. These results revealed the crucial role of high-level lexical information in word form recognition, deepening our understanding of the functional coupling among brain regions in word processing networks.     

Electrophysiological markers of syllable frequency during written word recognition in French

Several empirical lines of investigation support the idea that syllable-sized units may be involved in visual word recognition processes. In this perspective, the present study aimed at investigating further the nature of the process that causes syllabic effects in reading. To do so, the syllable frequency effect was investigated in French using event related potentials while participants performed a lexical decision task (Experiment 1). Consistent with previous studies, manipulating the frequency of the first syllable in words and pseudowords yielded two temporally distinct effects. Compared to items with a first syllable of low frequency, items with a syllable of high frequency elicited a weaker P200 component, reflecting early sub-lexical facilitation, and a larger N400 component, supposed to ensue from competition between syllabic neighbours. To examine which factors determine the strength of interference during lexical access, regression analyses were conducted on the late temporal window potentials. The inhibitory syllable frequency effect was best predicted by leader strength, that is, the frequency ratio between the most frequent syllabic neighbour and the others. When this variable was directly manipulated while controlling for syllable frequency and number of higher frequency syllabic neighbours (Experiment 2), electrophysiological data confirmed the impact of leader strength. The results are discussed in the context of interactive activation-based models augmented with syllabic representations.     

Phonological decoding involves left posterior fusiform gyrus

Aloud reading of novel words is achieved by phonological decoding, a process in which grapheme-to-phoneme conversion rules are applied to "sound out" a word's spoken representation. Numerous brain imaging studies have examined the neural bases of phonological decoding by contrasting pseudoword (pronounceable nonwords) to real word reading. However, only a few investigations have examined pseudoword reading under both aloud and silent conditions, task parameters that are likely to significantly alter the functional anatomy of phonological decoding. Subjects participated in an fMRI study of aloud pseudoword, aloud real word, silent pseudoword, and silent real word reading. Using this two-by-two design, we examined effects of word-type (real words vs. pseudowords) and response-modality (silent vs. aloud) and their interactions. We found 1) four regions to be invariantly active across the four reading conditions: the anterior aspect of the left precentral gyrus (Brodmann's Area (BA) 6), and three areas within the left ventral occipitotemporal cortex; 2) a main effect of word-type (pseudowords > words) in left inferior frontal gyrus and left intraparietal sulcus; 3) a main effect of response-modality (aloud > silent) that included bilateral motor, auditory, and extrastriate cortex; and 4) a single left hemisphere extrastriate region showing a word-type by response-modality interaction effect. This region, within the posterior fusiform cortex at BA 19, was uniquely modulated by varying phonological processing demands. This result suggests that when reading, word forms are subject to phonological analysis at the point they are first recognized as alphabetic stimuli and BA 19 is involved in processing the phonological properties of words.     

An fMRI examination of the effects of acoustic-phonetic and lexical competition on access to the lexical-semantic network

The current study explored how factors of acoustic-phonetic and lexical competition affect access to the lexical-semantic network during spoken word recognition. An auditory semantic priming lexical decision task was presented to subjects while in the MR scanner. Prime-target pairs consisted of prime words with the initial voiceless stop consonants /p/, /t/, and /k/ followed by word and nonword targets. To examine the neural consequences of lexical and sound structure competition, primes either had voiced minimal pair competitors or they did not, and they were either acoustically modified to be poorer exemplars of the voiceless phonetic category or not. Neural activation associated with semantic priming (Unrelated–Related conditions) revealed a bilateral fronto-temporo-parietal network. Within this network, clusters in the left insula/inferior frontal gyrus (IFG), left superior temporal gyrus (STG), and left posterior middle temporal gyrus (pMTG) showed sensitivity to lexical competition. The pMTG also demonstrated sensitivity to acoustic modification, and the insula/IFG showed an interaction between lexical competition and acoustic modification. These findings suggest the posterior lexical-semantic network is modulated by both acoustic-phonetic and lexical structure, and that the resolution of these two sources of competition recruits frontal structures.     

Reading aloud and lexical decision in neglect dyslexia patients: a dissociation

This study investigated the dissociation between reading aloud and lexical decision in six Italian right-brain-damaged patients with left neglect dyslexia. Patients were requested to perform two tasks: (a) reading aloud and lexical decision on monomorphemic words of different frequencies and non-words with different degrees of similarity to real words (Experiment 1); (b) reading aloud and lexical decision on morphologically complex (suffixed) derived words and morphologically complex (suffixed) non-words (Experiment 2). The patients' performance on lexical decision was compared to that of a group of matched control subjects. Patients showed left neglect dyslexia in the reading aloud task, but had a normal level of performance in the lexical decision task. Furthermore, patients were affected by the same morpho-lexical variables that influence lexical decision in normal subjects, suggesting a largely preserved morpho-lexical processing of written letter strings, as assessed by the task of lexical decision. The mechanisms underlying the preservation of lexical decision in patients with left neglect dyslexia are discussed in the light of dual route models of reading.     

Neural correlates of lexical access during visual word recognition

People can discriminate real words from nonwords even when the latter are orthographically and phonologically word-like, presumably because words activate specific lexical and/or semantic information. We investigated the neural correlates of this identification process using event-related functional magnetic resonance imaging (fMRI). Participants performed a visual lexical decision task under conditions that encouraged specific word identification: Nonwords were matched to words on orthographic and phonologic characteristics, and accuracy was emphasized over speed. To identify neural responses associated with activation of nonsemantic lexical information, processing of words and nonwords with many lexical neighbors was contrasted with processing of items with no neighbors. The fMRI data showed robust differences in activation by words and word-like nonwords, with stronger word activation occurring in a distributed, left hemisphere network previously associated with semantic processing, and stronger nonword activation occurring in a posterior inferior frontal area previously associated with grapheme-to-phoneme mapping. Contrary to lexicon-based models of word recognition, there were no brain areas in which activation increased with neighborhood size. For words, activation in the left prefrontal, angular gyrus, and ventrolateral temporal areas was stronger for items without neighbors, probably because accurate responses to these items were more dependent on activation of semantic information. The results show neural correlates of access to specific word information. The absence of facilitatory lexical neighborhood effects on activation in these brain regions argues for an interpretation in terms of semantic access. Because subjects performed the same task throughout, the results are unlikely to be due to task-specific attentional, strategic, or expectancy effects.     

Top-down influences on lexical selection during spoken word production: A 4T fMRI investigation of refractory effects in picture naming

Spoken word production is assumed to involve stages of processing in which activation spreads through layers of units comprising lexical-conceptual knowledge and their corresponding phonological word forms. Using high-field (4T) functional magnetic resonance imaging (fMRI), we assessed whether the relationship between these stages is strictly serial or involves cascaded-interactive processing, and whether central (decision/control) processing mechanisms are involved in lexical selection. Participants performed the competitor priming paradigm in which distractor words, named from a definition and semantically related to a subsequently presented target picture, slow picture-naming latency compared to that with unrelated words. The paradigm intersperses two trials between the definition and the picture to be named, temporally separating activation in the word perception and production networks. Priming semantic competitors of target picture names significantly increased activation in the left posterior temporal cortex, and to a lesser extent the left middle temporal cortex, consistent with the predictions of cascaded-interactive models of lexical access. In addition, extensive activation was detected in the anterior cingulate and pars orbitalis of the inferior frontal gyrus. The findings indicate that lexical selection during competitor priming is biased by top-down mechanisms to reverse associations between primed distractor words and target pictures to select words that meet the current goal of speech.     

Lexical and sublexical components of age-related changes in neural activation during visual word identification

Positron emission tomography data (Madden, Langley, et al., 2002) were analyzed to investigate adult age differences in the relation between neural activation and the lexical (word frequency) and sublexical (word length) components of visual word identification. The differential influence of these components on reaction time (RT) for word/nonword discrimination (lexical decision) was generally similar for the two age groups, with word frequency accounting for a greater proportion of lexical decision RT variance relative to word length. The influence of word length on RT, however, was relatively greater for older adults. Activation in regions of the ventral occipito-temporal cortex was related to the RT changes associated with word frequency and length for older adults, but not for younger adults. Specifically, older adults' frequency effects were related to activation in both anterior (Brodmann's area [BA] 37) and posterior (BAs 17 and 18) regions of the occipito-temporal pathway, whereas word length effects were only associated with posterior activation (BA 17). We conclude that aging affects the neural mechanisms supporting word identification performance although behavioral measures of this ability are generally constant as a function of age.     

Eye movement correlates of acquired central dyslexia

Based on recent progress in theory and measurement techniques, the analysis of eye movements has become one of the major methodological tools in experimental reading research. Our work uses this approach to advance the understanding of impaired information processing in acquired central dyslexia of stroke patients with aphasia. Up to now there has been no research attempting to analyze both word-based viewing time measures and local fixation patterns in dyslexic readers. The goal of the study was to find out whether specific eye movement parameters reflect pathologically preferred segmental reading in contrast to lexical reading.We compared oral reading of single words of normal controls (n = 11) with six aphasic participants (two cases of deep, surface and residual dyslexia each). Participants were asked to read aloud lines of target words differing in length and frequency. Segmental reading was characterized by deviant spatial distribution of saccadic landing positions with initial fixations located mainly at the beginning of the word, while lexical readers showed the normative ‘preferred landing positions’ left to the center of the words. Contrary to expectation, word length did not distinguish between segmental and lexical readers, while word frequency showed the expected effect for lexical readers only. Their mean fixation duration was already prolonged during first pass reading reflecting their attempts of immediate access to lexical information. After first pass reading, re-reading time was significantly increased in all participants with acquired central dyslexia due to their exceedingly higher monitoring demands for oral reading.     

A dual-route perspective on poor reading in a regular orthography: An fMRI study

This study examined functional brain abnormalities in dyslexic German readers who - due to the regularity of German in the reading direction - do not exhibit the reading accuracy problem of English dyslexic readers, but suffer primarily from a reading speed problem. The in-scanner task required phonological lexical decisions (i.e., Does xxx sound like an existing word?) and presented familiar and unfamiliar letter strings of existing phonological words (e.g., Taxi-Taksi) together with nonwords (e.g., Tazi). Dyslexic readers exhibited the same response latency pattern (words < pseudohomophones < nonwords) as nonimpaired readers, but latencies to all item types were much prolonged. The imaging results were suggestive for a different neural organization of reading processes in dyslexic readers. Specifically, dyslexic readers, in response to lexical route processes, exhibited underactivation in a left ventral occipitotemporal (OT) region which presumably is engaged by visual-orthographic whole word recognition. This region was also insensitive to the increased visual-orthographic processing demands of the sublexical route. Reduced engagement in response to sublexical route processes was also found in a left inferior parietal region, presumably engaged by attentional processes, and in a left inferior frontal region, presumably engaged by phonological processes. In contrast to this reduced engagement of the optimal left hemisphere reading network (ventral OT, inferior parietal, inferior frontal), our dyslexic readers exhibited increased engagement of visual occipital regions and of regions presumably engaged by silent articulatory processes (premotor/motor cortex and subcortical caudate and putamen).     

A neural signature of phonological access: distinguishing the effects of word frequency from familiarity and length in overt picture naming

Cognitive models of word production correlate the word frequency effect (i.e., the fact that words which appear with less frequency take longer to produce) with an increased processing cost to activate the whole-word (lexical) phonological representation. We performed functional magnetic resonance imaging (fMRI) while subjects produced overt naming responses to photographs of animals and manipulable objects that had high name agreement but were of varying frequency, with the purpose of identifying neural structures participating specifically in activating whole-word phonological representations, as opposed to activating lexical semantic representations or articulatory-motor routines. Blood oxygen level-dependent responses were analyzed using a parametric approach based on the frequency with which each word produced appears in the language. Parallel analyses were performed for concept familiarity and word length, which provided indices of semantic and articulatory loads. These analyses permitted us to identify regions related to word frequency alone, and therefore, likely to be related specifically to activation of phonological word forms. We hypothesized that the increased processing cost of producing lower-frequency words would correlate with activation of the left posterior inferotemporal (IT) cortex, the left posterior superior temporal gyrus (pSTG), and the left inferior frontal gyrus (IFG). Scan-time response latencies demonstrated the expected word frequency effect. Analysis of the fMRI data revealed that activity in the pSTG was modulated by frequency but not word length or concept familiarity. In contrast, parts of IT and IFG demonstrated conjoint frequency and familiarity effects, and parts of both primary motor regions demonstrated conjoint effects of frequency and word length. The results are consistent with a model of word production in which lexical-semantic and lexical-phonological information are accessed by overlapping neural systems within posterior and anterior language-related cortices, with pSTG specifically involved in accessing lexical phonology.     

Q:] When would you prefer a SOSSAGE to a SAUSAGE? [A:] At about 100 msec. ERP correlates of orthographic typicality and lexicality in written word recognition

Using a speeded lexical decision task, event-related potentials (ERPs), and minimum norm current source estimates, we investigated early spatiotemporal aspects of cortical activation elicited by words and pseudo-words that varied in their orthographic typicality, that is, in the frequency of their component letter pairs (bi-grams) and triplets (tri-grams). At around 100 msec after stimulus onset, the ERP pattern revealed a significant typicality effect, where words and pseudo-words with atypical orthography (e.g., yacht, cacht) elicited stronger brain activation than items characterized by typical spelling patterns (cart, yart). At approximately 200 msec, the ERP pattern revealed a significant lexicality effect, with pseudo-words eliciting stronger brain activity than words. The two main factors interacted significantly at around 160 msec, where words showed a typicality effect but pseudo-words did not. The principal cortical sources of the effects of both typicality and lexicality were localized in the inferior temporal cortex. Around 160 msec, atypical words elicited the stronger source currents in the left anterior inferior temporal cortex, whereas the left perisylvian cortex was the site of greater activation to typical words. Our data support distinct but interactive processing stages in word recognition, with surface features of the stimulus being processed before the word as a meaningful lexical entry. The interaction of typicality and lexicality can be explained by integration of information from the early form-based system and lexicosemantic processes.     

The neural circuitry involved in the reading of German words and pseudowords: A PET study.

Silent reading and reading aloud of German words and pseudowords were used in a PET study using (15O)butanol to examine the neural correlates of reading and of the phonological conversion of legal letter strings, with or without meaning. The results of 11 healthy, right-handed volunteers in the age range of 25 to 30 years showed activation of the lingual gyri during silent reading in comparison with viewing a fixation cross. Comparisons between the reading of words and pseudowords suggest the involvement of the middle temporal gyri in retrieving both the phonological and semantic code for words. The reading of pseudowords activates the left inferior frontal gyrus, including the ventral part of Broca's area, to a larger extent than the reading of words. This suggests that this area might be involved in the sublexical conversion of orthographic input strings into phonological output codes. (Pre)motor areas were found to be activated during both silent reading and reading aloud. On the basis of the obtained activation patterns, it is hypothesized that the articulation of high-frequency syllables requires the retrieval of their concomitant articulatory gestures from the SMA and that the articulation of low-frequency syllables recruits the left medial premotor cortex.