Here we address the contentious issue of how nouns and verbs are represented in the brain. The co-occurrence of noun and verb deficits with damage to different neural regions has led to the view that they are differentially represented in the brain. Recent neuroimaging evidence and inconsistent lesion-behavior associations challenge this view. We have suggested that nouns and verbs are not differentially represented in the brain, but that different patterns of neural activity are triggered by the different linguistic functions carried by nouns and verbs. We test these claims in a functional magnetic resonance imaging study using homophones -- words which function grammatically as nouns or verbs but have the same form and meaning -- ensuring that any neural differences reflect differences in grammatical function. Words were presented as single stems and in phrases in which each homophone was preceded by an article to create a noun phrase (NP) or a pronoun to create a verb phrase (VP), thus establishing the word's functional linguistic role. Activity for single-word homophones was not modulated by their frequency of usage as a noun or verb. In contrast, homophones marked as verbs by appearing in VPs elicited greater activity in the left posterior middle temporal gyrus (LpMTG) compared to homophones marked as nouns by occurring in NPs. Neuropsychological patients with grammatical deficits had lesions which overlapped with the greater LpMTG activity found for VPs. These results suggest that nouns and verbs do not invariably activate different neural regions; rather, differential cortical activity depends on the extent to which their different grammatical functions are engaged.
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"Modulating the inflectional model by verb dominance reveals how inflectional computations interact with the representational and combinatorial differences between verbs and nouns. Verbs have more complex lexical representations (argument structure) and carry more weight in grammatical structure building than nouns, as reflected in findings that they engage combinatorial processes more strongly than nouns when put in the appropriate grammatical environments [Longe et al., 2007; Tyler et al., 2008]. These differences emerged more clearly when we separated the activation patterns triggered by inflected verbs and inflected nouns using the dominance-modulated model. "
[Show abstract][Hide abstract]ABSTRACT: Language processing engages large-scale functional networks in both hemispheres. Although it is widely accepted that left perisylvian regions have a key role in supporting complex grammatical compu-tations, patient data suggest that some aspects of grammatical processing could be supported bilaterally. We investigated the distribution and the nature of grammatical computations across language processing networks by comparing two types of combinatorial grammatical sequences—inflectionally complex words and minimal phrases—and contrasting them with grammatically simple words. Novel multivariate analy-ses revealed that they engage a coalition of separable subsystems: inflected forms triggered left-lateralized activation, dissociable into dorsal processes supporting morphophonological parsing and ventral, lexically driven morphosyntactic processes. In contrast, simple phrases activated a consistently bilateral pattern of temporal regions, overlapping with inflectional activations in L middle temporal gyrus. These data confirm the role of the left-lateralized frontotemporal network in supporting complex grammatical computations. Critically, they also point to the capacity of bilateral temporal regions to support simple, linear grammati-cal computations. This is consistent with a dual neurobiological framework where phylogenetically older bihemispheric systems form part of the network that supports language function in the modern human, and where significant capacities for language comprehension remain intact even following severe left hemisphere damage. Hum Brain Mapp 00:000–000, 2014. V C 2014 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.
Full-text · Article · Mar 2015 · Human Brain Mapping
"And although a number of functional neuroimaging studies have found verb-preferring regions, these vary across studies (see Crepaldi, Berlingeri, Paulesu, & Luzzatti, 2011, for a critical review challenging the existence of a grammatical class distinction in the brain on the basis of across-study inconsistency). Still, a number of recent fMRI studies have consistently implicated the left lateral temporal cortex (LTC), including the posterior middle temporal gyrus (pMTG), in processing verbs relative to nouns (e.g., Peelen, Romagno, & Caramazza, 2012; Romagno, Rota, Ricciardi, & Pietrini, 2012; Willms et al., 2011; Burton, Krebs-Noble, Gullapalli, & Berndt, 2009; Bedny, Caramazza, Grossman, Pascual-Leone, & Saxe, 2008; Tyler et al., 2008; Shapiro et al., 2006; Yokoyama et al., 2006; Kable, Kan, Wilson, Thompson-Schill, & Chatterjee, 2005) and, less consistently, different left frontal regions. For the latter regions, some studies have not found any effects (e.g., Peelen et al., 2012), whereas others have implicated middle frontal (e.g., Willms et al., 2011; Shapiro et al., 2006) or inferior frontal (e.g., Bedny et al., 2008) regions. "
[Show abstract][Hide abstract]ABSTRACT: Verbs and nouns are fundamental units of language, but their neural instantiation remains poorly understood. Neuropsychological research has shown that nouns and verbs can be damaged independently of each other, and neuroimaging research has found that several brain regions respond differentially to the two word classes. However, the semantic-lexical properties of verbs and nouns that drive these effects remain unknown. Here we show that the most likely candidate is predication: a core lexical feature involved in binding constituent arguments (boy, candies) into a unified syntactic-semantic structure expressing a proposition (the boy likes the candies). We used functional neuroimaging to test whether the intrinsic "predication-building" function of verbs is what drives the verb-noun distinction in the brain. We first identified verb-preferring regions with a localizer experiment including verbs and nouns. Then, we examined whether these regions are sensitive to transitivity-an index measuring its tendency to select for a direct object. Transitivity is a verb-specific property lying at the core of its predication function. Neural activity in the left posterior middle temporal and inferior frontal gyri correlates with transitivity, indicating sensitivity to predication. This represents the first evidence that grammatical class preference in the brain is driven by a word's function to build predication structures.
No preview · Article · Feb 2014 · Journal of Cognitive Neuroscience
"For the earliest epoch (the first word in the central phrase), we predict effects associated with the activation of verb lexico-syntactic knowledge, but only after the lexical identity of the word has been established (e.g., after the word’s recognition point; Marslen-Wilson, 1987) or during the processing of the second word in the central phrase. Given the lexical nature of the direct object preference measure, and on the assumption that posterior middle temporal regions represent lexical-level information relevant to processing verbs in context (Hickok and Poeppel, 2007; Tyler et al., 2008; Rodd et al., 2010), these direct object preference effects are most likely to be seen in LpMTG. "
[Show abstract][Hide abstract]ABSTRACT: The core human capacity of syntactic analysis involves a left hemisphere network involving left inferior frontal gyrus (LIFG) and posterior middle temporal gyrus (LMTG) and the anatomical connections between them. Here we use magnetoencephalography (MEG) to determine the spatio-temporal properties of syntactic computations in this network. Listeners heard spoken sentences containing a local syntactic ambiguity (e.g., "… landing planes …"), at the offset of which they heard a disambiguating verb and decided whether it was an acceptable/unacceptable continuation of the sentence. We charted the time-course of processing and resolving syntactic ambiguity by measuring MEG responses from the onset of each word in the ambiguous phrase and the disambiguating word. We used representational similarity analysis (RSA) to characterize syntactic information represented in the LIFG and left posterior middle temporal gyrus (LpMTG) over time and to investigate their relationship to each other. Testing a variety of lexico-syntactic and ambiguity models against the MEG data, our results suggest early lexico-syntactic responses in the LpMTG and later effects of ambiguity in the LIFG, pointing to a clear differentiation in the functional roles of these two regions. Our results suggest the LpMTG represents and transmits lexical information to the LIFG, which responds to and resolves the ambiguity.
Full-text · Article · May 2013 · Frontiers in Psychology