The current study addresses the controversial issue of how different grammatical categories are neurally processed. Several lesion-deficit studies suggest that distinct neural substrates underlie the representation of nouns and verbs, with verb deficits associated with damage to left inferior frontal gyrus (LIFG) and noun deficits with damage to left temporal cortex. However, this view is not universally shared by neuropsychological and neuroimaging studies. We have suggested that these inconsistencies may reflect interactions between the morphological structure of nouns and verbs and the processing implications of this, rather than differences in their neural representations (Tyler et al. 2004). We tested this hypothesis using eventrelated functional magnetic resonance imaging, to scan subjects performing a valence judgment on unambiguous nouns and verbs, presented as stems (‘snail, hear’) and inflected forms (‘snails, hears’). We predicted that activations for noun and verb stems would not differ, whereas inflected verbs would generate more activation in left frontotemporal areas than inflected nouns. Our findings supported this hypothesis, with greater activation of this network for inflected verbs compared with inflected nouns. These results support the claim that form class is not a first-order organizing principle underlying the representation of words but rather interacts with the processes that operate over lexical representations.

& 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. &

The question of whether information relevant to meaning (semantics) and structure (syntax) relies on a common language processor or on separate subsystems has proved difficult to address definitively because of the confounds involved in comparing the two types of information. At the sentence level syntactic and semantic judgments make different cognitive demands, while at the single word level, the most commonly used syntactic distinction (between nouns and verbs) is confounded with a fundamental semantic difference (between objects and actions). The present study employs a different syntactic contrast (between count nouns and mass nouns), which is crossed with a semantic difference (between naturally occurring and man-made substances) applying to words within a circumscribed semantic field (foodstuffs). We show, first, that grammaticality judgments of a patient with semantic dementia are indistinguishable from those of a group of age-matched controls, and are similar regardless of the status of his semantic knowledge about the item. In a second experiment we use the triadic task in a group of age-matched controls to show that similarity judgments are influenced not only by meaning (natural vs. manmade), but also implicitly by syntactic information (count vs. mass). Using the same task in a patient with semantic dementia we show that the semantic influences on the syntactic dimension are unlikely to account for this pattern in normals. These data are discussed in relation to modular vs. nonmodular models of language processing, and in particular to the semantic-syntactic distinction.

In principle, a specific deficit in processing verbs relative to nouns might arise as a result of damage to any of several mechanisms involved in speech planning and lexical production. Here we describe a fluent aphasic patient HG who is much worse at retrieving verbs relative to nouns in picture naming and sentence generation, but who retains the ability to produce verbal morphology and even to generate novel verbs productively from nominal roots when she is unable to retrieve appropriate action words (e.g., looming for weaving). Moreover, the results of single-word and sentence comprehension tasks suggest that her ability to access lexical forms of verbs is sensitive to their thematic properties. When contrasted with patients who have specific deficits in processing morphosyntactic properties of verbs (Tsapkini, Jarema, & Kehayia, in press), HGs pattern of performance can be seen as evidence that grammatical properties are functionally distinct from other aspects of lexical representation. We discuss the implications of this dissociation, and of HGs performance specifically, in light of various models of lexical access. 3

The present study addresses the issue of the distinction between nouns and verbs in the lexicon and investigates if and to what extent the grammatical properties of nouns and verbs play a role in organizing the lexical knowledge. Evidence from linguistics, cognitive psychology and cognitive neuropsychology of language is reviewed in order to support the conclusions that, among many other dimensions, nouns and verbs are represented as grammatical classes in speakers ’ lexical knowledge. Furthermore, the grammatical knowledge of the two classes of words plays the role of an organizational principle in the lexicon, and contributes to explain the organization and the format of words ’ representations as well as their possible neural and functional damages *. 1.

Neuropsychological studies have demonstrated that the production of nouns and verbs can be dissociated in aphasia. These reports have been taken as evidence for separate representations of nouns and verbs in the human brain. We used whole-head magnetoencephalography to record cortical dynamics of action and object naming in 10 healthy adults and in 1 anomic patient with superior naming of verbs compared with nouns due to a left posterior parietal lesion. A single set of 100 line drawings was used for both action and object naming. In normal subjects, the activation sequences in action and object naming were essentially identical, advancing from the occipital to posterior temporoparietal and further to the left frontal cortex, without consistent involvement of the classical left inferior frontal (Broca) and temporal (Wernicke) language areas. In the anomic patient, pronounced differences between action and object naming emerged in the left hemisphere. The activation sequence was disrupted at the level of the damaged parietal cortex and did not reach the left frontal cortex even in the relatively easier action naming. The more severely impaired object naming was associated with exceptionally strong and early activation of the left inferior frontal cortex (Broca) and subsequent pronounced activation of the left middle temporal cortex, silent in action naming. Verb and noun retrieval thus utilized a spatiotemporally similar neuronal network in healthy individuals. A clear dissociation in cortical correlates of verb and noun retrieval only became evident in our anomic patient, in whom damage to the language network has resulted in disproportionately worse performance in object than action naming.

Introduction 1 1.1. Two plans for a brain A central question in the study of cognition concerns the way conceptual information is represented and organized in the mind/brain. If we presuppose, as most experimental scientists do, that cognitive processes are computational processes, it becomes self-evident that the presumably enormous amount of information over which these processes operate must be structured in some way in order to be accessible and useful. Given these two minimal criteria (accessibility and usefulness), along with the straightforward assumption of computational efficiency, we can reject as doubtful a host of potential models of organization---e.g., Borges' Chinese encyclopedia, the Boston telephone directory, the Internet, etc. The task of the cognitive scientist is then to sort through the remaining options and divine which has in fact been preferred in the course of neural evolution. In practice, of course, this undertaking is informed as much by em

Previous neuroimaging research indicates that English verbs and nouns are represented in frontal and posterior brain regions, respectively. For Chinese monolinguals, however, nouns and verbs are found to be associated with a wide range of overlapping areas without significant differences in neural signatures. This different pattern of findings led us to ask the question of where nouns and verbs of two different languages are represented in various areas in the brain in Chinese–English bilinguals. In this study, we utilized functional magnetic resonance imaging (fMRI) and a lexical decision paradigm involving Chinese and English verbs and nouns to address this question. We found that while Chinese nouns and verbs involved activation of common brain areas, the processing of English verbs engaged many more regions than did the processing of English nouns. Specifically, compared to English nouns, English verb presentation was associated with stronger activation of the left putamen and cerebellum, which are responsible for motor function, suggesting the involvement of the motor system in the processing of English verbs. Our findings are consistent with the theory that neural circuits for linguistic dimensions are weighted and modulated by the characteristics of a language. Key words: nouns and verbs; bilingualism; fMRI; reading; language; Chinese–English bilinguals; putamen; cerebellum

the nature of selective deficits involving nouns and verbs

Dissociations of nouns and verbs following brain damage have been interpreted as evidence for distinct neural substrates underlying different aspects of the language system. Some neuroimaging studies have supported this claim by finding neural differentiation for nouns