Neuropsychological dissociations between regular and irregular past tense verb processing have been explained in two ways: (a) separate mechanisms of a rule-governed process for regular verbs and a lexical-associative process for irregular verbs; (b) a single system drawing on phonological and semantic knowledge. The latter account invokes phonological impairment as the basis of poorer performance for regular than irregular past tense forms, due to greater phonological complexity of the regular past. In 10 nonfluent aphasic patients, the apparent disadvantage for the production of regular past tense forms disappeared when phonological complexity was controlled. In a same-different judgment task on spoken words, all patients were impaired at judging regular stem and past-tense verbs like man/ manned to be different, but equally poor at phonologically matched non-morphological discriminations like men/mend. These results indicate a central phonological deficit that is not limited to speech output nor to morphological processing; under such a deficit, distinctions lacking phonological salience, as typified by regular past tense English verbs, become especially vulnerable.

& How objects are represented and processed in the brain is a central topic in cognitive neuroscience. Previous studies have shown that knowledge of objects is represented in a featurebased distributed neural system primarily involving occipital and temporal cortical regions. Research with nonhuman primates suggest that these features are structured in a hierarchical system with posterior neurons in the inferior temporal cortex representing simple features and anterior neurons in the perirhinal cortex representing complex conjunctions of features (Bussey & Saksida, 2002; Murray & Bussey, 1999). On this account, the perirhinal cortex plays a crucial role in object identification by integrating information from different sensory systems into more complex polymodal feature conjunctions. We tested the implications of these claims for human object processing in an event-related fMRI study in which we presented colored pictures of common objects for 19 subjects to name at two levels of specificity—basic and domain. We reasoned that domain-level naming requires access to a coarsergrained representation of objects, thus involving only posterior regions of the inferior temporal cortex. In contrast, basic-level naming requires finer-grained discrimination to differentiate between similar objects, and thus should involve anterior temporal regions, including the perirhinal cortex. We found that object processing always activated the fusiform gyrus bilaterally, irrespective of the task, whereas the perirhinal cortex was only activated when the task required finer-grained discriminations. These results suggest that the same kind of hierarchical structure, which has been proposed for object processing in the monkey temporal cortex, functions in the human. &

& 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. &

www.elsevier.com/locate/b&l Neural responses to morphological, syntactic, and semantic properties of single words: An fMRI study q

Abstract not found

Can regular and irregular verb forms be accommodated by a single representational mechanism or is a dual mechanism account required? In a first experiment, we used a cross-modal repetition priming paradigm to investigate the mental representation of regular and irregular verb forms in French. Participants heard a spoken prime (such as aimons, ‘we love’) immediately followed by lexical decision to a visual probe (such as aimer, ‘to love’). We contrasted four types of French verbs, varying in the regularity and degree of allomorphy of their verb form inflection. These were (i) fully regular verbs (aimons/aimer, ‘we love/to love’) (ii) regular verbs that undergo minor and phonologically predictable allomorphic changes (sèment/semer, ‘they sow/to sow’) (iii) irregular verbs exhibiting subregularities (peignent/ peindre, ‘they paint/to paint’) and (iv) irregular verbs with idiosyncratic alternations (vont/aller, ‘they go/to go’). The infinitive forms of these verbs were presented as targets in three prime conditions, preceded either by a regular form, an allomorphic form (except for the fuller regular verbs), or an

A prominent issue in cognitive neuroscience is whether language function is instantiated in the brain as a single undifferentiated process, or whether regions of relative specialisation can be demonstrated. The contrast between regular and irregular English verb inflection has been pivotal to this debate. Behavioural dissociations related to different lesion sites in brain-damaged patients suggest that processing regular and irregular past tenses involves different neural systems. Using event-related fMRI in a group of unimpaired young adults, we contrast processing of spoken regular and irregular past tense forms in a same–different judgement task, shown in earlier research with patients to engage left hemisphere language systems. An extensive fronto-temporal network, linking anterior cingulate (ACC), left inferior frontal cortex (LIFC) and bilateral superior temporal gyrus (STG), was preferentially activated for regularly inflected forms. Access to meaning from speech is supported by temporal cortex, but additional processing is required for forms that end in regular inflections, which differentially engage LIFC processes that support morpho-phonological segmentation and grammatical analysis.

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

www.elsevier.com/locate/b&l

Cingulate control of fronto-temporal integration reflects linguistic demands: A three-way interaction in functional connectivity