The autocracy of meaning: Intact visuo-imitative processes may not compensate for meaningful gestures.

The dual-route models of action distinguish between a semantic and a non-semantic visuo-motor route to execute different types of gestures. Despite the large amount of evidence in support to the model, some aspects are debated. One issue concerns the recruitment of the visuo-motor route to correctly execute meaningful gestures when the semantic route is damaged. Debated predictions of the dual-route model were investigated in a sample of 32 patients with left hemisphere stroke lesions compared to 27 healthy controls. Group analysis showed that patients were equally impaired on meaningful and meaningless gestures. Single-case analysis demonstrated that most cases were more impaired on meaningful than on meaningless gestures both when they are given in separate lists and when they are intermingled. Impaired performance on the imitation of meaningful gestures in both the separate and mixed list but spared performance on meaningless gestures in the separate list is against the hypothesis that the intact visuo-motor route compensates for damage to the semantic route. These results suggest that the damaged semantic route interferes with the visuo-motor route and prevents the processing of meaningful gestures along the visuo-motor route. Furthermore, an explorative analysis was conducted to investigate the relationship between gestures imitation and pantomime of object use on verbal command and between gestures imitation and performance on linguistic tasks. Although no significant correlation emerged, patients with moderate/severe impairment on the AAT performed significantly worse on meaningful, but not on meaningless gestures than patients with mild/minimal language impairment, suggesting that praxis and language systems are independent but dynamically interact.

Disentangling phonological and articulatory processing: A neuroanatomical study in aphasia.

Phonological and articulatory programming impairments may co-occur in aphasic patients and previous research does not offer a clear-cut picture of their anatomical counterparts. Hickok and Poeppel (2007) put forward a seminal model of speech processes. The ventral stream (mostly bilateral) would be involved in speech recognition and phonological-lexical processing, whereas the dorsal stream (largely lateralized to the left hemisphere) would map phonological representations onto articulatory motor patterns. In this study we analyzed repetition errors for single words and spontaneous speech ratings on the Italian version of the Aachen Aphasia Test. Through a VLSM procedure we aimed at discriminating the neuroanatomical substrates of the phonological and articulatory impairment (and of their normal functional processing). We also estimated functional connectivity networks related to articulation and phonology using seed-to-voxel connectivity analysis with resting state fMRI data. Results indicate that repetition deficit of single words is associated with lesions in a network of left perisylvian areas including the central operculum, the Heschl's gyrus, the angular gyrus, and the supramarginal gyrus (posterior part). Articulatory impairment is associated with lesions in a number of areas in the left dorsal stream, such as the insula (anterior portion), the pars opercularis of the inferior frontal gyrus, the central operculum and the precentral gyrus. On the contrary, phonological impairment is underpinned by lesions of the Heschl's gyrus, and of the posterior portion of the superior temporal and supramarginal gyri. Anatomo-clinical correlative results partly support Hickok and Poeppel's functional model of phonological and articulatory processing.

Understanding the mental lexicon through neglect dyslexia: a study on compound noun reading.

The present study employs neglect dyslexia (ND) as an experimental model to study compound-word processing; in particular, it investigates whether compound constituents are hierarchically organized at mental level and addresses the possibility of whole-word representation. Seven Italian-speaking patients suffering from ND participated in a word naming task. Both left-headed (pescespada, swordfish) and right-headed (astronave, spaceship) Italian compound nouns were used as stimuli. Non-existent compounds, which were generated by substituting the leftmost constituent of a compound with an orthographically similar word (e.g., *pestespada, *plaguesword), were also employed. A significant headedness effect emerged in the group analysis: patients read left-headed compounds better than right-headed compounds. A significant lexicality effect was also found: the participants read real compounds better than their non-existent compound pairs. Moreover, logit mixed-effects analyses indicated a left-hand constituent frequency effect. Results are discussed in terms of hierarchical representation of compounds and direct access to compound lemma nodes.

The multiple-lemma representation of Italian compound nouns: a single case study of deep dyslexia.

It is not clear how compound words are represented within the influential framework of the lemma-lexeme theory. Theoretically, compounds could be structured through a multiple lemma architecture, in which the lemma nodes of both the compound and its constituents are involved in lexical processing. If this were the case, syntactic properties of both the compound and its constituents should play a role when performing tasks involving compound processing, e.g., compound-word reading. This issue is investigated in the present study through an assessment of the performance of a deep dyslexic patient (GR) in three compound-reading experiments. In the first experiment, verb-noun (VN) compound nouns (e.g., lavapiatti, "dishwasher", lit. wash-dishes) were employed as stimuli, while in the second, VN compound stimuli were embedded in sentences, and were compared to paired verb phrases (e.g., lui lava piatti, "he washes dishes"). Position-specific effects were ruled out by means of a third experiment, which investigated the retrieval of noun-noun compounds (e.g., pescespada, "swordfish", lit. fishsword). In experiment 1, GR made errors on the verb constituent more frequently than on the noun, an effect that did not emerge in Experiment 2: when embedded in sentences, VN compounds were read significantly better than verb-phrases and no grammatical-class effect emerged. In Experiment 3, the first and the second constituent were read with the same level of accuracy. The disproportionate impairment, which emerged in reading the verb component of nominal VN compounds, indicates that the grammatical properties of constituents are being retrieved, and thus confirms access to the constituent lemma-nodes. However, the results suggested a whole-word representation when compounds are embedded in sentences; since the sentence context affects the access to compounds through syntactic constraints, whole-word representation is arguably at the lemma level as well (multiple-lemma representation). Experiment 3 indicates that these effects cannot be accounted for by a position-specific impairment.

A new approach to rhythm cueing of cognitive functions: the case of ideomotor apraxia.

Although positive effects of rhythm cueing on motor control in neurologic disorders are known, no studies have yet focused on patients suffering from impaired programming of complex actions. One patient suffering from ideomotor apraxia (a potentially ideal experimental paradigm to test the effect of rhythm on high-level motor control) underwent two rehabilitation training sets differing only for the presence or absence of rhythm cueing. Both sets of training increased the patient's proficiency, but rhythm cueing was significantly more effective, during the training as well as during the post-training uncued test. Ideomotor apraxia represents an effective model to test the effects of rhythm on high-level motor control.

Neural dynamics of reading morphologically complex words.

Despite considerable research interest, it is still an open issue as to how morphologically complex words such as "car+s" are represented and processed in the brain. We studied the neural correlates of the processing of inflected nouns in the morphologically rich Finnish language. Previous behavioral studies in Finnish have yielded a robust inflectional processing cost, i.e., inflected words are harder to recognize than otherwise matched morphologically simple words. Theoretically this effect could stem either from decomposition of inflected words into a stem and a suffix at input level and/or from subsequent recombination at the semantic-syntactic level to arrive at an interpretation of the word. To shed light on this issue, we used magnetoencephalography to reveal the time course and localization of neural effects of morphological structure and frequency of written words. Ten subjects silently read high- and low-frequency Finnish words in inflected and monomorphemic form. Morphological complexity was accompanied by stronger and longer-lasting activation of the left superior temporal cortex from 200 ms onwards. Earlier effects of morphology were not found, supporting the view that the well-established behavioral processing cost for inflected words stems from the semantic-syntactic level rather than from early decomposition. Since the effect of morphology was detected throughout the range of word frequencies employed, the majority of inflected Finnish words appears to be represented in decomposed form and only very high-frequency inflected words may acquire full-form representations.

Verb-noun double dissociation in aphasia: theoretical and neuroanatomical foundations.

This paper reports the results of several studies on the mechanisms underlying Verb-Noun (V-N) dissociation. The objectives of the studies were to ascertain the location of the lesions causing predominant V or N impairment and to shed light on the different mental representations of these word classes through analyses of the data from neuropsychological patients. With regard to lesion sites, results obtained through an anatomo-correlative study on 15 V-impaired and 5 N-impaired aphasic patients indicate that lesions causing predominant N impairment were mostly located in the middle and inferior left temporal area. Three alternative lesion sites were associated with a V deficit (left posterior temporo-parietal lesions; large left fronto-temporal perisylvian lesions; deep lesions of the insula and/or the basal ganglia). In contrast to the results obtained from several neuropsychological and neuroimaging studies, none of the V-impaired patients had an isolated frontal lesion. The second aim is to discuss grammatical class interaction with semantic factors such as actionality or imageability (said to be the real cause of V-N dissociation). The retrieval of Ns and Vs in a sentence context was tested on 16 V-impaired aphasic patients and the resulting data indicate that imageability interacts with the retrieval of Ns and Vs, but cannot completely account for their dissociation.

Noun-verb dissociation in aphasia: the role of imageability and functional locus of the lesion.

Aphasic patients occasionally manifest a dissociated naming ability between objects and actions: this phenomenon has been interpreted as evidence of a separate organization for nouns and verbs in the mental lexicon. Nevertheless Bird et al. [Bird, H., Howard, D., Franklin, S. (2000). Why is a verb like an inanimate object? Grammatical category and semantic category deficits. BrainandLanguage, 72, 246-309], suggested that the damage underlying noun-verb dissociation affects the corresponding semantic concepts and not the lexical representation of words; moreover, they claimed that many dissociations reported in literature are caused merely by a strong imageability effect. In fact, most authors used a picture-naming task to assess patients' naming ability, and due to the fact that this test involves the use of pictures to represent actions and objects, nouns were frequently more imageable than verbs [Luzzatti, C., & Chierchia, G. (2002). On the nature of selective deficit involving nouns and verbs. RivistadiLinguistica, 14, 43-71]. In order to overcome this drawback, we devised a new task - nouns and verbs retrieval in a sentence context (NVR-SC) - in which nouns and verbs have the same imageability rate. Patients' performance on this task is compared with that obtained by the same patients on a standard picture-naming task. Of the 16 aphasic patients with a selective verb deficit, as revealed by the picture-naming task, two continued to show dissociation in the NVR-SC task, while 14 did not. The data indicate that at least some patients have an imageability-independent lexical deficit for verbs. The functional locus/i of the damage is also considered, with particular reference to the lemma/lexeme dichotomy suggested by Levelt et al. [Levelt, W. J. M., Roelofs, A., & Meyer, A. S. (1999). A theory of lexical access in speech production. BehavioralandBrainSciences, 22, 1-75].