Silvia Aggujaro

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.

The anatomical foundations of acquired reading disorders: a neuropsychological verification of the dual-route model of reading.

In this study we investigated the neural correlates of acquired reading disorders through an anatomo-correlative procedure of the lesions of 59 focal brain damaged patients suffering from acquired surface, phonological, deep, undifferentiated dyslexia and pure alexia. Two reading tasks, one of words and nonwords and one of words with unpredictable stress position, were used for this study. We found that surface dyslexia was predominantly associated with left temporal lesions, while in phonological dyslexia the lesions overlapped in the left insula and the left inferior frontal gyrus (pars opercularis) and that pure alexia was associated with lesions in the left fusiform gyrus. A number of areas and white matter tracts, which seemed to involve processing along both the lexical and the sublexical routes, were identified for undifferentiated dyslexia. Two cases of deep dyslexia with relatively dissimilar anatomical correlates were studied, one compatible with Colthearts right-hemisphere hypothesis (1980) whereas the other could be interpreted in the context of Morton and Pattersons (1980), multiply-damaged left-hemisphere hypothesis. In brief, the results of this study are only partially consistent with the current state of the art, and propose new and stimulating challenges; indeed, based on these results we suggest that different types of acquired dyslexia may ensue after different cortical damage, but white matter disconnection may play a crucial role in some cases.

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.

Does argument structure complexity affect reading? A case study of an Italian agrammatic patient with deep dyslexia

The argument structure complexity hypothesis (Thompson, 2003) was introduced to account for the verb production pattern of agrammatic patients, who show greater difficulty in producing transitive versus unergative verbs (argument number effect) and in producing unaccusative versus unergative verbs (syntactic movement effect). The present study investigates these two effects in the reading performance of a patient (GR) suffering from deep dyslexia. GR read nouns significantly better than verbs; moreover, her performance was better on unergative than on transitive verbs, whereas the comparison between unergative and unaccusative verbs did not differ significantly. Data support the extension of the argument structure complexity hypothesis to word naming and suggest that the two aspects of argument structure complexity occur at different levels within models of lexical processing.

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 patients 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.

Lexical and semantic access in letter-by-letter dyslexia: A case report

Letter-by-letter (LBL) dyslexia is a reading impairment caused by left occipital damage and characterized by significant increase in reading time according to the number of letters in a given string (word length effect). In analogy to Dejerine’s interpretation of pure alexia (1892), this disorder is said to be the consequence of a disconnection of the word-blind right hemisphere (RH) from the left hemisphere (LH) word recognition system (angular gyrus). However, several patients have been found to maintain some reading capacities. Coslett & Saffran (1989) described four LBL patients who performed better than chance either on lexical decision or on semantic judgment tasks with words that could not be explicitly identified (implicit reading). Results are controversial (Behrmann, Black & Bub, 1990) and not consistent with the assumption of a complete RH blindness. Data on pure alexia and LBL reading were mostly obtained on Frenchor English-speaking patients, i.e. patients speaking languages with largely irregular orthography, but similar results were also occasionally reported for languages with shallow orthography, like Italian (Perri, Bartolomeo, & Silveri, 1996). The purpose of the present study is to collect data on the nature of the implicit reading phenomenon, to analyze the explicit and implicit reading abilities of a bilingual English and Italian-speaking patient suffering from LBL dyslexia, and to verify for a possible different reading behavior in the two languages.

Disentangling phonological and articulatory processing: A neuroanatomical study in aphasia

ABSTRACT 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 Heschls 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 Heschls gyrus, and of the posterior portion of the superior temporal and supramarginal gyri. Anatomo‐clinical correlative results partly support Hickok and Poeppels functional model of phonological and articulatory processing. HIGHLIGHTSWe used an anatomo‐correlative procedure to disentangle the neuroanatomical foundation of phonological and articulatory damage in aphasia.We analyzed repetition errors for single words and spontaneous speech samples using VLSM.VLSM results partly support Hickok and Poeppels functional model of phonological and articulatory processing