Reaching to a target in the 3-D space

Reaching and grasping an object is an action that can be performed in light, under visual guidance, as well as in darkness, under proprioceptive control only. Area V6A is a visuomotor area involved in the control of reaching movements. V6A, besides neurons activated by the execution of reaching movements, shows passive somatosensory and visual responses. This suggests fro V6A a multimodal capability of integrating sensory and motor-related information, We wanted to know whether this integration occurrs in reaching movements and in the present study we tested whether the visual feedback influenced the reaching activity of V6A neurons. In order to better address this question, we wanted to interpret the neural data in the light of the kinematic of reaching performance. We used an experimental paradigm that could examine V6A responses in two different visual backgrounds, light and dark. In these conditions, the monkey performed an istructed-delay reaching task moving the hand towards different target positions located in the peripersonal space. During the execution of reaching task, the visual feedback is processed in a variety of patterns of modulation, sometimes not expected. In fact, having already demonstrated in V6A reach-related discharges in absence of visual feedback, we expected two types of neural modulation: 1) the addition of light in the environment enhanced reach-related discharges recorded in the dark; 2) the light left the neural response unmodified. Unexpectedly, the results show a complex pattern of modulation that argues against a simple additive interaction between visual and motor-related signals.

Coding of reaching in 3-D space

Many psychophysical studies suggest that target depth and direction during reaches are processed independently, but the neurophysiological support to this view is so far limited. Here, we investigated the representation of reach depth and direction by single neurons in an area of the medial posterior parietal cortex (V6A). Single-unit activity was recorded from V6A in two Macaca fascicularis monkeys performing a fixation-to-reach task to targets at different depths and directions. We found that in a substantial percentage of V6A neurons depth and direction signals jointly influenced fixation, planning and arm movement-related activity in 3D space. While target depth and direction were equally encoded during fixation, depth tuning became stronger during arm movement planning, execution and target holding. The spatial tuning of fixation activity was often maintained across epochs, and this occurred more frequently in depth. These findings support for the first time the existence of a common neural substrate for the encoding of target depth and direction during reaching movements in the posterior parietal cortex. Present results also highlight the presence in V6A of several types of cells that process independently or jointly eye position and arm movement planning and execution signals in order to control reaches in 3D space. It is possible that depth and direction influence also the metrics of the reach action and that this effect on the reach kinematic variables can account for the spatial tuning we found in V6A neural activity. For this reason, we recorded and analyzed behavioral data when one monkey performed reaching movements in 3-D space. We evaluated how the target spatial position, in particular target depth and target direction, affected the kinematic parameters and trajectories describing the motor action properties.

Traces de terre, traces d'encre... La rappresentazione dello spazio nella letteratura caraibica. (Francofona e Anglofona)

This study concerns the representation of space in Caribbean literature, both francophone and Anglophone and, in particular, but not only, in the martinican literature, in the works of the authors born in the island. The analysis focus on the second half of the last century, a period in which the martinican production of novels and romances increased considerably, and where the representation and the rule of space had a relevant place. So, the thesis explores the literary modalities of this representation. The work is constituted of 5 chapters and the critical and methodological approaches are both of an analytical and comparative type. The first chapter “The caribbean space: geography, history and society” presents the geographic context, through an analysis of the historical and political major events occurred in the Caribbean archipelago, in particular of the French Antilles, from the first colonization until the départementalisation. The first paragraph “The colonized space: historical-political excursus” the explores the history of the European colonization that marked forever the theatre of the relationship between Europe, Africa and the New World. This social situation take a long and complex process of “Re-appropriation and renegotiation of the space”, (second paragraph) always the space of the Other, that interest both the Antillean society and the writers’ universe. So, a series of questions take place in the third paragraph “Landscape and identity”: what is the function of space in the process of identity construction? What are the literary forms and representations of space in the Caribbean context? Could the writing be a tool of cultural identity definition, both individual and collective? The second chapter “The literary representation of the Antillean space” is a methodological analysis of the notions of literary space and descriptive gender. The first paragraph “The literary space of and in the novel” is an excursus of the theory of such critics like Blanchot, Bachelard, Genette and Greimas, and in particular the recent innovation of the 20th century; the second one “Space of the Antilles, space of the writing” is an attempt to apply this theory to the Antillean literary space. Finally the last paragraph “Signs on the page: the symbolic places of the antillean novel landscape” presents an inventory of the most recurrent antillean places (mornes, ravines, traces, cachots, En-ville,…), symbols of the history and the past, described in literary works, but according to new modalities of representation. The third chapter, the core of the thesis, “Re-drawing the map of the French Antilles” focused the study of space representation on francophone literature, in particular on a selected works of four martinican writers, like Roland Brival, Édouard Glissant, Patrick Chamoiseau and Raphaël Confiant. Through this section, a spatial evolution comes out step by step, from the first to the second paragraph, whose titles are linked together “The novel space evolution: from the forest of the morne… to the jungle of the ville”. The virgin and uncontaminated space of the Antilles, prior to the colonisation, where the Indios lived in harmony with the nature, find a representation in both works of Brival (Le sang du roucou, Le dernier des Aloukous) and of Glissant (Le Quatrième siècle, Ormerod). The arrival of the European colonizer brings a violent and sudden metamorphosis of the originary space and landscape, together with the traditions and culture of the Caraïbes population. These radical changes are visible in the works of Chamoiseau (Chronique des sept misères, Texaco, L’esclave vieil homme et le molosse, Livret des villes du deuxième monde, Un dimanche au cachot) and Confiant (Le Nègre et l’Amiral, Eau de Café, Ravines du devant-jour, Nègre marron) that explore the urban space of the creole En-ville. The fourth chapter represents the “2nd step: the Anglophone novel space” in the exploration of literary representation of space, through an analytical study of the works of three Anglophone writers, the 19th century Lafcadio Hearn (A Midsummer Trip To the West Indies, Two Years in the French West Indies, Youma) and the contemporary authors Derek Walcott (Omeros, Map of the New World, What the Twilight says) and Edward Kamau Brathwaite (The Arrivants: A New World Trilogy). The Anglophone voice of the Caribbean archipelago brings a very interesting contribution to the critical idea of a spatial evolution in the literary representation of space, started with francophone production: “The spatial evolution goes on: from the Martiniques Sketches of Hearn… to the modern bards of Caribbean archipelago” is the new linked title of the two paragraphs. The fifth chapter “Extended look, space shared: the Caribbean archipelago” is a comparative analysis of the results achieved in the prior sections, through a dialogue between all the texts in the first paragraph “Francophone and Anglophone representation of space compared: differences and analogies”. The last paragraph instead is an attempt of re-negotiate the conventional notions of space and place, from a geographical and physical meaning, to the new concept of “commonplace”, not synonym of prejudice, but “common place” of sharing and dialogue. The question sets in the last paragraph “The “commonplaces” of the physical and mental map of the Caribbean archipelago: toward a non-place?” contains the critical idea of the entire thesis.

La ville comme labyrinthe: réécritures d'un mythe entre les années 1950 et 1980

Entre les années 1950 et 1980, émerge une nouvelle forme de labyrinthe chez des romanciers européens comme Michel Butor, Alain Robbe-Grillet, Italo Calvino, Patrick Modiano et Alasdair Gray : un labyrinthe insaisissable et non cartographiable. Pour en rendre compte nous avons recours au modèle du rhizome, issu de la philosophie de Gilles Deleuze et de Félix Guattari, aussi bien qu'au concept d'hétérotopie de Michel Foucault. La spatialité de nos romans nous pousse à prendre en compte également les réécritures ironiques du mythe de Thésée, Ariane, le Minotaure, Dédale. Les citations et les allusions au mythe nous font remarquer la distance d'avec le modèle traditionnel et les effets de ce qu'on peut considérer comme un « bricolage mythique », dans le cadre d'un regard ironique, parodique ou satirique. La représentation romanesque du labyrinthe accentue d'un côté l'absence d'un centre, et de l'autre côté l'ouverture extrême de cet espace qu'est la ville contemporaine. En même temps, la présence de nombreux « espaces autres », les hétérotopies de Foucault, définit l'égarement des protagonistes des romans. Au fur et à mesure que les écrivains acquièrent conscience des caractéristiques « labyrinthiques » de ces espaces, celles-ci commencent à informer l'œuvre romanesque, créant ainsi un espace métafictionnel. Entre les années Cinquante et le début des années Soixante-dix, les Nouveaux romanciers français accentuent ainsi l'idée de pouvoir jouer avec les instruments de la fiction, pour exaspérer l'absence d'un sens dans la ville comme dans la pratique de l'écriture. Calvino reformule cette conception du roman, remarquant l'importance d'un sens, même s'il est caché et difficile à saisir. Pour cette raison, à la fin de l'époque que nous analysons, des auteurs comme Modiano et Gray absorbent les techniques d'écriture de ces prédécesseurs, en les faisant jouer avec la responsabilité éthique de l'auteur.

Forme di appartenenza, forme di resistenza: orizzonti e società della provincia turca di Iğdır

La ricerca nasce da un lavoro di campo condotto nella provincia turca di Iğdır, un altopiano al confine con l'Armenia e il Nakhichevan, vicino alla Georgia e all'Iran, ma morfologicamente isolato dal resto della Turchia. Dopo due secoli alquanto turbolenti, la società locale è oggi caratterizzata dalla presenza di un’ampia componente turco-azera (sciita) e di un’altrettanto ampia componente turco-curda (sunnita shafiita). Inizialmente, la ricerca propone un’analisi diacronica di alcune rappresentazioni europee dell’altopiano, con particolare attenzione alle migrazioni (James Clifford, 1997, Routes: Travel and Translation in the Late Twentieth Century), ai confini, ai limiti e alle frontiere, quest’ultime intese come orizzonti dell’immaginario (Vincent Crapanzano, 2003, Imaginative Horizons: An Essay in Literary-Philosophical Anthropology). Quindi, prendendo spunto dall’inserimento nella società di Iğdır di un insegnante originario della Turchia centrale, analizzo la pratica dello spazio pubblico come fenomenologia delle forme di appartenenza e di resistenza ai gruppi locali. In questa sezione, dopo un capitolo di disamina dell’etnia azera, lo studio affronta i modi di abitare il territorio, con una prospettiva che unisce il centro urbano di Iğdır e, attraverso una fitta rete stradale e sociale, il paese di Ortaköy — alla cui analisi dell'organizzazione sociale dello spazio, delle forme di appartenenza e di resistenza, dedico l’ultima riflessione.

Nuovi metodi di diagnosi precoce dei fallimenti di protesi d'anca con accoppiamento articolare ceramica-ceramica

L’accoppiamento articolare in ceramica è sempre più utilizzato in chirurgia protesica dell’anca per le sue eccellenti proprietà tribologiche. Tuttavia la fragilità della ceramica è causa di fallimenti meccanici. Abbiamo quindi condotto una serie di studi al fine di individuare un metodo efficace di diagnosi precoce del fallimento della ceramica. Abbiamo analizzato delle componenti ceramiche espiantate e abbiamo trovato un pattern di usura pre-frattura che faceva supporre una dispersione di particelle di ceramica nello spazio articolare. Per la diagnosi precoce abbiamo validato una metodica basata sulla microanalisi del liquido sinoviale. Per validare la metodica abbiamo eseguito un agoaspirato in 12 protesi ben funzionanti (bianchi) e confrontato i risultati di 39 protesi con segni di rottura con quelli di 7 senza segni di rottura. Per individuare i pazienti a rischio rottura i dati demografici di 26 pazienti con ceramica rotta sono stati confrontati con 49 controlli comparabili in termini demografici, tipo di ceramica e tipo di protesi. Infine è stata condotta una revisione sistematica della letteratura sulla diagnosi della rottura della ceramica. Nell’aspirato la presenza di almeno 11 particelle ceramiche di dimensioni inferiori a 3 micron o di una maggiore di 3 micron per ogni campo di osservazione sono segno di rottura della ceramica. La metodica con agoaspirato ha 100% di sensibilità e 88 % di specificità nel predire rotture della ceramica. Nel gruppo delle ceramiche rotte è stato trovato un maggior numero di malposizionamenti della protesi rispetto ai controlli (p=0,001). Il rumore in protesi con ceramica dovrebbe sollevare il sospetto di fallimento ed indurre ad eseguire una TC e un agoaspirato. Dal confronto con la letteratura la nostra metodica risulta essere la più efficace.