Aphasia is a communication disorder that arises from damage to the brain's language areas, affecting comprehension, expressive language, reading, and writing. This condition severely disrupts daily communication, leading to a reduced quality of life and limited social interactions. While speech and language therapy remains the primary treatment for aphasia, the mechanisms driving its success are not fully understood. Despite advancements in language processing theories and therapeutic interventions, variability in patient outcomes remains a challenge. Factors like lesion size, location, and co-existing cognitive deficits play roles, but their collective influence on recovery remains elusive. From a cognitive perspective, the source of language recovery—whether from new neural connections, reactivation of latent linguistic information, or a blend of both—is debated. Current treatments help patients access existing language skills, but some therapies tend to reintroduce known referents as new linguistic items to offer a therapeutic direction. Recent studies indicate that the ability to learn new words might be indeed pivotal for therapy outcomes in chronic aphasia patients. This thesis delves into novel word learning, emphasizing the potential of implicit learning, an unconscious knowledge acquisition method. The research covers four studies, all designed to compare implicit and explicit learning mechanisms. Participants were introduced to pseudowords and unfamiliar objects, aiming to discern their capacity to form associations through statistical co-occurrence in the implicit condition and through direct instruction in the explicit one. Their retention was assessed after a week. In Chapter 2, the first study begins by exploring the two learning mechanisms across various age groups and educational backgrounds, recognizing that insights from neurologically healthy individuals can enhance therapeutic approaches for aphasia. Younger participants demonstrated higher learning accuracy and speed. However, age differences were less pronounced in implicit learning. While education impacted explicit learning, its influence on implicit learning was subtle. Both age groups demonstrated reduced accuracy in the immediate recognition task for the implicit condition compared to the explicit one. This disparity diminished after one week, making accuracies for both conditions comparable. Chapter 3 encompasses two experiments, engaging both aphasia patients and controls. The first experiment's results, which showed limited learning outcomes for aphasia patients, led to a second experiment with adjusted vocabulary and more repetitions. Even if the control group consistently surpassed the aphasia cohorts in performance, implicit learning showed remarkable resilience, especially evident within aphasic patients. Notably, factors such as lesion location and severity played pivotal roles in shaping learning outcomes. Chapter 4 investigated the efficacy of transcranial direct current stimulation (tDCS) in augmenting implicit learning among aphasia patients. By focusing on the middle superior temporal gyrus (mSTG) - a region linked to implicit learning - the study evaluated the effects of anodal, cathodal, and sham stimulation. Notably, anodal stimulation enhanced both recall and the overall learning trajectory. In conclusion, this work emphasizes the need for tailored therapeutic strategies that account not only for lesion location and aphasia type but also for individual learning profiles. Finally Incorporating techniques like tDCS, and principles of implicit learning for aphasia offers promising avenues. However, more research is needed to further refine and expand these insights.
L'afasia, un disturbo comunicativo derivante da danni nelle aree cerebrali deputate al linguaggio, altera la capacità di espressione e/o di comprensione con conseguenze sulla qualità di vita. Sebbene la terapia logopedica sia il trattamento cardine dell’afasia, i meccanismi che ne determinano il successo sono solo parzialmente compresi. Infatti, nonostante i progressi nelle teorie linguistiche e terapeutiche, la variabilità dei risultati tra pazienti rimane una sfida significativa. Fattori come dimensione e posizione della lesione, presenza di deficit cognitivi concomitanti, influenzano il recupero, ma la loro esatta incidenza è ancora da definire. Rimane inoltre dibattuto se questo recupero sia dovuto alla formazione di nuove connessioni neurali, alla riattivazione di conoscenze linguistiche latenti o a una combinazione dei due. Benché i trattamenti attuali siano volti a facilitare l'accesso a competenze linguistiche preesistenti, l'acquisizione di nuovi contenuti linguistici potrebbe rappresentare una nuova frontiera terapeutica. In questo contesto, la tesi esplora il potenziale di apprendimento nell'afasia, con particolare attenzione all'apprendimento implicito. La ricerca si articola in quattro studi, nei quali i partecipanti sono stati esposti a non-parole e oggetti sconosciuti, con l'obiettivo di valutare la capacità di formare associazioni basate sulla co-occorrenza statistica, nel caso dell'apprendimento implicito, e attraverso l'istruzione diretta, nel caso di quello esplicito. La loro capacità di ritenzione è stata valutata nell’immediato e dopo una settimana. Considerando che lo studio su soggetti neurologicamente intatti può contribuire a perfezionare le teorie sulla riabilitazione del linguaggio, il secondo capitolo analizza i due tipi di apprendimento in soggetti sani in relazione a età e anni di istruzione. I risultati evidenziano prestazioni migliori nei partecipanti più giovani e minori discrepanze nell'apprendimento implicito, suggerendo una sua maggiore stabilità rispetto alle variazioni individuali. L’istruzione influisce sull'apprendimento esplicito, ma meno su quello implicito. Nonostante una performance iniziale inferiore nell'apprendimento implicito in entrambi i gruppi di età, le prestazioni si sono allineate dopo una settimana, mostrando una comparabilità tra le due modalità. Il terzo capitolo include due esperimenti con pazienti afasici e gruppi di controllo. I risultati del primo studio, che evidenziano capacità di apprendimento limitate nei pazienti afasici, hanno portato alla realizzazione di un secondo, caratterizzato da un vocabolario ridotto e un maggior numero di ripetizioni. In entrambi gli studi, i soggetti sani hanno mostrato prestazioni superiori rispetto ai pazienti afasici. L'apprendimento implicito ha dimostrato una notevole resilienza, particolarmente evidente nel contesto afasico. Il quarto capitolo esamina il potenziale della stimolazione transcranica a corrente continua (tDCS) nell'aumentare le capacità di apprendimento implicito in afasia. Concentrandosi sul giro temporale superiore medio, lo studio ha comparato diversi tipi di stimolazione: anodica, catodica e sham. I risultati hanno rivelato un miglioramento significativo nell'apprendimento con stimolazione anodica, sia durante la fase di apprendimento che nel successivo compito di riconoscimento. In tutti gli studi con pazienti afasici, variabili come sede della lesione e la gravità dell’afasia hanno giocato un ruolo determinante nell'influenzare l'apprendimento. In conclusione, questa tesi sottolinea l'importanza di adottare strategie terapeutiche personalizzate, tenendo conto non solo della gravità e del tipo di afasia, ma anche dei profili individuali di apprendimento. Inoltre, l'integrazione di tecniche come la tDCS e principi di apprendimento implicito potrebbe aprire nuove prospettive nella riabilitazione del linguaggio.
(2024). NOVEL WORD LEARNING IN APHASIA: A NEW APPROACH TO AN OLD PROBLEM. (Tesi di dottorato, Università degli Studi di Milano-Bicocca, 2024).
NOVEL WORD LEARNING IN APHASIA: A NEW APPROACH TO AN OLD PROBLEM
GUIDOTTI, LUCILLA
2024
Abstract
Aphasia is a communication disorder that arises from damage to the brain's language areas, affecting comprehension, expressive language, reading, and writing. This condition severely disrupts daily communication, leading to a reduced quality of life and limited social interactions. While speech and language therapy remains the primary treatment for aphasia, the mechanisms driving its success are not fully understood. Despite advancements in language processing theories and therapeutic interventions, variability in patient outcomes remains a challenge. Factors like lesion size, location, and co-existing cognitive deficits play roles, but their collective influence on recovery remains elusive. From a cognitive perspective, the source of language recovery—whether from new neural connections, reactivation of latent linguistic information, or a blend of both—is debated. Current treatments help patients access existing language skills, but some therapies tend to reintroduce known referents as new linguistic items to offer a therapeutic direction. Recent studies indicate that the ability to learn new words might be indeed pivotal for therapy outcomes in chronic aphasia patients. This thesis delves into novel word learning, emphasizing the potential of implicit learning, an unconscious knowledge acquisition method. The research covers four studies, all designed to compare implicit and explicit learning mechanisms. Participants were introduced to pseudowords and unfamiliar objects, aiming to discern their capacity to form associations through statistical co-occurrence in the implicit condition and through direct instruction in the explicit one. Their retention was assessed after a week. In Chapter 2, the first study begins by exploring the two learning mechanisms across various age groups and educational backgrounds, recognizing that insights from neurologically healthy individuals can enhance therapeutic approaches for aphasia. Younger participants demonstrated higher learning accuracy and speed. However, age differences were less pronounced in implicit learning. While education impacted explicit learning, its influence on implicit learning was subtle. Both age groups demonstrated reduced accuracy in the immediate recognition task for the implicit condition compared to the explicit one. This disparity diminished after one week, making accuracies for both conditions comparable. Chapter 3 encompasses two experiments, engaging both aphasia patients and controls. The first experiment's results, which showed limited learning outcomes for aphasia patients, led to a second experiment with adjusted vocabulary and more repetitions. Even if the control group consistently surpassed the aphasia cohorts in performance, implicit learning showed remarkable resilience, especially evident within aphasic patients. Notably, factors such as lesion location and severity played pivotal roles in shaping learning outcomes. Chapter 4 investigated the efficacy of transcranial direct current stimulation (tDCS) in augmenting implicit learning among aphasia patients. By focusing on the middle superior temporal gyrus (mSTG) - a region linked to implicit learning - the study evaluated the effects of anodal, cathodal, and sham stimulation. Notably, anodal stimulation enhanced both recall and the overall learning trajectory. In conclusion, this work emphasizes the need for tailored therapeutic strategies that account not only for lesion location and aphasia type but also for individual learning profiles. Finally Incorporating techniques like tDCS, and principles of implicit learning for aphasia offers promising avenues. However, more research is needed to further refine and expand these insights.File | Dimensione | Formato | |
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Descrizione: NOVEL WORD LEARNING IN APHASIA: A NEW APPROACH TO AN OLD PROBLEM
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