TY  - THES
T1  - Visual and auditory vocabulary acquisition in learning Chinese as a second language : the impact of modality-specific working memory training
A1  - Schneiders,Julia A.
Y1  - 2012/01/30
N2  - The global aim of this thesis was to investigate underlying working memory processes and neural correlates of visual and auditory vocabulary acquisition in Chinese. As an additional question and pre-condition for examining the main goal I questioned whether visual working memory can be trained separately from auditory and whether intra-modal can be distinguished from across-modal training effects in visual working memory on the behavioral and on the neural level. The Working Memory Training Study was designed to test whether visual working memory processes can be trained specifically on the behavioral and neural level and whether those effects can be separated from across-modal training effect. Decidedly larger training gains after visual working memory training compared with auditory or no training on a visual 2-back task were found. These effects were accompanied by specific training-related decreases in the right middle frontal gyrus arising from visual training only. Likewise, visual and auditory training led to decreased activations in the superior portion of the right middle frontal gyrus and the right posterior parietal lobule. I infer that the combination of effects resulted from increased neural efficiency of intra-modal (visual) processes on the one hand and of across-modal (general control) processes on the other hand. Therefore, visual processes of working memory can be trained specifically, and these effects can be functionally dissociated from alterations in general control processes common to both working memory trainings. These results offered a good starting point to use the training paradigm in the Language Training Study. As exemplified for the visual modality, the working memory training paradigm was successful in training a modality-specific process. Thus, the paradigm was applicable to investigate different transfer effects of visual and auditory working memory training on visual and auditory vocabulary learning in Chinese. The Language Training Study aimed at investigating whether visual working memory training exerts unique influence on learning Chinese visual words (orthographic learning) due to the greater complexity of the Chinese writing system, and, conversely, whether auditory working memory training has a specific impact on learning Chinese auditory words  (phonological learning). In addition, training induced modulations in language-related brain networks were examined using fMRI in a pretest-training-posttest design. Both working memory trainings led to positive transfer effects on orthographic learning as compared to no training, whereas for phonological learning no transfer effects were obtained. Differential activation changes after visual and auditory working memory training were found in areas engaged in visual and auditory word processing: Activation sustained/decreased after intra-modal (visual) training in the left mid-fusiform gyrus in the orthographic task. Similarly, activation decreased after intra-modal (auditory) training in the anterior insula in the phonological task. These findings are consistent with the view that working memory training in the equivalent modality enhances the efficiency of perceptual encoding in the orthographic task and incorporating novel sound patterns into long-term phonological representations in the phonological task. Surprisingly, activation increases after across-modal training emerged in both tasks within the same brain regions: Activation increased after auditory training in the mid-fusiform gyrus in the orthographic task and likewise after visual training in the anterior insula in the phonological task, suggesting that working memory training in the complementary modality reflects selective attention to the respective tasks presumably guided by modality-unspecific improvements in executive components of working memory. Moreover, visual training led to additional recruitment of brain regions in the orthographic task, i.e. the right precuneus, presumably mirroring the generation of a mental visual image of the to-be-retrieved character.
KW  - Vokabellernen
KW  - Modalität <Linguistik>
KW  - Arbeitsgedächtnis
KW  - Funktionelle NMR-Tomographie
CY  - Saarbrücken
PB  - Universitäts- und Landesbibliothek
AD  - Postfach 151141, 66041 Saarbrücken
UR  - http://scidok.sulb.uni-saarland.de/volltexte/2012/4532
ER  -