Wernicke’s aphasia (WA), an acquired impairment of language comprehension and word repetition, results from a cerebrovascular accident to the left temporoparietal junction. The disorder has been important to the development of neurobiological models of language, however neuropsychological investigations into the nature of the comprehension impairment have been limited. This thesis presents a series of four experiments, investigating the comprehension impairment in WA. Chapter 3, a behavioural neuropsychological study, investigates existing hypotheses of the comprehension impairment in WA: a phonological breakdown, a semantic breakdown, a dual phonological-semantic breakdown. A case series comparison methodology is utilised. Participants with WA are compared to participants from two other clinical, comprehension impaired groups: semantic dementia and semantic aphasia. Semantic dementia and semantic aphasia provide neuropsychological models of semantic breakdown, affecting semantic representations and semantic control respectively. Individuals with WA showed disrupted non-verbal semantic analysis of a similar magnitude to that in semantic dementia and semantic aphasia and of a qualitatively similar nature to that in semantic aphasia. A significantly greater impairment on assessments which required acoustic-phonological analysis was found for individuals with WA compared to semantic aphasia. Overall a dual breakdown in acoustic-phonological and semantic control best accounted for the comprehension impairment in WA. In Chapter 4, direct evidence was sought for a link between acoustic-phonological non-word analysis and auditory comprehension in WA. A novel test of non-word discrimination was created which was perceptually graded so as to provide a sensitive measure in severely impaired participants. Individuals with WA were significantly impaired at non-word discrimination compared to age and hearing matched control participants who performed at ceiling. The degree of non-word discrimination/acoustic-phonological analysis impairment correlated with auditory comprehension in WA. Chapter 5 investigated the extent to which the established acoustic-phonological impairment in WA was grounded in a more fundamental deficit in non-verbal auditory analysis. The capacity to detect structural changes in non-verbal auditory stimuli was measured. Participants with WA had an impaired capacity to detect differences in all but the most structurally simple auditory stimuli, compared to control participants. The degree of this impairment correlated with the degree of auditory comprehension impairment in the WA group. Chapter 6 revisits the semantic impairment observed in WA. Functional magnetic resonance imaging was used to investigate the residual neural networks recruited by individuals with WA, when performing a semantic animate-inanimate judgment task. Large portions of the inferior and anterior temporal lobes bilaterally were activated, regions remote from the lesion in WA. Age matched control participants recruited similar regions; however the activation in WA participants was significantly stronger. This indicated greater reliance on the residual semantic network in WA in response to damage to posterior temporoparietal semantic regions. The results from this series of studies indicated that the primary deficit in WA is one of impaired acoustic analysis and co-morbid damage to a phonological system. Additional disruption occurs to the semantic control network, which regulates the task directed use of semantic representations. A combination of all three factors accounts for the comprehension impairment in WA and it is the relative contributions of each factor that accounts for behavioural variation between individuals.

Though the current understanding of language processing is incomplete, it has been established that the left hemisphere is dominant for language in the majority of the population. Damage to language centers of the brain and to white matter tracts connecting these language centers results in a language deficit known as aphasia. Neuroplasticity in the brain can often compensate for these language deficits by strengthening neuronal connections between the right and left hemisphere, or by enhancing the neuronal connectivity of undamaged areas in the left hemisphere. Thus the brain can compensate for damaged language centers by using alternative cortical areas. These compensatory language areas may be homologous areas of the right hemisphere, or other undamaged portions of the left hemisphere. Various imaging techniques have been used to demonstrate this phenomenon. The current neuroimaging technique known as quantitative electroencephalographic brain imaging allows investigators to evaluate the functional anatomical location of language processing. When this mapping is overlaid on a magnetic resonance image, investigators are able to locate areas in the brain of the participant that are electrically activated during elicited speech tasks. This method was used in a single case study to examine the brain of an individual with a unique traumatic brain injury in which the anterior portion of the individual's left temporal lobe was surgically removed and considerable recovery of language subsequently occurred. The stimulus for the quantitative electroencephalography included identifying syntactically incorrect sentences. Imaging results from the participant with traumatic brain injury were compared to imaging results obtained from an age-matched control. Differences in quantitative electroencephalography between the two participants included a delayed P1-N1-P2 response and an absent P600 in the participant with traumatic brain injury. Behavioral results include an increased number of incorrect responses from the participant with traumatic brain injury as compared to the control participant. These results imply an interesting cortical distribution of language processing that could be further assessed by functional magnetic resonance imaging.

Für die Zuweisung von Genus im Deutschen wurden verschiedene Regeln vorgeschlagen. Genuszuweisung kann beispielsweise auf der Grundlage von Suffixregeln erfolgen. Diesen Regeln zufolge sind Derivations- und Diminutivsuffixe zuverlässige Genusindikatoren. Es finden sich nur wenige Ausnahmen zu diesen Regeln. Andere Nomen hingegen scheinen keine Genustransparenz zu haben. Ziel der durchgeführten Studien ist zu prüfen, inwieweit gesunde sowie aphasische Sprecher von formalen Genusindikatoren profitieren. Die Ergebnisse deuten darauf hin, daß gesunde Sprecher des Deutschen, anders als im Französischen oder Italienischen, in einer Genuszuweisungsaufgabe nicht von der Transparenz der Stimuli profitieren. Es wurden keine Reaktionszeitunterschiede zwischen der transparenten und intransparenten Bedingung gemessen. Aphasische Sprecher hingegen machen in der transparenten Bedingung weniger Fehler bei der Genuszuweisung als in der intransparenten Bedingung. Diese Ergebnisse werden im Kontext aktueller Sprachverarbeitungsmodelle diskutiert. Sie legen nah, daß Genus weder nur lexikalisch gespeichert ist noch ausschließlich auf der Basis von Regeln zugewiesen wird. Es wird angenommen, daß beide Strategien Teil der sprachlichen Kompetenz sind. / Different rules have been proposed for the assignment of gender to nouns in German. For instance, on the basis of derivational or diminutive suffixes gender can be assigned reliably, with only a few exceptions. However, there are several nouns that do not have any formal indication of gender. It was the aim to investigated whether normal and aphasic speakers benefit from formal gender cues. Results indicate that healthy speakers do not profit from gender cues in a gender assignment task. There are no differences in reaction times between the transparent and nontransparent condition. This contradicts findings from languages like French and Italian. However, Broca's and Wernicke's aphasics benefit from gender cues, although they do so in a different way. I interpret these findings within the context of current models of language processing and argue that gender is neither only lexically stored nor exclusively assigned on the basis of assignment rules. Both strategies seem to be part of German speakers' language competence.

正常人的語誤中可以取得在心理語言上何為音韻單位的證據，近來有許多針對失語症的病人語誤的研究，發現失語症病人的語誤也可當做測試語言表徵的重要來源資料。 　　本研究針對失語症病人在聲調方面表現，做聲調錯誤頻率分佈、語境影響錯誤、以及錯誤方向種類之分析 然後將整失語症病人聲調表現的分析跟心理語言學語言產出機制作連結。 　　本研究結果顯示，漢語失語症病人聲調表現上第四生錯誤雖然最多，但第四聲在漢語裡原本出現的頻率就最高，所以第四聲不應被認為對失語症病人最為困難。而第三聲雖然在漢語裡出現頻率最低，卻佔了失語症病人聲調錯誤頻率第二高位，因此我們判斷第三聲對失語症病人來說是最為困難的聲調。第二，我們發現漢語失語症病人聲調錯誤受語境影響比正常人低。第三，漢語失語症病人聲調錯誤裡，語境影響語誤之方向性中，錯誤來源在語誤出現前類型較多。第四，我們發現Dell的連續模型(connectionist model)，可以解釋失語症病人在聲調錯誤類型偏好原因。 / Naturally occurring speech errors have been used as evidence for testing the psychological reality of phonological units. A number of researchers start to look at evidence from aphasic speech for testing linguistic representation so the phenomena of aphasia provide tests of the validity of certain aspects of linguistic theory. 　　In this thesis, tone errors made by aphasics were examined and related overall analyses to psycholinguistic models of speech production. In light of the analysis of tone frequency in Mandarin written texts and oral data and tone errors produced by aphasics, relating issues concerning the research questions we put forward were elucidated. First, it seems that tone 4 is the most problematic tone for the aphasics in terms of error rate since tone 4 occurs the most often in errors. However, tone 4 errors intrinsically will occur more that other three tones because of its highest incidence in Mandarin. Thus, tone 4 may not be taken as the most difficult tone for aphasics merely from its high error rate. Second, the results indicated that non-contextual errors constitute most of the aphasic errors. Third, it has been shown that perseveration is a cross-linguistic feature of aphasia. Fourth, Dell’s connectionist model is proved to be able to account for and make predictions about the error patterns found in both aphasic and normal speech.