Selective impairment of masculine gender processing: evidence from a German aphasic.

The present single case study describes the performance of the German aphasic E.M. who exhibited a severe impairment of grammatical gender processing in masculine nouns but relatively spared performance regarding feminine and neuter ones. This error pattern was assessed with tests of gender assignment to orally or visually presented words, with oral or written responses, and with tests of gender congruency decision on noun phrases. The pattern occurred across tasks and modalities, thus suggesting a gender-specific impairment at a modality-independent level of processing. It was sensitive to frequency, thus supporting the assumption that access to gender features as part of grammatical processing is frequency sensitive. Besides being the first description of a gender-specific impairment in an aphasic subject, the data therefore have implications regarding the modelling of representation and processing of grammatical gender information within the mental lexicon.

Verbal planning in a case of 'Dynamic Aphasia': an impairment at the level of macroplanning.

Patients with 'dynamic aphasia' exhibit reduced spontaneous speech despite well preserved basic language functions. This disorder may allow insights into the conceptual preparation of messages. Various cognitive approaches have located the patients' impairment at the level of preverbal message generation, including verbal planning, loss of inhibition of lexical concepts, and, most recently, generation of sequences of novel thoughts. We report the case of HK who presented with dynamic aphasia. The study had two goals: first, as HK was assessed over a longer period of time, changes in his performances could be documented which were relevant for the interpretation of the underlying disorder. The present study is the first to document changes across time and improvements of some of the skills involved in language production. Second, further investigations were carried out to clarify HK's underlying deficits. He was unimpaired on a number of 'verbal planning' tasks which argues for the preservation of those specific processes of verbal planning which Levelt (1989) termed 'microplanning'. It is suggested that HK's performance may be best described as an impairment at the level of 'macroplanning'. The deficit may lie in the generation of novel thoughts though minor modifications of this recent approach are being suggested.

"Fragment errors" in deep dysgraphia: further support for a lexical hypothesis.

In addition to various lexical errors, the writing of patients with deep dysgraphia may include a large number of segmental spelling errors, which increase towards the end of the word. Frequently, these errors involve deletion of two or more letters resulting in so-called "fragment errors". Different positions have been brought forward regarding their origin, including rapid decay of activation in the graphemic buffer and an impairment of more central (i.e., lexical or semantic) processing. We present data from a patient (M.D.) with deep dysgraphia who showed an increase of segmental spelling errors towards the end of the word. Several tasks were carried out to explore M.D.'s underlying functional impairment. Errors affected word-final positions in tasks like backward spelling and fragment completion. In a delayed copying task, length of the delay had no influence. In addition, when asked to recall three serially presented letters, a task which had not been carried out before, M.D. exhibited a preference for the first and the third letter and poor performance for the second letter. M.D.'s performance on these tasks contradicts the rapid decay account and instead supports a lexical-semantic account of segmental errors in deep dysgraphia. In addition, the results fit well with an implemented computational model of deep dysgraphia and segmental spelling errors.

Omissions and semantic errors in aphasic naming: is there a link?

Within a discrete two-stage model of lexicalization, semantic errors and errors of omission are assumed to be independent events. In contrast, cascading and interactive models allow for an influence of word form on lexical selection and thus for an inherent relationship in accounting for both error types. A group of 17 aphasic patients was assessed with a naming test controlling for semantic competition of the target items. Semantic errors were more frequent for targets with many competitors than for targets with few competitors while omissions were more frequent when few competitors were available. However, the overall sums of errors in both item groups were comparable. These results imply a common source of both error types and thus speak against a strictly serial model of naming.

Parallel or serial activation of word forms in speech production? Neurolinguistic evidence from an aphasic patient.

We report the oral picture naming performance of the German aphasic MW who presented with frequent meaning related word substitutions (e.g. tiger ==> lion) and word finding blockings (omissions) while his phonological capacities at the single word level were nearly preserved. Targets were controlled for their 'semantic competitiveness', that is, whether there exist closely meaning related lexical competitors or not. Semantic errors were far more numerous with the highly competitive targets than with the low competitive ones. However, omissions were more frequent with the low competitive items so that the sum of the semantic errors and of the omissions was comparable in both conditions. This inverse and compensatory relationship suggests that both error types are not mutually independent. The found pattern is at odds with serial psycholinguistic theories which locate word selection (and misselection) and word form access (and blockings) at different and serially connected stages of word production but supports theories which allow for a parallel architecture in lexical activation and selection involving the word form level.

LEXICALISATION IN SPEECH PRODUCTION: EVIDENCE FROM FORM RELATED WORD SUBSTITUTIONS IN APHASIA.

One of the major empirical sources of theories of speech production are speech errors in normal speakers. Speech errors occurring during lexicalisation of a concept to be expressed can result in whole-word substitutions that are target related in form and/ or meaning or can appear as nonword productions (neologism). Similar error phenomena have been reported for aphasic patients. The present study describes the aphasic, HZ, who produced mainly form-related word substitutions and neologisms in several single-word processing tasks (picture naming, repetition, and reading aloud). In picture naming, meaning-related substitutions also occurred as well as substitutions that were related both in meaning and form (mixed errors). Three hypotheses of the origin of formal errors were tested: the full interactive activation hypothesis postulating meaning-form interactions, the lexical (form) retrieval hypothesis, and the post-lexical phonological encoding hypothesis. HZ's performance on repetition and reading aloud (tests showed no mixed errors and no effects of imageability and of target frequency on formal errors) failed to support the predictions of the first two hypotheses. However, the phonological encoding hypotheses (enriched by a comprehensionbased editor) could also not account for the data (e.g. for some task-specific asymmetries in the error pattern). Instead, an attempt is made to account for formal and mixed errors by construing word form encoding as an interactively organised component within a two-stage model of lexicalisation. Formal errors are traced back to interactions between lexical forms and sublexical phonological information during the second stage of lexicalisation. Mixed errors occur when lexical forms of the target's semantic competitors are involved in word form encoding.