Semantic interference and facilitation in picture naming: The effects of type of impairment and compensatory strategies.

We assessed effects of semantic interference in people with aphasia (PWA). Two naming tasks (continuous naming and cyclic blocking) were contrasted with tasks which required suppression of competitors but minimized lexical access (probe task) or required extra-lexical mechanisms of control (Stroop task). In continuous naming, some PWA showed increased interference compared to control participants, with slower RTs and increased omissions. Others showed normal or weaker interference effects in terms of RTs but increased semantic errors. Patterns were consistent only between naming tasks. We explain results by assuming that some PWA are slow at implementing mechanisms of control/selection which weed-out competitors. Others, instead, will have activation difficulties which will induce them to lower the threshold needed for selection. Results highlight how different kinds of brain damage may induce different compensatory strategies and how semantic relatedness may induce both interference and facilitation. Implications for models of lexical selection are discussed.

Phonological simplifications, apraxia of speech and the interaction between phonological and phonetic processing.

Research on aphasia has struggled to identify apraxia of speech (AoS) as an independent deficit affecting a processing level separate from phonological assembly and motor implementation. This is because AoS is characterized by both phonological and phonetic errors and, therefore, can be interpreted as a combination of deficits at the phonological and the motoric level rather than as an independent impairment. We apply novel psycholinguistic analyses to the perceptually phonological errors made by 24 Italian aphasic patients. We show that only patients with relative high rate (>10%) of phonetic errors make sound errors which simplify the phonology of the target. Moreover, simplifications are strongly associated with other variables indicative of articulatory difficulties - such as a predominance of errors on consonants rather than vowels - but not with other measures - such as rate of words reproduced correctly or rates of lexical errors. These results indicate that sound errors cannot arise at a single phonological level because they are different in different patients. Instead, different patterns: (1) provide evidence for separate impairments and the existence of a level of articulatory planning/programming intermediate between phonological selection and motor implementation; (2) validate AoS as an independent impairment at this level, characterized by phonetic errors and phonological simplifications; (3) support the claim that linguistic principles of complexity have an articulatory basis since they only apply in patients with associated articulatory difficulties.

Effects of syllable structure in aphasic errors: implications for a new model of speech production.

Current models of word production assume that words are stored as linear sequences of phonemes which are structured into syllables only at the moment of production. This is because syllable structure is always recoverable from the sequence of phonemes. In contrast, we present theoretical and empirical evidence that syllable structure is lexically represented. Storing syllable structure would have the advantage of making representations more stable and resistant to damage. On the other hand, re-syllabifications affect only a minimal part of phonological representations and occur only in some languages and depending on speech register. Evidence for these claims comes from analyses of aphasic errors which not only respect phonotactic constraints, but also avoid transformations which move the syllabic structure of the word further away from the original structure, even when equating for segmental complexity. This is true across tasks, types of errors, and, crucially, types of patients. The same syllabic effects are shown by apraxic patients and by phonological patients who have more central difficulties in retrieving phonological representations. If syllable structure was only computed after phoneme retrieval, it would have no way to influence the errors of phonological patients. Our results have implications for psycholinguistic and computational models of language as well as for clinical and educational practices.

An open-label pilot study of the use of rivastigmine to promote functional recovery in patients with unilateral spatial neglect due to first ischemic stroke.

The aim of this study was to evaluate the efficacy and safety of rivastigmine as add-on treatment to specific cognitive rehabilitation for unilateral spatial neglect (USN). Twenty patients were randomly assigned either to rehabilitation treatment only (No-RIV) or to rivastigmine (3 mg twice a day, for 8 weeks) add-on treatment (RIV+,). USN and functional status were evaluated by means of specific and validated instruments at baseline, at discharge and at one-month follow up. Compared with the untreated patients, the RIV+ subjects, at discharge, recorded significantly better discharge scores and higher effectiveness on two of the scales. However, subsequent further improvement of the No-RIV patients meant that at follow up there was no significant difference between the two groups. No other statistically significant difference was found. Rivastigmine as add-on treatment to specific cognitive training for USN may improve and accelerate recovery on some specific impairment tests as compared with cognitive training alone.

Hemispheric contribution to categorical and coordinate representational processes: a study on brain-damaged patients.

According to Kosslyn, two types of spatial relations can be used to arrange parts in mental imagery, i.e., categorical spatial relations and coordinate spatial relations, which are processed respectively by the left and right hemispheres. To investigate this possible hemispheric specialization in the imagery domain, we tested 34 left or right brain-damaged patients using both a categorical and a coordinate mental imagery task. The results show that left brain-damaged patients were selectively impaired on processing categorical representations, while right brain-damaged patients were more impaired on the processing the coordinate ones, regardless of the presence of visuo-spatial neglect. The present study partly support Kosslyn's theory and, despite data reported in previous studies of brain-damaged patients, it also supports the hypothesis of a possible bilateral neural representation of mental imagery, with the two hemispheres taking part in this process in different ways.

Efficacy of visuo-spatial training in right-brain damaged patients with spatial hemineglect and attention disorders.

Several rehabilitative approaches have been used to reduce neglect disorders. Some studies tried to demonstrate that hemineglect can be ameliorated by using tasks promoting attentional activation towards the neglected hemispace (Robertson et al., 1995, 2001). As a consequence, a functional link between level of attention and disorders of space exploration has been proposed. For this reason we tried to explore the possible role of attentional deficits on the efficacy of a standard neglect treatment based on visuo spatial rehabilitation. In this study we then examined the performances of a selected group of seven right brain damaged patients, suffering from both severe hemineglect and attentional deficits (of both phasic and tonic components of attention), to several tasks before and after a visuo-spatial training (VST) whose efficacy has been already demonstrated (Pizzamiglio et al., 1992). Results showed that VST induces a significant remission of hemineglect symptoms independently from disorders of attention. Moreover, after visuo-spatial rehabilitation, no improvement of attentional deficits is detectable.

Rehabilitation of left brain-damaged ischemic stroke patients: the role of comprehension language deficits. A matched comparison.

BACKGROUND: Aphasia is considered a risk factor for disability after stroke. The aim of this study was to assess the specific influence of aphasia on rehabilitation results. METHOD: A case-control study in consecutive left brain-damaged stroke inpatients, enrolled in three homogeneous subgroups [nonaphasic (NA) patients, aphasic with comprehension deficit (CD), and without comprehension deficit (NCD)] matched for age and onset-admission interval. Rehabilitation results (gain, efficiency, effectiveness of treatment, percentage and odds ratio of dropouts and of each degree of therapeutic response, assessed by Barthel Index and Rivermead Mobility Index) were compared among the subgroups. RESULTS: Two hundred and forty patients with sequelae of a first stroke were enrolled. CD patients, as compared with NCD and NA ones, had a significantly more severe basal neurological and functional status at admission, minor effectiveness on ADL and mobility, a higher percentage of low responders on ADL and urinary incontinence at discharge, and a risk of low therapeutic response on ADL nearly 4 times higher than the other patients (OR = 4.22, 95% CI = 1.90-9.38). The rehabilitative behavior between NCD and NA was similar. However, all subgroups (NA, CD and NCD) showed a significant improvement (p < 0.001) between their basal and discharge score, both on BI and RMI. CONCLUSIONS: Comprehension language deficit was confirmed to be a strong negative rehabilitation prognostic factor despite the speech therapy done by all CD patients.