Lexicality Effects in Word and Nonword Recall of Semantic Dementia and Progressive Nonfluent Aphasia

Effects of semantic context on access to words of low imageability in deep-phonological dysphasia: a treatment case study

BACKGROUND

Deep dysphasia is a relatively rare subcategory of aphasia, characterised by word repetition impairment and a profound auditory-verbal short-term memory (STM) limitation. Repetition of words is better than nonwords (lexicality effect) and better for high-image than low-image words (imageability effect). Another related language impairment profile is phonological dysphasia, which includes all of the characteristics of deep dysphasia except for the occurrence of semantic errors in single word repetition. The overlap in symptoms of deep and phonological dysphasia has led to the hypothesis that they share the same root cause, impaired maintenance of activated representation of words, but that they differ in severity of that impairment, with deep dysphasia being more severe.

AIMS

We report a single-subject multiple baseline, multiple probe treatment study of a person who presented with a pattern of repetition that was consistent with the continuum of deep-phonological dysphasia: imageability and lexicality effects in repetition of single and multiple words and semantic errors in repetition of multiple-word utterances. The aim of this treatment study was to improve access to and repetition of low-imageability words by embedding them in modifier-noun phrases that enhanced their imageability.

METHODS & PROCEDURES

The treatment involved repetition of abstract noun pairs. We created modifier-abstract noun phrases that increased the semantic and syntactic cohesiveness of the words in the pair. For example, the phrases "long distance" and "social exclusion" were developed to improve repetition of the abstract pair "distance-exclusion". The goal of this manipulation was to increase the probability of accessing lexical and semantic representations of abstract words in repetition by enriching their semantic -syntactic context. We predicted that this increase in accessibility would be maintained when the words were repeated as pairs, but without the contextual phrase.

OUTCOMES & RESULTS

Treatment outcomes indicated that increasing the semantic and syntactic cohesiveness of low-imageability and low-frequency words later improved this participant's ability to repeat those words when presented in isolation.

CONCLUSIONS

This treatment approach to improving access to abstract word pairs for repetition was successful for our participant with phonological dysphasia. The approach exemplifies the potential value in manipulating linguistic characteristics of stimuli in ways that improve access between phonological and lexical-semantic levels of representation. Additionally, this study demonstrates how principles of a cognitive model of word processing can be used to guide treatment of word processing impairments in aphasia.

Behavioral/Nonpharmacological Approaches to Addressing Cognitive-Linguistic Symptoms in Individuals With Dementia

Despite current barriers to developing and implementing nonpharmacological or behavioral cognitive-linguistic treatments for dementia, a growing evidence base indicates that individuals with dementia may indeed benefit from a range of nonpharmacological intervention approaches in terms of helping them maintain and/or improve their language and cognitive abilities as well as general functioning and emotional well being. With respect to the current dementia literature, this article describes restorative and compensatory approaches for cognitive symptoms, including direct stimulation of cognitive functions and internal and external strategies to maximize use of residual cognitive skills. We also summarize various language treatment techniques designed to address word retrieval deficits or functional communication issues in a range of dementia types and severity. Broader stimulation approaches such as Montessori-based treatment, reminiscence therapy, and exercise/movement therapy are also reviewed given their potential to benefit not only the cognitive-linguistic symptoms of individuals with dementia, but also other aspects of physical, emotional, and behavioral functioning. Last, we conclude by highlighting limitations in the current research literature along with factors to consider for maximizing nonpharmacological treatment effects (i.e., generalization and maintenance of treatment gains) in clinical or research settings.

For richer or poorer? Imageability effects in semantic dementia patients' reading aloud

The degree to which a word's meaning evokes a mental image exerts an influence on performance across a variety of conceptual and linguistic tasks. In normal healthy participants, this effect takes the form of an advantage for high over low imageability words. Consideration of the influence of imageability on performance of patients with semantic dementia can provide information concerning its cognitive and neural bases. Semantic dementia patients show deficits in conceptual processing tasks, and an associated enhancement of the advantage for high over low imageability words. Semantic dementia patients also show deficits in linguistic processing tasks, including reading aloud words with inconsistent spelling-sound correspondences. This study provides the first systematic exploration of the influence of imageability on semantic dementia patients' reading aloud performance. Over 10 cases, the imageability effect seen for inconsistent words was actually reversed in reaction times, with faster performance for low than high imageability items. The same reversal was observed for inconsistent words when the frequency of legitimate alternative reading of components errors was considered, and this reversed effect grew larger with increasing semantic impairment. This result is interpreted in terms of the development of stronger connections along the direct pathway between spelling and sound for low than high imageability items that are then revealed under diminished semantic activation. This interpretation emphasises the interaction between form and meaning that occurs throughout learning in connectionist models.