This study examined the effects of lesion location (frontal vs. posterior) and nature of distraction (nonverbal vs. verbal secondary, competing task) on mildly aphasic individuals' performances of listening tasks that required semantic judgments and lexical decisions under isolation focused attention and divided attention conditions. Despite comparable accuracy among all groups during isolation conditions the aphasic groups responded less accurately and more slowly than the normal control group during focused and divided attention conditions. Generally, the two aphasic groups performed similarly, quantitatively and qualitatively. Demographic characteristics such as time post stroke did not correlate with performance decrements. Independent of group, all individuals showed greater disruption of auditory processing skills when the secondary task was verbal rather than nonverbal. Within a limited-capacity model of attention, the results suggest that aphasic individuals display impairments of attention and resource allocation and that these impairments negatively interact with their auditory processing abilities.
PMID: 18348092;PMCID: PMC2699352;Abstract:
Anomia is a striking and consistent clinical feature of semantic dementia (SD), a progressive aphasia syndrome associated with focal cortical atrophy of the anterior temporal lobes. Word retrieval deficits in patients with SD have been attributed to the loss of conceptual knowledge, resulting in an impairment referred to as semantic anomia. Whereas an abundance of research has been dedicated to treatment for anomia in individuals with focal brain damage due to stroke, considerably less work has been done regarding treatment for patients with progressive language decline. The purpose of this article is to review the available literature concerning the nature and treatment of anomia in individuals with SD. Several studies have shown that new lexical learning remains possible in these patients. However, newly learned information is likely to be constrained by the learning context, and increased reliance on perceptual and autobiographical contextual information may be necessary to provide critical support for new vocabulary acquisition. There is also evidence suggesting that treatment may slow the progression of anomia over time, even affording some protective benefit to lexical items that are not yet lost. However, treatment efforts are likely to be most beneficial at early stages of the disease, when residual semantic knowledge as well as relatively spared episodic memory may support new learning. Copyright © 2008 by Thieme Medical Publishers, Inc.