Expectation in Auditory Processing of Environmental Sounds in People with Fluent Aphasia

Abstract

The purpose of this study was to examine the integrity of the nonverbal auditory system in subjects with fluent aphasia, and determine the relative preservation of the nonverbal auditory system in comparison to the lexical system. This was attempted through the task of expectation, a high level processing skill. Two groups of participants were examined: a group with fluent aphasia, and a group of non-neurologically damaged individuals. Participants were administered two nonverbal auditory conditions devoid of lexical information, a simple condition and a complex condition in which they were required to determine if the last sound heard in a sequence of four was expected or unexpected. Two lexical conditions were also administered in a similar manner. In the simple lexical condition, participants were required to identify if the last word heard in a sequence of four was expected or unexpected. In the complex lexical condition, participants were instructed to identify if a sentence ended in a logical or illogical word. The measures in this study included reaction times, percent correct, and incongruent percent correct for each condition. Results revealed that subjects with aphasia may have deficits in auditory processing of both nonverbal and lexical information. A significant difference was found in that subjects with aphasia performed better on lexical tasks as compared to nonverbal auditory tasks. Subjects with aphasia appeared to have a damaged nonverbal auditory system; however, it is inconclusive as to if these results were exacerbated by the complexity of the nonverbal stimuli or the manner in which these complex stimuli were presented devoid of visual and situational context.