Computer-mediated tools for the investigation and rehabilitation of auditory and phonological processing in aphasia

Abstract

Background : Advances in technology have enhanced our ability to use computers to manipulate the spectrotemporal characteristics of speech waveforms in ways that can influence the processing of linguistically important features. These modifications are important in patients with auditory/phonetic processing disorders. Aims : We present some preliminary data detailing the effect of modifying the spectrotemporal structure of speech on the ability to discriminate consonant-vowel syllables and comprehend spoken words and sentences in a case of Pure Word Deafness (PWD). Methods & Procedures : We documented severe phonemic processing deficits in a patient with PWD resulting from a unilateral left temporal lesion. Her ability to distinguish between stop consonants was severely impaired while her perception of vowels was relatively spared. This pattern suggested problems with online perceptual elaboration of short-term acoustic features such as rapid formant frequency transitions. We digitally synthesised consonant-vowels with normal (40 millisecond) and extended (80 millisecond) formant frequency transitions and examined her ability to discriminate these stimuli when presented in rapid sequence. In addition, we temporally expanded natural words and sentences by 1.5 and 2 times their original duration (without altering voice pitch) and examined the effects of these manipulations on her auditory comprehension. Outcomes & Results : Altering the temporal parameters of speech had varied effects on decoding auditory linguistic information. Temporal expansion of sentences produced a small but noteworthy increase in performance on an auditory language comprehension task. Extension of brief formant transitions had no substantial effect on phonemic discrimination of rapidly presented CV pairs. Conclusions : These findings illustrate that temporal conditioning of auditory stimuli can potentially enhance the ability of patients with PWD to comprehend speech. The implications of the findings for aphasia therapy are discussed.