Therapy of short-term memory disorders in fluent aphasia: A single case study

Background: Repetition conduction aphasia is defined as a phonological short-term memory (STM) deficit. The interactive activation model of verbal STM proposed by N. Martin and Saffran (1992) accounts for this deficit by an increased activation decay rate. Recently Majerus and van der Linden (2001) suggested that these short-term memory impairments could be improved by therapy. Aims: The purpose of our single case study was to investigate whether the temporary storage of verbal information could be improved by therapy in a patient with repetition conduction aphasia. Methods & Procedures: A patient suffering from a fluent aphasia was trained over 31 therapy sessions. In the therapy task he had to repeat sentences of four to seven words with an increasing delay between stimulus and response. The control task consisted of repeating sentences of four to six words without delay. Outcomes & Results: The treatment improved sentence repetition significantly. In addition, sentence length in oral production and spans for digits and bisyllabic words, i. e., measures for phonological STM, improved. Conclusions: Verbal STM performances were improved through therapy. It is argued that in the light of N. Martin and Saffran's theory, these improvements reflect a partially normalised activation decay, although the role of a probably very mild reduction of connection strength remains unclear.