Treffer: Effects of increased memory load on short-term facilitation of repetition in persons with aphasia

The ability to repeat a word involves activation of phonological and semantic representations of words that must be maintained until the utterance is produced. In aphasia, the language and verbal STM impairment frequently co-occur and studies indicate that the severity of these impairments are highly correlated (Martin & Ayala, 2004). One account of this co-occurrence is that the word processing impairment in aphasia is due to an inability to maintain activation of semantic and phonological representations of words over the time course of comprehending, repeating, or producing a word. When severe, this impairment affects single and multiple word processing as well as verbal STM capacity, as measured by verbal span. When milder, the impairment affects multiple word processing and verbal STM capacity. This intimate relationship of lexical access/retrieval and the ability to maintain activation of a word’s representations suggests a need to consider the role of verbal memory load on language performance. For example, it has been shown recently that performance on semantic judgment tasks is significantly reduced when memory load on the task is increased (Martin, Kohen, Kalinyak-Fliszar, Soveri & Laine, 2012). This study also identified two factors contributing to this effect, semantic STM capacity and an executive function, inhibition (performance on the Simon Task). Additionally, it has been shown that performance on phonological and lexical-semantic tasks is compromised by imposing an interval between stimulus and response (Martin, Kohen & Kalinayk-Fliszar, 2010; Martin, 2012). Evidence that increased memory load impairs language performance has prompted some researchers to target the ability to tolerate increased memory load in language tasks as a means of improving language function as well as increasing verbal STM capacity. For example, Majerus, Van der Kaa, Renard, Van der Linden, & Poncelet (2005) treated a phonological STM deficit using delayed repetition of wor