Stability of Temporal Processing Effects in Aphasia

The interactive activation model attributes the language impairment in aphasia to disruption of two temporal components of lexical activation: (a) transmission, which determines how quickly activation spreads through the language system, and (b) maintenance, which controls the rate at which activation decays. Breakdowns in temporal processing in people with aphasia (PWA) are revealed when language tasks include response delays. People with slow transmission perform relatively better when provided with extra time, while those with maintenance failures perform worse after a response delay. The purpose of this study was to determine if the changes in accuracy caused by response delays were evidence of stable temporal processing effects or simply random fluctuations in performance.

We collected naming and repetition data from eight PWA and 10 neurotypical controls. Items presented were then followed by a 1-, 5-, or 10-s response delay. Data were collected for each item at multiple timepoints to assess stability of temporal processing effects.

We used logistic mixed-effects models to regress accuracy on response interval separately for each participant with a random slope for delay by date to establish stability of the effects across sessions. Eleven of the 12 temporal processing effects in PWA and six of the eight in controls were stable over multiple days of testing.

Our results showed that temporal processing effects were stable for most PWA and controls. Additionally, temporal processing effects interacted with task and specific interval condition. Patterns of performance and implications are discussed.