Implicit learning and implicit treatment outcomes in individuals with aphasia

Abstract

Background: Implicit learning is a process of learning that occurs outside of conscious awareness and may be involved in implicit, exposure-based language training. However, research shows that implicit learning abilities are variable among individuals with aphasia, and it remains unknown whether individuals who show basic implicit learning abilities also benefit from implicit language training.

Aims: The aims of this series of experiments were to test implicit learning in individuals with agrammatic aphasia, examine the effects of a novel implicit language treatment, and investigate whether individuals with aphasia who show implicit learning ability also benefit from implicit treatment focused on passive sentence comprehension.

Methods & procedures: Nine participants with chronic agrammatic aphasia and 21 neurologically intact participants completed a visuomotor serial reaction time test of implicit learning (Experiment 1). The participants with aphasia also completed a short-term novel implicit sentence comprehension treatment (Experiment 2) that consisted of five sessions of repeated exposure to grammatically correct passive sentences and matching photographs. Sentence comprehension was tested in multiple baseline sessions and on each day of training using a sentence-picture matching task. The relation between participants' learning patterns across experiments was also examined.

Outcomes & results: Individuals with agrammatic aphasia as well as neurologically intact adults demonstrated significant implicit sequence learning in the serial reaction time task. However, the participants with aphasia did not show concomitant improvement in sentence comprehension as a result of the implicit treatment protocol.

Conclusions: This study suggests that individuals with agrammatic aphasia demonstrate implicit learning ability; however, this ability does not necessarily promote successful outcomes in treatment that is based solely on implicit training methods.

Keywords: agrammatic aphasia; implicit learning; implicit treatment; sentence comprehension; serial reaction time task.

Figures

Figure 1

Average standardized reaction time (1a) and percent accuracy (1b) across the seven blocks of the SRTT for the group of individuals with aphasia and the group of neurologically intact adults. Bars indicate one standard error above and below the mean. Implicit sequence learning in this paradigm is indicated by significantly higher reaction time in the final random block (Block 7) compared to the preceding sequenced block (Block 6).

Figure 2

Percent correct performance on the sentence comprehension test for passive sentences with trained verbs (“Trained Passive”) and passive sentences with untrained verbs (“Untrained Passive”) for each participant in Experiment 2a. Chance performance is 50% correct. Missing data for training sessions 2-4 for P5 are due to technical errors on those days.

Figure 3

Percent correct performance on the sentence comprehension test for passive sentences with trained verbs (“Trained Passive”) and passive sentences with untrained verbs (“Untrained Passive”) for each participant in Experiment 2b. Chance performance is 50% correct. Tests administered immediately prior to and after each session of the training phase included only trained passives. Vertical lines show changes in accuracy within days, and horizontal or diagonal lines show changes in accuracy across days.