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.

Artificial grammar learning in vascular and progressive non-fluent aphasias

“…Clearly our study does not provide evidence that such a therapy would be more efficacious than existing methods for addressing asyntactic deficits after stroke, nor do we have any evidence of how well our strategies would work within an already-learned but now-impaired natural language. Indeed, a recent small study of nine patients who had chronic agrammatic aphasia secondary to stroke suggests that implicit learning alone (on a visuo-motor serial reaction time task) does not necessarily translate into improved real-world performance ( Schuchard et al, 2017 ). Larger scale trials and assessment with other tasks are clearly required in more acute disease cohorts.…”

Sequential learning in individuals with agrammatic aphasia: evidence from artificial grammar learning

“…Individuals with agrammatic aphasia show sequential learning in SRT tasks (Dominey et al, 2003; Goschke et al, 2001; Schuchard et al, 2017; Schuchard & Thompson, 2014), although they may be impaired in learning certain types of sequences (Goschke et al, 2001) or in learning the abstract underlying structures of sequences (Dominey et al, 2003). In contrast, Christiansen et al (2010) found no evidence of sequential learning in a group of seven agrammatic individuals who were exposed to an artificial grammar composed of visual shapes.…”

“…However, studies examining sequential learning in people with agrammatic aphasia have shown mixed results. Several studies using serial reaction time (SRT) tasks, in which participants respond to a repeating sequence of stimuli, have shown evidence of sequential learning (Dominey et al, 2003; Goschke, Friederici, Kotz, & van Kampen, 2001; Schuchard, Nerantzini, & Thompson, 2017; Schuchard & Thompson, 2014). In contrast, artificial grammar learning studies, in which participants make judgments after exposure to multiple sequences of stimuli that follow an underlying rule structure, have shown abnormal learning ability in agrammatic aphasia (Christiansen et al, 2010; Zimmerer, Cowell, & Varley, 2014).…”

“…One strategy for aphasia treatment involves repeated exposure to linguistic stimuli to maximise correct responding during training (Fillingham, Hodgson, Sage, & Lambon Ralph, 2003), but purely exposure-based training is not always efficacious for relearning sequential linguistic stimuli, such as complex sentence structures (Schuchard et al, 2017). Knowledge of aphasia symptom profiles that are associated with exposure-based sequential learning abilities may help identify individuals who will benefit from this type of language training.…”

Implicit-statistical learning in aphasia and its relation to lesion location

“…These are the same anatomical regions that are activated during ISL tasks. This anatomical convergence has motivated a wealth of research that seeks to examine whether the syntactic impairment in Broca's aphasia might stem from a deficit in domain-general ISL mechanisms, rather than from a selective impairment to the syntax module (Cope et al, 2017;Dominey et al, 2003;Goschke et al, 2001;Schuchard and Thompson, 2013;Schuchard et al, 2016;Zimmerer et al, 2014). The majority of the aforementioned research has shown that patients with Broca's aphasia manifest impaired ISL abilities (but see Cope et al, 2017), which was suggested to support the hypothesis that ISL mechanisms play a prominent role in syntactic processing.…”