Re-learning and remembering in the lesioned brain

Abstract

It is well known that re-learning language skills after a brain lesion can be very difficult. However, while learning and memory challenges have been extensively researched in amnesic individuals, very little research attention has been directed at understanding the characteristics of learning and memory that are relevant to recovery and rehabilitation of acquired language impairments. Even in the absence of damage to the medial temporal lobe regions classically associated with learning and memory, these individuals often suffer damage to frontal and other subcortical areas associated with learning and memory that may contribute to the learning challenges they face. Therefore, an understanding of the learning and memory profiles of post-stroke language impairments is important for the development and optimization of rehabilitation approaches. In two studies, we examine the degree to which certain basic characteristics of learning and memory, identified in neurotypical individuals, are intact in individuals with post-stroke language impairment. We specifically consider fundamental principles regarding the optimal spacing of learning trials that have been shown to reliably operate in neurotypical adults, across a wide range of language domains. We report on two studies that examine whether or not these principles also apply in language re-learning and retention for individuals with acquired deficits in written language production. Study 1 compared distributed vs. clustered training schedules, while Study 2 examined—for the first time in the context of re-learning—the relationship between the spacing of training trials and the retention period. This investigation revealed that, despite significant cognitive deficits and brain lesions, remarkably similar principles govern re-learning and retention in the lesioned brain as have been found to apply in neurologically healthy individuals. These results allow us to begin to integrate our understanding of recovery with the broader literature on learning and memory and have implications for the optimal organization of rehabilitation. Specifically, the findings raise questions regarding the traditional compression of rehabilitation within relatively short time windows.