Aphasia is a disorder that is particularly prevalent after stroke, but it can also occur after other forms of brain injury. Aphasia impairs the production and/or comprehension of spoken, written, or gestured speech. However, in aphasia, a person’s intellect and personality typically remain intact, despite their language problems. Because it affects one’s ability to express themself, aphasia can be very disruptive to everyday life. It is estimated that between 2.5 and 4 million Americans are living with aphasia today.
A major focus of MRRI’s Language and Learning Lab, directed by Erica Middleton, PhD, is to better understand aphasia, including how the processes involved in language are disrupted after stroke and the best methods for repairing these processes. Work conducted by the Language and Learning Lab seeks to leverage a scientific understanding of fundamental learning principles to improve rehabilitation for people with aphasia.
Naming impairment – difficulty in naming familiar, everyday objects, people, places, etc. – is a major barrier to functional communication in people with aphasia. Previous research from the Language and Learning Lab has shown that practice retrieving names for things from long-term memory (retrieval practice) is generally more beneficial to future naming performance in people with aphasia compared to practice that does not involve retrieval from long-term memory (e.g., repeating the name after the clinician)1, 2, 3. Furthermore, presenting training experiences for items in ways that make retrieval more difficult actually can increase the durability of benefits from retrieval practice.4
In a recently accepted article, to appear in the journal Language, Cognition and Neuroscience, former MRRI postdoctoral fellow Abhijeet Patra, PhD, (currently at Manchester Metropolitan University, UK) along with his mentor Dr. Middleton and colleagues examined possible clinical relevance of a well-studied factor that makes naming more difficult. Specifically, when items that belong to the same semantic category (e.g., dog, cat, elephant) are presented sequentially during naming practice, the time required for naming the items increases, as does the number of naming errors. These findings have been consistent across multiple studies in both people with aphasia and people who have not experienced stroke. Drs. Patra and Middleton completed a study to examine the possibility that when people with aphasia engage in retrieval practice with more semantically-related items, their naming performance at a later naming test held the next day may improve. Indeed, they found that though greater semantic similarity was related to greater error during retrieval practice in an initial session, greater semantic similarity was also related to greater naming accuracy at the next-day naming test. This is the first study to examine and find learning benefits from grouping items semantically for naming practice in any speaker population.
From a theoretical point of view, this study provides original evidence that increasing the effort required for the retrieval of a target word by manipulating preceding semantic context affects a target word’s retrievability at a future session. Eventually, findings from this study may be applied to naming therapy for people with aphasia. Follow-up studies may ultimately suggest that items can simply be rearranged into the same semantic category versus multiple semantic categories during naming therapy to get maximal benefits from retrieval practice. However, it will be important to conduct additional studies of the effects of effortful retrieval in aphasia, to replicate this initial finding and explore the types of people with aphasia who may be more likely to benefit from organizing naming training by semantic category.