Can you recall a time when you couldn’t think of the name for something? Perhaps it was a familiar object you could picture in your mind. The word was “on the tip of your tongue,” but you just couldn’t name it.
Scientists who study language call this experience the tip of the tongue phenomenon. It happens occasionally to people with healthy brains, and it seems to become more prevalent as a part of healthy aging. The phenomenon is more common and persistent for people with aphasia—a disorder arising from brain damage that affects the production or comprehension of spoken, written or gestured speech. Aphasia affects more than one million people in the U.S., most of whom have suffered a left-hemisphere stroke.
Aphasia can be quite frustrating and embarrassing for people who struggle to communicate. In addition to naming difficulties, some people with aphasia experience comprehension impairment, where hearing or reading the name of an object conveys the wrong image or meaning.
Erica Middleton, PhD, has been studying naming problems for eight years. Her last six years have been spent researching how people with aphasia can relearn and comprehend names, first as a Post-Doc at Moss Rehabilitation Research Institute (MRRI), and now as the Institute Scientist leading MRRI’s Language and Learning Laboratory.
A five year, $2.4 million grant award from the National Institutes of Health will help Dr. Middleton and colleagues conduct an exciting series of studies to develop a theory of learning needed to advance aphasia rehabilitation.
By establishing core principles for how people with aphasia overcome naming impairments, Dr. Middleton’s team will clarify how a damaged language system responds to different kinds of learning experiences, explain why and for whom familiar naming treatments work, and predict how to maximize aphasia treatment benefits.
Reconciling divergent approaches to therapy
Years ago, when Dr. Middleton reviewed published research on naming rehabilitation practices in aphasia, she noticed that it made little contact with a vast and important body of literature pertaining to principles of human learning. In fact, these two research traditions advocated contradictory practices based on different theoretical foundations.
“There are two bodies of work relevant here—one in cognitive rehabilitation, and the other in human learning,” Dr. Middleton explains, “In the rehabilitation field of speech-language pathology, there is a growing interest in ‘errorless learning’ as a therapy strategy, and it is a common technique clinically used to treat aphasia.”
The errorless learning approach to rehabilitation originated in B.F. Skinner’s behaviorism and comes from principles of learning in animals. It’s based on the idea that errors do not help the learning process. From the perspective of Hebbian learning (“Neurons that fire together, wire together”), the association between a stimulus and response is reinforced regardless of whether the response is an error.
Therefore, the errorless learning approach to naming avoids wrong answers, for fear of strengthening the link between a wrong answer and an object (such as “giraffe” for a picture of a zebra) in the patient’s mind. Instead of testing the patient’s ability to generate the correct name on their own, a therapist will provide the correct name for an object, which the patient repeats.
This contrasts with the “retrieval practice” method researched and applied in the fields of psychology and education. Within this tradition, evidence has shown that retrieval from memory enables learning.
“The principle underlying retrieval practice is that the act of retrieving the name of an object from memory is the best way to promote naming success in the future,” Dr. Middleton explains, “What’s more, research has shown that attempting and failing to retrieve a name (resulting in error) confers learning if the therapist provides the correct answer after the failed retrieval attempt. This phenomenon is known as the ‘potentiated processing of feedback.’”
Clearly, the two traditions suggest different approaches to the rehabilitation of aphasia.
Building the scientific foundation for aphasia rehabilitation
As a necessary building block for future rehabilitation research, a well-developed theory of learning is needed to reconcile and unify prior approaches to aphasia treatment.
“That’s the vision we have for MRRI’s Language and Learning Lab,” says Dr. Middleton, “We want to create a translational pipeline that can bridge the aphasia rehabilitation research tradition with basic psychological research on learning and memory.”
Dr. Middleton and colleagues want to understand the core principles of aphasia rehabilitation by looking for patterns that relate individuals’ behavioral deficits—specific problems with word processing and cognition—to how well they respond to therapies grounded in errorless learning or retrieval practice.
“It could be that different treatments work best for different people, for different impairments, or for different kinds of injuries,” Dr. Middleton says.
Lessons learned so far
With a previous research grant from the National Institute on Deafness and other Communication Disorders (NIDCD), Dr. Middleton’s team began to build the empirical foundation for their retrieval practice (RP) theory of learning for people with aphasia. Their most recent findings demonstrated that compared with errorless learning, RP conferred more persistent benefit for people with aphasia, and that treatment benefits (from both methods) were superior when training trials for an item were spaced over time.
The next phase
With this new grant award, Dr. Middleton and colleagues will take important next steps to define what types of people with aphasia benefit from RP-based naming treatments (versus other treatments), and what cognitive-linguistic characteristics predict such differential benefit. They will also apply RP principles to treat people with comprehension deficits, and develop a theoretical account of how and why RP principles impact naming.
Formalizing RP theory will bring rehabilitation and psychology researchers closer to an integrated account of language use and language change for naming.
“We know that every act of speech is an act of learning,“ Dr. Middleton says, “By better understanding how and why that is, we believe this research program can make existing aphasia treatments more principled and effective.”
In coming years, Dr. Middleton wants to generalize theories of language use and learning to help other patient populations, such as people with traumatic brain injuries and people experiencing the tip of the tongue phenomenon so common in healthy aging.
“Every time you use language, you change underlying processes in a persistent way,” Dr. Middleton explains, “It’s exciting to think that when we better understand how and why this occurs, we may be able to help all kinds of people improve their ability to communicate.”