Interview With Dr. Nadine Martin of Temple University

Dr. Martin’s research focuses on questions about the architecture of lexical retrieval processes and their relation to verbal STM processes. Her studies of people with and without aphasia include analysis of patterns of word retrieval errors, effects of memory load on language abilities and effects of language impairment on verbal learning. Data from these behavioral studies coupled with evidence from computational modeling provide support for a theory of lexical processing that assumes interaction of semantic and phonological representations and short-term maintenance processes that keep representations active over the time course of lexical retrieval. Based on this theory, Dr. Martin has developed diagnostic tools and treatment protocols for impairments of word processing and verbal short-term memory.

Note: You should consult with your doctor or speech pathologist for recommendations on treatment. The views and opinions expressed in this article are those of Dr. Martin and do not necessarily reflect the official policy or position of SpeechPathologyMastersPrograms.com

How did you become interested in aphasia and word retrieval?

My career began working with children, especially children with neurologically based communication disorders. I was working for a collaborative of school systems outside Boston in the late 1970s. They had established several programs for children and teenagers with neurogenic communication disorders. I was always interested in the brain and especially how language and cognitive processes were organized in the brain. Boston was a good place to be in this regard, as it was a vibrant center of research in the neurosciences. During this time, Norman Geschwind was at the Boston VA hospital and was teaching at one of the medical schools in Boston. My roommate and I learned that it was possible to audit his course on brain and behavioral relationships and somehow, we managed to get permission to do this. This experience was transformative for me. Dr. Geschwind was an amazing and inspiring teacher.  He presented case studies and ideas that were new and exciting to me. I decided soon after this course to take the first opportunity that came along to work with people with aphasia or other acquired neurogenic disorders. The opportunity came within in a year. I took a position in New Jersey in an adult rehabilitation hospital and later took a part time position at Stockton College. I wanted to go back to school but wasn’t sure whether I wanted a medical degree or a Ph.D. During this time, I had heard of the work on aphasia by Eleanor Saffran and Myrna Schwartz (in Philadelphia). Making a long story short, I went to a talk by Dr. Schwartz, who was at UPenn. I spoke with her after the talk about my interests and learned that a research assistant position was open in Dr. Saffran’s lab. This wasn’t graduate school, but it was a golden opportunity to get research experience in the neuropsychology of language and studies of aphasia. I would say at this point, I was quite settled on a research career focusing on aphasia.

How did you get interested in word retrieval?  

Dr Saffran studied many topics in neuropsychology and in aphasia. While working in Dr. Saffran’s lab, I enrolled in Temple’s doctoral program in Experimental Cognitive Psychology. At this time (early 1980s) the psychology department did not favor doing neuropsychological research. I needed to find a topic for my research that related to my interests, but also fell within the scope of language in typical speakers. I chose normal speech errors as my topic and discovered there was quite a large literature on this. Fascinating. About this time, Dr. Saffran and Dr. Schwartz were beginning a collaboration with Gary Dell from the University of Illinois. Dr. Dell’s work was in normal language processing and much of his research began with the study of normal speech errors. The collaboration among these three amazing scientists was to apply Gary Dell’s model of word processing to an account of word retrieval difficulties in aphasia. I was still working in Dr. Saffran’s lab and so, was involved to some extent in theses studies. I also had the opportunity to share my dissertation research in normal speech errors with Dr. Dell.  These experiences all came together as strong influences on my interest in word retrieval.

What have you learned about the relationship of word processing and short-term memory (STM)?  

I could write a book about what I’ve learned about this relationship and another book about all there is still to know. Short-term memory processes support all our sensory systems. There may be a domain general STM system that governs cognition globally. However, I firmly endorse the view that there are domain specific short-term memory systems that mediate the temporal course of processing in specific sensory systems (e.g., visual, auditory). Thus, I view the auditory-verbal system as being supported by a short-term retention process specific to verbal representations (both input and output processing). I view this as a form of short-term memory that is integrated with processing of sounds, word forms, and word meanings and which is necessary to maintain the activation of these representations of words over the course of completing any language task. This includes verbal span tasks which is one type of task we use to measure verbal STM capacity. It just so happens that verbal spans are language tasks and like all language tasks, the phonological, lexical and semantic representations of the words being accessed and retrieved need to be kept active until that task (whether it be comprehension, production or repetition) is complete. This short-term maintenance function is essential to language processing. This idea extends our understanding of the nature of impairment in aphasia. That is, the language impairment in aphasia affects the activation strength and short-term maintenance of activated representations of language. It is this domain-specific form of short-term memory, specifically verbal STM, that is impaired in aphasia and affects performance on language tasks including verbal span tasks.  

How has what we have learned about word retrieval improved outcomes for aphasia patients?

We know a lot more about how words are processed. This window into the dynamics of word access and retrieval informs us about how to manipulate the dynamics of our verbal input to facilitate word processing. What I mean is that we understand more about variables that make processing words easier or more difficult. This knowledge can be used to help us choose the right stimuli in priming tasks, for example to promote restoration of connections between phonological-lexical and semantic representations. We are working with linguistic representations of words, but that knowledge is not lost. Rather, the ability to access or retrieve that knowledge to support word processing is what is impaired in aphasia. So, how we choose to facilitate word retrieval is important. Some factors may get in the way, while others facilitate. These sorts of dynamics of processing are important for us to understand and incorporate in our approaches to treatment.  A recent example comes from a treatment study in my lab (McCarthy, Kohen, Kalinyak-Fliszar and Martin, 2017) in which we tested an important assumption of the interactive activation mode of word retrieval (Dell, 1986), that naming and repetition of words are influenced by feedforward and feedback activation of semantic and phonological representations of words. We developed a treatment for someone with phonological dysphasia who was not able to repeat abstract (or low image) words. She demonstrated imageability effects in repetition, which is common in phonological dysphasia (in classical aphasia typology, conduction aphasia). We know that abstract words are supported more by phonological activation relative to activation from their semantic representations. High image words, on the other hand receive stronger support form semantics. Their semantic representations are perceptually rich, e.g., color, form, texture, action-specific features. Abstract or low image words are not so semantically rich. To facilitate activation of an abstract word such as “occasion”, we added a modifier that enriched the imageable context of that word “formal occasion”. Just adding the modifier, created a context in which it was easier for our therapy participant to access and retrieve the word “occasion”. Eventually, through much practice of words and modifier – noun pairs such as this, the therapy participant was able to retrieve the abstract words more reliably without the context of the semantically enriching modifier-noun phrase. The model’s assumptions, along with empirical evidence to support this model, guided the choice of stimuli and task to bolster the semantic input to the abstract words’ activations and allow for a successful episode of retrieval. With more successful episodes like this, it was predicted that activation of these words would become stronger and more reliable. This is what we observed.

What do we still need to know to continue to improve these outcomes?

We need to understand more about how brain damage affects processing of words and sentences and how our treatment methods (e.g., priming, cueing, metalinguistic tasks, etc.) interact with processing in the normal brain and  in the damaged brain.

We need to learn more about “learning processes” and how these relate to treatment. For example, we should be knowledgeable about principles of learning and incorporate some of these principles into our treatment approaches.

We need to find effective ways to connect our direct impairment-based approaches to treatment with functional communication activities, e.g., discourse level processing, conversation.

These are just a few areas to consider.

Are there obstacles to implementing current aphasia treatment protocols?

Yes. Many. We all know that time spent with clients in busy hospital and rehab settings is quite limited. It is difficult to gain a diagnosis that is sufficiently refined to develop a treatment protocol that is effectively addressing a person’s specific problem in language function.  

Relative to this, it is important that our developments of new treatments for aphasia emphasize basic principles that underscore the effects of the treatment. If the strict adherence to a protocol cannot be maintained in the context of a busy clinical practice environment, a clinician can be creative in applying the basic principles of the treatment in tasks that can be accomplished in the clinic or in a home program developed for the client.

It is also of critical importance to promote functional communication abilities of our clients. This goal should not necessarily be separate form improving specific language skills. In fact, it is better to address both and to relate the direct impairment-based therapies to functional communication activities.

How do you decide on new research projects?

Much of my research involves understanding the theory behind word processing and verbal STM and then applying this to the development of diagnostic and treatment protocols. The outcomes of those treatment studies also act as a test of the theories from which they were developed. This broad aim to connect theory with diagnosis and treatment does guide my choice of projects. I also am interested in learning abilities in aphasia, so this is another broad domain in which I identify projects to work on.

What aspect of your work are you most proud of?  

I am very pleased that my early research establishing evidence for a theory of the relation of short-term memory and language processing is at a point where I can apply this theory to the development and testing of diagnostic and treatment protocols for people with aphasia

What is your advice for graduate SLPs?

Remember that you are a clinician and a clinical scientist. Speech-language pathology is a science. It is also a profession that values its compassion for the clients we serve. Both elements of our profession must be drawn on to be effective clinicians. Learn the theories and basic principles that guide development of treatments. Understand the cognition and neural basis of language, learning and recovery. These basic tools are necessary to develop both direct impairment-based treatment approaches as well as effective means of generalization to functional communication. Be sensitive to the needs of your clients, always. Often, people want to work directly on their communication abilities, and that is important. At the same time this component of treatment must be coupled with opportunities to learn how to communicate effectively with their residual language abilities and other means of communication (e.g., gestures, expressions etc.). Involve your client’s significant others in the rehabilitation program.  Communication is not a singular activity. An important overall goal of treatment is to help someone achieve their functional communication goals. Your knowledge, combined with an openness to understanding your client’s communication needs and goals, will help you achieve this goal.

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