Here we outline the main findings from recent FTD center publications. Learn more about our research in easy to digest terms!
In this issue, we are highlight a recent 2018 publication (“Longitudinal changes in semantic concreteness in semantic variant primary progressive aphasia”) from FTDC post-doctoral fellow, Katie Cousins. Great work, Katie!
Background: What we already knew
- Previous work has shown that patients with svPPA demonstrate severe loss of concrete noun knowledge. For example, patients with svPPA may struggle to identify that a particular tool is a screwdriver or a particular animal is a pelican. You may notice that they use more “empty” speech, using words like “thing” or “that.”
- Impaired noun knowledge and decreased use of nouns is linked to damage to the ventral temporal lobe– a region of the brain important for representing visual features of concrete objects.
- Unlike concrete concepts, abstract concepts (e.g. “truth”, “love,” or “justice”) tend to be relatively preserved in svPPA.
Question: What we wanted to know
- Why do some svPPA patients show more or less severe concrete noun impairment?
- How does concreteness of patient speech change over time, as disease progresses?
Findings: What this study shows
- Cousins and colleagues collected brief speech samples of svPPA patients describing a picture at two different time points (at least 1 year apart). Patients also underwent structural MRI imaging of the brain.
- All nouns in the speech samples were scored for concreteness on a scale of 1-5 using previously published ratings (where 1=abstract, and 5=concrete). Examples of the concreteness of nouns produced by patients include way (2.34), distraction (2.46), time (3.07), stuff (3.13), story (3.3), home (4.11), mother (4.5), stool (4.9), cookie (5), and water (5). The average concreteness of nouns produced was calculated for each subject.
- Statistical analyses shows that noun concreteness decreases significantly as disease progresses in svPPA. The same was not true in a comparison group of patients with bvFTD, whose speech remained highly concrete throughout the testing period.
- Cortical thinning is a quantitative measure of brain cell integrity in the outer layers of the brain, and thinner cortex indicates greater cell loss. Analyses of MRI imaging data indicates that cortical thinning in the ventral portions of the temporal lobe contributes to declining concrete noun production over time in svPPA.
Conclusions: What this study means
- This study has implications for patients and caregivers who must develop strategies for communication in the face of progressive semantic impairment.
Future Directions: What are the next steps
- This study only examined speech production at two timepoints. Future work should examine if deficits in abstract noun production also emerge in svPPA at even later stages of disease.
- Therapeutic studies in svPPA (and other forms of PPA) are underway to promote retention of concrete concepts (typically objects and words frequently used in daily life and needed for functional communiation) despite disease progression and the worsening symptoms.
Want to learn more? Check out Katie’s paper here!