Language and neurodegenerative diseases

While much of my work has focused on how language may change in healthy aging, I am also very interested in the effects that neurodegenerative diseases have on language outcomes.

In a handful of studies, we have investigated the extent to which individuals with Parkinson’s disease differ in their language abilities from healthy control participants. Interestingly, while for some aspects of language there are virtually no differences between healthy participants and the patient group (e.g., irregular verb forms and words unrelated to movement), individuals with Parkinson’s disease do show impairments in other domains of language (such as syntax/grammar, regular verb forms, and words related to movement). What is more, the magnitude of these differences appears to be impacted by different factors. For example, we found striking sex differences (with women being able to compensate for some impairments, likely thanks to their better memory), as well as effects of disease severity (with greater language impairments the more the disease had progressed) and of how recently a participant had taken their medication (with fewer deficits soon after having taken levodopa, the most commonly used type of medication).

In future studies, I plan to extend my work to forms of neurodegeneration, including Mild Cognitive Impairment and Alzheimer’s disease.

Relevant research (including the studies mentioned above):

• Reifegerste, J., Estabrooke, I. V., Russell, L. E., Veríssimo, J., Johari, K., Wilmarth, B., Pagan, F., Moussa, C., & Ullman, M. T. (2020). Can sex influence the neurocognition of language? Evidence from Parkinson’s disease. Neuropsychologia, 148, 107633. https://doi.org/10.1016/j.neuropsychologia.2020.107633

• Johari, K., Walenski, M., Reifegerste, J., Ashrafi, F., & Ullman, M. T. (2019). Sex, Dopamine, and Hypokinesia: A Study of Inflectional Morphology in Parkinson’s Disease. Neuropsychology, 33(4), 508–522.

• Johari, K., Walenski, M., Reifegerste, J., Ashrafi, F., Behroozmand, R., Daemi, M., & Ullman, M. T. (2019). A dissociation between syntactic and lexical processing in Parkinson’s disease. Journal of Neurolinguistics, 51(March), 221–235. https://doi.org/10.1016/j.jneuroling.2019.03.004