Rehabilitating and Decelerating Language Loss in Primary Progressive Aphasia With tDCS Plus Language Therapy

Primary Progressive Aphasia (PPA) is a debilitating disorder characterized by the gradual loss of language functioning, even though cognitive functioning is relatively well preserved until the advanced stages of the disease. There are three main PPA variants classified based on the pattern of language impairments and areas of atrophy, but anomia is present across all variants in the earliest stages. While there is a significant amount of research investigating multiple treatment approaches for individuals with aphasia resulting from stroke, individuals with PPA have far fewer treatment options to choose from. Recently, a growing body of literature of treatment in stroke-based aphasia have found promising results for pairing traditional language therapy with non-invasive neurostimulation via transcranial direct current stimulation (tDCS). The small amount of studies of the effects of tDCS applied to left inferior frontal gyrus (IFG) in PPA also yield promising results that show tDCS can enhance generalization to untreated structures. Research in stroke-based aphasia has also shown that language outcomes significantly improve when participants are treated with more complex language stimuli, because this treatment approach results in enhanced generalization. For example, therapy that has participants build sentences around verbs has been found to improve word-level verb and noun naming. The current proposal aims to investigate whether combining the benefits of tDCS while providing verb retrieval therapy that uses sentence building to improve word-level retrieval deficits, will enhance word retrieval deficits in PPA and slow the loss of language functioning. It is hypothesized that Furthermore, the proposed study will investigate the atrophy patterns at baseline, to determine which atrophy patterns are predictive of improved word retrieval. Specifically, this proposal aims: 1) to determine whether tDCS to left IFG coupled with therapy promoting verb retrieval within sentences improve noun and verb retrieval in treated and untreated items in individuals with PPA, and 2) To investigate which patterns of atrophy are predictive of maintenance and generalization of word-retrieval in individuals with PPA following tDCS+therapy vs. sham+therapy. This proposed research will allow the investigators to evaluate the potential benefits and sustainability of tDCS in PPA, the generalization of trained items to untrained items, as well as the deceleration of language loss.

Inclusion criteria

• Diagnosis of PPA, based on the PPA criteria and presence of naming deficits
• Capable of giving informed consent or indicating another to provide informed consent
• 18 years of age to 100 years of age..

Exclusion criteria

• Did not speak English before the age of five
• Less than 10 years of education
• Severe naming deficits
• Significant history of drug or alcohol abuse
• History of psychiatric or neurological problems affecting the brain (besides PPA)
• Has experienced seizures during the previous 12 months
• History of brain surgery or any metal in the head
• Uncorrected visual loss or hearing loss by self-report
• Use of medications that lower the seizure threshold (e.g., methylphenidate) or use of N-Methyl-D-aspartate (NMDA) receptor antagonists (e.g., memantine)
• Scalp sensitivity (per participant report)