Treating lexical retrieval using letter fluency and tDCS in primary progressive aphasia: a single-case study

Area of Science:

• Neuroscience
• Neurology
• Speech and Language Pathology

Background:

• Individuals with Primary Progressive Aphasia (PPA) often experience early language symptoms not detected by standard tests.
• Early intervention is crucial for managing the progressive nature of PPA.

Purpose of the Study:

• To investigate the efficacy of letter fluency therapy (LeFT) combined with transcranial direct current stimulation (tDCS) for improving lexical retrieval in logopenic PPA (lvPPA).
• To compare the effects of tDCS targeting the left inferior frontal gyrus (IFG) versus the left inferior parietal lobe (IPL).

Main Methods:

• A single case study of an lvPPA patient.
• Two therapy phases involving LeFT with anodal tDCS to either left IFG or left IPL, separated by a 3-month washout period.
• Assessment of word retrieval during letter fluency tasks and picture-naming tasks.

Main Results:

• LeFT with anodal tDCS increased word retrieval for both trained and untrained letters.
• Left IFG stimulation resulted in the retrieval of lower-frequency words and words with a higher age of acquisition.
• Untrained picture-naming tasks showed increased accuracy and response times with left IFG stimulation.

Conclusions:

• LeFT combined with anodal tDCS is an effective strategy for enhancing lexical retrieval in lvPPA.
• Left IFG stimulation appears particularly beneficial for improving word retrieval quality.
• The therapy shows generalization effects, suggesting potential for treating mild anomia.