From The Aphasia Center at Steps Forward blog.

This treatment has been used thus far to examine naming in aphasia, apraxia treatment, and language recovery. Current studies in Italy have used this treatment for 20 minutes daily for 10 non-consecutive days, showing that clients keep the trained skills weeks to months after training. We use this treatment daily for 4-8 weeks while providing another 4 hours of treatment with great results thus far. It is unknown at this time what the best brain areas are for treatment, how long the best treatment lasts, how long the results last, and the optimum number of treatment sessions. Each person’s brain is set up slightly differently, so stimulating one area may have different effects for different people. This treatment is only offered to intensive program clients at this time since treatment/training must accompany stimulation and our results have all been from intensive clients.