Brain scans find that therapy to slow stutterers’ speech changes neurological activity while increasing speaking rate, fluency, and speech naturalness.

A $3 million, six-year study [ref]Ingham, R.J., et al. Regional brain activity change predicts responsiveness to treatment for stuttering in adults. Brain & Language (2013),[/ref] used brain imaging to see neurological changes after two types of stuttering treatment. Some of the stutterers did fluency shaping stuttering therapy, in which they prolonged their vowels to slow down their speech. Other stutterers did Modifying Phonation Interval (MPI) stuttering therapy, in which they eliminated too-fast elements of speech but retained a normal speaking rate.

The results found that successful participants had decreased putamen activity. The putamen area of the brain is associated with motor learning and control. Increased activity is associated with slower, more controlled speech and decreased activity associated with faster, more natural speech.

Twenty-two adults who stutter were divided into two therapy groups:

Treatment success was measured with, first, zero stuttering in the speech clinic, including three minutes oral reading, three minutes monologue, and a three-minute telephone conversation with a friend. Next, zero stuttering was required in beyond-clinic speaking tasks, including a conversation with a friend, a telephone call to a business, and “a self-selected task that the participant identified as a personally problematic speaking task.” The beyond-clinic speaking tasks had to be completed in a single day.

The average duration of the treatment programs was eight weeks (ending with in-clinic tests). Completing the beyond-clinic speaking tasks successfully required on average another 27 weeks.

Speech was also measured during four brain scans. For the successful participants and for seven or eight of the unsuccessful participants, stuttering diminished 85-90%, speaking rate increased 14-21%, and speech naturalness increased 80-100%. Two or three unsuccessful participants had much worse results (one went to prison and another had domestic violence issues).

The brain scans found decreased activity in the left putamen for the successful participants, and no change for the unsuccessful participants. The putamen is involved (for non-stutterers) in “the initiation and execution of speech” and for “suppressing unintended [speech] responses.” Also, the putamen is “more activated for slower (more controlled) speech production.” Another study found that “repeating a short phonated utterance at different rates” associated decreased putamen activity with faster speaking rates.

Decreased activity was also seen in the left claustrum. This brain area is next to the putamen yet little is known about it. It may be one of the routes of speech production between Wernicke’s and Broca’s areas.