Speech recovery after a stroke

Introduction: Damage to Broca's area, in the left frontal lobe, often leaves people able to understand language but struggling to produce it. In this study, researchers followed one man through six months of speech therapy after a stroke and looked for changes in his brain activity as his speech changed.

Participant: The participant, called R.T. in the report, is a 61-year-old right-handed man and retired bus driver whose only language is English. Seven weeks before the study began, he had a stroke that damaged tissue in his left frontal lobe, including Broca's area. Before the stroke, his speech was fluent. At the start of the study, he understood spoken sentences well, but his speech was slow and effortful and made up mostly of two- or three-word phrases.

Method: The hospital's institutional review board approved the study, and R.T. gave written informed consent. To protect his privacy, the report uses only his initials and leaves out his hometown and other identifying details. R.T. attended three 45-minute speech therapy sessions per week for 24 weeks. Every 4 weeks, he described three standard pictures (for example, a busy kitchen scene) while being audio-recorded. Two trained raters, who did not know which week each recording came from, counted the correct content words he produced per minute. Correct content words were meaningful nouns, verbs and adjectives that accurately described the picture. His score for each testing week was the mean of his three picture descriptions.

At week 0 and again at week 24, R.T. had a functional MRI (fMRI) scan while silently naming pictures of everyday objects.

Results and Discussion: R.T.'s speech production rose steadily across the 24 weeks (see Table 1), and his understanding of spoken sentences stayed high throughout. For comparison, adults of a similar age with no brain injury averaged 45 correct content words per minute on the same picture task. In the week 0 scan, activity during naming was weak and limited mostly to undamaged parts of the left hemisphere. In the week 24 scan, there was stronger activity in left-hemisphere tissue surrounding the damaged area and in the matching region of the right frontal lobe. The researchers concluded that R.T.'s brain appeared to have reorganized so that other areas took over some of the damaged area's work. They noted that some recovery after a stroke happens without therapy, so this study cannot show how much of R.T.'s improvement the therapy itself caused.