One-third of stroke survivors experience deficits in word retrieval as a core characteristic of their aphasia, which is frustrating, socially limiting and disabling for their professional and everyday lives. The, as yet, undiscovered ‘holy grail’ of clinical practice is to establish a treatment that not only improves item naming, but also generalizes to patients’ connected speech. Speech production in healthy participants is a remarkable feat of cognitive processing being both rapid (at least 120 words per minute) and accurate (∼one error per 1000 words). Accordingly, we tested the hypothesis that word-finding treatment will only be successful and generalize to connected speech if word retrieval is both accurate and quick. This study compared a novel combined speed- and accuracy-focused intervention—‘repeated, increasingly-speeded production’—to standard accuracy-focused treatment. Both treatments were evaluated for naming, connected speech outcomes, and related to participants’ neuropsychological and lesion profiles. Twenty participants with post-stroke chronic aphasia of varying severity and subtype took part in 12 computer-based treatment sessions over 6 weeks. Four carefully matched word sets were randomly allocated either to the speed- and accuracy-focused treatment, standard accuracy-only treatment, or untreated (two control sets). In the standard treatment, sound-based naming cues facilitated naming accuracy. The speed- and accuracy-focused treatment encouraged naming to become gradually quicker, aiming towards the naming time of age-matched controls. The novel treatment was significantly more effective in improving and maintaining picture naming accuracy and speed (reduced latencies). Generalization of treated vocabulary to connected speech was significantly increased for all items relative to the baseline. The speed- and accuracy-focused treatment generated substantial and significantly greater deployment of targeted items in connected speech. These gains were maintained at 1-month post-intervention. There was a significant negative correlation for the speed- and accuracy-focused treatment between the patients’ phonological scores and the magnitude of the therapy effect, which may have reflected the fact that the substantial beneficial effect of the novel treatment generated a ceiling effect in the milder patients. Maintenance of the speed- and accuracy-treatment effect correlated positively with executive skills. The neural correlate analyses revealed that participants with the greatest damage to the posterior superior temporal gyrus extending into the white matter of the inferior longitudinal fasciculus, showed the greatest speed- and accuracy treatment benefit. The novel treatment was well tolerated by participants across the range of severity and aphasia subtype, indicating that this type of intervention has considerable clinical utility and broad applicability.
CORE (COnnecting REpositories)
CORE (COnnecting REpositories)