Abstract
See Thompson and Woollams (doi:10.1093/brain/awx264) for a scientific commentary on this article. Previous research with aphasic patients has shown that picture naming can be facilitated by concurrent phonemic cueing [e.g. initial phoneme(s) of the word that the patient is trying to retrieve], both as an immediate word retrieval technique, and when practiced repeatedly over time as a long-term anomia treatment. Here, to investigate the neural mechanisms supporting word retrieval, we adopted—for the first time—a functional magnetic resonance imaging task using the same naming procedure as it occurs during the anomia treatment process. Before and directly after a 6-week anomia treatment programme, 18 chronic aphasic stroke patients completed our functional magnetic resonance imaging protocol—a picture naming task aided by three different types of phonemic cues (whole words, initial phonemes, final phonemes) and a noise-control condition. Patients completed a naming task based on the training materials, and a more general comprehensive battery of language tests both before and after the anomia treatment, to determine the effectiveness and specificity of the therapy. Our results demonstrate that the anomia treatment was effective and specific to speech production, significantly improving both patients’ naming accuracy and reaction time immediately post-treatment (unstandardized effect size: 29% and 17%, respectively; Cohen’s d: 3.45 and 1.83). Longer term gains in naming were maintained 3 months later. Functional imaging results showed that both immediate and long-term facilitation of naming involved a largely overlapping bilateral frontal network including the right anterior insula, inferior frontal and dorsal anterior cingulate cortices, and the left premotor cortex. These areas were associated with a neural priming effect (i.e. reduced blood oxygen level-dependent signal) during both immediate (phonemically-cued versus control-cue conditions), and long-term facilitation of naming (i.e. treated versus untreated items). Of note is that different brain regions were sensitive to different phonemic cue types. Processing of whole word cues was associated with increased activity in the right angular gyrus; whereas partial word cues (initial and final phonemes) recruited the left supplementary motor area, and right anterior insula, inferior frontal cortex, and basal ganglia. The recruitment of multiple and bilateral areas may help explain why phonemic cueing is such a successful behavioural facilitation tool for anomia treatment. Our results have important implications for optimizing current anomia treatment approaches, developing new treatments, and improving speech outcome for aphasic patients.
Highlights
Anomia—the inability to retrieve words an individual wants to say—is the most common symptom of aphasia post-stroke, often regardless of severity and lesion location (Goodglass, 1993; Crinion and Leff, 2007)
We investigated whether the different auditory cuetypes that contained varying amounts of phonemic/semantic information—i.e. whole words, initial phonemes, final phonemes—had a differential effect on brain activity during picture naming, considering that differential behavioural effects of cue-types were identified in terms of naming accuracy and reaction time (RT) between them (Fig. 3C and D)
Relationship between naming performance and brain activity As a final step, we investigated whether and how individual patients’ change in brain activity (BOLD response: Experiment 2) following anomia treatment was related to their change in free-naming performance (Experiment 1)
Summary
Anomia—the inability to retrieve words an individual wants to say—is the most common symptom of aphasia post-stroke, often regardless of severity and lesion location (Goodglass, 1993; Crinion and Leff, 2007). In the case of speech production, the contribution of language homologue areas in the right hemisphere and the direction of these effects (i.e. increase versus decrease of task-dependent activation) remains hotly debated, with respect to whether right frontal cortices—including Broca’s area homologue—play a beneficial (Blasi et al, 2002; Crinion and Price, 2005) or detrimental (Naeser et al, 2005; Winhuisen et al, 2005) role in recovery Accompanying these functional brain changes within the language network itself (e.g. left inferior frontal and superior temporal cortices, as in Fridriksson et al, 2012), are reported changes in additional non-language cognitive networks (Fridriksson et al, 2007; van Hees et al, 2014), leading some authors to propose that successful aphasia ( speech) treatment requires recruitment of both language and domain-general networks to facilitate recovery (Vitali et al, 2007; Fridriksson, 2010; Rochon et al, 2010; Abel et al, 2014, 2015; Brownsett et al, 2014)
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