Upregulating action semantics with neuromodulation and gesture observation to facilitate verb retrieval in aphasia
Although many individuals with chronic aphasia respond to language therapy, there remains a need for adjunctive interventions that can enhance treatment response. Approaches targeting multiple modalities, such as gesture cueing, and neuromodulation techniques, such as transcranial magnetic stimulation, have shown promise for supporting language recovery. The present pilot study investigated whether enhancing activation of the action semantic network could facilitate verb production in individuals with chronic aphasia. Participants were recruited as a convenience sample and completed a within-subject design in which all individuals received each condition. Two non-linguistic methods of activating the action semantic network were evaluated: (1) pantomimed gesture cues to prime action concepts and (2) intermittent theta-burst stimulation to the left posterior middle temporal gyrus (pMTG), an intact action-semantic network node in our participants. We examined individual and combined effects of gesture priming and stimulation to test whether a combined approach would yield additive or interactive benefits. Using a Bayesian generalized linear mixed-effects model, we observed a moderate interaction between gesture priming and stimulation site. Contrary to predictions, combining gesture priming with pMTG stimulation did not produce additional benefits over either intervention alone. Instead, pMTG stimulation attenuated the priming advantage observed under vertex stimulation, and gesture priming attenuated the advantage observed with pMTG stimulation alone. Posterior estimates provided substantial preliminary evidence for this interaction in our pilot sample size. These findings suggest that combined activation of the action semantic network through gesture and neuromodulation approaches may not benefit verb retrieval above and beyond each approach alone.