Search Abstracts | Symposia | Slide Sessions | Poster Sessions
Behavioral and neurophysiological effects of transcranial direct current stimulation to the left inferior frontal gyrus in patients with expressive aphasia
Poster Session F, Friday, October 2, 2:45 - 4:45 pm, Wangari Maathai
Silvia Marchesotti1, Naz Doganci1,2, Camille Farcy1,3, Marion Corre2, Cynthia Dery2, Radek Ptak1,2, Adrian Guggisberg1,2; 1Network Plasticity and Modulation Laboratory, Department of Clinical Neurosciences, Faculty of Medicine, University of Geneva, Geneva, Switzerland, 2Division of Neurorehabilitation, University Hospitals of Geneva, Geneva, Switzerland, 3Clinical Research Unit, Centre Hospitalier Émile Roux, Le Puy-en-Velay, France
Neurological conditions affecting the ability to communicate are known to profoundly diminish the quality of life of patients and their caregivers. Among these, aphasia is a language disorder most commonly caused by a stroke in the perisylvian region of the left hemisphere language network, with severe word-retrieval difficulties being one of its main consequences. In recent years, transcranial direct current stimulation (tDCS) has emerged as a promising approach to improve these deficits (Marangolo, 2020; Matar et al., 2022; Ilardi et al., 2026). Similarly, in healthy individuals, our group demonstrated that anodal high-definition tDCS applied to the left inferior frontal gyrus (IFG) facilitates verb learning (Farcy et al. 2024). Importantly, this behavioral effect was accompanied by an increased functional connectivity (FC) between the left IFG and the temporo-parietal junction (TPJ), two key areas of the language network that are commonly affected in aphasia. Building upon this previous work, the present study investigated whether such naming improvement could be observed in individuals with aphasia using the same experimental approach, by means of enhanced network interactions. To do so, we conducted a randomized, sham-controlled crossover clinical trial in fourteen chronic post-stroke patients with expressive aphasia. Patients received both sham and real tDCS stimulation to the left IFG under two conditions separated by a one-month washout period. Each stimulation condition was administered twice over two consecutive days and was coupled with computerized verb learning. Resting-state electroencephalography (EEG) activity was recorded, and naming abilities were assessed using a verb-naming task and a connected speech task (Nicholas & Brookshire 1993) on the day before, the day after, and one month after the stimulation sessions. We found that tDCS significantly improved verb naming performance at the verb-naming task, and this effect generalized to both trained and untrained verbs during the computerized task. The improvement was observed immediately after stimulation but was not maintained at the one-month follow-up. In contrast, sham stimulation led to improvement only for trained verbs. Although not significant, a trend towards a positive correlation between the improvement after tDCS and baseline performance, suggested a stronger benefit of the intervention in patients with a less severe impairment. For narrative speech, verb fluency improved over time independently of stimulation condition, likely reflecting a training effect. Conversely, global fluency (words/min) decreased the day after the stimulation sessions. Other connected speech measures, such as the percentage of Correct Information Units (CIU) and informative fluency (CIU/min), did not show any significant effect due to time or stimulation condition. Preliminary resting-state analyses of global FC indicate that tDCS, compared to sham stimulation, induced changes in regions beyond those directly stimulated. These included enhanced alpha band (8–13 Hz) FC over posterior regions and a decrease in theta band (4–7 Hz) FC over the right frontal region, near the homologue of Broca’s area. Taken together, these findings suggest that tDCS applied to the left IFG may contribute to improved verb naming in chronic expressive aphasia and support the hypothesis that the underlying mechanism may involve widespread interhemispheric changes in functional connectivity.
Topic Areas: Speech-Language Treatment, Disorders: Acquired