Exploring the Effects of a Computerized Naming Intervention Combined With Cerebellar tDCS in Cantonese-Speaking Individuals With Aphasia

Aphasia is a frequent consequence of stroke, affecting about one-third of survivors and leading to significant emotional distress, functional limitations, and reduced social participation, all of which diminish quality of life. Speech-language therapy remains the primary treatment for language impairments, but its effectiveness varies considerably, and recovery is often incomplete. Non-invasive brain stimulation techniques, particularly transcranial direct current stimulation (tDCS), have emerged as promising adjuncts to therapy due to their portability, low cost, ease of use, and ability to enhance neural plasticity and cortical excitability in a polarity-dependent manner (anodal for excitation, cathodal for inhibition).

Traditionally, tDCS has targeted left-hemisphere cortical language areas, but post-stroke brain damage can disrupt current flow due to lesions and fluid accumulation. This has shifted attention to the cerebellum, which is often spared in aphasia, plays roles in linguistic and cognitive processing (especially right posterolateral regions), and connects to language networks. Despite its potential, few studies have examined cerebellar tDCS combined with language therapy for post-stroke aphasia, with existing evidence mostly from small trials in Western languages and limited data on tonal languages like Cantonese.

Additional Technical Information on the Methods

1. Study design: This study employs a randomized, double-blind, sham-controlled, crossover clinical trial design: participants randomly assigned to either the "tDCS-first" or "sham-first" group; both participants and researchers administering clinical testing and treatment blinded to the type of tDCS delivered until data analysis is concluded and, two independent study coordinators conduct the randomization and facilitate the setup for either active or sham tDCS sessions. Each treatment phase consists of five consecutive daily sessions, in which participants receive 60-minute-computerized naming treatment, with the first 20 minutes involving either active or sham tDCS. A 2-week washout period separates the two phases to minimize carryover effects.
2. Outcome measures:

Timed confrontation naming task comprising 120 picture stimuli from the Object and Action Naming Battery (OANB) using the DMDX software for data collection. Each trial starts with a central fixation point displayed for 500 ms, followed immediately by a single picture stimulus presented centrally on the screen. The stimulus remains visible until a response is detected or 5000 ms had elapsed. DMDX records an error if no response is produced within the 2000 ms time limit. The task consisted of 60 trained and 60 untrained words, matched for imageability. 3. Computerized Naming Treatment - described in "Arms and Interventions" The 60-minute computerized naming treatment was adapted to Cantonese from Fridriksson et al. and delivered using DMDX. The treatment engages all domains of lexical-semantic processing by providing auditory and visual articulatory cues. The program features 100 Cantonese picture stimuli (50 objects and 50 actions) from the OANB, 60 of which included in the outcome naming task (trained items). 4. Adverse effects questionnaire: Participants were asked about adverse effects such as pain and/or discomfort (e.g., itching, irritation, tingling, or burning) before and after each session. The Wong-Baker FACES Pain Rating Scale was used to assess any tDCS-related discomfort. 5. tDCS protocol Cerebellar tDCS was delivered using a Soterix Medical MxN High Definition tDCS Stimulator. Intervention described in "Arms and Interventions"