Efficacy of Low-frequency rTMS in Aphasia

In a randomized controlled trial, efficacy of low-frequency, inhibitory rTMS will be examined in rehabilitation of acquired aphasia. Two cortical sites will be targeted: Right-hemispheric homologues of Broca's and Wernicke's areas. In addition to cognitive screening prior to onset of rTMS, language assessments will be conducted before, during and after the intervention. An eyetracking-while-listening experiment will also be conducted before and after the intervention to investigate morphosyntactic processing.

Efficacy of low-frequency (1hz), inhibitory rTMS will be examined in rehabilitation of acquired aphasia. Two cortical sites will be targeted: Right-hemispheric homologues of Broca's and Wernicke's areas. In other words, right frontal and right temporal sites will be targeted. In addition to cognitive screening prior to onset of rTMS, language assessments will be conducted before, during and after the intervention. The language assessment will be conducted using the Turkish Aphasia Language Assessment Test (ADD) and sets of pictures used to assess naming performance. ADD will be carried out before and after the intervention. Six picture sets will be used, one at baseline, four on different days during the intervention, and the last one immediately after the last day of the intervention. Cognitive screening will be conducted at baseline using the digit span test and Raven's colored progressive matrices. In addition, a pre- and post-treatment eyetracking-while-listening experiment will be conducted to investigate morphosyntactic processing in Turkish and to examine whether the two brain stimulation interventions differentially affect online (dynamic, time-dependent) measures of morphosyntactic processing. The eyetracking paradigm will request the participants to listen to Turkish sentences varying in morphosyntactic complexity (canonical versus noncanonical sentences) and to look at the picture (out of two pictures presented on the screen) corresponding to the sentence they are listening to.

The participant and the outcomes assessor (speech and language therapist conducting the assessment tests and the eyetracking experiment) will be blind as to which experiment group the participant belongs to. The investigator / clinician providing rTMS will not be blind to the experimental condition.

Low-frequency (1 Hz) inhibitory rTMS will be administered to right inferior frontal gyrus with the following parameters: Frequency: 1 Hz Stimulation site: Right IFG (as determined using EEG 10-20 system) Intensity: 100% of motor threshold Dosage: 20 minutes per day Duration: 10 days over 2 weeks (no stimulation during weekends)

Low-frequency (1 Hz) inhibitory rTMS will be administered to right posterior superior temporal gyrus with the following parameters: Frequency: 1 Hz Stimulation site: Right posterior superior temporal gyrus (as determined using EEG 10-20 system) Intensity: 100% of motor threshold Dosage: 20 minutes per day Duration: 10 days over 2 weeks (no stimulation during weekends)

Baseline scores obtained from the Turkish Aphasia Language Assessment Test (ADD) Minimum score: 0 points Maximum score: 292 points Higher scores indicate a better outcome

Scores obtained from the Turkish Aphasia Language Assessment Test (ADD) at the end of the first week of treatment Minimum score: 0 points Maximum score: 292 points Higher scores indicate a better outcome

Post-treatment scores obtained from the Turkish Aphasia Language Assessment Test (ADD) at the end of the treatment Minimum score: 0 points Maximum score: 292 points Higher scores indicate a better outcome

Post-treatment scores obtained from the Turkish Aphasia Language Assessment Test (ADD) one month after the end of the treatment Minimum score: 0 points Maximum score: 292 points Higher scores indicate a better outcome

Post-treatment scores obtained from the Turkish Aphasia Language Assessment Test (ADD) six months after the end of the treatment Minimum score: 0 points Maximum score: 292 points Higher scores indicate a better outcome

Picture naming performance (number of accurately named pictures & naming latency for correctly named pictures) There are 20 pictures in total, of which half are objects and half actions. Minimum score: 0 points Maximum score: 20 points Higher scores indicate a better outcome

Picture naming performance (number of accurately named pictures & naming latency for correctly named pictures) There are 20 pictures in total, of which half are objects and half actions. Minimum score: 0 points Maximum score: 20 points Higher scores indicate a better outcome

Picture naming performance (number of accurately named pictures & naming latency for correctly named pictures) There are 20 pictures in total, of which half are objects and half actions. Minimum score: 0 points Maximum score: 20 points Higher scores indicate a better outcome

Picture naming performance (number of accurately named pictures & naming latency for correctly named pictures) There are 20 pictures in total, of which half are objects and half actions. Minimum score: 0 points Maximum score: 20 points Higher scores indicate a better outcome

Picture naming performance (number of accurately named pictures & naming latency for correctly named pictures) There are 20 pictures in total, of which half are objects and half actions. Minimum score: 0 points Maximum score: 20 points Higher scores indicate a better outcome

An eyetracking-while-listening paradigm will be used to determine proportions of dwell time on the correct picture (out of two alternatives) corresponding to auditorily presented Turkish sentences varying in morphosyntactic complexity.

An eyetracking-while-listening paradigm will be used to determine proportions of dwell time on the correct picture (out of two alternatives) corresponding to auditorily presented Turkish sentences varying in morphosyntactic complexity.

Inclusion Criteria: Right-handedness, Normal or corrected-to-normal vision and hearing, Aphasia following cerebrovascular accident, Cerebrovascular accident at least 6 months prior to enrolment in the study, Satisfying current TMS safety guidelines (Rossi et al. 2009, 2021), which are: No previous history of epilepsy, No implant (e.g., cochlear implant) or stimulator (e.g., deep brain stimulation) in the head which may interact with the magnetic field, No use of central nervous system active drugs that lower seizure threshold (as listed in the aforementioned guidelines) Exclusion Criteria: Left-handedness, ambidexterity, Impaired and uncorrected vision or hearing, No aphasia symptoms following cerebrovascular accident, Time since cerebrovascular accident less than 6 months, Violating current TMS safety guidelines (Rossi et al. 2009, 2021). In other words: Having a previous history of epilepsy, Having an implant (e.g., cochlear implant) or stimulator (e.g., deep brain stimulation) in the head which may interact with the magnetic field, Taking central nervous system active drugs that lower seizure threshold (as listed in the aforementioned guidelines)

Participants' anonymized data will be shared with the scientific community as part of open science practices. IPD refer to the data collected from the participants (language and cognitive test scores; i.e., ADD and naming performance, number/percentage of correct answers, raw and scaled scores, short-term memory scores (digit span), nonverbal intelligence scores (Raven's colored progressive matrices). IPD also include eye movements data obtained in the eyetracking experiment; i.e., proportions of dwell time on the target picture.

No access criteria required; a permanent link to the dataset will be made available so that the public can access the data (e.g., using https://osf.io/ or Mendeley Data)