Overnight Thalamic TES-TI to Modulate Sleep Spindles in Individuals With Schizophrenia Spectrum Disorders and Matched Healthy Controls

This single-site, single-blind, proof-of-concept feasibility study will evaluate the feasibility of overnight thalamic transcranial electrical stimulation with temporal interference (TES-TI) to modulate sleep spindle activity during N2 sleep in individuals with schizophrenia spectrum disorders (SSD) and matched healthy controls (HC). The study is investigational and is not designed or intended to provide therapeutic benefit; no treatment effect is claimed. After screening, consent, and clinical interview for individuals with SSD, participants will complete an MRI visit (T1, T2, DWI, and 10 min resting-state fMRI) for individualized montage optimization and two overnight hdEEG/PSG sessions in randomized, counterbalanced order, separated by at least two weeks: one baseline/control night with ramp-sham stimulation only, and one stimulation night. During the stimulation night, TES-TI will be delivered during stable N2 sleep in 3-minute epochs separated by 6-minute intervals, with up to 20 protocols per night, using randomized 10 Hz, 14 Hz, and carrier-only control conditions under continuous sleep-technician monitoring. Primary physiological outcomes will assess changes in spindle-frequency activity and related spindle measures relative to baseline and carrier-only control. Exploratory analyses will compare baseline spindle deficits and TES-TI responsiveness across groups and examine whether stimulation-related changes are associated with cognitive performance, assessed using the Boston Cognitive Assessment (BoCA).