Impact of transcranial electrical stimulation on simultaneous stereoelectroencephalography recordings: A randomized sham-controlled study

• Published in: Clinical neurophysiology Vol. 166; pp. 211 - 222
• Main Authors: Simula, Sara, Makhalova, Julia, Pizzo, Francesca, Garnier, Elodie, Damiani, Giada, Mercadal, Borja, Chiara Biagi, Maria, Salvador, Ricardo, Medina-Villalon, Samuel, Ruffini, Giulio, Wendling, Fabrice, George Bénar, Christian, Bartolomei, Fabrice
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.10.2024; Elsevier
• Subjects: Adolescent; Adult; Bioengineering; Brain - physiology; Brain - physiopathology; Electroencephalography - methods; Epilepsies, Partial - physiopathology; Epilepsies, Partial - therapy; Epilepsy; Female; Functional connectivity; Humans; Life Sciences; Male; Middle Aged; Neurology; SEEG; Transcranial Direct Current Stimulation - methods; Transcranial electrical stimulation; Young Adult; Functional connectivity; PSD; EF; tES; Epilepsy; tACS; IED; Transcranial electrical stimulation; AUC; SEEG; tDCS; DRE; FC; epilepsy; Area Under the Curve; Power Spectral Density; transcranial Alternating Current Stimulation; Interictal Epileptiform Discharges; functional connectivity; transcranial Direct Current Stimulation; Drug-Resistant Epilepsy; Electric Field; Stereoelectroencephalography
• ISSN: 1388-2457; 1872-8952; 1872-8952
• DOI: 10.1016/j.clinph.2024.08.003

•This is the first study to examine tES (transcranial electrical stimulation) effects using simultaneous intracranial recordings.•We quantify local and network changes during and closely following application of direct and alternating current stimulation.•Highlighting the variability in tES physiological effects, our findings underscore the importance of sham in clinical studies. Clinical exploitation of transcranial electrical stimulation for focal epilepsy treatment lacks quantification of the underlying neurophysiological changes. This study explores the immediate effects of transcranial alternating (tACS) and direct (tDCS) current stimulation on local and network brain activity using simultaneous stereoelectroencephalography (SEEG) recordings. Patients were randomized for personalized tACS (n = 5) or tDCS (n = 6). Active stimulation (20 min) was preceded by sham stimulation (20 min). Changes in interictal epileptiform discharges (IED), functional connectivity (FC) and power spectral density (PSD) were quantified against baseline. Results demonstrated variable responses. Spike rate decreased in 2/6 subjects following sham and tDCS, while 2/6 showed an increase. Alpha power and aperiodic PSD components generally increased during and after tDCS but decreased following tACS. FC changes varied among subjects and were detectable even during sham sessions. Strong variability suggests that tES does not have a univocal effect on immediate changes in IED or FC, possibly due to the single session format and challenges in affecting subcortical areas. This is the first study to examine intracranial FC changes during tACS and tDCS, highlighting the importance of sham comparisons and individual variability in tES response, offering valuable insights into its application for epilepsy treatment.