Neurophysiological effects of repetitive transcranial magnetic stimulation (rTMS) in treatment resistant depression

Neurophysiological effects of rTMS: Revisiting the role of the N100 as a clinically useful marker in depression

“…Furthermore, N100 is also an important component of the Loudness Dependent Auditory Evoked Potential (LDAEP) that has been shown to index serotonergic and possibly glutamatergic innervation (Kenemans and Kähkönen, 2010), and has received interest as a diagnostic and predictive biomarker in MDD. Using an auditory oddball paradigm instead of TMS-EEG, we also reported a decreased N100 amplitude from pre-to post-rTMS in MDD, that was specifically confined to the left pre-frontal cortex (Spronk et al, 2008), conceptually in line with the TEP-N100 results as reported by Voineskos and colleagues (Voineskos et al, 2021). This raises the question, how specific the N100 TEP as reported by Voineskos and colleagues (Voineskos et al, 2021) is to transcranial stimulation, auditory stimulation, a combination thereof, or simply an overlap in neural underpinnings.…”

“…Using an auditory oddball paradigm instead of TMS-EEG, we also reported a decreased N100 amplitude from pre-to post-rTMS in MDD, that was specifically confined to the left pre-frontal cortex (Spronk et al, 2008), conceptually in line with the TEP-N100 results as reported by Voineskos and colleagues (Voineskos et al, 2021). This raises the question, how specific the N100 TEP as reported by Voineskos and colleagues (Voineskos et al, 2021) is to transcranial stimulation, auditory stimulation, a combination thereof, or simply an overlap in neural underpinnings. This will require further elucidation, since, if similar associations could be obtained using an auditory oddball paradigm, this might be preferred over TMS-EEG, for ease of use and higher yield of good quality signal which is crucial for clinical applications (e.g., only for 30/ 66 people TEPs could be determined due to excessive artifacts, inadequately low trial numbers with TMS pulses and incomplete recordings).…”

“…The finding from Voineskos and colleagues (Voineskos et al, 2021) regarding the more focal left DLPFC TEP amplitude so strongly predicting suicidality response to rTMS treatment are novel and intriguing. Clinical implications for such a predictive marker would be immense (and literally life-saving), since it could help prioritize rTMS treatment for specific high-risk patient groups that present with that specific marker.…”

“…Future studies might collect both TEP as well as auditory oddball ERP data within the same MDD patients to shed further light on similarities and differences and unique signal between both approaches to further uncover the added value of both techniques. Nonetheless, the results from Voineskos and colleagues (Voineskos et al, 2021) posits an important role for the N100 ERP/TEP component in tracking and predicting antidepressant response. This suggests that the N100 might be more relevant than other commonly investigated ERP components such as the P300 that yielded relatively little success and inconsistent findings (van Dinteren et al, 2015).…”

“…In this issue of Clinical Neurophysiology, Voineskos and colleagues (Voineskos et al, 2021) assessed TEPs before and after real and sham-rTMS. In their study, they nicely demonstrate rTMS treatment effects on two negative components of the TEP (N45 and N100), whereas no such effects were found for the sham rTMS group.…”