Physiological symmetry of transcranial magnetic stimulation‐evoked EEG spectral features

Abstract

Transcranial magnetic stimulation (TMS)-evoked EEG potentials (TEPs) have been used to study the excitability of different cortical areas (CAs) in humans. Characterising the interhemispheric symmetry of TMS-EEG may provide further understanding of structure-function association in physiological and pathological conditions. We hypothesise that, in keeping with the underlying cytoarchitectonics, TEPs in contralateral homologous CAs share similar, symmetric spectral features, whilst ipsilateral TEPs from different CAs diverge in their waveshape and frequency content. We performed single-pulse (<1 Hz) navigated monophasic TMS, combined with high-density EEG with active electrodes, in 10 healthy participants. We targeted two bilateral CAs: premotor and motor. We compared frequency power bands, computed Pearson correlation coefficient (R) and Correlated Component Analysis (CorrCA) to detect divergences, as well as common components across TEPs. The main frequency of TEPs was faster in premotor than in motor CAs (p < .05) across all participants. Frequencies were not different between contralateral homologous CAs, whilst, despite closer proximity, there was a significant difference between ipsilateral premotor and motor CAs (p > .5), with frequency decreasing from anterior to posterior CAs. Correlation was high between contralateral homologous CAs and low between ipsilateral CAs. When applying CorrCA, specific components were shared by contralateral homologous TEPs. We show physiological symmetry of TEP spectral features between contralateral homologous CAs, whilst ipsilateral premotor and motor TEPs differ despite lower geometrical distance. Our findings support the role of TEPs as biomarker of local cortical properties and provide a first reference dataset for TMS-EEG studies in asymmetric brain disorders.

Natural Oscillatory Frequency Slowing in the Premotor Cortex of Early-Course Schizophrenia Patients: A TMS-EEG Study

“…Specifically, in healthy individuals, the prefrontal natural frequency is in the gamma frequency band, the premotor natural frequency is in the high beta/low gamma range, the parietal natural frequency is in the beta band, and the occipital natural frequency is in the alpha range [ 16 , 17 ]. These findings were recently replicated in a study investigating TMS-EEG natural frequencies from both the right and left hemisphere [ 18 ] as well as with concurrent EEG and intracranial stimulation and recordings [ 19 ].…”

“…Third, our investigation was limited to the left hemisphere. Interestingly, one recent study in healthy subjects did not find significant differences in the natural frequencies between homologous areas of the left and right hemispheres, including between the left and right premotor cortices [ 18 ]. However, given the broad literature on altered lateralization of brain functions in schizophrenia [ 64 , 65 , 66 ], future studies should explore the symmetry of EEG responses to TMS in this disorder while investigating potential (lateralized) functional correlates (e.g., language, handedness).…”

Exploring the Therapeutic Potential of Quadripulse rTMS over the Visual Cortex: A Proof-of-Concept Study in Healthy Volunteers and Chronic Migraine Patients with Medication Overuse Headache

“…Moreover, the habituation deficit paradigm is able to capture changes induced by pharmacological and non-pharmacological migraine preventive therapies [17,52,53]. In the future, new neurophysiological instruments, such as high-density EEG responses induced by TMS (TMS-EEG) should contribute to disentangling the underpinnings of hyperresponsivity and abnormal habituation in migraine patients and to identify more precisely the effects of neurostimulation not only for one sensory cortex but for the entire brain [54][55][56][57] as well as regions of interest with abnormal activity [58].…”

Repetitive transcranial magnetic stimulation to the motor cortex leads to a sequential increase in phase synchronization and power of TMS-evoked electroencephalographic recordings

“…EEG signals were segmented into trials of 1600 ms around the TMS pulse, which occurred at time zero (±800 ms). In the M1 TMS-EEG epoch, a segment of the pre-TMS EEG signal (-11 to -3 ms) was used to substitute the peri-TMS EEG recordings from -2 to 6 ms [30]. The same procedure was applied for deep TMS targets (ACC and PSI) in a larger peri-TMS interval (0-20 ms) to adapt to the double-cone coil electric field.…”