Assessing SICI Cortical Inhibition With DLPFC TMS-EEG Using Different ISI Values

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Neurophysiology

Background:

• Cortical inhibition (CI) assessment in the dorsolateral prefrontal cortex (DLPFC) using transcranial magnetic stimulation combined with electroencephalography (TMS-EEG) is a growing research area.
• Short-interval cortical inhibition (SICI), a paired-pulse TMS paradigm, is commonly used but its application and optimal parameters for the DLPFC are less understood compared to the motor cortex.

Purpose of the Study:

• To quantitatively compare the effects of different interstimulus interval (ISI) values (2 ms and 4 ms) within the SICI protocol on cortical inhibition in the DLPFC.
• To assess how varying ISIs influence TMS-evoked potentials (TEPs) in the DLPFC.

Main Methods:

• Eighteen healthy subjects participated in the study.
• The SICI protocol was administered using two distinct ISIs: 2 ms and 4 ms.
• TMS-EEG responses were analyzed for TEP amplitude, latency, peak-to-peak amplitudes, and area under the rectified curve.

Main Results:

• Significant differences in TEPs were observed between the 2 ms and 4 ms ISI conditions.
• A 2 ms ISI resulted in significantly greater cortical inhibition, evidenced by a more pronounced reduction in TEP amplitude.
• These findings align with previous research on motor cortex stimulation.

Conclusions:

• The 2 ms ISI appears to be more effective in eliciting greater cortical inhibition in the DLPFC.
• This study provides valuable data for the standardization of the SICI protocol when applied to the DLPFC.
• Understanding optimal ISI parameters is crucial for accurate assessment of DLPFC function.