Photic drive response in people with epilepsy: Exploring the interaction with background alpha rhythm

Area of Science:

• Neuroscience
• Clinical Electrophysiology
• Epilepsy Research

Background:

• Cortical hyperexcitability is a key feature in epilepsy.
• Photic drive responses (PDRs) and alpha rhythm are electrophysiological measures.
• Understanding their interaction may reveal epilepsy biomarkers.

Purpose of the Study:

• To quantify PDRs and alpha-band gain in people with epilepsy (PwE).
• To investigate the interaction between PDRs, alpha rhythm, and epilepsy characteristics.
• To assess alpha-band gain as a measure of cortical hyperexcitability.

Main Methods:

• Used modified intermittent photic stimulation (IPS) during EEG in 15 PwE and 15 controls.
• Measured alpha-band gain, defined as N-fold changes in PDR when IPS or its harmonics overlapped with alpha bands.
• Analyzed interactions with recent epileptic attacks, epilepsy type (generalized vs. focal), and age.

Main Results:

• An epileptic attack within 1 month of testing significantly increased alpha-band gain (1.36×).
• Generalized epilepsy significantly decreased alpha-band gain (0.79×), while focal epilepsy did not.
• Each decade of age increased alpha-band gain (1.09×).
• Interactions between alpha and IPS harmonics were significant for recent attacks and generalized epilepsy, particularly at occipital electrodes (O1, O2).

Conclusions:

• Modified IPS effectively quantifies alpha-band gain, reflecting cortical hyperexcitability in PwE.
• Alpha-band gain is sensitive to recent epileptic activity, epilepsy type, and age.
• These findings suggest interactions between cortical outputs and the alpha rhythm generator, offering insights into predictive coding.