Background Mind-wandering is a pervasive human brain state and, when in excess, may promote negative affect and neuropsychiatric conditions. Mindfulness meditation may promote alternate brain states, improving affect and reducing stress. An understanding of the neural basis between these brain states could thus advance treatment of neuropsychiatric conditions. Patients with epilepsy suffer from high rates of neuropsychiatric conditions including anxiety and depression that may be mediated by mind-wandering and improved by mindfulness meditation. Patients with drug-resistant epilepsy routinely undergo intracranial recordings using stereo electroencephalography (sEEG) to locate and treat the anatomical origin of seizures. SEEG recordings over several days in these patients therefore afford a unique opportunity to study the effects of mind-wandering and mindfulness on the human brain.

Methods To explore the neural basis of mindfulness meditation versus mind-wandering, we enrolled eight patients in a trial of structured mindfulness meditation and open mind-wandering who underwent sEEG within the mesial temporal lobe for seizure localization. Electrophysiology was compared between mind-wandering and mindfulness separately for epileptic and non-epileptic tissue. Using fitting-one-over-f modeling, periodic components of electrophysiology were compared in canonical frequency bands of theta (4-8Hz), alpha (8-13Hz), beta (13-30Hz), and gamma (30-55Hz). Aperiodic components of the power spectra were assessed by the model offset, knee, and exponent.

Results We found a significant reduction in gamma power (30-55Hz) within the mesial temporal lobe during mindfulness meditation compared with mind-wandering in non-epileptic (p=1.20E-4) but not in epileptic brain (p=0.352).There was also a significant difference between epileptic versus non-epileptic brain in difference in gamma power between conditions (p=0.011). There were no significant changes in power across any frequency band within epileptic mesial temporal brain tissue between brain states. Conversely, there were significant differences between mind-wandering and mindfulness within epileptic brain in aperiodic components (offset, knee, and exponent, all p<0.05), while no differences in aperiodic components were seen in non-epileptic brain (all p>0.70).

Conclusion Intracranial electrophysiologic modulations between brain state (mind-wandering versus mindfulness) may differ between epileptic and non-epileptic brain tissue. Modulations in gamma activity in non-epileptic brain may represent functional changes in brain state, while aperiodic changes in epileptic brain may modulate propensity for seizures.