Transcranial stimulability of phosphenes by long lightning electromagnetic pulses

TL;DR

This paper investigates whether lightning electromagnetic pulses can stimulate visual phosphenes in the brain similarly to clinical TMS, suggesting thunderstorms might induce luminous perceptions through transcranial stimulation.

Contribution

It demonstrates that lightning magnetic fields can produce electric fields comparable to TMS, proposing lightning as a natural source of phosphene induction and explaining luminous perceptions during thunderstorms.

Findings

Lightning magnetic fields are similar in magnitude and frequency to TMS fields.

Lightning-induced electric fields can stimulate cortical phosphenes at short distances.

Retinal phosphene stimulation is more likely during thunderstorms.

Abstract

The electromagnetic pulses of rare long (order of seconds) repetitive lightning discharges near strike point (order of 100m) are analyzed and compared to magnetic fields applied in standard clinical transcranial magnetic stimulation (TMS) practice. It is shown that the time-varying lightning magnetic fields and locally induced potentials are in the same order of magnitude and frequency as those established in TMS experiments to study stimulated perception phenomena, like magnetophosphenes. Lightning electromagnetic pulse induced transcranial magnetic stimulation of phosphenes in the visual cortex is concluded to be a plausible interpretation of a large class of reports on luminous perceptions during thunderstorms. APPENDIX (Erratum and Addendum by J. Peer, V. Cooray, G. Cooray and A. Kendl): The comparison of electric fields transcranially induced by lightning discharges and by TMS brain stimulators via View E = - dA/dt is shown to be inappropriate. Corrected results with respect to evaluation of phosphene stimulability are presented. For average lightning parameters the correct induced electric fields appear more than an order of magnitude smaller. For typical ranges of stronger than average lightning currents, electric fields above the threshold for cortical phosphene stimulation can be induced only for short distances (order of meters), or in medium distances (order of 50 m) only for pulses shorter than established axon excitation periods. Stimulation of retinal phosphene perception has much lower threshold and appears most probable for lightning electromagnetic fields.