scintillating scotoma: when the cortex fails, brilliant inner white light appears

During a migraine aura, a failing visual cortex produces brilliant, structured light rather than darkness. The conventional explanation—that Cortical Spreading Depression (CSD) generates this light through spontaneous excitation—is internally inconsistent because CSD consistently causes functional deficits (hemiparesis, numbness, aphasia) in other cortical regions. Three lines of evidence show the visual cortex is profoundly suppressed during aura: MEG data show collapse of alpha- and gamma-band rhythms; VEP studies show no response to external light; and novel SEEG recordings reveal a near-silent cortical signal precisely correlating with the scintillating scotoma. The paper extends this to near-death experiences, where intense light phenomena may correspond to the ultimate cortical silence of Terminal Spreading Depolarization. A double dissociation emerges: retinal ischaemia causes darkness, cortical ischaemia causes brilliant light, consistent with filter theory of consciousness.

Study at a glance

Abstract

This paper investigates a fundamental paradox within neuroscience and the philosophy of consciousness: why does a failing visual cortex during a migraine aura produce not darkness, but a brilliant, structured, and luminous scotoma? The conventional materialist explanation holds that Cortical Spreading Depression (CSD) generates this light through spontaneous excitation. This paper demonstrates, however, that this explanation is internally inconsistent. Extensive clinical evidence shows that the sustained phase of CSD consistently produces functional deficits (such as hemiparesis, numbness, and aphasia) in all other cortical regions. It would be inconsistent to suppose that the very same neurophysiological wave produces a sustained "gain of function" (light) exclusively in the visual cortex. Three independent and converging lines of neurophysiological evidence indicate that the visual cortex is in a state of profound suppression and cortical silence during the aura: MEG data demonstrate that alpha- and gamma-band rhythms collapse. VEP studies show that the cortex no longer responds to external light. Novel SEEG evidence (McLeod et al., 2025) offers the most direct confirmation to date: intracranial recording reveals a low-voltage suppression — a near-silent cortical signal — that correlates precisely with the scintillating scotoma. The paper extends this reasoning along the CSD–TSD continuum, where Terminal Spreading Depolarization (TSD) represents the permanent, irreversible form of CSD that occurs at death. The hypothesis is advanced that the intense light phenomena reported during near-death experiences (NDEs) may correspond to this ultimate cortical silence. Finally, a clarifying double dissociation is presented: retinal ischaemia (failure of the eye) leads to darkness, whereas cortical ischaemia (failure of the brain) leads to brilliant light. This pattern is consistent with the filter theory of consciousness (as proposed by Bergson, Huxley, and Kastrup), which holds that when the brain's filtering function fails, a broader, intrinsic dimension of experience is revealed — not produced, but uncovered.