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

Summary

During a migraine aura, a failing visual cortex produces brilliant, structured light instead of darkness. This paper argues that the standard explanation—spontaneous excitation from Cortical Spreading Depression (CSD)—is inconsistent because CSD causes functional deficits in other brain regions. Evidence from MEG, VEP, and intracranial SEEG recordings shows the visual cortex is profoundly suppressed and nearly silent during the aura. The paper extends this to near-death experiences, suggesting that intense light at death may correspond to terminal cortical silence. This supports the filter theory of consciousness: brain failure reveals, rather than generates, intrinsic light.

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.

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