Altered sense of self during seizures in the posteromedial cortex
J. Parvizi, R. Braga, A. Kucyi, Mike J. Veit, Pedro Pinheiro-chagas, Claire Perry, Clara Sava-segal, M. Zeineh, Eric K van Staalduinen, J. Henderson, Matthew Markert
Proceedings of the National Academy of Sciences of the United States of America July 16, 2021 Peer reviewed DOI: 10.1073/pnas.2100522118 via Semantic Scholar
Summary
A patient with seizures originating in the posteromedial cortex reported a reproducible sense of self-dissociation, feeling like an outside observer to his own thoughts. Electrical stimulation of the seizure zone and a corresponding region in the opposite hemisphere induced a similar state. This rare case suggests the posteromedial cortex plays a causal role in integrating self-referential information, offering clues about self-dissociation in neuropsychiatric conditions.
Study at a glance
| Design | case study |
|---|---|
| Sample size | 1 |
| Population | a patient (S19_137) with confirmed seizures originating within the posteromedial cortex |
| Key finding | Seizures and electrical stimulation of the posteromedial cortex causally induced a sense of self-dissociation in a patient. |
Abstract
Significance In this manuscript, we report a rare case of a patient with localized seizures originating from the right anterior and dorsal posteromedial cortex (PMC). We mapped the electrophysiological and neuroimaging connectivity of the ictal onset site and replicated seizure auras by stimulating the homotopical PMC site in the left hemisphere. Our findings provide a causal link between PMC and the sense of self and provide unique clues about the pathophysiology of self-dissociation in neuropsychiatric conditions. The posteromedial cortex (PMC) is known to be a core node of the default mode network. Given its anatomical location and blood supply pattern, the effects of targeted disruption of this part of the brain are largely unknown. Here, we report a rare case of a patient (S19_137) with confirmed seizures originating within the PMC. Intracranial recordings confirmed the onset of seizures in the right dorsal posterior cingulate cortex, adjacent to the marginal sulcus, likely corresponding to Brodmann area 31. Upon the onset of seizures, the patient reported a reproducible sense of self-dissociation—a condition he described as a distorted awareness of the position of his body in space and feeling as if he had temporarily become an outside observer to his own thoughts, his “me” having become a separate entity that was listening to different parts of his brain speak to each other. Importantly, 50-Hz electrical stimulation of the seizure zone and a homotopical region within the contralateral PMC induced a subjectively similar state, reproducibly. We supplement our clinical findings with the definition of the patient’s network anatomy at sites of interest using cortico-cortical–evoked potentials, experimental and resting-state electrophysiological connectivity, and individual-level functional imaging. This rare case of patient S19_137 highlights the potential causal importance of the PMC for integrating self-referential information and provides clues for future mechanistic studies of self-dissociation in neuropsychiatric populations.