Non-traumatic fMRI of identity-state expression and switching in co-conscious DID
S. Kajimura, K. Okano, Senkei Ueno, Junko Yamada, H. Fukui, Aiko Hirai, Ayahito Ito, Nobuhito Abe, R. Nakai, Shun’ichi Noma, Toshiya Murai
bioRxiv April 23, 2026 preprint DOI: 10.64898/2026.04.20.718646 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Case study Longitudinal Case report |
|---|---|
| Sample size | 1 |
| Population | A DSM-5-diagnosed woman with persistent co-consciousness between Adult and Adolescent identity-states |
| Key findings | Identity-state expression and switching showed convergent within-person neural signatures even under persistent co-consciousness and without trauma provocation. Switching to Adult produced larger neural reconfiguration than switching to Adolescent (mean between-cluster beta separation 4.30 versus 0.85; permutation p = 0.0001). |
Abstract
Dissociative identity disorder (DID) remains debated because identity-state phenomena are privately experienced and may be attributed to suggestion, simulation or role enactment. Most neuroimaging studies rely on symptom provocation or traumatic recall, which complicates interpretation and is poorly suited to co-conscious presentations where simultaneous awareness should make state differences hardest to detect. We applied Identity-State Characterization and Analysis (ID-SCAN), a non-traumatic, identity-cued functional magnetic resonance imaging protocol, to a DSM-5-diagnosed woman with persistent co-consciousness between Adult and Adolescent identity-states. One task used identical insect images that evoked opposite preferences across identity-states; the other used trait judgments about self, the other identity-state and a shared intimate other. Analyses combined Bayesian single-case general linear modelling, generalized psychophysiological interaction connectivity and searchlight representational similarity analysis. Identity-instruction cue epochs were pooled across tasks to assess switch direction. The same insect stimuli engaged different valuation-related configurations across identity-states: Adolescent-selective effects centred on striato-thalamic regions, whereas Adult-selective effects extended to amygdala and orbitofrontal/medial prefrontal cortex, with distinct task-evoked coupling. Adult-as-self and Adolescent-as-self occupied separable positions within canonical self-referential regions. Cue-locked activity differed by switch direction across tasks, with larger reconfiguration when switching to Adult (mean between-cluster beta separation 4.30 versus 0.85; permutation p = 0.0001). Cross-task overlap localized a limited shared task-related substrate mainly to posterior visual and dorsal parietal cortex. Even under persistent co-consciousness and without trauma provocation, identity-state expression and switching showed convergent within-person neural signatures. The findings support non-traumatic mechanistic phenotyping of dissociative presentations and motivate cohort and longitudinal studies, including treatment-tracking work.