ID-SCAN: a functional MRI protocol for neurophenomenological phenotyping of dissociative identity disorder without trauma provocation

Background: Dissociative identity disorder (DID) is a trauma-related dissociative disorder in which two or more identity-agents recur within one person, each experiencing and evaluating itself and its surroundings. Most existing neuroimaging paradigms rely on symptom provocation using trauma-related autobiographical material. Identity-agent effects that are independent of symptom provocation need to be disentangled from emotional responses to trauma-related material and from the co-consciousness of other identity-agents.Objective: To introduce ID-SCAN (Identity-agent State Characterisation and Analysis), a functional MRI protocol without trauma provocation for within-person neurophenomenological characterisation of identity-agent expression and switching, and to test its feasibility in a co-conscious case.Method: A woman with DID living with persistent co-consciousness between two identity-agents (Adu and Ado) completed two fMRI tasks: identity-cued evaluation of identical insect photographs the agents made sense of in opposite ways, and trait judgments about self, the other agent and a shared intimate other. Within-person analyses combined Bayesian general linear modelling, generalised psychophysiological interaction, representational similarity analysis and a pooled identity-cue switching analysis, with cross-task overlap providing a task-general baseline.Results: Adu and Ado made sense of the same insect photographs differently. Ado showed greater activation in striato-thalamic regions, whereas Adu showed greater activation in the amygdala and in the orbitofrontal and medial prefrontal cortex; the two also differed in task-evoked connectivity. Adu-as-self and Ado-as-self occupied separable positions within self-referential regions. Cue-locked activity differed by switch direction, with greater reconfiguration when switching to the less-foregrounded Adu. Cross-task overlap localised to posterior visual and dorsal parietal cortex.Conclusions: Two co-conscious identity-agents showed distinct, convergent neurophenomeno-logical signatures of expression and switching in this single case without trauma provocation. ID-SCAN suits single-case and groupwise, simulator-controlled designs and provides a candidate framework for future longitudinal and treatment-related research whose test–retest reliability and clinical sensitivity remain to be established.