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Finding the imposter: brain connectivity of lesions causing delusional misidentifications
R Ryan Darby1,2,3, Simon Laganiere4, Alvaro Pascual-Leone4
1Berenson-Allen Center for Non-Invasive Brain Stimulation and Division of Cognitive Neurology, Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA rdarby@bidmc.harvard.edu.
A single brain lesion can cause complex delusions like Capgras syndrome by affecting specific brain networks. This study links lesion locations to impaired familiarity and belief evaluation, explaining these unusual neurological symptoms.
Area of Science:
- Neuroscience
- Neurology
- Psychiatry
Background:
- Focal brain injuries can cause complex symptoms like Capgras syndrome, where patients believe loved ones are imposters.
- The neuroanatomical basis for such delusions, particularly how a single lesion causes complex symptoms, remains unclear.
- Previous theories often required multiple lesions or co-occurring conditions.
Purpose of the Study:
- To propose and test the hypothesis that delusional misidentification syndromes result from single lesions in specific brain connectome locations.
- To identify the precise brain regions and functional connections associated with lesion-induced delusional misidentifications.
- To differentiate the neural correlates of delusional misidentifications from other delusion types.
Main Methods:
- Mapped lesion locations from 17 cases of delusional misidentification to a common brain atlas.
- Utilized lesion network mapping to identify brain regions functionally connected to the identified lesion sites.
- Conducted meta-analyses of functional magnetic resonance imaging (fMRI) studies to identify brain regions involved in familiarity perception and belief evaluation.
Main Results:
- All 17 lesion locations were functionally connected to the left retrosplenial cortex (familiarity region).
- 16 of 17 lesion locations were functionally connected to the right frontal cortex (belief evaluation/expectation violation region).
- This specific connectivity pattern was unique to delusional misidentifications compared to other neurological syndromes and delusions.
Conclusions:
- Single lesions in unique brain connectome locations can cause complex neuropsychiatric syndromes like delusional misidentifications.
- Impaired familiarity perception and belief evaluation are linked to specific neuroanatomical correlates in these patients.
- The findings demonstrate a mechanism for complex symptom generation from single lesions based on functional connectivity patterns.
