Insights Into Other Neuropsychiatric Disorders
Lesion network mapping is now being applied to other types of delusions. Dr. Darby described work with neurologic and psychiatric disorders associated with a perception that free will has been lost. These include neuropsychiatric conditions such as akinetic mutism, alien limb syndrome, catatonia, and psychogenic nonepileptic seizures. According to Dr. Darby, there are two potential components involved in a delusion involving an impaired sense of free will. There is a change in the volitional component that captures the motivation and desire to move, as well as an impaired sense of agency, which refers to the feeling of responsibility for movement.
Describing ongoing work with these types of delusions, Dr. Darby reported that neurologic lesion locations, like those in Capgras syndrome, were heterogeneous. Again, most of these lesions could be connected to a network functional map that was not shared by those without these symptoms.
“For many of these complex disorders, what we are seeing is that pathology in different areas causes the same behavior syndrome by affecting different parts of the same network,” Dr. Darby said. He believes neurologic and psychiatric diseases producing the same delusions are likely to be mediated by dysfunction in the same areas of the brain.
In patients with psychiatric diseases who have delusions associated with loss of a sense of free will, lesions are not readily observed, but Dr. Darby reported that there is evidence of modest changes, such as atrophy or diminished metabolism, that can be “linked up to those areas of the brain involved in agency and volition, and not to areas that are associated with other comorbid symptoms.”
Broader Implications
The fact that the same or similar delusions are shared by neurologic and psychiatric disorders provides the basis for speculating that this work may lead to a more detailed understanding of brain function. According to Dr. Darby, the work with lesion network mapping in neurologic disorders “may tell us where to look for the pathology in psychiatric diseases.”
The lesion network testing may be an important tool for understanding the relationship of brain pathology to behavior, according to Dr. Darby. Prior to lesion network mapping, the heterogeneity of lesion location for patients with shared types of delusion has been difficult to understand, but Dr. Darby indicated that lesion network mapping shows potential for placing specific symptom expression into a context of neuroanatomy.
—Theodore Bosworth
Suggested Reading
Boes AD, Prasad S, Liu Q, et al. Network localization of neurological symptoms from focal brain lesions. Brain. 2015;138(Pt 10):3061-3075.
Darby RR, Laganiere S, Pascual-Leone A, et al. Finding the imposter: brain connectivity of lesions causing delusional misidentifications. Brain. 2017;140(2):497-507.