What does neuroscience say?

Neuroscience studies have identified the following processes as being involved in the neurobiology of FND:

• Abnormal attention to the affected body part

  (Alluri et al., 2020; Simani et al., 2020, Vechetova et al., 2023)

• Defects in the agency of the self

  (feeling in control of one's actions/movements; Von et al., 2010b; Zito et al., 2020)

• Impairments in emotion regulation and emotion processing

  (Aybek et al., 2015; Espay et al., 2018; Perez et al., 2021; Voon et al., 2010a)

• Impairments in interoception or perception of internal processes

  (Cretton et al., 2019; Espay et al., 2018)

• Active interference faults

  (The theory that the brain predicts and processes sensory information based on past experience; Edwards et al., 2012)

Structural and functional changes have also been found in the brain area responsible for processing motor information and in the area tasked with dual processing of motor and emotional information in patients with FND (Aybek et al., 2014; Baizabal-Carvallo et al., 2019).

Studies have also found abnormal functional connectivity in areas associated with cognitive control, behavioural inhibition and cognitive awareness. Studies also show abnormal brain activity in the brain region that regulates sensory integration (Perez et al., 2015). 

Aybek et al., (2014) reported an association between increased grey in the supplementary motor area and duration FND and an association between increased grey in the left premotor cortex and severity of functional neurological symptoms.

It is important to note that these are results from cross-sectional studies, so we do not know for sure whether these changes are the cause or the consequence of functional neurological symptoms. 

• Resources

  • Alluri, P. R., Solit, J., Leveroni, C. L., Goldberg, K., Vehar, J. V., Pollak, L. E., ... and Perez, D. L. (2020). Cognitive complaints in motor functional neurological (conversion) disorders: a focused review and clinical perspective. Cognitive and Behavioral Neurology, 33(2), 77-89.

  • Apazoglou, K., Mazzola, V., Wegrzyk, J., Frasca Polara, G., and Aybek, S. (2017). Biological and perceived stress in motor functional neurological disorders. Psychoneuroendocrinology, 85, 142-150. doi:10.1016/j.psyneuen.2017.08.0

  • Aybek, S., Nicholson, T. R., O'Daly, O., Zelaya, F., Kanaan, R. A., & David, A. S. (2015). Emotion-motion interactions in conversion disorder: an fMRI study. PloS one, 10(4), e0123273.

  • Aybek, S., Nicholson, T. R., Draganski, B., Daly, E., Murphy, D. G., David, A. S., & Kanaan, R. A. (2014). Grey matter changes in motor conversion disorder. Journal of Neurology, Neurosurgery & Psychiatry, 85(2), 236-238.

  • Aybek, S., Nicholson, T. R., Zelaya, F., O'Daly, O. G., Craig, T. J., David, A. S., & Kanaan, R. A. (2014). Neural correlates of recall of life events in conversion disorder. JAMA Psychiatry, 71(1), 52-60.

  • Cretton, A., Brown, R. J., LaFrance, W. C., and Aybek, S. (2019). What Does Neuroscience Tell Us About the Conversion Model of Functional Neurological Disorders? The Journal of Neuropsychiatry and Clinical Neurosciences, appi.neuropsych. doi:10.1176/appi.neuropsych.1904

  • De Vroege, L., Koppenol, I., Kop, W. J., Riem, M. M. E., and van der Feltz-Cornelis, C. M. (2020). Neurocognitive functioning in patients with conversion disorder/functional neurological disorder. Journal of Neuropsychology. doi:10.1111/jnp.12206

  • Espay, A. J., Aybek, S., Carson, A., Edwards, M. J., Goldstein, L. H., Hallett, M., ... Morgante, F. (2018). Current Concepts in Diagnosis and Treatment of Functional Neurological Disorders. JAMA Neurology. doi:10.1001/jamaneurol.2018.1264

  • Fobian, A. D., & Elliott, L. (2019). A review of functional neurological symptom disorder etiology and the integrated etiological summary model. Journal of Psychiatry & Neuroscience, 44(1), 8-18.

  • Maurer, C. W., LaFaver, K., Ameli, R., Epstein, S. A., Hallett, M., & Horovitz, S. G. (2016). Impaired self-agency in functional movement disorders. Neurology, doi:10.1212/wnl.0000000000002940

  • Perez, D. L., Nicholson, T. R., Asadi-Pooya, A. A., Bègue, I., Butler, M., Carson, A. J., ... Aybek, S. (2021). Neuroimaging in Functional Neurological Disorder: State of the Field and Research Agenda. NeuroImage: Clinical, 30, 102623. doi:10.1016/j.nicl.2021.102623.

  • Teodoro, T., Edwards, M. J., and Isaacs, J. D. (2018). A unifying theory for cognitive abnormalities in functional neurological disorders, fibromyalgia and chronic fatigue syndrome: a systematic review. Journal of Neurology, Neurosurgery in Psychiatry, doi:10.1136/jnnp-2017-317823

  • Voon, V., Brezing, C., Gallea, C., Ameli, R., Roelofs, K., LaFrance Jr, W. C., & Hallett, M. (2010a). Emotional stimuli and motor conversion disorder. Brain, 133(5), 1526-1536.

  • Voon, V., Gallea, C., Hattori, N., Bruno, M., Ekanayake, V., & Hallett, M. (2010b). The involuntary nature of conversion disorder. Neurology, 74(3), 223-228.

  • Voon, V., Cavanna, A. E., Coburn, K., Sampson, S., Reeve, A., and LaFrance, W. C. (2016). Functional Neuroanatomy and Neurophysiology of Functional Neurological Disorders (Conversion Disorder). The Journal of Neuropsychiatry and Clinical Neurosciences, 28(3), 168-190. doi:10.1176/appi.neuropsych.1409