A neuroscientific perspective
The sense of ownership of one's own body is generated by a mechanism of multisensory integration that requires the integration of visual, somatosensory and other sensory body signals into a coherent multisensory perception (Ehrsson et al., 2020), while the agency of the self is due to the correspondence between the expected sensory consequences of a movement and their sensory feedback (Abdulkarim et al., 2023).
The neural correlates that create this experience are so efficient and so unconsciously automated that most of the time our sense of movement choice can seem minimal and even trivial ( Haggard, 2017).
A sense of ownership of one's own body is associated with activation in a set of premotor-parieto-cerebral regions, while agency of the self is associated with activations in the temporoparietal junction( TPJ), the pre-supplementary motor area (SMA), insula, right inferior parietal cortex, superior temporal gyrus and left primary sensorimotor cortex (Abdulkarim et al, 2023; Haggard, 2017).
Voluntary movements are produced by the primary motor cortex, which is mainly activated by the proximal premotor and supplementary motor cortices. The TPJ represents a multimodal integrative brain network that verifies the correspondence between the desired movement and the movement actually performed (Drane et al., 2022). The key neural correlates of agency are thus thought to represent the functional connectivity between frontal and prefrontal areas that trigger action initiation and between parietal areas that represent the key brain region for controlling perceptual events (Haggard, 2017).
Some patients with FND experience a deficit in the agency of the self, which is reflected in the experience of movements as involuntary. It is hypothesised that in some patients the brain's agentic network is not functioning optimally, as supported by studies showing dysfunction of the right temporoparietal junction in patients with hyperkinetic movement disorder and functional tremors (Maurer et al., 2016).
Drane et al., (2022) hypothesise that patients with FND either have impaired brain function of the temporoparietal junction or abnormal influences on the motor cortex cause an abnormality in the signal used to confirm the correspondence between the intended and the actual movement.
In any case, further research in this area is needed, also to test the activity of the TPJ with other brain regions such as the insula and anterior cingulate cortex..
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Maurer, C. W., LaFaver, K., Ameli, R., Epstein, S. A., Hallett, M., and Horovitz, S. G. (2016). Impaired self-agency in functional movement disorders: a resting-state fMRI study. Neurology, 87(6), 564-570.
Haggard, P. (2017). Sense of agency in the human brain. Nature Reviews Neuroscience, 18(4), 196-207.
Nahab, F. B., Kundu, P., Gallea, C., Kakareka, J., Pursley, R., Pohida, T., ... and Hallett, M. (2011). The neural processes underlying self-agency. Cerebral cortex, 21(1), 48-55.
Perez, D. L., Nicholson, T. R., Asadi-Pooya, A. A., Bègue, I., Butler, M., Carson, A. J., ... and Aybek, S. (2021). Neuroimaging in functional neurological disorder: state of the field and research agenda. NeuroImage: Clinical, 30, 102623.