Figure 1. Model and evidence supporting the role for sensorimotor expectations and mis-directed attention in the pathophysiology of motor functional neurological disorder (mFND).

Based on Edwards et al., Panel A shows the hierarchical anatomy that is theorized to underlie false inference in patients with functional motor symptoms.²² Within this model, abnormal prior expectation is formed within prediction units of intermediate motor areas (here the supplementary motor area (SMA)) (black triangles). This prior is afforded abnormal precision by attentional processes (blue arrow) that cause intermediate level motor predictions (thick black arrows) to elicit movement, and prediction errors (thick red arrows) from prediction error units (red triangles) to report the unpredicted content of the movement to higher cortical areas (here, pre-SMA (pSMA)). The secondary consequence of these prediction errors is that prefrontal regions try to explain them in terms of symptomatic interpretation or misattribution of agency to external causes. Based on findings of Lin et al., Panel B (top portion) displays the broken escalator phenomenon.²³ Following a series of initial ‘BEFORE’ tasks where participants step onto and off of a stationary platform (not shown), participants then go on to step onto a moving sled performed 10 times (‘MOVING’). In the ‘AFTER’ trials, participants once again step onto a stationary sled 5 times. The ‘broken escalator’ phenomenon, also called the locomotor after-effect, occurs when the learned motor response during the ‘MOVING’ phase is carried forward in the ‘AFTER’ trials. In Panel B (lower panel), linear trunk displacement measurements show that only patients with a functional gait displayed persistence of the locomotor after-effect across repeated ‘AFTER’ trials. Lin and colleagues suggested this reflected evidence of failed de-adaptation (failure to update expectations).