Altered connectivity between prefrontal and sensorimotor cortex in conversion paralysis

Conversion paralysis (CP) is a frequent and impairing psychiatric disorder, affecting voluntary motor function. Yet, we have previously shown that the motor system of CP patients with a unilateral conversion paresis is recruited to a similar degree during imagined movements of the affected and unaffected limb. In contrast, imagery of movements with the affected limb results in larger prefrontal activation. It remains unclear how this hand-specific increased prefrontal activity relates to the reduced responsiveness of motor and somatosensory areas, a consistent and important feature of CP patients. In the current study, we investigated changes in the inter-regional coupling between prefrontal cortex (PFC) and sensorimotor regions when CP patients imagined movements involving either the affected or the unaffected hand. We found that there were distinct connectivity patterns for different parts of the PFC. While ventromedial PFC was not functionally connected to the motor system, we observed strong functional coupling between the dorsolateral PFC and various sensorimotor areas. Furthermore, this coupling was modulated by whether patients imagined movements of their affected or unaffected hand. Together, these results suggest that the reduced motor responsitivity observed in CP may be linked to altered dorsolateral prefrontal-motor connectivity. (C) 2010 Elsevier Ltd. All rights reserved.