Patients with temporomandibular disorder (TMD) perform poorly in neuropsychological tests of cognitive function. These deficits might be related to dysfunction in brain networks that support pain and cognition, due to the impact of chronic pain and its related emotional processes on cognitive ability. We therefore tested whether patients with TMD perform poorly in cognitive and emotion tasks and whether they had abnormal task-evoked brain activity. Seventeen female subjects with nontraumatic TMD and 17 age-matched healthy female subjects underwent functional magnetic resonance imaging while performing counting Stroop tasks comprising neutral words, incongruent numbers, or emotional words, including TMD-specific words. Group differences in task-related brain responses were assessed. Connectivity between 2 pairs of coupled brain regions during the cognitive and emotional tasks (prefrontal-cingulate and amygdala-cingulate) was also examined. The patients had sluggish Stroop reaction times for all Stroop tasks. Furthermore, compared to controls, patients showed increased task-evoked responses in brain areas implicated in attention (eg, lateral prefrontal, inferior parietal), emotional processes (eg, amygdala, pregenual anterior cingulate), motor planning and performance (eg, supplementary and primary motor areas), and activation of the default-mode network (medial prefrontal and posterior cingulate). The patients also exhibited decoupling of the normally correlated activity between the prefrontal and cingulate cortices and between the amygdala and cingulate cortex. These findings suggest that the slow behavioral responses in idiopathic TMD may be due to attenuated, slower, and/or unsynchronized recruitment of attention/cognition processing areas. These abnormalities may be due to the salience of chronic pain, which inherently requires attention.
Sluggish performance in cognitive and emotional interference tasks in patients with nontraumatic temporomandibular disorder is associated with pronounced and unsynchronized task-evoked fMRI brain responses.
aToronto Western Research Institute, University Health Network, Toronto, Canada
bInstitute of Medical Science, University of Toronto, Toronto, Canada
cMount Sinai Hospital, Toronto, Canada
dDepartment of Surgery, University of Toronto, Toronto, Canada
*Corresponding author. Address: Division of Brain, Imaging and Behaviour, Systems Neuroscience, Toronto Western Research Institute, Toronto Western Hospital, University Health Network, 399 Bathurst Street, Room MP14-306, Toronto, ON, Canada M5T 2S8. Tel.: +1 416 603 5662; fax: +1 416 603 5745.
Submitted February 22, 2010; revised and accepted October 28, 2010.