γ Oscillations are involved in the sensorimotor transformation of pain

Pain signals threat and initiates motor responses to avoid harm. The transformation of pain into a motor response is thus an essential part of pain. Here, we investigated the neural mechanisms subserving the sensorimotor transformation of pain at the cortical level by using electroencephalography. In a simple reaction time experiment, brief painful stimuli were delivered to the left hand of healthy human subjects who responded with button presses of the right hand. The results show that the simple reaction time task was associated with neuronal responses at delta/theta, alpha/beta, and gamma frequencies. The analysis of the relationship between neuronal activity and response speed revealed that gamma oscillations, which were temporally coupled to the painful stimuli, but not temporally coupled to the motor response, predicted reaction times. Lateralization of gamma oscillations indicates that they originate from motor areas rather than from sensory areas. We conclude that gamma oscillations are involved in the sensorimotor transformation of pain whose efficiency they reflect. We hypothesize that the relationship between stimulus-locked gamma oscillations and reaction times reflects a direct thalamo-motor route of nociceptive information that is central to the biological function of pain.