Modulation of the mechano-nociceptive neural activities in the ventral posterolateral nucleus in thalamus

Deep brain stimulation (DBS) of the periaqueductal gray (PAG) has been shown to be an option for chronic pain inhibition. Drawbacks exist due to electrical stimulation doses given in an open-loop and manual fashion based on patients´ subjective feedback. In response, we have developed a closed-loop system capable of detecting nociceptive signals from the spinal cord while delivering electrical stimulation to the PAG based on the recorded signals. However, such a system is difficult to be utilized on freely moving small animals since spine movement displaces electrodes during recording. Therefore, we aim to find the reference signals within the brain as the probe movement may be able to be minimized. In this study, we recorded single-unit action potentials (APs) from the ventral posterior lateral (VPL) nucleus of the thalamus in response to graded mechanical stimuli (brush, pressure and pinch). Results obtained from forty neurons showed that the mean rate of the action potentials during pinch was significantly higher in compare to that during brush while no significant difference was found between the pressure with the other two stimuli. Experiments also show that DBS delivered to the PAG could significantly decrease the neural activities in the VPL.