Neuromodulation has been used for treating patients with neuropathic pain resistant to other therapeutic approaches. However, the efficiency of such methods only remains partial, hence the need to find a new target for neurostimulation. The posterior insula has been shown to represent a significant part of the nociceptive matrix as it partly embodies the first-order matrix in the cortical pain experience and has been suggested as a new target for analgesic neurostimulation. The aim of this study is to assess the effects of epidural electrical insular stimulation on the activity of the somatosensory thalamus, comparing the effect of low frequency stimulation (50 Hz, LF-IS) and high frequency stimulation (150 Hz, HF-IS), in a healthy cat model.
Epidural electrodes were placed over the posterior insular cortex in anesthetized cats. Then, a microelectrode was inserted in different thalamic nuclei (VPL and POm) to isolate an extracellular single-cell signal. After labelling 61 isolated thalamic cells as non-nociceptive (low threshold), nociceptive (high threshold) or wide dynamic range, their firing rate was recorded before, during and after a 10-minute LF-IS or HF-IS. 
Our preliminary results show that LF-IS could have better modulatory effects on the somatosensory thalamic activity than HF-IS as it significantly reduces the spontaneous burst firing rate of nociceptive cells, whereas it significantly enhances the spontaneous tonic firing rate of non-nociceptive cells. 
This data supports the hypothesis that the posterior insula could be a potential neuromodulation target for central anti-nociception, and thus for the treatment of refractory neuropathic pain.

POSTERIOR INSULA AS A POTENTIAL TARGET FOR NEUROPATHIC PAIN TREATMENT - AN EXPERIMENTAL STUDY ON A CAT MODEL OF LOW AND HIGH FREQUENCY INSULAR STIMULATION