Pain perception involves not only the ascending pathway but also the descending pathway. The ascending pathway is the bottom-up process starting with nociceptive sensory information which is transferred to the brain via the spinal code, while the descending pathway is the descending process going from the brain to the sensory parts of the body via the spinal code. Melzack proposes to explain the experience of pain through neuromatrix theory as “a complex and multifactorial subjective experience” produced by a widely distributed cerebral neural network (Melzack, 1999; Tracey and Mantyh, 2007). In other words, the neuromatrix (an integrative neural network) integrates inputs from all factors of the individual such as sensory information, emotional distress, stress, moods, memories, genetics, etc. and generates the outputs of one's perception of pain (Melzeck, 2001). Thus, pain perception involves large brain regions that include primarily subcortical structures (e.g., hypothalamus, amygdala, thalamus) and areas of cortex (e.g., primary and secondary somatosensory cortex (S1 and S2), the insular cortex, the anterior cingulate cortex, the prefrontal cortex (Goldstein, 2016; Apkarian et al., 2005). Parietal and temporal cortex may also be involved in pain perception, depending on each individual's situation (Tracey and Mantyh.,