Facial expression responsible for controlling the expression differ in each case. Voluntary facial expressions are often socially conditioned and follow a cortical route in the brain. Conversely, involuntary facial expressions are believed to be innate and follow a subcortical route in the brain. Facial recognition is often an emotional experience for the brain and the amygdala is highly involved in the recognition process. The eyes are often viewed as important features of facial expressions. Aspects such as blinking rate can possibly be used to indicate whether a person is nervous or whether he or she is lying. Also, eye contact is considered
Atypical facial pain involves constant, often burning pain and trigeminal neuralgia classically shows paroxysmal, shooting pain, but in reality there is some overlap in their features. In 2005 researchers proposed a new classification of trigeminal neuralgia which described a type of trigeminal neuralgia where the pain was constant and burning. They theorized that this type was a progression of untreated classic trigeminal neuralgia, and represented worsening neural injury. There were seven proposed sub-types of trigeminal neuralgia (TN) in this classification (see table), and the final category was reserved for facial pain caused by somatoform disorder. This last category (TN7) was termed atypical facial