We have all experienced the cascade of emotion evoked by a child’s hug or the simple act of taking the hand of someone that loves us. Dr. Francis McGlone and colleagues at Liverpool John Moores University in England have elucidated the structure and position of the nerve cells that produce emotions that are linked to the touch of another human. The research was published in the May 21, 2014, edition of the journal Neuron. This work is the first to begin characterizing nerve cells that are involved with touch and emotion and have provided a practical application in autism.
Touch that produces emotion is transmitted by neurons in the skin that are considered to transmit impulses slowly compared to the rates of transfer of other types of nerve cells. The nerve cells that convey emotion from touch are called c-tactile afferents. This type of cell only responds to gentle touch. The structure of the cell is extremely like the structure of pain receptors. Perhaps the Marquis de Sade was right. There may have been some point in evolutionary time when both the cells that respond to pain and c-tactile afferents were the same type of cell.
The researchers presume without proof that similar cells exist in primates and possibly other social animals that respond to touch. The scientists also note that humans need to be touched softly and kindly. Specific cells that respond to a certain type of touch would not have evolved without a purpose. The scientists also note that modern technological society and social media may be producing an alteration in humans that do not receive sufficient human touch.
The discovery has practical applications in the treatment of autism. Autistic people do not respond to human touch or social situations the way most people do. Some autistic people are actually frightened by the touch of soft clothing. The lack of comforting tactile input may be a part of the autism mystery according to Temple Grandin, assistant professor of animal sciences at Colorado State University. Professor Gardin is autistic and his research has shown that the lack of tactile input early in life can produce erratic behaviors in people who are not autistic.