New research has discovered how the enteric nervous system -- or 'second brain' -- can communicate with both the brain and spinal cord, which up until now had remained a major mystery. The study found specialized cells within the gut wall release serotonin when stimulated by food, which then acts on the nerves to communicate with the brain. The authors say as there is a direct connection between serotonin levels in our body and depression and how we feel, understanding how the gut communicates with the brain is of major importance.