Functionally, these neurons are either motor (conducting impulses that will cause activity such as the contraction of muscles) or association (conducting impulses and permitting 'communication' between neurons within the central nervous system).
The scant research that has been done on the causes of pica suggests that the disorder is a specific appetite caused by mineral deficiency in many cases, such as iron deficiency, which sometimes is a result of celiac disease or hookworm infection.
Illness: Certain diseases and illnesses can cause a dog to eat feces. A symptom of some diseases is increased appetite or ingestion of inappropriate items (called pica). An illness that changes the consistency or smell of the stool might make a dog want to eat his own stool. Sudden onset of coprophagia calls for a veterinary exam. Anxiety, Fear, and Stress: A dog in fear or under a great deal of stress may eat his own stool. This may be a kind of self-soothing mechanism in some cases. However, if a dog is punished for inappropriate defecation or other action related to feces, he may associate the punishment with the presence of feces.