Roundworms are used to study communication between neurons.
Credit: (2005) The Evolution of Self-Fertile Hermaphroditism: The Fog Is Clearing. PLoS Biol 3: e30. doi:10.1371/journal.pbio.003003.
Although an invertebrate with a primitive brain, the nematode (C. elegans) has a nervous system that uses neurotransmitters, receptors, and signaling pathways similar to those in the human brain. What's more, C. elegans shares about 21 percent of their genes with humans.
Scientists have studied the development of the C. elegans nerve cells extensively and found that adults have 302 neurons. Therefore, scientists have been able to map the connectivity between these neurons with precision, enabling them to match individual functions to neurons and their networks.
Another plus: C. elegans is very small (about 1 millimeter or, 0.04 of an inch long) and requires little care. In the laboratory, these animals live in petri dishes filled with a mix specially formulated for C. elegans health and food (they can use E. coli as a food source). Their life expectancy is about two to three weeks.