Researchers from the University of California, San Francisco published a study in the Journal of the American Medical Association. The study analyzed data from dozens of medical reports and other studies. The researchers concluded that fetuses are unlikely to feel pain until the third trimester of pregnancy. However a number of medical critics have since disputed these conclusions. There are certain connections in the thalamus of the fetuse. These connections develop at about twenty-six weeks of pregnancy. At the end of the 20th century there was an emerging consensus among developmental neurobiologists that these connections are very important when it comes to the perception of pain in the fetus. Other researchers such as Anand and Fisk have challenged this late date, positing that pain can be felt around twenty weeks.