Which one is stronger: the desire to sex or the need to avoid someone who is sick? New research suggests that, at least in mice it is the latter.Gloria Choi, an associate professor at MIT of brain and cognitive sciences and a member the Picower Institute for Learning and Memory found that male mice who encounter a sickly female mouse had a lower level of interaction and a decreased likelihood of attempting to mate. Researchers also found that the brain circuit in the amygdala controls this behavior. It detects distinct odors and signals to stay away.Choi says that animals need to be able socially to distance themselves from sick people. It is essential to have a mechanism to stop mating in species such as mice.Chois' lab studies how illness affects behavior and neurological development of mice. This includes the appearance of autism-like behaviors after maternal illness. This is Chois' first study to show how illness can alter healthy individuals behavior and override their instinctive programming for activities like mating.She says that we wanted to find out if there was a brain mechanism that activates when an animal meets a sick member from the same species. This would allow us to modulate our innate, automatic social behavior.Previous research has shown that mice are able to use the odor of LPS (a bacterial component) to differentiate between healthy and sick individuals. The researchers put male mice in cages with healthy or LPS-infected females. The males were less interested in the sick females than they were with the healthy ones and did not attempt to mate.Researchers discovered that social distancing can be caused by activating a portion of the amygdala, called the COApm. This organ is fed into by the vomeronasal. LPS-injected animals activated COApm and suppressed males' desire to mate with sick females. They also showed little interest in healthy females when the COApm activity was artificially stimulated. However, when COApm activity was shut off, males attempted to mate with sickly females.Communication within the amygdala, which is responsible for controlling thyroid activity and thyrotropin-releasing hormone (TRH), was found to be key to suppressing mate behavior. Choi points out that thyroid dysfunction has been linked to depression and social withdrawal in people.This is part of an ongoing effort by her lab to examine the role of neuroimmune interactions in coordinating sickness behaviors.
