The Brain, Society, and Disease Transmission
Dr. Patricia Lopes
Khaoula Ben Haj Frej
A Dr. Patricia Lopes’ “The Brain, Society, and Disease Transmission” lecture focused on neuroimmonumodulation and more importantly, the social acceptability of being ill. According to the speaker, disease exerts neural and hormonal changes, changes behavior, and that disease-induced changes in behavior are context-dependent. In fact, the “presence of mates, caring for offspring, competing for territories or maintaining social status” can impact how organisms behave in times of illness (Lopes, 2014). This research, though conducted on animals, can provide insight with human significance.
The speaker’s model animal for one study was the finch. Male finches tend to mate to exhaustion when introduced to a new female. In the study, a sick male, injected with LBS, under normal conditions would lie on the floor, acting completely abnormally, with a drastic drop in behavior. However, when introduced to a new female, the sick male completely transformed, moving around the cage and expressing courtship behavior, such as hopping and singing. A novel male had absolutely no effect, so it was the potential of mating which had the effect. These results back-up the claim that “sickness behaviors could be considered a motivational state” (Lopes, 2014). After all, the study animals act differently based on their surroundings and particular factors, whether in captivity or in their natural environment. Other studies involved postpartum parental care, early-age separation from parents, and male territorialism; in all cases, animals, regardless of model, showed different behaviors when ill (or when a partner was ill) in these situations and outside them (Lopes, 2014). Illness impacts behavior, but social “expectations,” if one may call them that for animals, can reverse or alter that impact.
Next, in her lecture, Dr. Lopes discussed how she also looked at the physiology, searching for changes in markers of inflammation in the brain. At this point, the researcher also chose to get more data form the birds, measuring their activity remotely and continuously, by providing them with a small “backpack” that acts somewhat like a smartphone, capable of measuring changes in acceleration. Low levels of acceleration are considered resting, slightly higher was hopping, and high levels were denoted flying. What was found was that birds that spent more time resting when sick had a higher level of immune-defenses but had diminished chances of mating. Those that did not voluntarily partake in sickness behavior pretended to be healthy and had higher chances of mating but also more of a risk of morbidity. As aforementioned, many animals seem to choose this latter option, often males in the presence of females, or others with young in need of care. This study showed the cost/profit balance considered among ill animals (Lopes, 2014).
When selecting a mate, animals produce signals for communication, which send certain signals denoting compatibility and other characteristics. The speaker explained that she decide to look for changes in these signals, this time in mice. Male mice produce ultrasonic vocalizations in the presence of females (or their urine, since it contains darcin, an attractive protein for mating). In this experiment, one male had an induced sickness (through a LPS injection) and another was healthy and they were placed on either side of a female, separated by a wall. Observations were made, then the windows between the animals were opened and they were observed. It was found that the sick male was not able to provide the attractive vocalizations and had lowered darcin levels. Furthermore, the female, after exploring their options, discriminated between the males, and spent more time at the window of the healthy male than the sick one. In this study, the female was able of realizing the cost and profit of mating with either male (Lopes, 2014), and thus chose the most profitable mate.
Why do these studies matter? According to the speaker, more than 50% of diseases come from wildlife and humans have a high amount of interaction with animals, as wildlife and food. Therefore, understanding animal diseases can affect one’s understanding of human illness. For example, disease has been shown to impact mouse social behavior, where a LPS-injected animal becomes removed from the animals within its social group, despite having interacted with them before becoming ill. It was found that this self-imposed isolation allowed for a better fate for the rest of the animals, resulting in less spread of the disease and thus fewer mortalities, than calculated for if interaction levels been higher.