Good Judgement Depends On Brain Connectivity
It's well known that judgements about value and risk depend on development of the prefrontal cortex, but a recent study has added to that understanding. Volunteers aged 13 to 20 years played a game in which they were to press a button to one version of a stimulus and withhold response to a slightly different one; correct responses were rewarded with 20 cents under the low stakes condition and $1 under the high stakes condition. Ordinarily we would expect performance to improve when larger rewards are available, but this was the case only among the 19-20 year-olds. Scanning with fMRI showed that better performance was associated with increased activity in the prefrontal cortex and more powerful connections with subcortical striatal areas. In other words, differential reward was poor at regulating behavior in the younger individuals, apparently in part because they were less able to access reward information, which helps explain why rewards and punishments are not very effective with teens. Nature Communications, Vol 8, #1605 (online).

The Amygadala's Role in Assessing Facial Emotions
Work at the California Institute of Technology is helping us understand how the amygdala processes facial cues of emotion. The researchers showed volunteers photos of fearful, happy, or ambiguous faces while making single-neuron recordings in neurological patients. They found two groups of responsive neurons. Emotion-tracking neurons responded exclusively either to fearful faces or to happy faces and fired more rapidly to more intense expressions of emotion. Ambiguity-coding neurons indicated the ambiguity of the emotional expression. In ambiguous situations the emotion-tracking neurons indicated the emotion that was ultimately chosen. Besides defining how the amygdala processes emotions at the neuronal level, the results indicate that the amygdala does more than simply respond to emotions by playing a decision making role as well. Nature Communications, Vol 8, #14821 (online).

Stress Effects Transmitted to Offspring Via MicroRNAs
Some environmental conditions exert epigenetic effects by changing the levels of microRNAs. MicroRNA (miRNA) is short, non-coding RNA that represses protein production by disrupting messenger RNA (see p 90 of the text). In some cases miRNA levels are altered in the sperm; in mice, this has resulted in transmission of stress effects from the male parent to offspring. Human sperm mRNA is affected by smoking and obesity, and now a study has found that early abuse reduces levels of two sperm miRNAs, miR-449 and miR-34, the same ones that are altered in mice. Reductions were as much as 300-fold in the men with the highest levels of abuse. Subsequent research will investigate whether this affects the men's offspring and, if so, whether the effects can be reversed. This is promising, because previous research has reduced stress transmission across generations of mice by enhancing their social and physical environments, and weight loss restores levels of sperm miRNAs in obese men. Translational Psychiatry, 8: 101.



Politics Can Affect Your Health
If you think politics can be stressful, you're right. Researchers with Nokia and Nokia Bell Labs monitored sleep, activity, and heart rates among 11,500 wearers of Nokia smart watches during the U.S. presidential election and the UK's Brexit vote (to leave the European Union). Both events were associated with sleep disruption and increased heart rates. Following Brexit, for example, sleep time in London dropped by 10 percent; in San Francisco, average heart rates increased from 66 beats per minute to 70, and had not returned to baseline four months later. The changes were greater than those seen around Christmas and New Year's Eve. arXiv (Cornell University Library), arXiv:1804.06931.

Mirror Neuron Synesthesia
Mirror neurons are active when we observe another person's movements or expressions of emotions (text, pp 213-214). We don't ordinarily feel what the other person does, but a few people, those with mirror-touch synesthesia, do. Subject TC has this experience to such an extreme that she laughs uncontrollably when she sees someone else being tickled, and places her hand on her body in the area being tickled in the other person, as if to make it stop. She is not emotionally labile in other situations. Neurocase, DOI: 10.1080/13554794.2018.1464583.

Gut Bacteria Linked to Emotion in Humans
Sudies in rodents have demonstrated a relationship between microorganisms in the gut—the microbiota—and emotional and social behaviors such as anxiety and depression, but until now it has not been reported in humans. A group of 40 healthy women was divided into two subgroups, one with more Prevotella bacteria and the other with more Bacteroides. The Prevotella group expressed higher levels of negative feelings such as anxiety, distress, and irritability after looking at photos with negative content. They also had more connections among emotional, attentional, and sensory brain regions, along with lower brain volumes in several areas, such as the hippocampus, and lower hippocampal activity while viewing the images. It is tempting to assume that the bacteria were the cause of these differences but more definitive testing is needed to support that conclusion, such as manipulating the microbiota populations in animals and observing the results. Psychosomatic Medicine, Vol 79, 905-913.

Cat Parasite May Contribute to Entrepreneurship
Toxoplasma gondii, a protozoan parasite spread in cat feces, makes rats lose their fear of cats, and there is evidence in humans that it contributes to aggression and road rage; now it has been linked to an entrepreneural business spirit, apparently because of its ability to reduce fear of risk and failure. Students exposed to T. gondii were 1.7 times more likey to be business majors, and more likely to be focusing on management and entrepreneurship. Professionals attending business events who were T. gondii positive were almost twice as likely to have started their own business. Proceedings of the Royal Society B, DOI: 10.1098/rspb.2018.0822.