Testosterone appears to increase activity in the amygdala –the emotional center of the brain — when a person is approaching a socially threatening situation but decreases the activity when such a situation is avoided, according to a new study at Radboud University. This suggests that the amygdala may be more responsive to motivation rather than the emotions themselves.

Prior research has shown that the amygdala response to images of angry faces is stronger in a person who had received testosterone. However, the new findings show that this only occurs when people approach angry faces and not when they avoid them.

“It seems that testosterone facilitates social approach by specifically activating the amygdalae only if social approach is desired,” says Karin Roelofs, Professor of Experimental Psychopathology at the Donders Institute for Brain, Cognition and Behaviour, Radboud University.

“This is interesting for two reasons. It explains previous research that showed that testosterone makes approaching a social threat easier. Even more important, it shows that the amygdalae are not necessarily linked to dealing with emotions, but rather to motivation.

“Many studies forget to look at motivation. We are the first to demonstrate that the impact of testosterone on amygdala response depends on the motivational context,” added Roelofs.

For the study, which was double-blind and placebo-controlled, 54 young healthy women were given 0.5 mg of testosterone (or a placebo) four hours before a brain scan. This dosage is much lower than, for example, what is used for a sex change treatment, or as a supplement for athletes, but it is sufficient to have a measurable effect on brain activity.

The participants underwent fMRI-scanning while they were shown photos of happy and angry faces. They were asked to give a sign of rejection (away from) or of approach (towards).

People normally have less of a problem approaching someone who looks friendly than someone who looks angry: making a sign of approach when seeing an angry face actually requires more effort and control.

The study confirmed this as reaction times were longer when an angry face was approached. The amygdala activity was greater in women who had been given testosterone only when they approached angry faces.

“Previous research has shown that higher testosterone levels lead to an intensified amygdala reaction in the presence of angry faces,” said Roelofs.

“Those earlier investigations looked at what happens in non-active situations and not during action. The focus was on what you should do if you see an angry face.”

“We’re now going to repeat this study in people with social anxieties. We have already discovered that these people have lower testosterone levels. We are going consider how we can apply these results with testosterone to improving the treatment for anxiety disorders.”

Source: Radboud University