Neural Pathways in Macaque Monkeys to Help Understand Social Behavior

James Fallon’s The Psychopath Inside conveys a captivating story that ventures the realm of psychopathy, and how his personal life and career come to turmoil when he realizes that he has the mind of a psychopath.  To better understand the mind of a psychopath, one needs to journey into what makes them who they are. Psychopaths are known to use unforgivable means to gain what they desire, while lacking guilt or empathy towards others. In order to further understand empathy, one has to journey into the expressive act of compassion. Generosity is a direct representation of our ability to express our own empathy of others.  Virginia Hughes looks into the work of University of Pennsylvania graduate Michael Platt in the National Geographic post Generosity and the Social Brain, One Neuron at a Time.  His newest study focuses on the firing patterns of neurons in monkeys. The brain of the macaque monkey has structures and wirings that are similar to the brains of humans. Brain scans also show that we use the same region of our brains to make social decisions as the macaque monkeys.  

Ellen van Yperen

Platt directly observes the neurological pathways that are expressed when monkeys receive a reward or gives a reward to another monkey. In Platt’s experiment, he uses an ‘actor’ monkey and a ‘recipient’ monkey while recording eye gaze and brain activity. While being able to look at both a screen and the other monkey, the actor monkey views shapes of different colors on a screen. The actor monkey is then trained to understand that if it gazes to a specific shape, it can either be rewarded, the other monkey is rewarded, or nothing will happen. When the monkey was given the option of choosing between nothing happening or rewarding the other monkey, it chose to reward the other monkey. If it was given the opportunity to reward itself, the monkey typically chose to do so.  Platt and his associates recorded from three regions in the frontal cortex, including 85 neurons in the orbitofrontal cortex (OFC), 101 in the anterior cingulate sulcus (ACCs), and 81 in the anterior cingulate gyrus (ACCg). Through his research he found that the OFC showed more activity when the monkey chose to reward itself, and the ACCs had more activity when the monkey did not receive any form of reward.  In the ACCg, Platt discovered three different types of neurons that fired for self-rewards, when another individual is rewarded, and neurons that fire when both situations occur.  These findings show neurons that integrate self-awareness and the awareness of what is happening to others.  Platt’s research can aid in the understanding of our ability to empathize with other people, while also raising the question of whether these pathways properly function in the brains a psychopaths. Hopefully to one day be able to gain more knowledge and earlier signs of a psychopathic mind. 

Fallon, J. (2013). The Psychopath Inside: A Neuroscientist’s Personal Journey into the Dark Side of the Brain. New York: Penguin

Hughes, V. (2012). Generosity and the Social Brain, One Neuron at a Time. National Geographic.