The Biological Roots of Empathy

Empathy is understanding another’s experience by shared emotions and thoughts, while being clear that the experience is the other’s and not one’s own. Empathy is central to patient care and, in a larger sense, essential for the development of language, relationships, and civilization. Over the last century, psychoanalysts and behavioral scientists have struggled to understand what is going on when we experience this emotional and cognitive resonance with someone else. Since the 1990’s, when mirror neurons, which fire when an animal observes another animal act as well as when the animal acts itself, were discovered in monkeys, researchers have discovered a great deal about the neurocircuitry of empathy. As I noted in an earlier post, experts now agree that empathy involves emotional sharing, cognitive perspective-taking, regulation of emotion, and desire to help the other.

A fascinating review by Jaak and Jules Panksepp of basic emotional sharing posits three biological levels of empathy. The most basic, which they call emotional contagion, is best studied in animals, since it operates outside of consciousness in deeply subcortical regions of the brain. Experiments involving electrode implantation, lesions, and manipulation of genes and their expression are necessary. These basic affects feed upward to a second level the Panskepps call empathic habits or secondary-process learning, involving basal ganglia and upper limbic regions. These can be studied both in animals and humans. (Joseph Ledoux’s work on anxiety, which I discussed in an earlier post, looks at these intermediate-level events.) These then feed up as ruminations and thoughts into full cognitive empathy, which can only be studied in humans. The higher levels of empathy cannot be understood biologically without reference to the lower levels, since the lower levels are the foundations of empathy in both evolution and human development. Nevertheless, the higher levels exert top-down control over the lower levels.

Drawing on animal research, Panksepps go on to lay out what is known about the first level, identifying seven systems. These are integrated with each other, project upward to higher brain levels, and receive regulatory feedback from above, but operate well below the level of conscious awareness.

The seeking/desire system is the general-purpose motivational system that enables animals to find resources to survive and, when conditioned, to anticipate these resources. This well-known brain reward system is fundamental to the brain’s operation and the organism’s survival and, as I have discussed, central to the pathophysiology of addiction. The regions involved are the ventral tegmental area, the medial forebrain bundle, the nucleus accumbens, and the medial prefrontal cortex. It utilizes the neurotransmitters dopamine, neurotensin (a neuropeptide involved in regulation of dopamine systems and in some ways mimicking the action of antipsychotic drugs,) and orexin (a hypothalamic peptide involved in regulation of arousal and appetite.)

The rage/anger system produces aggressive behavior when animals are irritated or confined and facilitates self-defense by arousing fear in opponents. It operates in the dorsal periaqueductal gray, the ventral median forebrain bundle, the medial amygdala, and the prefrontal cortex and uses the neurotransmitters substance P (a peptide involved in regulation of emotions and pain) and neuropeptide Y (another peptide involved in food intake, anxiety, pain perception, and circadian rhythms.)

The fear/anxiety system, which I discussed last month, involves the ventral and dorsal periaqueductal gray, the ventral medial forebrain bundle, the lateral and central amygdala, and the prefrontal cortex. Its main neurotransmitters are corticotropin releasing factor and neuropeptide Y.

The lust/sexual system’s role in empathy is not clear, although empathy is generally higher in females than males. This system, like the fear/anxiety system, involves the ventral and dorsal periaqueductal gray, the ventral medial forebrain bundle, the lateral and central amygdala, and the prefrontal cortex. Neurochemically, estrogen facilitates oxytocin action, while testosterone facilitates vasopressin action. (In addition to its role in water retention and vasoconstriction, vasopressin has been found to play a role in aggression, pair-bonding, and regulation of anxiety.)

The care/maternal nurturance system, which is thought to contribute to the desire to care for others, involves the ventral periaqueductal gray, the medial forebrain bundle, the medial hypothalamus and preoptic area, the corticomedial amygdala, and the mid-cingulate gyrus. The neurotransmitters are oxytocin and vasopressin.

The panic/grief system may also contribute to empathy. The Panksepps note that young mammals’ distress calls resemble panic attacks. (If this is true, then panic disorder would differ from generalized anxiety and fear at a fundamental neurobiological level.) In adults, the system is associated with sadness and depression. The anatomy involves the dorsal periaqueductal gray, the dorsomedial thalamus, the bed nucleus of the stria terminalis, and the anterior cingulate. The neurotransmitters are corticotropin releasing factor, endogenous opioids, oxytocin, and prolactin.

Finally, a play/physical social-engagement system underlies young animals’ strong tendency toward rough-and-tumble play; it involves the ventral tegmental area, the parafascicular thalamus, and the medial prefrontal cortex and utilizes endocannabinoids, endogenous opioids, and probably many other neuropeptides.

The Panksepps’ effort to organize this complex and rapidly-evolving neurobiological picture is helpful, though others might put things together differently. They, like LeDoux, for the most part avoid using the term “emotion” when discussing these lower-level processes. The suggest that “primal empathy is a shared neurobehavioral. . . process rather than a unique emotional state per se. . . In LeDoux’s schema, only for the highest level, which involves conscious awareness, would “emotion” be appropriate.

The Panksepps argue that primitive responses produce aspects of empathy below the level of conscious awarness. This is not surprising, but it is worth keeping in mind, since so many clinical discussions of empathy focus on understanding the patient’s cognitive understanding of his situation. As Damasio argued years ago, thoughts are intimately connected with unconscious bodily processes; the Panksepps' paper contributes to understanding those processes.

Seven systems are a lot to stitch into a coherent picture of empathy, and the Panksepps note that the contributions of the lust/sexual and panic/grief systems to empathy are not clear. They also avoid speculation about just how activations of these basic brain systems operate to produce either primitive or higher level empathy. Here we may need to distinguish between the how and the what of empathy—how the primitive, unconscious areas of person’s brain comes to resonate with another person’s, as distinguished from the particular affective processes that are being shared. At first glance, the seeking/desire, care/maternal nurturance, and possibly the play/physical social-engagement systems might be most involved in facilitating affective resonance, while the other systems might be activated in the empathizing person when they are activated in the other.

Much human empathy research has focused on empathy with pain. The Panksepps’ system does not identify a basic pain system, but the fear/anxiety and rage/anger systems appear to be involved.

Their identification of a panic/grief system distinct from the fear/anxiety system brings up psychiatry’s long struggle to understand the different kinds of anxiety—see my post on anxiety—as well as anxiety’s relationship to depression, since many patients suffer from both, and treatments such as SSRI’s and cognitive-behavioral therapy are effective for both.

The Panksepp’s explication of the basic biology of empathy expands our view of empathy and provides a wide-angle x-ray of the emotional and social brain.

Further reading: Jaak Panksepp and Jules B. Panksepp, Toward a cross-species understanding of empathy. Trends Neurosci 2013 August; 36(8)

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