The Emotional Foundations of Personality

by Kenneth L Davis

  In sum, early life stressors, especially traumatic experiences, are major risk factors for amplifying affectively negative brain circuits, most of which currently remain to be well studied. The evidence for diverse gene × environment interactions promoting personality and other psychiatric disorders is mounting, including transgenerational epigenetic inheritance. The cycles of negative affect become ingrained as characteristic ways of being (aka shifts in personality). Conversely, early affectively positive remedial interventions can facilitate affectively positive resilience against life adversities. Indeed, the long-term consequences of poverty are among the most salient, and potentially remediable with changing social policies (Johnson, Riis, & Noble, 2016). As noted by Bruce McEwen, one of the fathers of modern neuroendocrinology and stress research, “The healthy brain has a considerable capacity for resilience, based upon its ability to respond to interventions designed to open ‘windows of plasticity’ and redirect its function toward better health” (2016, p. 56). Indeed, the title of one recent review proclaimed “The Miraculous Ability of the Human Genome to Adapt, and Then Adapt Again” (Gershon & High, 2015). It will be both interesting and important to see how societies respond to the growing evidence base that various social-emotional interventions can ameliorate, even prevent, psychological damage inflicted by unconscionable stress in the early life of our youngsters.

  CONCLUSIONS

  For centuries, animal breeders have known that they can select for practically any physical or behavioral trait by selective breeding (see Chapter 8 on fox domestication). These same lessons have been learned by generations of psychologists that have bred for specific traits (see Chapter 9 on the breeding of many specialized rat strains), but rarely have the specific genes been identified. With the clarification of the mechanisms—the molecular biology of heredity—that is now possible. In a sense Darwin’s evolutionary vision has been fulfilled. But the ensuing genetic breakthroughs that are leading to powerful biomedical diagnostics and treatments are now being supplemented by the recognition that the promise of some of the other proposed paths of evolution, such as the focus on acquired traits—a view originally championed by the French biologist Jean-Baptiste Lamarck (1744–1829)—was not as far off the mark as commonly believed through most of the twentieth century.

  The finding that parents can pass on characteristics to their offspring that they have acquired during their lives has now been affirmed by modern epigenetic research, including work on environmental toxins (e.g., Skinner, 2015, 2016). Indeed, it now looks like some of these characteristics can be acquired emotional personality traits. Studies of “Lamarckian inheritance” have blossomed in the twenty-first century and are amplifying our understanding of the true complexities of our human-animal nature.

  The bottom line is clear for parents: As the twig is bent, so the tree will grow—now supported by the fact that children’s genes are affected by more than their nucleotide sequences. Psychologically, the best inheritance parents can give their children is abundant quality emotional time each day, especially, perhaps, abundant natural social play each and every day. This may promote epigenetic pathways that diminish childhood problems like attention-deficit hyperactive disorder, reducing the need to give children medicines that are well known to be addictive (Panksepp, 2007b, 2008b). Indeed, one can envision epigenesis operating at a cultural rather than just an individual level, with social play-promoting cultural values influencing how the brains of our young people mature.

  CHAPTER 16

  Human Brain Imaging

  The basic emotions are natural kinds that have specifiable neural substrates within the mammalian brain. If we do not come to terms with such foundation principles, we will have impoverished views of psychological and cultural complexities that ultimately arise from emotional learning.

  —Jaak Panksepp, “Emotions as Natural Kinds Within the Mammalian Brain”

  BRAIN IMAGING HAS BECOME a popular tool in the neurosciences. The brain imaging procedure that has become the most common and easiest to administer is functional magnetic resonance imaging (fMRI). Like computed tomography (CT), MRI is able to generate cross-sectional images of human anatomy without using X-rays. However, fMRI combines MRI technology with highly specialized statistical analyses to measure localized brain activity. Typically, fMRI uses the blood-oxygen-level dependent signal contrast to measure blood flow in a brain region. The assumption is that when brain activity increases, blood flows to that region and hence oxygen levels increase as well. While this assumption generally holds when measuring the activity of cortical regions of the brain, with their rapidly firing neurons, subcortical neurons tend to fire at much lower rates than cortical neurons creating a detection bias against finding statistically significant estimates of brain activity increases in subcortical regions. In addition, functionally relevant subcortical regions are generally smaller in size, with many nearby, overlapping functional circuits, making them even more difficult to detect.

  PET ALTERNATIVE: THE DAMASIO GROUP

  An alternate brain scanning procedure, positron emission tomography (PET), is more invasive but substantially more relevant for imaging emotional feelings and particularly so for the smaller, slower-firing subcortical regions of the brain. With PET, not only can general brain activity measures be monitored, typically, by measuring glucose utilization (because the main fuel for brain activity is glucose) but there is also the possibility of measuring various neurochemicals from traditional transmitters—biogenic amines such as dopamine, serotonin, and norepinephrine to more specific functional controls such as brain opioids, as long as positron emitting forms of these molecules have been synthesized.

  A landmark study published in the prestigious scientific journal Nature by Antonio Damasio’s research group, which included his wife Hanna who is a specialist in brain anatomy (Damasio et al. 2000), used PET technology to image the whole brain while their subjects actually experienced emotionally powerful states evoked by reminiscences of their own lives. In other words, their goal was to identify neuroanatomical regions whose activity correlated with the experiencing of specific personal memories of past emotional feelings. To ensure optimal results, they first screened their subjects for their ability to self-induce emotions through recalling autobiographical memories of emotionally powerful personal experiences, as well as a neutral episode recalling normal daily events.

  For this project, the Damasio group investigated four target emotions: sadness, happiness, anger, and fear. Because of the emotionally taxing reenactment of these powerful experiences, for example, the death of a relative or close friend for the sadness emotion, subjects were assigned to recall only two of the four emotions, based on their prescreening demonstrations, as well as a neutral experience serving as the experimental control. Importantly, the PET brain data were collected (i.e., the radioisotope was intravenously infused) only after the subject reported actually feeling the emotion.

  As might be expected, a whole-brain image analysis during the generation of different emotions would produce complex results. However, many of the remarkable correlational findings using their forty-one carefully selected human subjects were consistent with the experimental animal research using deep brain stimulation and related procedures to study primary emotions. These investigators also collected physiological measures of bodily arousals, such as skin conductance and heart rate, that had previously been used to monitor emotional states in humans.

  One of the main findings from this Damasio study was the consistent activation of brainstem regions such as the periaqueductal gray (PAG) when these emotions were aroused, regions that are often cited in animal studies of primary emotions. This finding was especially interesting because up to this time “The brainstem has not been noted to be active in other human studies of emotion” (Damasio et al., 2000, p. 1052). Indeed, most previous brain imaging research studying human emotions had focused on cortical brain regions. For example, a meta-analysis (Phan, Wager, Taylor, & Liberzon, 2002) fo
und that, of fourteen studies imaging sadness, a cortical region known as the subgenual anterior cingulate cortex (also known as Brodmann area 25, an evolutionarily older cortical midline structure located just below the anterior portion of the corpus callosum and just posterior to the prefrontal cortical region known as Brodmann area 11) was the most consistently activated brain region, which, although evolutionarily older than neocortex, was not a subcortical brain region. Thus, Damasio et al. (2000) were among the first to confirm previous primary emotion research in animals by using human subjects to illuminate the activation of subcortical brain regions during their experience of personally relevant emotional arousals, in stark contrast with the dominant picture emerging from other human brain imaging studies attempting to discern which cortical brain regions correlated with the generation of specific human emotions. For an easily interpretable picture summary of Damasio et al.’s (2000) PET imaging results, see Panksepp, 2011a, which is readily available.

  Another of Damasio et al.’s (2000) findings that contrasted with the opinions of many psychologists, who believed that emotional feelings arise from neocortex, was that during the experience of strong human emotions, many neocortical brain areas were deactivated rather than activated. In accord with previous affective neuroscience research using animals, not only were subcortical areas consistently activated when humans experienced strong emotions but neocortical regions were, if anything, commonly deactivated, which was consistent with the animal evidence that cortical regions were not necessary for the experience of emotions. Animals as well as humans are able to express and experience a full range of primary emotions even if the neocortex had been removed at birth or, in the case of humans, when they were born without neocortex (Panksepp, Normansell, Cox, & Siviy, 1994; Merker, 2007; Solms & Panksepp, 2012).

  The activation of ancient subcortical brain regions such as the PAG and the deactivation of more recently evolved neocortical brain regions, such as the dorsolateral prefrontal cortex, during the experience of primary emotions is also consistent with the idea that these physically as well as evolutionarily separate brain regions exhibit a kind of reciprocal “seesaw” interaction as the human brain contends with events that trigger or inhibit the expression of primary emotions (Liotti & Panksepp, 2004). With psychopathology, this seesaw relationship may become imbalanced as the emotional regulation processes become impaired, leading to consistent and persistent dysfunctional biases in the interpretation of socioenvironmental events, which may lead to less-regulated emotional experiences.

  As the subcortical brain perceives various survival challenges and we experience intense emotional feelings, the subcortically based primal emotional systems may impose “states of mind” over many regions of the cerebral cortex, thereby altering the “color”, “tone”, and “interpretation” of experiences without changing the neocortical processing of specific cognitive contents (Mesulam, 2000, p. 79). While the connections from the cerebral cortex to the subcortical-limbic networks may be less extensive even in the human brain than the reciprocal subcortical to cortical connections, the recovery from emotional arousals likely involves the activation of diverse cortical-cognitive regulatory processes and thereby the reciprocal deactivation of emotional arousals as the subcortical emotional substrates are downregulated (Liotti et al., 2000). Indeed, Frank et al. (2014) have summarized the field of emotional regulation and provided consistent evidence of prefrontal cortex (PFC) regions becoming activated in service of downregulating negative emotions.

  Related to the previous two findings, a third result from this Damasio study was another big surprise. One of the major areas focused on in studies of conditioned fear in animals has been the amygdala (LeDoux, 2012b). However, arousal of the amygdala in human fear experiences was not prominent in the Damasio results. Indeed, the authors noted: “There was no significant activation of the amygdala on either side [of the brain] for any of the emotion/feeling states” (Damasio et al., 2000, p. 1050). While it is clear that the amygdala plays a role in the expression and learning of fear and anger, it is also true that the amygdala is not essential for the experience and expression of fear or of anger, although its participation is more extensive for the learning of specific fear responses (Panksepp, 1998a).

  Earlier animal research (preceding brain imaging technology) by A. Fernandez De Molina and Robert W. Hunsperger at the University of Zurich (building on the work of their colleague, the Nobel Laureate Walter Hess introduced in Chapter 7) strongly supports the Damasio group’s third finding. These Swiss brain studies were the first to demonstrate that what we call the basic mammalian RAGE/Anger system runs from the PAG in the midbrain up to the medial hypothalamus and further up to the medial amygdala. De Molina and Hunsperger (1962) showed that the rage responses of cats can be evoked using electric brain stimulation from all three sites. However, the system is hierarchically organized, in levels of progressively increasing importance, such that aggressive responses evoked from the amygdala were abolished by lesions at the hypothalamic or PAG levels, aggressive responses elicited from the hypothalamus were dependent on the PAG but not on the amygdala, and aggression triggered from the PAG was not dependent on either of the other two “higher” brain regions. But, De Molina and Hunsperger were not satisfied by laboratory demonstrations. Cats receiving the small lesion of what they called the “hissing zone” of the PAG, “when confronted with a dog, no longer hissed or attacked” (p. 201). For a hierarchical illustration of this system, see Figure 16.1.

  While the amygdala likely integrates psychological learning into the RAGE/Anger system and the hypothalamus blends in physiological influences, the PAG seems to be the primal source of RAGE/Anger responses, with damage to the PAG dramatically reducing rage evoked from the other two regions (Panksepp, 1998a). An additional corroborating demonstration in humans from the Mobbs group will be covered but first a brief summary.

  In sum, the Damasio group’s 2000 PET study yielded three remarkable results, which still need to be more fully integrated into psychological and psychiatric thinking about human emotions: the emphasis on subcortical activation, bilateral neocortical deactivations, and the lack of amygdala activation during strong emotional arousal. The Damasio et al. paper, along with the supporting animal findings, also provides compelling evidence for the affective neuroscience interpretation of where raw emotional feelings arise in the brain (Panksepp, 1998a). Indeed, the subcortical regions of the brain, which are homologously shared by all mammals (and many other vertebrates), provide more than just the evolutionary foundations of human emotional experience. In other words, their functional role in the generation of primary human emotional experiences remains as “primary” for humans as it is for other mammals.

  Figure 16.1. Hierarchical control of RAGE in the brain. Lesions of higher areas do not diminish responses from lower areas, while damage of lower areas compromises the functions of higher ones.

  WHEN FEAR IS NEAR: MOBBS’S VIRTUAL PREDATOR RESEARCH

  Dean Mobbs of the University College London and colleagues, took a very evolutionary approach to studying fear that largely confirmed the Damasio group’s work described above, as well as De Molina and Hunsperger’s work emphasizing the emotional importance of the PAG. Mobbs’s group used high-resolution fMRI, rather than PET, to acquire participants’ brain images during a computer-simulated survival challenge called the virtual predator and prey paradigm (Mobbs et al., 2007, p. 1080), or what they sometimes referred to as an active escape-from-pain task.

  This task required volunteer subjects to escape from the virtual predator to avoid receiving a painful electric shock intended to simulate the predator’s bite. It involved displaying the positions of the predator and the participant (who was the prey) on a two-dimensional maze grid that appeared on a screen, which the subject could see while in the scanner. In an initial neutral “pre-encounter” phase, the symbol depicting the inactive predator was displayed in the lower left corner of the grid or wandering about the maze but posing no
immediate danger, and the symbol for the subject appeared in the upper right corner of the grid. Next, in a “postencounter” cue phase, the threat was detected: the subject saw that the “flashing” predator was active and also learned whether being captured by the predator would result in one shock (for the low level of pain) or three shocks (for the high level of pain). Then, when the predator symbol ceased flashing, the “chase” phase was on, and the participant could now attempt to move his or her symbol to escape the predator. If captured by the predator, the subject received the amount of painful shock previously indicated. Importantly, Mobbs et al.’s (2007) results showed that their subjects were motivated to escape the shocks, especially the higher level.

  When the threat was first detected but not yet imminent, their analysis showed enhanced activity in frontal cortical areas such as the medial orbitofrontal cortex (mOFC; just above the eyes—orbit is another term for eye socket), the ventromedial prefrontal cortex (vmPFC) (just above the mOFC), and the anterior cingulate cortex (ACC), an adjacent older cortical area known to be involved in pain processing. During the chase phase, increased activity was observed in subcortical areas such as the PAG. As the threat became more imminent (regardless of whether subjects were caught and received the shock, or managed to escape from the virtual predator and received no shock), PAG and amygdala activity were evident, with the highest PAG activity occurring when subjects were facing the highest imminent shock level. These researchers also asked their subjects to rate the levels of “dread” of being chased and “confidence” of escaping capture that they had experienced. Increased dread and lower confidence were also associated with increased PAG activity, whereas diminished dread and higher confidence of escaping were associated with stronger prefrontal cortical activity.