It appears that as the self-representational capacities of mammalian brains became more elaborate, the ability to integrate varied sources of information and the complexity of the self increase correspondingly. Especially with primates, this means becoming ever more reliant on the cerebral mantle (neocortex) for more refined analyses of sensory data as the cortex learns to provide ever more sophisticated interpretations in the service of more sophisticated behavioral strategies. This mantle allows us to have more sophisticated strategies to find, construct, and hold resources, just like an overcoat allows us to survive in cold weather. However, this does not mean that a more cerebrally complex self can be sustained on its own without the continuous support of primary (evolutionarily more ancient) affective BrainMind functions. And, with the increased reliance on refined cortical abilities and interpretations, some new mental “problems” can emerge as well.
We now summarize a series of fascinating ways human self-referential bodily feelings can be projected into the inanimate world. We do this to help highlight that our sense of personal ownership of our personalities may be less stable than we commonly believe. Although how these issues relate to understanding human personality remains ambiguous, the following fascinating laboratory demonstrations show that our neocortex and the higher sense of ourselves can fool us about the sources of experience.
ANOSOGNOSIA
One interesting body ownership phenomenon is called anosognosia (a literal Greek translation is “without disease knowledge”), a deficit of self-awareness that can occur after a stroke. For example, a person whose left arm is paralyzed as a result of a stroke may deny that the paralyzed limb is part of the body. This sounds bizarre. Although the condition occurs in about 10 percent of acute stroke patients, it usually does not persist for long (Starkstein, Jorge, & Robinson, 2010).
There are also a related series of fascinating demonstrations that we can project our feelings into inanimate objects as if they were part of our body. For instance, a faulty body ownership phenomenon that can be easily induced in a laboratory is called the rubber hand illusion, in which subjects begin experiencing that an artificial hand belongs to their own body (Botvinick & Cohen, 1998). These researchers created the illusion by placing the subject’s left arm on a table but hiding it from the subject’s view with a small standing screen. Then a full-sized rubber model of a left arm and hand was placed on the table in front of the subject. While the subject viewed the rubber hand, two small paintbrushes were used to simultaneously stroke the rubber hand and the subject’s own hidden hand. After ten minutes of “synchronous” stroking, the subject was asked to complete a questionnaire, which showed . subjects strongly agreed that “I felt as if the rubber hand were my hand” and that “It seemed as though the touch I felt was caused by the paintbrush touching the rubber hand.” The researchers also asked subjects to close their eyes and slide their right index finger under the table until it aligned with the index finger of their left hand. Experimental subjects shifted their alignment an average of 2.3 centimeters toward the rubber hand, while control subjects who received “asynchronous” brushing shifted alignment away from the rubber hand.
Armel and Ramachandran (2003) took this illusion several steps further by demonstrating that, in addition to brushing, sensory tapping could also generate the illusion. They also provided what they called an absurd situation in which they successfully substituted the tabletop for the rubber hand. These researchers further showed that strong skin conductance responses, a physiological measure of autonomic arousal, were elicited if either the adopted rubber hand or adopted tabletop was “injured” despite the fact that all surprise was ruled out by showing the participants in advance the painful procedures, such as extreme finger bending or ripping off a bandage, and assuring them these would not be performed on their real hand.
Henrik Ehrsson’s group at the Brain, Body and Self Laboratory at the Karolinska Institutet in Stockholm provided fMRI data to test the feeling of ownership and the extent to which the rubber hand was incorporated into the body. They were able to show that threatening the adopted rubber hand by making stabbing movements toward that hand with a needle (without actually touching the rubber hand) could induce activity in the anterior cingulate cortex (ACC) and insula—areas of the brain associated with the anticipation of pain—similar to when the subject’s real hand was threatened, and the effect was stronger than the effect of just seeing the needle (Ehrsson, Wiech, Weiskopf, Dolan, & Passingham, 2007). Moreover, “the more strongly the participants felt the rubber hand to be their own hand, the greater the activity in the ACC and left insular cortex when the hand was under threat” (p. 9,831). These researchers were also able to show a positive correlation between anxiety ratings collected after the threat procedures and ACC and insular cortex brain activation during the synchronous stroking condition, with no corresponding effects during the asynchronous control condition.
Petkova and Ehrsson (2008) were able to extend this distortion of body ownership to complete “body swapping”—the feeling that another person’s body is your own. Using a mannequin with cameras mounted on its head that projected its image to a head-mounted visual display worn by the subject, when the subject looked down, he or she saw the abdomen of the mannequin. In addition to this visual stimulation, the subject and mannequin both received simultaneous tactile strokes on the abdomen with a short rod. Via the headset, the subject could only view the strokes to the abdomen of the mannequin. After synchronous visual and tactile stimulation, the subject showed a significantly greater skin conductance response when the abdomen of the mannequin was threatened with a knife than when threatened by a spoon or when threatened with a knife after having received only asynchronous stimulation. While humans normally experience a spatial unity between their self and their body, a lab in Switzerland further tested the extent of these body illusions by showing how we can experimentally induce “out-of-body” experiences in which a person’s sense of bodily location was shifted toward a virtual body in front of the person (Lenggenhager, Tadi, Metzinger, & Blanke, 2007).
Others had previously reported that operating a robot would lead to feeling embodied within the arms and body of the robot (Cole, Sacks, & Waterman, 2000). The robot had human-like arms and fingers, which were directly activated, after a short delay, by sensors placed on the operator’s arms and hands. Cameras placed on the robot projected images of the robot’s arms to a headset worn by the operator, which provided a viewpoint similar to the view of the operator’s own arms and which eliminated any direct vision of the operator’s own body. After a few minutes of operating the robot and experiencing the proprioceptive feedback from their unseen arms, coupled with seeing the nearly simultaneous movements of the robot’s arms, participants “became at ease with the feeling of being ‘in’ the robot” (p. 167). The sense of embodiment was sufficiently strong that one operator had the sensation that “he had better be careful for if he dropped a wrench it would land on his leg” (p. 167), even though the robot holding the wrench was on the other side of the room. Clearly, our neocortex can easily construct delusional perspectives. But as a side note, these shifts in perspective might also relate to the human capacity for empathy, the affective foundations of which are shared with other mammals (J.B Panksepp & Panksepp, 2017).
H. Henrik Ehrsson’s group (Ehrsson, Spence, & Passingham, 2004) has also conducted human experiments in which they acquired fMRI brain images during the induction of the rubber hand illusion and found that activity in the premotor cortex, an area just in front of the primary and supplementary motor cortex, is associated with the feeling of ownership of the seen rubber limb. Further, the level of brain activity in the premotor cortex was directly proportional to the degree of subjective ownership reported by the participant. These authors argued that self-attribution of body parts depended on multisensory integration occurring in the ventral premotor cortex, which is connected to visual and somatosensory (tactile) areas of the cortex. However, it should be no
ted that their fMRI procedures did not adequately explore subcortical regions of the brain.
This Swedish research group was also able to reverse the illusion: rather than inducing participants to adopt a rubber hand, they induced them to “disown” their own hand. This was accomplished by using a video recording of the participant’s hand being stroked (made previously with the participant’s eyes closed). In the experiment, participants were able to see only the video recording while their own hand was being stroked either synchronously or asynchonously with the viewed video image. On a postscan questionnaire, participants receiving stroking that was asynchronous with their viewed image strongly reported that “it felt as if I was looking at somebody else’s hand.” Under the asynchronous stroking condition, subjects also exhibited significantly smaller skin conductance responses when the viewed hand was threatened with a kitchen knife and did not exhibit the expected fMRI responses compared to when the tactile stroking was synchronous with their viewed image (Gentile, Guterstam, Brozzoli, & Ehrsson, 2013). This loss of self-ownership of the participant’s own hand was consistent with their premise that “maintenance of updated representation of the body is an essential prerequisite for goal-directed or defensive interactions with the external world and the sense of a bodily self” (p. 13,350).
COULD THE HUMAN SELF BE PRIMARILY CORTICAL?
While body ownership illusions and the associated brain data are impressive, these novel self-attribution adaptations are also as easily reversed as they were generated. Do they mean that in humans the core self has become a cortically induced phenomenon? Does this all mean that, like with the senses, the neocortex has also become the dominant provider of the sense of our experienced core self and hence that a complex human cognitive sense of self—what has been called the idiographic self (Panksepp & Biven, 2012)—relies on and cannot survive without these cortical representations?
Brain damage studies and other brain research suggest otherwise for at least core self processes. Indeed, even in neurologically intact humans, the core self remains deeply rooted in the subcortical emotional foundations of the brain with links to other brain structures evolutionarily older than the neocortex. The evidence does not support the idea that the cortex, especially the neocortex, is essential to maintaining a stable sense of an affective core self.
It is well documented that brain damage in humans to the frontal motor regions of the neocortex (where plans and intentions are generated) results in greater personality changes than damage to posterior sensory regions of the neocortex (Eslinger et al., 1992; Passingham, 1993). Neocortical sensory losses may include numbness or the loss of vision or hearing. Neocortical damage often influences the ability to use language. Neocortical motor losses may also include reduced muscular control, paralysis, or personality-altering reduced impulse control. Yet, these patients still have an affective sense of self and feel they are still very much the same person they always were despite their life-changing cognitive or physical limitations. Their fundamental sense of self and affective experience have not been eliminated, and as with anosognosia, any self-disturbance resulting from damage to these more lateral (more recently evolved) brain regions typically does not persist.
Nobel Prize winner Roger Sperry’s famous split-brain studies (for an historical overview, see Gazzaniga, 2015) likewise do not support the idea that the cortex is essential for a coherent sense of self. At that time, almost half a century ago, the split-brain procedure had become a successful treatment for patients with severe epileptic seizures. In these patients, surgeons completely cut through the corpus callosum, the brain structure connecting the left and right cerebral hemispheres, thus separating the two cerebral hemispheres and greatly reducing the intensity of life-threatening seizures by preventing their spread from one hemisphere to the other. One might assume that this procedure would greatly disrupt the self, possibly creating two selves, if the basis that the self lies primarily in the cortex. However, no such dramatic shift occurred. Indeed, after the patients recovered from surgery there were no signs of changes to their outward behavior or functioning. Special experiments on these subjects were required to demonstrate any differences, and these differences had little to do with the self.
These patients did not exhibit split personalities and displayed fluid, whole-body intentional behavior. As Michael Gazzaniga, one of Sperry’s students, pointed out in his book The Mind’s Past, “Split-brain effects have to be exposed in a laboratory, where special techniques separately test each half-brain” (1998, p. 132). He does goes on to say that split-brain patients seem to have two minds with different skills and abilities—we might say learned cortical representations. But, also that during laboratory tests, in which the nonspeaking right hemisphere was given a command, while the speaking left brain couldn’t say what command had been given to the right hemisphere, “it [the left hemisphere] didn’t seem perturbed about the right brain carrying out whatever the command might be. There was never a complaint about this odd state of affairs” (p. 132).
The ease with which split-brain patients conducted their lives may relate to the fact that their entire brains had not been split; only their evolutionarily newer cortical hemispheres had been separated. The surgeon’s scalpel had not entered their evolutionarily older subcortical brain regions such as the thalamus, hypothalamus, and midbrain. Because these subjects had no difficulty leading normal coherent lives, this would argue that the basis of the core self, where our action-oriented raw emotions are processed, is likely rooted in subcortical areas of the brain that had not been cut.
THE ROLE OF CORTICAL MIDLINE STRUCTURE
However, there are also evolutionarily older, more medial (closer to the middle) cortical areas, with a simpler anatomical infrastructure, that seem to be more closely linked with more primal self-related processes. These areas, often called cortical midline structures, have been examined in neuroimaging studies focusing on self-related activities. Representative studies have observed subjects performing (1) verbal tasks, such as judging whether a trait like “trustworthy” applied to oneself or to another person, (2) memory tasks, such as determining whether self-related trait adjectives would be remembered better than trait adjectives judged not to be self-related, (3) emotional processing, such as rating the self-relatedness of emotional pictures, and (4) ownership of actions, such as being aware that the circle on a computer screen was drawn by yourself or by someone else (Northoff et al., 2006).
In such studies, the brain regions most predominately activated were not in the neocortex but, rather, in the evolutionarily older cortical midline structures, especially in frontal midline regions, such as the dorsomedial prefrontal cortex, ventromedial prefrontal cortex, and pre/subgenual anterior cingulate cortex. However, it should again be noted that these fMRI studies did not typically examine subcortical regions, which are commonly difficult to monitor using fMRI procedures. Each of these evolutionarily older cortical midline structures is widely connected to other cortical and, importantly, to subcortical regions of the brain, especially subcortical regions such as the hypothalamus and PAG that are closely related with the brain’s primal emotion networks. The Northoff et al. (2006) meta-analysis of brain imaging studies related to the self found that the cortical midline structures were intimately associated with the processes generating the sense that information is self-relevant. It follows that patients with brain damage to these evolutionarily older midline cortical areas would exhibit an impaired capacity for developing a coherent sense of self, as well as disturbances in their social interactions (Damasio, 1999).
SUBCORTICAL MIDLINE SYSTEM
If brain damage extends into subcortical midline systems, and into the PAG lying at the heart of subcortical affective systems, even conscious awareness can be dramatically compromised. Complete destruction of the PAG impairs all self-related processing of environmental events (Panksepp & Biven, 2012, p. 409), indeed, consciousness itself. Animals with complete PAG lesions no longer exhibit spontaneous sel
f-care activities and no longer respond to environmental events in anticipatory ways. For instance, they no longer show anticipatory interest in food, although they will chew and swallow food placed in their mouths (Bailey & Davis, 1942, 1943). For unknown reasons, without special care, such animals spontaneously die within a few months of surgery—no physiological cause of death could be identified.
SUMMARY
As we traverse progressively more ancient medial regions of the brain related to survival, we find neural systems that are essential for generating and maintaining organismic coherence—much more than the neocortex. It is there, in those ancient brain regions, that we find the highest concentrations of all the basic emotional systems that provide an essential affective foundation for the development of personality. It would appear that a core sense of self and even consciousness itself are not possible without the support of the diverse primary emotional networks that help developmentally constitute our higher personality structures. This said, abundant higher cerebral programming is required to bring out the full richness of personality development. In the final accounting, the emotional foundations alone are essential, but not sufficient, for the full flowering of human and animal personalities.
The Emotional Foundations of Personality Page 35