Though the brain is enclosed in a single skull, it is actually made of two separate lumps…which are designed to disagree with each other.
—Jonah Lehrer
We now switch our focus from the multiple and diverse systems of memory to another realm of neural complexity—cortical laterality. As you know, the human cerebral cortex is divided into right and left hemispheres, each controlling the opposite side of the body. The term laterality refers to the specialization of certain tasks to one side of the brain or the other, and is reflected in how the hemispheres differ in their organization, processing strategies, and neural connectivity. Keep in mind also that laterality shows variability among individuals, and left-and right-handed people, as well as males and females.
Although most neural processing requires the contribution of both hemispheres, there are situations when the hemispheres not only think differently but also compete with one another. This struggle for dominance and control may be one cause of our psychological struggles, giving new meaning to why we sometimes feel “beside ourselves” or “of two minds.” By the end of this chapter, you may be left wondering whether we in fact have one brain or two.
John Hughlings Jackson, the eminent 19th-century neurologist, believed that the left side of the brain was, for most people, the “leading” side. This seemed logical given Broca’s finding that the left hemisphere was responsible for our ability to use semantic language. Jackson later suggested that the right hemisphere was the leading side of the brain in visual-spatial abilities.
Over the years, it has become clear that dividing the brain into two discrete halves is not the best approach. Given that most neural systems integrate circuitry from the left and right sides of the brain, research attempting to localize functions in one hemisphere or the other often results in “untidy” findings (Christman, 1994). When we speak of functions of the right or left brain, we are more accurately referring to functions that are either represented more fully or performed more efficiently in one hemisphere than the other. Over the past 40 years, much has been written about the artistic right brain and the logical left. Although this view may be appealing to the imagination, it is far too simplistic. Assigning specific functions to particular areas of the brain needs to be done with both caution and the recognition that our knowledge is still evolving.
Evolution and Development
A scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die and a new generation grows up that is familiar with it.
—Max Planck
Lateral specialization is an evolutionary choice, and does not exist in all animals. Many birds and fish, for example, have identical hemispheres. These animals are able to sleep one hemisphere at a time, allowing them to keep swimming or flying to avoid predators, continue feeding, or rest during long migrations. Although redundant hemispheres provide certain benefits, such as a backup system in case of injury, hemispheric specialization via natural selection promotes neural complexity. Through human evolution, the right and left cerebral hemispheres have become increasingly dissimilar (Geschwind & Galaburda, 1985). Lateral dominance appears to have been delegated depending on the functional domain in question (Cutting, 1992; Goldberg & Costa, 1981; Semmes, 1968). For example, areas of the left and right cortices have become specialized in the organization of the conscious linguistic self in the left and the physical emotional self in the right.
During the first 2 years of life, the right hemisphere has a growth spurt that parallels the rapid development of sensorimotor, emotional, and relational capabilities (Casey, Galvan, et al., 2005; Chiron et al., 1997; Thatcher, Walker, & Giudice, 1987). The child learns hand–eye coordination, crawling, and walking while becoming attached to caretakers. An organized sense of the body in space and the embodied self form in subcortical and cortical networks involving the thalamus, cerebellum, and parietal cortex. At the same time, middle portions of the prefrontal cortex are maturing and integrating with subcortical structures to establish the basic structures of emotional regulation and attachment. During this period, the development of the left hemisphere is slowed a bit and reserved for later-developing functions (Gould, 1977).
In the middle of the second year, a growth spurt occurs in the left hemisphere and an explosion in language and locomotion launches children into the broader physical and social worlds. In the frontal lobes, there is a shift of development to the dorsolateral areas, linking back to other cortical regions, that sculpts the language network (Tucker, 1992) while connecting the movements of hands and eyes to visual stimuli and words. The corpus callosum begins to develop at the end of the first year, is significantly developed by age 4, and continues to mature past the age of 10. Because of this slow maturation, the two hemispheres at first function relatively autonomously, gradually gaining interconnection and coordination through childhood (Galin, Johnstone, Nakell, & Herron, 1979).
A great deal of what is known about the functions of the different hemispheres has been the result of the split-brain research of Sperry and his colleagues (Sperry, Gazzaniga, & Bogen, 1969). Split-brain patients are individuals suffering from medication-resistant epilepsy, who have their corpus callosum surgically severed to limit seizures to one side of the brain. Presenting information separately to each of their hemispheres has revealed divisions of awareness and specialization in a range of cognitive and emotional tasks, thereby expanding our knowledge of cortical laterality (LeDoux, Wilson, & Gazzaniga, 1977; Ross et al., 1994; Sperry, 1968).
Lateral Asymmetry
All organs of an animal form a single system…and no modification can appear in one part without bringing about corresponding modifications in all the rest.
—George Cuvier
The earliest form of language was most likely hand gestures, which may explain why handedness and language functions are so closely linked in the brain. Most of us are right-handed (controlled by the left brain) and have semantic language lateralized in the left hemisphere. Neural networks for both spoken and sign language are located in the left hemisphere for most adults, and damage to the left hemisphere usually results in language disturbances such as aphasia (Corina, Vaid, & Bellugi, 1992). In left-handed or ambidextrous individuals, lateralization of language is somewhat less clear. As the semantic functions of the cortex expanded during evolution and language became more descriptive and useful, words gradually replaced gestures in importance. Our present use of hand gestures to augment spoken language may betray this evolutionary path. Our tendency to use hand gestures even when talking on the telephone suggests that they not only play a role in communication but also in organizing and supporting our thinking.
The left hemisphere appears to be more involved in conscious coping and problem solving than the right. This is most likely a function of its language skills and prosocial orientation. The left hemisphere functions best within the middle range of affect and is biased toward positive emotions and approach behaviors (Silberman & Weingartner, 1986). Strong affect, especially anxiety and terror, result in high levels of right hemisphere activation and appears to inhibit the left hemisphere and language—hence, the experience of stage fright and speechless terror.
It has been suggested that Wernicke’s area in the left temporal lobe, known to be centrally involved in language comprehension, acts as a probability calculator for other forms of behavior as well as language (Bischoff-Grethe, Proper, Mao, Daniels, & Berns, 2000). Given the rapidity with which we process speech, Wernicke’s area may process what is heard based as much on what it expects to hear as what is actually said. This would certainly help to explain why human communication can be so problematic and misunderstandings so common. Broca’s area may have similar predictive functions, which allow us to speak faster than we think and even, at times, be surprised by what we hear ourselves saying (Nishitani et al., 2004). In fact, William James, one of the fathers of American psychology, said that he needed to hear himself talk to know what was on his mind.
For most individuals, the right hemisphere processes information in a holistic fashion and is densely connected to the limbic systems and the viscera (Nebes, 1971). The left hemisphere, on the other hand, processes information in a linear, sequential manner and has less connection with the body. The right hemisphere is heavily wired to the limbic system and is more directly involved in the regulation of the endocrine and autonomic nervous systems than the left (Wittling & Pfluger, 1990). It also contains centers within the parietal lobes that might contain a representation of the entire body.
The right hemisphere is generally responsible for both appraising the safety and danger of others and organizing a sense of the corporeal and emotional self (Devinsky, 2000). Appraisal simply means attaching a positive or negative association to a stimulus, while emotion is the conscious manifestation of this appraisal process (Fischer, Shaver, & Carnochan, 1990; Fox, 1991). The vast majority of appraisal occurs at an unconscious level. This is why the right hemisphere is more often associated with the unconscious mind, that is, what guides our thoughts and behavior outside of our awareness.
The bias against left-handedness across many cultures may reflect an intuitive understanding of the left hand’s (right brain’s) relationship to the dark, primitive aspects of our nature. These biases likely date back into prehistory, when the left hemisphere may have exerted less inhibitory control over the right. Think about the French word gauche and the Italian sinestre for left and all their tasteless and evil connotations. By offering the right hand in greeting, early humans may have been more likely to behave in a civilized manner, and less likely to act out selfish or violent impulses. An examination of cave drawings in Southern Europe suggests that the bias toward right-handedness has existed for at least the last 5,000 years (Coren & Porac, 1977).
Although the left hemisphere generally produces semantic language, it is unclear whether it has any advantage in language comprehension. The right hemisphere may, in fact, be better at comprehending the emotional aspects of language such as the tone of voice or the attitude with which words are said (Searleman, 1977). Emotions in general, the ability to evaluate emotional facial expressions, and visual-spatial and musical abilities are primarily right-hemisphere processes (Ahern et al., 1991). Damage to the right hemisphere results not only in an impairment of our ability to assess facial gestures, but also to comprehend other nonverbal aspects of communication such as hand gestures and tone of voice (Blonder, Bowers, & Heilman, 1991).
Laterality and Emotion
When angry, count to four; when very angry, swear.
—Mark Twain
Evidence suggestive of a relationship between laterality and emotionality was first observed in cases of damage to the prefrontal cortex. Patients with damage to the left hemisphere appeared to be far more likely to have a depressive reaction than those with damage to the right (Gainotti, 1972; Goldstein, 1939; Sackheim et al., 1982). It was later found that the closer these lesions were to the prefrontal regions, the more severe the symptoms of depression (Robinson et al., 1984). Right brain-damaged patients were also found to describe experiences with less emotional intensity than left brain-damaged patients or normal controls (Borod et al., 1998).
Imaging studies have shown that people without brain damage who suffer from depression have lower levels of glucose metabolism and cerebral blood flow in the left prefrontal cortex (Galynker et al., 1998; Kalia, 2005; Mathew et al., 1980). In addition, people experiencing mania in the absence of brain damage demonstrate decreased right prefrontal activity (Al-Mousawi et al., 1996). These studies expand the association between laterality and emotion to the general population. An examination of Table 6.1 reveals that the left hemisphere is biased toward positive affect, safety, and positive social approach, as well as anger and aggression directed toward others. Overall, the left side of the brain appears to be in charge of the successful navigation of the social world.
TABLE 6.1
Laterality and Emotion
Increased left hemisphere activation occurs in response to:
Happy stimuli1
Positive pictures2
Positive affect in response to positive films3
Approach-related dispositional tendencies4
More positive disposition5
Smiling and facial expressions of enjoyment6
Reported well-being7
Infant smiling in response to mother approach8
Trait anger9
State anger10
State aggression11
Increased right hemisphere activation occurs in response to:
Facial expressions of disgust12
Tastes associated with disgust13
Negative pictures14
Avoidance behavior15
Negative affect in response to negative films16
Threat-related vigilance17
Stranger approach18
Maternal separation19
The intimate association between emotion and cognition has been demonstrated in many laterality studies. For example, sad faces are rated as relatively sadder when presented to the left visual field compared to the right (Sackheim et al., 1988). Negative stimuli are consciously perceived most often when presented to the right hemisphere (Smith & Bulman-Fleming, 2004). Research has shown that anesthesia of the left hemisphere results in greater expressions of negative emotions and less prosocial explanations of experience (Dimond & Farrington, 1977; Ross et al., 1994). Orienting eye gaze to the left (stimulating the right hemisphere) results in decreased optimism, while the opposite is true with rightward eye gaze (Drake, 1984; Thayer & Cohen, 1985). Righthemisphere-biased neural processing correlates with low self-esteem (Persinger & Makarec, 1991).
Higher levels of left prefrontal activation have been associated with a resilient affective style, faster recovery following negative events, and lower levels of the stress hormone cortisol (Davidson, 2004; Jackson et al., 2003; Kalin, Larson, Shelton, & Davidson, 1998). While there appears to be an overall bias of positive left/negative right, the picture is more complicated. The hemispheres are also lateralized for social/private and approach/avoidance (left/right) behavior. These patterns of left/right activation suggest that health and happiness may be associated with general lateral balance as well as the ability to be aggressive and express anger biased toward the left and grief and shame biased toward the right.
The Integration of the Body in the Right Hemisphere
The body never lies.
—Martha Graham
The parietal lobes, located above our ears toward the top of our heads, are at the crossroads of neural networks responsible for vision, hearing, and sensation. They serve as a high-level association area for the coordination and integration of these functions. The anterior (front) portion of the parietal lobes organizes tactile perception, while the posterior (back) portion interconnects the senses to organize sensory-motor with conceptual events (Joseph, 1996). Accordingly, cells in the parietal lobes respond to hand position, eye movement, words, motivational relevance, body position, and other factors relevant to the integration of experience.
The purpose of the association of all of these high-order processing networks is to provide a coordinated and integrated awareness of one’s own body and its relation to the external environment (Ropper & Brown, 2005). This makes sense in that the parietal lobes evolved from the hippocampus, which, in lower mammals, serves as a cognitive map for external space (O’Keefe & Nadel, 1978). Part of the job of the parietal lobes is to organize an integrative map of our bodies in space, which is available for conscious reflection. Thus, damage to the parietal lobes, especially on the right side, results in a variety of disruptions in our experience of the self and the world around us.
Although the left hemisphere seems to contain a network to monitor attention on the right side of the body, the right hemisphere of right-handers has a specialized ability to direct attention bilaterally to both the right and left sides of “extrapersonal space” (Mesulam, 1981). Hemi-neglect, or the denial of the existence of the left side of the body, can result from lesions to the right parietal lobe. When neglect is severe, the patient behaves as if the left half of the world has ceased to exist. Patients with hemi-neglect will dress and put makeup only on the right side of their bodies while denying ownership of their left arm or leg. Asked to draw the face of a clock, they may put all 12 numbers on the right side or simply stop at 6 o’clock.
The phenomenon of hemi-neglect has also been shown to exist in imaginary space. Bisiach and Luzzatti (1978) examined two patients with right parietal injuries and left-sided neglect who were asked to describe the Piazza del Duomo in Milan. The piazza was very familiar to both patients. But when asked to imagine the piazza from one end, they could recall and describe the details on their imagined right side and not their left. Later, they were asked to reimagine the piazza from the other end. Looking back to where they previously pictured themselves sitting, they were now able to accurately describe what was on the right side but not on the left. In other words, once they imagined turning around 180 degrees, they now had access to memories that they were unable to remember just a short while earlier. Further, the information they provided previously was no longer accessible. This remarkable demonstration suggests neural networks that organize and attend to the body in space are also utilized in imagination.
In later research, Bisiach and his colleagues (Bisiach, Rusconi, & Vallar, 1991; Cappa, Sterzi, Vallar, & Bisiach, 1987; Vallar, Sterzi, Bottini, Cappa, & Rusconi, 1990) found that vestibular stimulation via cold water irrigation of the left ear (the caloric test) in patients with right parietal lobe lesions resulted in temporary remission of their left hemi-neglect. Putting cold water into the left inner ear stimulated areas within the right temporal lobe and caused the patients to orient toward the left (Friberg, Olsen, Roland, Paulsen, & Lassen, 1985). Although the mechanism of action is not certain, one possible explanation could be that activation of the right temporal lobe resulted in a reintegration of right and left hemispheric attentional processes, bringing the world temporarily into an organized whole (Rubens, 1985). This theory is supported by the fact that being shown fearful faces also appears to overcome the attentional neglect of these patients (Tamietto et al., 2007). The survival value of these faces may surpass a higher threshold established in the hemi-neglect phenomenon.
The Language Network and the Left Hemisphere Interpreter
All men are frauds. The only difference between them is that some admit it. I myself deny it.
—H. L. Mencken
The left hemisphere language network relies on the convergence of auditory, visual, and sensory information from the temporal, occipital, and parietal lobes. Wernicke’s area in the temporal lobe receives input from the primary auditory area and organizes it into meaningful bits of information. The convergence zone connects sounds, sights, and touch, so that cross-modal connections can be made, allowing us to name things we touch and hear without visual cues. It is also necessary for the development of sign language, where words take the form of gestures. This sophisticated and highly processed information projects forward to Broca’s area where expressive speech is organized.
Neural networks linking language areas to the rest of the frontal lobes allow both spoken and internal language to guide behavior and regulate affect. Although the semantic aspects of language are usually lateralized to the left hemisphere, the right contributes the emotional and prosodic element of speech. The integrative properties of language may be unequaled by any other function of the brain. Creating and recalling a story requires the convergence of multisensory emotional, temporal, and memory capabilities that bridge all vectors of neural networks. In this way, language integrates, organizes, and regulates the brain, and is therefore used to great benefit in everyday storytelling as well as in psychotherapy.
Consistent findings across a variety of settings have led to a general acceptance that the verbal neocortex organizes conscious experience and embodies the social self as arbiter of rules, expectations, and social presentation (Nasrallah, 1985; Ross et al., 1994). Working with split-brain patients, Gazzaniga and his colleagues found that the left hemisphere could create an explanation of experience when right hemisphere information was unavailable (Gazzaniga, LeDoux, & Wilson, 1977). Gazzaniga (1989) later developed the concept of the left hemisphere interpreter that synthesizes available information and generates a coherent narrative for the conscious social self.
The strategy of filling in gaps in experience and memory, and making a guess at an explanation, parallels confabulatory processes seen in patients with psychosis, dementia, and other forms of brain damage. Confabulation appears to be a reflexive function of the left hemisphere interpreter as it attempts to make sense of nonsense, organize experience, and present the self in the best possible light. This phenomenon is likely related to Freudian defense mechanisms that distort reality in order to reduce anxiety.
A good example of this kind of confabulatory behavior was demonstrated by S.M., a 77-year-old suffering from parietal and temporal lobe atrophy in her right hemisphere. One day her son saw her using sign language in front of the mirror in her bedroom (Feinberg & Shapiro, 1989). When asked what she was doing, the patient told him that she was communicating with the “other S.M.” She went on to tell him that there was another S.M. who was identical to her in appearance, age, background, and education who was always in the mirror. She and the other S.M. had gone to the same school, but did not know each other from that time. The other S.M. also had a son with the same name who looked just like him.
S.M. and her double were identical in every respect, except that the other S.M. had a tendency to talk too much and did not communicate as well as she did in sign language. If her son or the examiner appeared behind her in the mirror, she would correctly label that person’s mirror reflection. Thus, the phenomenon of a double was only evident for her own image. When it was pointed out that this was her own image in the mirror, she would reply, “Oh sure, that’s what you think” (Feinberg & Shapiro, 1989, Chapter 3). While S.M.’s comprehension and identification of herself and the world had been disrupted by her right hemisphere lesion, her left hemisphere interpreter remained intact. It is somewhat comical to think that she experienced her reflection in the mirror as talking too much and being less skilled than herself in sign language. Perhaps the left hemisphere interpreter may explain why we are all above average in our own minds.
This confabulatory and positive self-bias of S.M. versus her reflection is a perfect example of the left hemisphere interpreter at work. It also reflects the brain’s basic instinct to engage in explanatory behavior for things it cannot understand. Some version of the interpreter concept has previously been used to explain the development of paranormal beliefs (Cozolino, 1997), schizophrenic delusions (Maher, 1974), and religious beliefs (Gazzaniga, 1995). The concept is especially relevant to psychotherapy, because the construction of reality is at work in the worldviews of patients with character disorders, the defense mechanisms of neurotics, and the day-to-day reality of healthy individuals. The left hemisphere interpreter is an internal press agent for the self, putting a positive spin on what is experienced and how it is presented to others. If the interpreter is not doing its job adequately, as in the case of left hemisphere damage or decreased activation of the left frontal cortex, we can become realistic, pessimistic, and depressed.
Communication and Coordination Between the Hemispheres
Is the brain, which is notably double in structure, a double organ,
“seeming parted, but yet a union in partition”?
—H. Maudsley
As our left and right hemispheres differentiated during evolution, each came to gain dominance for specific functions after failed experiments with transcortical democracy (Levy, Trevarthan, & Sperry, 1972). At the same time, the blending of the strengths of each hemisphere allows for the maximum integration of our cognitive and emotional functioning. When we are awake, the right hemisphere constantly provides information to the left. Nasrallah (1985) suggested that this input relates to intuition, feelings, fantasy, and visual images. The momentary bubbling up of feelings or images, which are then quickly lost, may reflect one aspect of the intrusion of right hemisphere processing into left hemisphere control. The filtration of right hemispheric processes may be necessary to allow us to remain focused on the tasks in which we are engaged, although it may not necessarily register, understand, or allow the information into consciousness.
What happens when the hemispheres find themselves disconnected from one another? Jason and Pajurkova (1992) reported a case of a 41-year-old right-handed man who suffered damage to the front portion of his corpus callosum and the medial portion of his frontal cortex. The most salient aspect of his behavior after his injury was that the two sides of his body seemed to be in conflict with one another. During neuropsychological testing, the patient’s right hand would attempt to perform a task but the left would move in and disrupt what had been accomplished. When he would try to go down a set of stairs, his right foot would lead but then his left hand would grab the doorjamb and refuse to let him move forward. He found himself unable to do things that required the cooperation of both hands.
The patient said, “My left foot and my left hand want to do the opposite of what my right one does all the time” (Jason & Pajurkova, Chapter 13). On another occasion he stated, “My left hand doesn’t go where I want it to” (Chapter 13). In each situation, the right hand and side (controlled by the left hemisphere) attempted to carry out the conscious will of the patient. But the left side (controlled by the right hemisphere) would have no part of it. The authors reported that it seemed as if the right hemisphere was acting like a spiteful sibling, competing for attention and control (Jason & Pajurkova, 1992). Although this conflictual behavior decreased over time, it was still evident 6 months after the injury. Similar left–right conflicts, usually resolving in the first few weeks after surgery, have also been reported in split-brain patients.
It is clear in these cases that the left hemisphere is experienced as the conscious self (ego) while the behavior of the right hemisphere is experienced as a force from outside the self (ego-alien). The experience and behavior of such patients suggests not only alternate ways of processing information in each hemisphere, but also two separate wills. The unconscious and oppositional quality of the behavior of this client’s right hemisphere suggests that the left hand may have been acting out unconscious emotional reactions.
Right-Left Integration and Psychopathology
We use our brains too little and when we do, it is only to make excuses for our reflexes and instincts.
—Martin Fischer
I postulated earlier that neural network integration should correlate with mental health, while dissociation or imbalance among neural networks should correlate with mental illness. If this is true, we can assume that integration between the right and left hemispheres is one element of optimal brain functioning. It turns out that anxiety, affective disorders, psychosis, alexithymia, and psychosomatic conditions have all been linked to deficits in the integration and balance among the cerebral hemispheres.
Anxiety and Depression
Anxiety is love’s greatest killer…
—Anaïs Nin
As mentioned earlier, each hemisphere has an emotional bias, and so it appears that the proper balance of right-left activation allows us to experience a healthy mix of positive and negative emotional experiences, as well as to regulate and manage anxiety (Silberman & Weingartner, 1986). The left hemisphere has a bias toward positive affect, prosocial behavior, and assertiveness, all of which help us to connect with others and find safety in the group, while the right hemisphere’s bias toward suspiciousness and negativity keeps us vigilant and alert to danger.
Frontal lobe activation, when biased toward the right hemisphere, correlates with the signs and symptoms of depression (Nikolaenko, Egorov, & Freiman, 1997). The same phenomenon holds true for anxiety. Primates with extreme right frontal activity are more fearful and defensive, and have higher levels of stress hormones, than do those with activity biased toward the left hemisphere (Kalin et al., 1998). Adults with a history of childhood trauma demonstrate a significantly greater shift to right hemispheric processing when asked to think about unpleasant memories (Schiffer, Teicher, & Papanicolaou, 1995). Activation of many structures of the right hemisphere is also evident during posttraumatic flashbacks (Rauch et al., 1996).
If anxiety and depression are, in part, the result of a bias toward right hemisphere processing, then any form of successful treatment will enhance a rebalancing of these systems. Cognitive therapies for both anxiety and depression utilize rational thought that may work by activating left hemisphere processes to regain lateral balance. Symptomatic relief can also be achieved by a downregulation of the right hemisphere processes through relaxation training.
An unfortunate artifact of the evolution of laterality may be that the right hemisphere is biased toward negative emotions while also having primary control over emotional self-awareness (Keenan et al., 1999). In addition, because there is so much early, unconscious right hemisphere emotional learning, early negative experiences have a long-lasting yet hidden impact on our self-esteem, attitudes, and personalities. These aspects of laterality may create a bias toward shame, guilt, and pessimism while possibly explaining the neurobiological mechanism underlying Nietzsche’s statement that “Man is the only animal who has to be encouraged to live.”
Alexithymia and Psychosomatic Illness
It is precisely because a child’s feelings are so strong that they cannot be repressed without serious consequences.
—Alice Miller
Alexithymia—the inability to consciously experience and describe feelings—is characterized by deficits in the awareness and integration of right hemisphere functions. These patients are not prone to depression or mania but instead have a poverty of emotional expression and experience. They are able to recognize that others have feelings, but report being unable to locate any within themselves.
From a psychodynamic perspective, these patients seem trapped in secondary process thinking, disconnected from their inner physical and emotional worlds. Patients with alexithymia are described as having a concrete or stimulus-bound cognitive style, restricted imagination, and a lack of memory for dreams (Bagby & Taylor, 1997). They have difficulty benefiting from traditional modes of talk therapy because of their inability to bring emotions into the session, or to use imagination or role-playing to expand their thinking about themselves. Although the neurological correlates of this disorder are still unknown, alexithymia has been described as a “bidirectional interhemispheric transfer deficit” (Taylor, 2000). The resultant failure of the integration of affect and cognition leaves the conscious self of the left hemisphere with little input from the emotional, intuitive, and imaginative right.
Patients with other psychiatric disorders reveal patterns similar to those with alexithymia. Hoppe (1977) found that patients with psychosomatic disorders have characteristics similar to those with alexithymia such as impoverished dreams, a paucity of symbolic thinking, and trouble putting feelings into words. Similar difficulties were also found in Holocaust survivors, split-brain patients, and individuals with traumatic brain injuries. Hoppe and Bogen (1977) hypothesized that problems during development or underlying genetic processes could lead hemispheres to organize and function autonomously. The theory of such an “interhemispheric transfer deficit” was supported by research with patients suffering from PTSD and alexithymia who were found to have deficits in transferring sensorimotor information between hemispheres (Zeitlin, Lane, O’Leary, & Schrift, 1989).
Psychosis
Reality is merely an illusion, albeit a very persistent one.
—Albert Einstein
Whereas normal states of awareness are comprised of an integration and balance of right and left hemisphere processing, psychosis may be a result of the intrusion of right hemisphere functioning into conscious awareness. Hyperactivation of the right hemisphere, or a decrease in the inhibitory capacities of the left, may diminish the ability to filter primary process input from the right hemisphere. This shift in right-left bias may occur for many reasons, including changes in levels of important neurochemicals such as dopamine, neuroanatomical abnormalities, or changing activation in subcortical brain areas such as the thalamus. Schizophrenic patients and their close relatives demonstrate reduced left hemisphere volumes in the hippocampus and the amygdala, which has been shown to correlate with thought disorder (Seidman et al., 1999; Shenton et al., 1992).
Auditory hallucinations, or hearing one or more voices talking, are a core symptom of schizophrenia. In fact, the term schizophrenia means split mind. These aberrant, intrusive, and ego-dystonic experiences may reflect right hemisphere language (related to primary process thinking and/or implicit memories) breaking into left hemisphere awareness. These voices, often heard as single words with strong emotional value, are experienced as coming from outside the self. For example, patients report hearing profanities or critical words (jerk, idiot) as people walk by them on the street. Command hallucinations to hurt oneself or others or to engage in dangerous behaviors have the same qualities. Schizophrenic patients appear to openly struggle with shameful aspects of their inner world (likely stored in the right hemisphere) that the rest of us are better able to inhibit, repress, and deny.
In psychosis, primary process thinking breaks into normal states of awareness to create what are diagnosed as deficits in reality testing and thought disorders. Patients describe this as a feeling of dreaming while awake and struggling to make sense of the simultaneous superimposition of primary and secondary process experiences. This attempt to make sense out of nonsense fires up the left hemisphere interpreter, leading to the elaboration of bizarre delusions (Maher, 1974). Although a hemispheric model of psychosis is still speculative, tests of lateral dominance (measured by a listening task) have shown that decreased lateral dominance in these patients correlates with more severe psychotic symptoms (Wexler & Heninger, 1979).
Inspired by both modern science and ancient texts, the neuropsychologist Julian Jaynes (1976) developed a theory of the evolution of human consciousness based on the increasing ability of the left hemisphere to inhibit input from the right. Jaynes argued that prior to 1000 B.C., the two halves of the human brain acted independently; the right hemisphere unconsciously controlled the body, while the left witnessed and described the social environment and actions of the body. This model of laterality may have reflected an intermediate evolutionary stage between having two modes of conscious awareness and our current bias toward right hemisphere inhibition.
Jaynes suggested that when our forebears were in situations of extreme stress, such as combat, the right hemisphere provided auditory commands to the left, which were experienced as coming from outside the self. This could reflect an internalized auditory memory of the tribal leaders and warriors, commands similar to those reported by modern-day schizophrenics. With the expansion of the corpus callosum and increasing dominance of the left hemisphere, a more unified sense of self grounded in the left hemisphere has become dominant and able to inhibit these inner voices. Jaynes felt that psychotic symptoms seen in patients in modern times may be the result of a breakdown of the left hemisphere’s capacity to inhibit these messages from the right.
Laterality and Psychotherapy
Happiness is not a matter of intensity but of balance, order, rhythm and harmony.
—Thomas Merton
The proper balance and integration of the right and left hemispheres does not appear to be a given in the course of development. I strongly suspect that left-right integration is an experience-dependent process that relies on adequate assistance with affect regulation through secure attachment. It is also dependent on the co-construction of narratives where a model is presented for the recognition and labeling of feelings, as well as integrating them into experience. Psychotherapy can serve as a means to reintegrate the patient’s disconnected hemispheres through reality testing, emotional expression, and putting words to feelings in the context of a caring relationship.
Examples from psychiatry and neurology strongly suggest that psychological health is related to the proper balance of activation, inhibition, and integration of systems biased toward the left and right hemispheres. Genetic and neuroanatomical factors can combine with early neglect or trauma to interfere with the development of optimal neural network integration and regulation. The similarity between hemispheric specialization and Freud’s notion of the conscious and unconscious mind has not been lost on psychotherapists. Right hemisphere functions are similar to Freud’s model of the unconscious in that they develop first and are emotional, nonverbal, and sensorimotor (Galin, 1974). This nonlinear mode of processing allows the right hemisphere to contain multiple overlapping realities, similar to Freud’s primary process thinking most clearly demonstrated in dreams. The linear processing of conscious thought in the left hemisphere parallels Freud’s concept of secondary process, which is bound by time, reality, and social constraints.
When patients come to therapy, the left hemisphere interpreter tells its story. But something is usually wrong: the story does not fully account for what is happening in their lives. The narratives that organize their identities inadequately account for their experiences, feelings, and behaviors. The right hemisphere also speaks via facial expressions, body language, emotions, and attitudes. Thus, we listen to both stories for the congruence between the verbal narrative, and nonverbal and emotional communication. In this process, we analyze the integration and coherence of left-right and top-down neural networks. A primary tool across all models of therapy is editing and expanding the self-narrative of the left hemisphere to include the silent wisdom of the right.
Hopefully, the therapist will be better integrated than the client in a therapeutic relationship. This will allow the therapist to react to what is said with emotion, resonate with the client’s emotions, and then share thoughts about those emotions with the client. Thus, the therapist’s ability to traverse the colossal bridge between his or her own right and left hemispheres serves as a model and guide for the client.
Another way of describing therapy from the perspective of laterality is that we teach clients a method by which they can learn to attend to and translate right hemisphere processing into left hemisphere language. We teach them about the limitations and distortions of their own conscious beliefs presented by their left hemisphere interpreter. Many clients need to be suspicious of the ideas that their left hemispheres offer them. This is why reality testing is so important for treatment success. It is the therapist’s job to hear what is not said, resonate with what the client is unable to consciously experience, and communicate it back to him or her in a way that will allow it to become integrated. This human process serves hemispheric integration.
Summary
The integration of dissociated processing systems is often a central focus of treatment. Gradually, clients come to learn how the therapist gathers and interprets the information presented to them (Gedo, 1991). This process closely parallels what is done during positive interactions with parents during childhood. If the method taught during childhood is maladaptive, it leaves the child (and later the adult) in a state of limited self-awareness and neural network dissociation. The learning of these skills in therapy occurs in the context of emotional and cognitive integration, requiring the participation of both hemispheres, reflective language, feelings, sensations, and behaviors. In the language of neuroscience, we are integrating dissociated systems of memory and processing systems by teaching new strategies for integrating rational and emotional information. These processes aid in the construction of a more inclusive self-narrative, which, in turn, serves as a blueprint for ongoing neural integration.