Title:

Hemisphericity Reconstituted: The Dual Quadbrain Model of Behavioral Laterality

ã 2000

Author and Address:

Bruce E. Morton, Ph.D., Professor Emeritus

Department of Biochemistry and Biophysics

University of Hawaii School of Medicine

1960 East-West Road

Honolulu, Hawaii 96822 U.S.A.

email: bemorton@hawaii.edu

ABSTRACT: (196 words)

Recently, subjects have been separated into right and left brain-oriented groups by six inter-correlated measures of brain laterality, three of which were biophysical. Moreover, upon comparing biophysically determined brain lateralities of entering college students with those in upper level classes, or with academics from fifteen professions, it was observed that laterality sorting had occurred during higher education. Thus, it appears that the phenomenon of human hemisphericity does exist, and can be measured quantitatively both within individuals and among populations.

Here, a brain model demanding hemisphericity was developed. It was based both upon duality of four evolutionary layers of brain structure, and anatomical and functional brain laterality constraints. The Dual Quadbrain Model’s capacity to account for the entirety of human behavior from the diabolic to the sublime was used to derive a more accurate, brain-dependent, operational definition for hemisphericity. The phenomenon of hemisphericity exists because the single unilateral Executive Ego has limited access to functions based in the opposite half of the brain. Thus for example, those individuals who’s Executive Ego innately is in their left cingulate limbic cortex, manifest a left brain behavioral orientation because left brain functions are more accessible to it, and vise versa.

Keywords: brain dominance-asymmetry, personality, epilepsy, inductive-deductive, line-bisection, dichotic

INTRODUCTION: (880 words)

Origin, Meaning, and Distinction between the Three Brain Laterality Terms: Dominance, Asymmetry, and Hemisphericity.

Hemispheric Dominance: Although Diocles of fourth century BC Greece may have been the first to write about brain laterality (Lockhorst, 1985), Marc Dax was the first in the modern era to note a difference in function between the cerebral hemispheres. In 1836, he noted that victims of injury to the left hemisphere (LH), but not right hemisphere (RH) could not speak. This hemispheric asymmetry for language was thought to be tied to contra-lateral hand preference by Paul Broca (1865) in an example of over generalization (see below). Nearly a century passed before any further manifestations of hemispheric laterality were discovered. Then, a large study by Weisenberg and McBride (1935) demonstrated a RH preeminence in visiospatial skills.

Cerebral Asymmetry: During that first century, the laterality term, “dominant hemisphere”, became inextricably tied to the language-dominant hemisphere, usually the LH, because of its association with the brain areas required for speech and dominant handedness. This forced the creation of different terms, such as “cerebral asymmetry” to describe the many, more-recently discovered non-language differences in cerebral structure and function.

Hemisphericity: Among those 90% of humans who are right handed (Coren, 1992), language is located in the LH in over 95% of them (Smith and Moscovitch, 1979). Of the remaining 10% left handed individuals, about 60% of these also have language in their left cerebrum (Levy and Reid, 1976). Thus, the LH houses language ability in at least 9 out of 10 humans. It is of interest that within this huge group of LH-based speakers, the existence of two major human sub-populations have repeatedly been inferred, whose characteristic behavior styles differ in a manner hypothesized directly to be related their non-language cerebral asymmetries.

That is, in right-handed, LH languaged individuals, putative right hemisphere traits are proposed to be more prominent in some individuals, resulting in a “Right brain”-oriented personality style (Davidson and Hugdahl, 1995; Shiffer, 1996), while in others the left hemisphere traits are more ascendant, producing a contrasting “Left brain”-oriented style (Springer and Deutch; 1998; Fink et.al., 1996). Thus, original assignment of the term “hemispheric dominance” to language laterality has ultimately forced the creation of yet a third laterality term, that of hemisphericity (Bogen, 1969; Bogen, DeZure, Tenhouten, and Marsh, 1969) to account for this third hypothesized laterality phenomenon. Barriers to pronunciation of hexasyllabic “hemisphericity” are bypassed by use of the abbreviation, hemisity.

Narrowly defined, hemisphericity referred to the idea that people rely on a preferred mode of cognitive processing that is linked to the predominant activity of either the left or the right cerebral hemisphere (Beaumont, Young, and McManus, 1984). More broadly, the term specifies which side of the brain is involuntarily more ascendant in terms of the production of an individual’s habitual mood, personality, and characteristic thinking and behavioral style. A more precise definition will be possible at the end of this report.

However, attempts at assignment of hemisphericity have been plagued by the lack of an assay based upon readily quantifyable biophysical differences. This has prevented proper evaluation of the speculations about hemisphericity that abound in the mass media. In the absence of accurate measurements of hemisphericity, research on this topic has made little headway.

Development of New Biophysical Methods to Measure Brain Laterality

Recently, three independent biophysical methods have been reported, each of which divided subjects into brain laterality groups that were significantly correlated with those of the other two methods. The first of these was the Dichotic Deafness Test based upon differences in minor ear reporting of simultaneous dissonant consonant-vowel syllables (Morton, 2000a). The second was Phased Mirror Tracing, where subjects having affect on their right were divided into two groups, based upon which hand was faster at tracing the perimeter of a five pointed star viewed from a mirror (Morton, 2000c). The third was the Best Hand Test, a two-hand line bisection task where right handed subjects were separated into two groups depending on which hand was more accurate at estimating the midpoint of horizontal lines (Morton, 2000d).

Significant Correlation of Hemisphericity-type Questionnaire Outcomes with the Brain Laterality Determined by Biophysical Measures:

Not only were the outcomes of these three biophysical measures significantly correlated with each other, but also they were significantly correlated with many specific non-overlapping statements within three hemisphericity-type questionnaires, one old and two new. That is, they were correlated with six of twenty statements within the Preference Questionnaire (Zenhausern, 1978), ten of eleven statements within the Polarity Questionnaire (Morton, 2000b), and thirteen of fifteen statements within the Asymmetry Questionnaire (Morton, 2000e). These diverse binary statements could be integrated into a coherent dualistic structure under headings of: memory and logic, personal and professional orientation, and pair bonding style (Morton, 2000f). Moreover this was highly compatible both with right or left unilateral temporal lobe epilepsy interictal personality traits, and many hemisphericity elements in popular psychology (Morton, 2000f).

Development of a Brain Laterality Model Generating the Properties of Hemisphericity: Here, a brain laterality model is developed upon documented asymmetry of inputs, internal distributions, and outputs of the mammalian brain, and based upon five defensible behavior-anatomical assumptions. The resulting Dual Quadbrain Model appears to have the capacity to account for the entire range of human behavior from the diabolic to the sublime, including a requirement for the existence of hemisphericity.

METHODS (86 words)

Medline searches were conducted of the neuroscience literature catalogued in the National Library of Medicine. This was combined with searches from of a highly organized and accessible personal collection of reprints and other hard copy duplicates, which at this time is more than ten meters wide. These sources were used to give a global perspective of brain laterality along with its important details. This perspective was incorporated into creation of the Dual Quadbrain Model of behavioral laterality that was logically supported from the literature in every particular.

RESULTS (1857 words)

First, four background elements are described which must be included in any brain laterality model. Then the five postulates upon which the Dual Quadbrain Model was built are presented and illustrated.

Background Element 1: Bilaterality of the Entire Brain, Except the Pineal Body.

All structural elements of the mammalian brain are represented bilaterally, the pineal body being Descarte’s important exception. This bilaterality includes, not only the cerebrum, but also the cerebellum, hippocampus, basal ganglia, thalamus, hypothalamus, brain stem and spine. Even the midline ventricles (third ventricle) are mechanically separated from each other in the center by a membrane, the abnormality of which (cavum septi pellucidi) has been associated with psychosis (Nopoulos, Swayze, Flaum, Ehrhardt, Yuh, and Andreasen, 1997). Furthermore, the existence of separate, independently functioning right and left-brain aversive emotion systems has been reported (Sandner, Oberling, Silveira, Di Scala, Rocha, Bagri, Depoortere, 1993). These dual brain systems intercommunicate in varying degrees via modulated cerebral cross-connections, such as those occurring in the corpus callosum, the anterior and posterior commissures, and the many other subcortical brain interconnections (Sperry, 1968).

Background Element 2: Asymmetric Inputs to the Cerebral Hemispheres:

There are many non-symmetrical inputs to the cerebral hemispheres. These include the often illustrated visual pathways where each visual hemifield projects to the retinal half of both eyes that is on the same side as the target hemisphere (Sperry, 1968). In contrast, auditory inputs are bilateral except for during auditory conflict when immediate ipsilateral pathway inhibitions occur, as in dichotic listening (Kimura, 1967). The missing half of the conflicted auditory information is secondarily transferred to the language hemisphere to a variable degree by the corpus callosum (Yazgan, Wexler, Kinsbourne, Peterson, and Leckman, 1995). These auditory asymmetries provide the basis of the Dichotic Deafness Test (Morton, 2000a).

While touch inputs are bilateral except for contralateral appendage extremities, the limbic emotion-associated inputs to the hemispheres appear to be unequal, both due anatomical asymmetries (Biler, Craven, Hugg, Gillian, Martin Faught and Kuzniecky, 1998) and due to the higher levels in the left brain of catecholamines and their receptors, especially dopamine and norepinephrine (Glick, Ross, and Hough, 1982; Oke, Keller, Mefford, and Adams, 1978).

Recently, it has been found that the right anterior prefrontal cortex is selectively activated not only by the retrieval of episodic memory via the right hippocampus (Squire, Ojemann, Miezin, Petersen, Videen, and Raichle, 1992), but also by selective word surveillance tasks (MacLeod, Bucknere, Meizin, Petersen, Raichle, 1998). In view of the newly established input into the prefrontal cortex by fast loops from the cerebellum and basal ganglia (Middleton and Strick, 1994) and the association of timing and memory systems with those elements (Knowlton, Mangels and Squire, 1996; Thompson, Bao, Cipriano, Grethe, Kim, Thompson, Tracy, Weniger, and Krupa, 1997), this prefrontal cortex input asymmetry is most likely the source of implicit timing and memory abilities of the RH not found in the LH (Harrington, Haaland, and Knight, 1998). It also makes the RH the more promising candidate for parallel processing, compared to the LH, whose dependence upon serial input was indeed demonstrated in Dichotic Deafness Test outcomes (Morton, 2000a)

Background Element 3: Contrasting Data Processing Orientations of the Asymmetric Hemispheres

As has been long known, when the RH of an individual is injured by a unilateral stroke, the continued normal function of the undamaged LH leads to the classical left-field, hemi-neglect syndrome (where, for example, clocks or flowers are drawn lacking left side features, Keilman, Watson, and Valenstein, 1997). Not only do these stroke victims adamantly deny their left side paralysis deficits, but occasionally they even emotionally reject their own left arm or leg (Alien Hand Syndrome) due to its involuntary, often oppositional actions (Ventura, Goldman, and Hildebrand, 1995). In contrast, aside from the usual loss of speech (Dax, 1836), injury to an individual’s LH does not lead to dysfunction or disorientation by the remaining undamaged RH, other than a transient, acknowledged right hemi-paresis (Schenkenberg, Bradford, and Ajax, 1980). How then are these large differences between the effects of right and left unilateral cerebral stroke to be explained?

It is been clear that the two cerebral hemispheres are not anatomical mirror images (Geshwind and Levitsky, 1968), and that they differ fundamentally in their internal organization (Kosslyn, 1987; Van Kleek, 1989). For example, it has been shown that the LH possesses localized processing sites for categorical words, and objects, while the RH utilizes coordinate processing sites, distributed hemisphere-wide, for image formation (Kosslyn, Chabris, and Marsolek, 1992; Lamb, Robertson, and Knight, 1990). The existence of these differences are further reinforced by the discovery that the LH primarily attends to details in the near-right hemifield, while the RH pays most attention to both far hemifields, consistent with its more global orientation (Weintraub and Mesulam, 1987). Thus, left hemi-neglect in unilateral strokes is consistent with the LH’s normal focus on near right visual quadrant details to the exclusion of almost all else, including the contents of the near left field.

The above functional asymmetries appear to be logically compatible with the usual dictums that the RH sees the “forest” (synthetic, structural assembly-orientation) while the LH sees the “trees” (reductive, building-block orientation) (Fink, Halligan, Marshall, Frith, Frackowiak, and Dolan, 1996). Reinforcing this model, the RH has been shown to be much better than the LH, both at the recognition of faces (Sergent, 1992) and also in the recognition of the emotional messages conveyed on those faces (Landis, 1979; McLaren and Bryson, 1987), as is consistent with a RH global visual orientation.

Because the frontal pole of only the RH is activated during memory retrieval and associated activities (MacLeod, et al, 1998), it would appear reasonable to speculate that the RH would be capable of supporting planning and executive qualities in a manner not possessed by the LH. These inherently would give the RH a more long-term processing orientation with a sensitivity to the past and future, as opposed to the LH=s more short-term focus on the here and now.

Background Element 4: Differing Behavioral Outputs of the Asymmetric Hemispheres

In addition to unilateral control of motor outputs to face, trunk, and appendages, other hemispheric outputs are also very asymmetric, as might be predicted. For example, motor output to eye scanning is dominated both by the RH’s need to evaluate the entire scene, and also by the LH’s orientation toward detailed evaluation of the content of the near right hemispace (Weintraub and Mesulam, 1987) but not of near left hemispace (Halligan and Marshall, 1991). Even more obvious is the LH’s predominant output of speech (Dax, 1836), contrasted to the RH’s less conspicuous output of singing (Dalon, 1745) and crying (Lee, Loring, Meader, and Brooks, 1990). Recently, evidence has been obtained that the LH is the source of parasympathetic control of the heart (Wittling, Block, Genzel, and Schweiger, 1998) while the RH participates in sympathetic control of the heart (Whittling, Block, Schweiger, and Genzel, 1998), importantly, along with the stress response (Wittling, 1997).

Regarding classical hemispheric differences in output of emotions and mood, individuals with RH injury or chemical inhibition (Wada, 1949) tended to be indifferent or inappropriately euphoric, sometimes bordering on mania. This is in contrast to those with LH injury who became anxious and often depressed (Lee et al, 1990). However, these results, along with many others briefly covered by Elias, Bryden, and Bulman-Fleming, (1998), have in general suggested that the right was the more emotional side of the brain.

The above essential background elements of 1) bilaterality of the entire brain, 2) asymmetric inputs to the cerebral hemispheres, 3) contrasting data processing orientations of the asymmetric hemispheres, and 4) differing behavioral outputs of the asymmetric hemispheres, were combined with other evolutionary and neuroscience information to form the following five postulates. These create the Dual Quadbrain Model of behavioral laterality.

Dual Quadbrain Model, Postulate 1: Self vs. Group Survival as Bilateral Functional Axes for the Entire Brain

In the Dual Quadbrain Model, it is postulated that the four elements of the left half of the brain are dedicated primarily to self-survival and self-sufficiency, either when alone or in the presence of competition against other species. In contrast, the four right side elements of the brain are postulated to be devoted to group, herd, and species survival and cooperative social interaction. Each side of the brain is alternatively actuated or suppressed as appropriate to the social environment and directed by a single unilateral Executive Ego. Figure 1 illustrates the anatomical layout of the Dual Quadbrain Model.

Figure 1, The Dual Quadbrain: The Anatomy

Dual Quadbrain Model, Postulate 2: Contrasting Right and Left Cerebral Hemisphere Data Processing Procedures (Induction vs. Deduction) are Physically Incompatible and Require Separation.

Figure 2 summarizes known asymmetries of the left and right cerebral hemispheres (from Background Element #3, above) and their probable logical (induction vs. deduction) and behavioral ramifications.

Figure 2, The Dual Quadbrain: Dichotomous Cerebral Hemispheric Function

Dual Quadbrain Model, Postulate 3: Hemisphericity Results from Localization of the Executive Ego within either the Left or the Right Cingulate Cortex, with Consequent Reduced Access to the Skills of the more Distant Asymmetric Hemisphere.

Figure 3 summarizes the asymmetries resulting from the localization of the Executive Ego in the left or right anterior cingulate limbic cortex, along with other known or probable limbic asymmetries (defense mechanisms vs. social emotions) and their possible behavioral ramifications.

Figure 3, The Dual Quadbrain: Dichotomous Limbic System Function

Dual Quadbrain Model Postulate 4: Separable Id-like Punished and Rewarded Behavioral Elements of the Brain Core

An evolutionarily ancient, Id-like, self-survival element within the left side of the lower, archaic brain is associated with sympathetic punished avoidance via flight and fight. Paired on the right side, is a complimentary species-survival, Id-like element, tied to parasympathetic rewarded approach, feeding, rest, repair, and reproduction. Figure 4 summarizes the asymmetries of the left and right lower brain elements producing these contrasting punished and rewarded Id-like behaviors.

Figure 4, The Dual Quadbrain: Dichotomous Lower Brain Function

Dual Quadbrain Model Postulate 5: Superego-like Social and Thanatos-like Antisocial Behaviors are Among those NonMotor Functions Contributed by the Paired Neocerebellum.

Superego-like, higher-intelligence, constructive ideology, and derivative religiosity are proposed to be among the non-motor functions (Schmahmann, 1991) of the recently evolving neocerebellum (Leiner, Leiner, and Dow, 1991). Due to crossed cerebellar diaschisis, this paired brain element is in some functions contralateral (left) to the cerebrum (Barker, Yoshii, Loewenstein, Chang, Apicella, Pascal, Boothe, Ginsberg and Duara (1991). However, for the sake of simplicity this is ignored (as were possible limbic or other ipsilateral vs. contralateral crossover distributions). These Superego-like properties oppose those of the Thanatos with its destructive death-wish, derivative suicide, superstition, human sacrifice, and cannibalism. Figure 5 summarizes the asymmetries of the opposed neocerebelli producing the opposite survival behavioral logics of the Superego and Thanatos.

Figure 5, The Dual Quadbrain: Dichotomous Cerebellar Function

In the Dual Quadbrain Model, the cerebellum is proposed to be the site of an individual’s vast store of experiential primary memory. This concept has some experimental support (Desmond, Gabrieli, Wagner, Ginier, and Glover, 1997; Schreurs, Gusev, Tomsic, Alkon, and Shi, 1998; Bracha, Zhao, Wunderlich, Morrissy, and Boedel, 1997; Kleim, Vij, Ballard, Greenough, 1997). Recording and retrieval to cerebral consciousness of parts of this lifetime cerebellar database somehow requires the participation of the hippocampus (Bontempi, Laurent-Demir, Destrade and Jaffard, 1999; Squire, Ojeman, Miezin, Petersen, Videen, and Raichle , 1992; Teng and Squire, 1999).

The Complete Dual Quadbrain Model:

The entire Dual Quadbrain Model is assembled in Figure 6.

Figure 6, The Dual Quadbrain: An Evolutionary Model Organizing Brain Asymmetries

DISCUSSION: ( 3339 words)

Summary of The Dual Quadbrain Model of Functional Asymmetry: The Dual Quadbrain Model, which accounts for the entire spectrum of human behavior, was built from the known laterality properties of the brain and upon the evolutionary survival optimization imperatives present within mammals in general and the higher primates in particular. Consistent with a bipartite lateral structural anatomy of the entire brain, in general the focus of the left half of the brain appears to be on self-survival and self-sufficiency, while the right side of the brain is devoted to group-herd-species survival and social interaction, where each half is available alternatively to be utilized by the Executive Ego as appropriate to circumstances. Beneath the most recently emerging dual brain element, the double cerebrum, wherein normal language and image consciousness reside, are the more ancient dual elements reminiscent of Freud’s subconscious Ego, Superego, Thanatos, and Id.

Individual right or left hemisphericity status is determined by whether the Executive Ego is congenitally located in the left or right cingulate cortex. That is, due to crossover limitations Executive Ego has less access to functional elements in opposite side of the brain. As a result, left or right brain-oriented individuals must show distinct and quantifiable biophysical and behavioral biases characteristic of their hemisphericity category.

In this model, the fifteen Ego-defenses of the Id (Plutchik, Kellerman, and Conte, 1979), all of which are lies (i.e., denial, rationalization, displacement, etc.) that have evolved to reduce punished Id discomfort, are generated by the left limbic system. Manic individuals, those with right brain stroke, or left brain oriented unlateral epileptics are said to be filled with ego defenses, such as denial, confabulation, jocularity, etc., regarding both their behavior and their obvious neurological deficits (Bear and Fedio, 1977). The social emotions of the Ego are the product of the right limbic system (Teasdale, Howard, Cox, Ha, Brammer, Williams, Chechley, 1999). The Id-like elements of the evolutionarily most primitive brain are, on the left associated with sympathetically punished avoidance via flight and fight, while on the right with parasympathetic rewarded approach, feeding and reproduction. Last, the social brain Superego, and its derivative religiosity, one of the functional outputs of the neocerebellum, is paired against the death drive (Thanatos) and superstition generation.

Anatomical Relationships of the Dual Quadbrain Model (Figure 1):

Regarding the anatomical relationship of brain systems illustrated in Figure 1, priority for rapid survival optimizing responses, either avoidance or approach, is facilitated. This issue was recognized when it was noted that for each of multiple brain elements (striatum, hippocampus, etc.), one pole was directly coupled to the approach driver, reward (opiate-dopamine dependent pleasure, ultimately produced by multiple elements of the nucleus accumbens septi), while the other end of that brain organ was connected to the avoidance driver, punishment, (norepinephrine-CRF dependent pain-terror of the locus coeruleus and amygdala).

It is known that excitation of the locus coeruleus causes inhibitory norepinephrine release at hemispheric cortices not only in the cerebrum, but also at those of the hippocampus and cerebellum (Aston-Jones, 1985). Thus, sufficient alarm and consequent downstream arousal (Morton and Chesire, 1998) can produce temporary decortication of the entire brain and activation of primitive behavior. That is, the inhibition of cerebral intellect, cerebellar intuition, and hippocampal retrieval to language based logic, leaving only decorticate instinctual behavior output available from the ancient midbrain of the Id. The nature of such behavioral output is familiar to all: sex and violence; the salacious or morbid primitive fascination of which resonating within us, brings profit to the entertainment industry.

The loss of control of a process (of perceived survival importance) which ultimately leads to the decortication of upset, unmasks the seeming irrational, primitive, but effective responses of the most ancient survival brain core elements for regaining control of a process. These are a compliment of highly successful retained behaviors, upon which our survival was won. These attempts to regain control of a process can ultimately escalate to resorts of physical forcing. At their extreme, they are the source of the claustrophobic, murderous aggression and violence of an overpowered, cornered animal who expects to die unless induced into an all-out fight mode, supported by a totally activated short-term stress response. Many survivors of such an ordeal are afflicted with the chronic alarm state of the Post-Traumatic Stress Disorder.

Functional Opposite Nature of the Left and Right Cerebri (Figure 2):

The two sides of the mammalian cerebrum appear to be structurally specialized for two different, incompatible, mutually exclusive, survival-maximizing data processing operations (Figure 2). In the right brain, incoming data (for example, a black dog) is inductively compared with earlier-similar memory data to see how the two data sets might be similar and related. It is of great survival value rapidly to know if both sets of data are related. If so, earlier-similar outcome memories can next be scanned in terms of past survival harm or benefit. Then avoidance or approach behavior can be initiated and coordinated to increase the survival benefit of the present situation. In exclusive contrast, in the left-brain the incoming data (a black dog) is deductively compared with earlier-similar memory data to see how the two data sets are different and unrelated. It is also of great survival value for the differences rapidly to be detected, for example between the playful Labrador retriever of the past, and this rapidly approaching foaming Rottweiler guard dog.

This necessary segregation of two incompatible brain processes into separate top-down and bottom up data analysis systems is supported by the presence of the global wiring motif of the right hemisphere and the local architecture of the left hemisphere (Kosslyn, 1987; Van Kleek, 1989; Lamb, et. al., 1990; Kosslyn, et. al., 1992; Fink, et. al., 1996). This separation is further reinforced, both by the eye input assignments given the two hemispheres where the more visual-global RH attends to the entire spatial-visual field while the left attends only to the right foreground and results in left hemi-neglect upon right hemisphere injury). It is also emphasized by the localized language centers in the LH making it the more auditory-speech oriented of the two sides. The cerebral asymmetries caused by the left local vs. a right distributed wiring organization, ultimately such differences should lead to detectible laterality differences in how the corresponding vertical columns themselves are organized and interconnected in general.

Local vs. global structural and functional hemispheric differences have prompted the speculation that the “content” orientation of the LH facilitates the detection of differences (it is a “splitter”) in a top-down, deductive, analytical, intelligent manner. In contrast, the “concept-context” orientation of the RH assists in the detection of global similarities (it is a “lumper”) in a bottom-up, inductive, intuitive, at times metaphorical way (Bottini, Concoran, Sterzi, Paulesu, Schenone, Scarpa, Frackowiak, and Firth, 1994).

Thus, the consciousness orientation for the LH is said to be toward abstractions, where a symbol is worth a thousand words, while that of the RH is thought to be for visual-concrete images where a picture is worth a thousand words. To have two such high speed specialized data analysis systems on-board and intercommunicating with the Executive Ego has enabled the mammals to be highly successful during the intense, ongoing process of survival.

The contrasting processing motifs of the two cerebra that would be expected show behavioral output differences that influence the social behavioral orientation of each side of the dual brain. For example: it is logical that the right brain, through its search for similarity and relatedness would tend to perceive commonality, thus family and community that is implicit in species preservation (Henry and Wang, 1998). These would be complimented by right Id associated social behaviors of cooperativity, humor, constructive support, as well as promoting Superego-religiosity behaviors.

In contrast, the left-brain, while searching for differences, would tend to see non-family and non-related alien-ness, together with the associated antisocial responses of anger, conscience-guilt-free, self-preservation. This could be tied to a competitive coronary type-A behavior pattern (Henry and Wang, 1998) and combativeness. Thus, left brain-oriented individuals without adequate socialization would be expected to show more self-survival orientation than the group-survival orientation of their right brain associates.

Additional duality regarding the cerebrum function should also result from unique right cerebral frontal pole connections to cerebellar and basal gangliar fast loops, apparently absent at that site on the left (Middleton and Strick, 1997; Harrington, et al., 1998). Asymmetric activation during memory retrieval (McLeod, et al., 1998) including cerebellar and basal gangliar timing inputs, would provide the right brain with the ability to make projections into the past or future regarding the overall survival outcome of the current situation. This would result in the potential for production by the right brain, of not only of emotion, but also of mood and personality.

Sidedness of Limbic Anterior Cingulate Executive Ego Determines Hemisphericity (Figure 3):

The idea that the phenomenon of hemisphericity results from the localization of the solo Executive Ego on either the right or left side of the cingulate limbic cortex is a concept of substantial functional parsimony (Figure 3). Although, direct anatomical or functional evidence supporting this idea no doubt already exist in the literature, none is known to the author. However, with proper experimental design, this idea readily could be tested. As to the origin of an individual=s hemisphericity type, it appears to be genetically determined before birth (Crowell, Jones, Kapuniai, and Nakagawa, 1973; Wada, 1977).

Left Limbic Ego Defenses of the Id vs. the Right Limbic Social Emotions: (Figure 3):

The association of the right limbic system with mood would also provide a basis for interpreting the effects of the separate viewing by each side of the brain of sex or violence in comparison to viewing emotionally neutral video scenes (Wittling, 1990; Wittling and Pfluger, 1990). No changes in mood, blood pressure, or salivary cortisol occurred when only the viewer=s LH was allowed to view see this strongly evocative material (Figure 3). Possibly this result occurred because the sophisticated LH of the viewers perceived that the audiovisual material had no personal bearing on their immediate survival. However, when only the RH was allowed to watch the sex or violence videos, there were large changes in mood and significant increases in blood pressure and in salivary cortisol compared to the viewing of neutral scenes (Wittling and Roschmann, 1993). This is consistent with the report of predominant alterations of EEG signals on the right side during sexual orgasm (Cohen, Rosen, Goldstein, 1976).

Use of the "Win-Lose" Orientation against Non-Family (Aliens) by the Left Id vs. Right Id Use of "Win-Win" Orientation for Family Members (Figure 4):

In both hemisphericity types there is an inherent brain duality, which is not Descarte’s mind-body dualism, but rather appears to be the more familiar dichotomy of “Right now, shall I be self-oriented or other-oriented”. This self vs. others duality results from conflict between the left brain’s (Figure 4) immediate gratification, “self against the jungle” survival concerns, and those of the right brain whose orientation is more toward long-term, self-disciplined goals that benefit the survival of the larger group and that paradoxically also indirectly but significantly benefit its individual members (Henry and Wang, 1998).

Right Neocerebellar Thanatos-Inner Devil vs. Left Neocerebellar Superego-God-Within (Figure 5):

Making the by now unavoidable assumption that all behavior is brain-originated, what can be said about the anatomical source of human behavior of the type that has been called bad, evil, sinful, hateful, or diabolical? Such includes nonsexual rape, sadistic torture, ritual murder, mutilation, necrophilia, cult human sacrifice, and vengeful cannibalism. People tend to deny that humans really have the potential for such society-rending behavior and avoid thinking about it, except under the protective sanctions of the media, possibly because it seems so frighteningly close to the surface, once fostered. Individual behavior that destroys the survival of one’s own species underlies all definitions of evil-devil, or diabolic. This makes one’s species-centric point- of-view a highly critical issue. For example: is frying and eating chicken or chimpanzee “bush meat” parts a necessity and hereditary right? Or, it is a murder, mutilation, and cannibalism that more than justifies the violence of the animal rights movement on behalf of domestic rodents?

In contrast, there also must be an anatomical brain source for the human behaviors called good, righteous, kind, loving, holy, or divine. Such acts include generosity, benevolence, compassion, mercy, humanity, and altruism. The latter includes self-sacrifice up to and including the point of willingness to die for another, others, or even for a valued religious or humanitarian cause. Individual behavior dedicated to enhancing the survival of one’s own species underlies all definitions of good and God likeness. Again the absolutely critical issue is the individual=s definition of who their conspecifics are. Thus, the age-old problem: is self-sacrifice is appropriate in behalf of one’s offspring during calamity, in family feuds, or in struggles against pagans, infidels, confederates, Nazis, Vietnamese, or Somalis?

In the Dual Quadbrain Model of behavioral laterality, the above-defined traits of good and evil are included among the subconsciously generated nonmotor behaviors of the neocerebellum, and integrated by the cerebellar vermis (Figure 5). The basis for this assignment comes from primate and human cerebellar activity, lesion, and implant research (Reiman, Raichle, Robins, Mintun, Fusselman, Fox, Price, and Hackman, 1989; Ricklan, Cullinan, and Cooper, 1977; Heath, 1977; Heath, Llewellyn and Rouchell, 1980; Heath, Rouchell, Llewellyn, and Walker, 1981). There, temporary failure of cerebellar self-stimulation equipment, used to transform the behavior of the criminally insane, demonstrated a readily reversible switching between states of benevolent sociability and agitated homicide.

Finally, in terms of the human ability to imagine extremes of survival benefit or harm caused by supernatural sources, under certain circumstances brain-based ideas of the divine or diabolic associated with religiosity or superstition would be expected to arise.

Daily Life Options for Use of the Dual Quadbrain (Figure 6):

A higher focus is brought to minute-by-minute existence by the recognition that an unavoidable fundamental choice is ongoing, that is, whether to accept the way things are or to resist them. From this knowledge, experiential wisdom is gained to know when and where to apply the fulcrum of personal power.

Clearly, the Dual Quadbrain Model of behavioral laterality is only an organizational metaphor, a cartoon simplification of the real (Figure 6). At some level it must break down as inadequate to represent the actual complexity of brain and behavior, finally demanding the brain itself as the ultimate reality. One of the first levels upon which this model may be found to be wrong in particular, is that of the relative sidedness of subcortical elements. That is, the existence of both ipsilateral and contralateral tracts between the cortex and the cerebellum, limbic system and brain core guarantee a brain laterality that is more complex than this model.

Yet, the overall clarification of behavioral motivation, brought by the context of a self vs. species brain duality, may be a critical step required to facilitate the ultimate lateral distribution of the important anatomical details. Furthermore, the logical localization within this evolutionary model of Freud=s theoretical constructs of the Id, Ego, Superego and Thanatos provides an integration of human behavior which hopefully will stimulate the discovery of ever more accurate information about locations of these important behavior-generating motifs.

Toward a More Accurate Definition of Hemisphericity:

According to a critical review by Beaumont, Young, and McMannus (1984), "Hemisphericity refers to the idea that people may rely on a preferred mode of cognitive processing, which is linked to activity on the part of the left or right cerebral hemispheres." Based upon this definition, the concept of hemisphericity was understandably declared bankrupt by those authors. However, the recent development of more powerful biophysical measures of brain laterality has enabled a number of significant correlations between biophysical properties of brain laterality and behavioral laterality to be demonstrated (Morton, 2000abcdefg). This, together with the development here of a modular context, which accounts for the entire phenomenon, has made it possible to now revisit the topic of hemisphericity with some new insight and alternatives.

First, recognition of the presence of multiple cortical hemispheres, not only as part of the structure of the cerebrum, but also as inherent in the structures of the hippocampus and cerebellum, allows the term, hemisphericity, to be expanded from cerebral asymmetry to encompass laterality of the entire brain. Furthermore, the three previously unestablished assumptions of hemisphericity listed by Beaumont, et. al., (1984) now appear to have been met. That is, 1.) It is becoming clear that the two sides of the brain including the cerebral hemispheres are actually qualitatively different in their skills, beyond just small differences in output. This was demonstrated by the Dichotic Deafness Test (Morton, 2000a.). 2.) In addition, it is appears quite probable that there actually are global structural differences between the two cerebral hemispheres in terms of their local vs. distributed connectivity motifs. 3.) It is also likely that the cerebral hemispheres house incompatible processes, namely the opposite processes of inductive and deductive reasoning, i.e., bottom-up and top-down data analysis, between which there can be no gradient.

The perplexing issue of metacontrol (Levy and Trevarthen, 1976) in the phenomenon of hemisphericity, as to what regulates which hemisphere does what and when (Beaumont, Young, and McManus, 1984) has been eliminated by introduction here of the concept of the single unilateral executive center. Apparently this so-called, Executive Ego is permanently localized within one hemisphere or the other of the hemispheres before birth. As a result, individuals do not have voluntary control over their innate brain laterality orientation. However, they can consciously develop and improve their ability to practice the skills of the contra-lateral hemisphere. Thus, members of professions found to be enriched in right brain individuals, such as astronomer and architects (Morton, 2000f), have developed their less accessible left-brain analytical skills to a high degree.

The emergent phenomenon of hemisphericity occurs because the Executive Ego of the individual congenitally and permanently resides in only one of the two lateral cingulate cortices, and more readily accesses skills on the same side than those on the opposite side of the brain. When the executive resides in the right hemisphere, there is an inherent inductive logic bias (small or large) that looks globally for commonality and relationship (from the particular to the general, a form of parallel processing). This similarity seeking orientation appears logically and behaviorally to extend to include an emphasis on family, community, sharing, inclusiveness, cooperation, construction, society, government, and religion.

In contrast, when the executive resides in the left hemisphere, there is an inherent deductive logic bias (small or large) that looks at the “details” for differences and unrelatedness (checks from the general to the particular, a form of serial processing). This difference-seeking orientation appears logically and behaviorally to extend toward an emphasis on the special, the individual, independence, exclusiveness, competition against others (as non-family, non species, alien), confrontation, hoarding, destructiveness, dehumanization of adversaries (stereotyping and prejudice), and combat.

Thus, a right-brain oriented person (R-bop), whether male (R-bom) or female (R-bof), in general will tend to be slightly more talkative, emotionally outgoing, accepting, intense, physically daring, cooperative, creative-constructive, community survival-oriented, and with a personal experience type of religious orientation. In contrast, a left brain-oriented person (L-bop), male (L-bom) or female (L-bof), would tend to be somewhat less talkative, emotionally constrained, rejecting, sensitive, physically conservative, more adversarial, more inclined to destroy enemies, more oriented toward the immediate survival of self and children, and with a more rigid, legalistic religious perspective.

As the survival benefiting dedicated but conflicting brain processes of induction and deduction can be complimentary, so the inherently conflicting biases of R-bops and L-bops are both equally valid and can powerfully compliment each other in partnership. That is, practical realism and survival optimization ends up being a compromise lying somewhere in between the natural tension of the two logical extremes imbedded in the phenomenon of hemisphericity.

Finally, the following can be offered as a more accurate definition: Hemisphericity is a duality created by an executive system laterality which determines whether a person’s thinking orientation, behavioral style, and personality are innately to some degree biased toward a left brain, important-details, self-survival view, or a right brain, global, species-survival view.

ACKNOWLEDGMENTS

The fortitude and candor of my subjects was much appreciated and was essential for the completion of this unfunded research.

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