The Right Hemisphere
"The Right Hemisphere" From: Neuropsychiatry, Neuropsychology, Clinical Neuroscience by Rhawn Joseph, Ph.D
THE RIGHT CEREBRAL HEMISPHERE
It has now been well established that the right cerebral hemisphere is dominant over the left in regard to the perception, expression and mediation of almost all aspects of social and emotional functioning (e.g. Borod, 1992; Cancelliere & Kertesz, 1990; Freeman & Traugott, 1993; Heilman & Bowers 1995; Heilman et al. 1985; Joseph 1988a; Tucker & Frederick, 1989; see below), including the recall of emotional memories (Cimino et al., 1991; Rauch et al., 1996; Shin et al., 1997). This emotional dominance extends to bilateral control over the autonomic nervous system, including heart rate, blood pressure regulation, galvanic skin conductance and the secretion of cortisol in emotionally upsetting or exciting situations (Rosen et al. 1982; Wittling, 1990; Wittling & Pfluger, 1990; Yamour et al. 1980; Zamarini et al. 1990). However, this dominance does not appear to extend to the immune system (Meador et al., 1999).
Further, the right hemisphere is dominant for most aspects of visual-spatial perceptual functioning, the recognition of faces including friend's loved ones, and one's own face in the mirror. Faces, of course, convey emotion.
Recognition of one's own body and the maintenance of the personal body images is also the dominant realm of the right half of the brain. The body image, for many, is tied to personal identity; and the same is true of the recognition of faces.
Visual-spatial, facial recognition, and body image dominance appears to be tied to a greater representation of these functions in the right vs the left hemisphere.
In part, it is believed that the right hemisphere dominance over social and emotional functioning is due to more extensive interconnections with the limbic system (Joseph, 1982, 1988a), including the fact that limbic system appears to be functionally and structurally lateralized (see chapter 13). For example, the appear to be more axonal connections between the neocortex of the right hemisphere and subcortical structures as the white matter connections are more extensive. The neocortex of the right hemisphere is also about 4% greater in size as compared to the left, the right amygdala is significantly (9%) larger than the left (Caviness, et al., 1997), whereas the left amygdala contains heavier concentrations of dopamine (Bradbury, Costall, Domeney, & Naylor, 1985; Stevens, 1992).
It has also been theorized that over the course of evolution and development, limbic social-emotional functions have come to be hierarchically subserved by the right cerebrum due in part to the initial earlier maturation of the non-motor portions of the right cerebral neocortex and due to limbic laterality (Joseph, 1982, 1988a, see chapter 13). This right hemisphere limbic dominance came to include the expression and representation of limbic language, thus providing the right cerebrum with a functional dominance in regard to the expression and comprehension of emotional speech as well as all aspects of emotional perceptions, such as the image of the body and the recognition of friends and loved ones.
The right hemisphere, in fact, appears to maintain a realm of conscious-awareness which is completely different from that of the left. Right hemisphere mental functioning is more visual, spatial, emotional, personal, and non-verbal. By contrast, the mental realm of the left is more tied to language, including thinking in words.
RIGHT VS LEFT HEMISPHERE Over the course of evolution, the limbic system and each half of the brain have developed their own unique strategies for perceiving, processing, and expressing information, as well as specialized neuroanatomical interconnections that assist in mediating these functions (Bogen 1969, Galin, 1974; Joseph, 1986b, 1988ab, 1992ab; Levy, 1974, 1983; MacLean 1990; Ornstein 1972; Seymour et al. 1994; Sperry 1966, 1982). Indeed, whereas the limbic system mediates the more unconscious aspects of social-emotional and personal awareness, the neocortex and the cerebral hemispheres are organized such that two potentially independent mental systems coexist, literally side by side.
For example, expressive and receptive speech, linguistic knowledge and thought, mathematical and analytical reasoning, as well as the temporal-sequential and rhythmical aspects of consciousness, are associated with the functional integrity of the left half of the brain in the majority of the population (Frost, et al., 1999; Goodglass & Kaplan, 1999; Heiss, et al., 1999; Pujol, et al., 1999; Wagner et al., 1998). In contrast, the right cerebral hemisphere is associated with visual spatial, non-verbal and emotional memory (Cimino et al., 1991; Nunn et al., 1999; Ploner et al., 1999), and in fact demonstrates an increase in activity when recalling traumatic memories (Rauch et al., 1996, Shin et al., 1997) or when presented with stimuli which trigger positive or negative feelings (Teasdale et al., 1999), and when reporting sad memories or expressing feelings of depression (Abrams & Taylor, 1979; Cohen, Penick & Tarter, 1974; Deglin & Nikolaenko, 1975; Shagass et al.,1979).
The right hemisphere is also associated with nonlinguistic environmental awareness, visual-spatial perceptual functioning including analysis of depth, figure-ground and stereopsis, facial recognition, the maintanance of the body image (Bradshaw & Mattingley, 1995; Joseph, 1988a; Sterzi et al., 1993) and even the sense of smell.
As indicated by functional imaging, when presented with various odors, the right orbital area becomes highly active (Zatarre et al., 1992) whereas electrical stimulation of the right orbital frontal lobe evokes olfactory hallucinations (Munari & Bancaud, 1992).
The right hemisphere is dominant in the perception, expression and mediation of almost all aspects of emotional intelligence (Borod, 1992; Cimino et al., 1991; Joseph, 1988ab; Ross, 1993), including emotional vocalization and comprehension (Lalande et al. 1992; Ross, 1981; Shapiro & Danly, 1985; Tucker et al., 1977). In fact, although the left hemisphere is dominant for language, the right hemisphere continues to participate in language processing by evoking or sensing feeling, as demonstrated by functional imaging studies (Bottini et al., 1994; Cuenod, et al., 1995; Price et al., 1996). For example, the right temporal and parietal areas are activated when reading (Bottini et al., 1994; Price et al., 1996), and the right temporal lobe becomes highly active when engage in interpreting the figurative aspects of language (Bottini et al., 1994). This activity increases if the language is emotional.
To best understand the unique capabilities of the right hemisphere, it is important to review the functions associated with the left. The left cerebral hemisphere is associated with the organization and categorization of information into discrete temporal units, the sequential control of finger, hand, arm, gestural, and articulatory movements (Beaumont 1974; Corina, et al. 1992; Haaland & Harrington, 1994; Heilman et al. 1983; Kimura 1977, 1993; Mateer 1983; McDonald et al. 1994; Wang & Goodglass, 1992) and the perception rhythm (Evers et al., 1999) and the labeling of material that can be coded linguistically or within a linear and sequential time frame (Efron, 1963; Lenneberg, 1967; Mills & Rollman, 1980).
As is generally well known, within the neocortical surface of the left hemisphere there is one area that largely controls the capacity to speak, and another region that mediates the ability to understand speech (Frost, et al., 1999; Goodglass & Kaplan, 1999; Heiss, et al., 1999; Pujol, et al., 1999). Specifically, Broca's expressive speech area is located along the left frontal convexity, whereas Wernicke's receptive speech area is found within the superior temporal lobe and becomes coextensive with the inferior parietal lobule.
If an individual were to sustain massive damage to the left frontal convexity, his or her ability to speak would be curtailed dramatically. Even if only partially damaged, disturbances that involve grammar and syntax, and reductions in vocabulary and word fluency in both speech and writing result (Benson, 1993; Goodglass & Berko, 1960; Hofstede & Kolk, 1994; Milner, 1964). However, the ability to comprehend language is often (but not completely) intact (Bastiaanse, 1995; Tyler et al. 1995). This disorder is called Broca's (or expressive) aphasia (Benson, 1993; Goodglass & Kaplan, 1999; Levine & Sweet, 1983) and has also been referred to as "motor aphasia."
Wernicke's area (in conjunction with the inferior parietal lobule) acts to organize and separate incoming sounds into a temporal and interrelated series so as to extract linguistic meaning via the perception of the resulting sequences (Efron, 1963; Lackner & Teuber, 1973; Lenneberg, 1967). When damaged a spoken sentence such as the "big black dog" might be perceived as "the klabgigdod." This is referred to as Wernicke's aphasia. However, comprehension is improved when the spoken words are separated by long intervals.
THE RIGHT HEMISPHERE & LANGUAGE COMPREHENSION AND EXPRESSION OF EMOTIONAL SPEECH
Although language is often discussed in terms of grammar and vocabulary, there is a third major aspect to linguistic expression and comprehension by which a speaker may convey and a listener discern intent, attitude, feeling, mood, context, and meaning. Language is both emotional and grammatically descriptive. A listener comprehends not only the content and grammar of what is said, but the emotion and melody of how it is said -what a speaker feels.
Feeling, be it anger, happiness, sadness, sarcasm, empathy, etc., often is communicated by varying the rate, amplitude, pitch, inflection, timbre, melody and stress contours of the voice. When devoid of intonational contours, language becomes monotone and bland and a listener experiences difficulty discerning attitude, context, intent, and feeling. Conditions such as these arise after damage to select areas of the right hemisphere or when the entire right half of the brain is anesthetized (e.g., during sodium amytal procedures).
It is now well established (based on studies of normal and brain-damaged subjects) that the right hemisphere is superior to the left in distinguishing, interpreting, and processing vocal inflectional nuances, including intensity, stress and melodic pitch contours, timbre, cadence, emotional tone, frequency, amplitude, melody, duration, and intonation (Blumstein & Cooper, 1974; Bowers et al. 1987; Carmon & Nachshon, 1973; Heilman et al. 1975; Ley & Bryden, 1979; Mahoney & Sainsbury, 1987; Ross, 1981; Safer & Leventhal, 1977; Samson & Zatorre, 1988, 1992; Shapiro & Danly, 1985; Tucker et al. 1977). The right hemisphere, therefore, is fully capable of determining and deducing not only what a persons feels about what he or she is saying, but why and in what context he is saying it --even in the absence of vocabulary and other denotative linguistic features (Blumstein & Cooper, 1974; DeUrso et al. 1986; Dwyer & Rinn, 1981). This occurs through the analysis of tone and melody.
Hence, if I were to say, "Do you want to go outside?" although both hemispheres are able to determine whether a question vs. a statements has been made (Heilman et al. 1984; Weintraub et al. 1981), it is the right cerebrum which analyzes the paralinguistic emotional features of the voice so as to determine whether "going outside" will be fun or whether I am going to punch you in the nose. In fact, even without the aid of the actual words, based merely on melody and tone the right cerebrum can determine context and the feelings of the speaker (Blumstein & Cooper, 1974; DeUrso et al. 1986; Dwyer & Rinn, 1981). This may well explain why even preverbal infants are able to make these same determinations even when spoken to in a foreign language (Fernald, 1993; Haviland & Lelwica, 1987). The left hemisphere has great difficulty with such tasks.
For example, in experiments in which verbal information was filtered and the individual was to determine the context in which a person was speaking (e.g. talking about the death of a friend, speaking to a lost child), the right hemisphere was found to be dominant (Dwyer & Rinn, 1981). It is for these and other reasons that the right half of the brain sometimes is thought to be the more intuitive half of the cerebrum.
Correspondingly when the right hemisphere is damaged, the ability to process, recall, or even recognize these nonverbal nuances is greatly attenuated. For example, although able to comprehend individual sentences and paragraphs, such patients have difficulty understanding context and emotional connotation, drawing inferences, relating what is heard to its proper context, determining the overall gist or theme, and recognizing discrepancies such that they are likely to miss the point, respond to inappropriate details, and fail to appreciate fully when they are being presented with information that is sarcastic, incongruent or even implausible (Beeman 1993; Brownell et al. 1986; Foldi et al. 1983; Gardner et al. 1983; Kaplan et al. 1990; Rehak et al. 1992; Wapner et al. 1981).
RIGHT HEMISPHERE EMOTIONAL-MELODIC LANGUAGE AXIS Just as there are areas in the left frontal and temporal-parietal lobes which mediate the expression and comprehension of the denotative, temporal-sequential, grammatical-syntactial aspects of language, there are similar regions within the right hemisphere that mediate emotional speech and comprehension (Gorelick & Ross, 1987; Heilman et al. 1975; Joseph, 1982, 1988a, 1993; Lalande et al. 1992; Ross, 1981; Shapiro & Danly, 1985; Tucker et al., 1977); regions which become highly active when presented with complex nonverbal auditory stimuli (Roland et al. 1981) and when engaged in interpreting the figurative aspects of language (Bottini et al., 1994).
For example, right frontal damage has been associated with a loss of emotional speech and emotional gesturing and a significantly reduced ability to mimic various nonlinguistic vocal patterns (Joseph 1988a; Ross, 1981, 1993; Shapiro & Danly, 1985). In these instances, speech can becomes flat and monotone or characterized by inflectional distortions.
With lesions that involve the right temporal-parietal area, the ability to comprehend or produce appropriate verbal prosody, emotional speech, or to repeat emotional statements is reduced significantly (Gorelick & Ross, 1987; Heilman et al. 1975; Lalande et al. 1992; Ross, 1981; Starkstein et al. 1994; Tucker et al. 1977). Indeed, when presented with neutral sentences spoken in an emotional manner, right hemisphere damage disrupts perception and discrimination (Heilman et al. 1975; Lalande et al. 1992) and the comprehension of emotional prosody (Heilman et al. 1984; Starkstein et al. 1994) regardless of whether it is positive or negative in content. Moreover, the ability to differentiate between different and even oppositional emotional qualities (e.g., "sarcasm vs irony" or "love" vs "hate") can become distorted (Cicone et al. 1980; Kaplan et al. 1990), and the capacity to appreciate and comprehend humor or mirth may be attenuated (Gardner et al. 1975).
The semantic-contextual ability of the right hemisphere is not limited to prosodic and paralinguistic features, however, but includes the ability to process and recognize familiar, concrete, highly imaginable words (J. Day, 1977; Deloch et al. 1987; Ellis & Shephard, 1975; Hines, 1976; Joseph 1988b; Landis et al., 1982; Mannhaupt, 1983), as well as emotional language in general.
The disconnected right hemisphere also can read printed words (Gazzaniga, 1970; Joseph, 1986b, 1988b; Levy, 1983; Sperry, 1982; Zaidel, 1983), retrieve objects with the left hand in response to direct and indirect verbal commands, e.g. "a container for liquids" (Joseph, 1988b; Sperry, 1982), and spell simple three- and four-letter words with cut-out letters (Sperry, 1982). However, it cannot comprehend complex, non-emotional, written or spoken language.
Limbic Language: The Amygdala & Cingulate. The amygdala appears to contribute to the perception and comprehension of emotional vocalizations which it extracts and imparts to the neocortical language centers via the axonal pathway, the arcuate fasiculus, which links the frontal convexity, the inferior parietal lobule, Wernicke's area, the primary auditory area, and the lateral amygdala (Joseph, 1993). That is, sounds perceived are shunted to and fro between the primary and secondary auditory receiving areas and the amygdala which then acts to sample and analyze them for motivational significance (see chapter 13). Indeed, the amygdala becomes activated when listening to emotional words and sentences (Halgren, 1992; Heith et al., 1989), and if damaged, the ability to vocalize emotional nuances can be disrupted (see chapter 13). "I am not a crook" --President Richard Nixon before resigning from the Presidency. CONFABULATION In addition, the anterior cingulate becomes activated when speaking (Dolan et al., 1997; Passingham, 1997) processes and expressed emotional vocalization (Jurgens, 1990; MacLean, 1990) and contributes to emotional sound production via axonal interconnections with the right and left frontal convexity (Broca's area). Indeed, it has been repeatedly demonstrated, using functional imagery, that the anterior cingulate, the right cingulate in particular becomes highly active when vocalizing (Frith & Dolan, 1997; Passingham, 1997; Paulesu et al., 1997; Peterson et al., 1988).As noted in chapters 5,13,15, over the course of evolution the anterior cingulate appears to have given rise to large portions of the medial frontal lobe and the supplementary motor areas which in turn continued to evolve thus forming the lateral convexity including Broca's area. Via these interconnections, emotional nuances may be imparted directly into the stream of vocal utterances.
It is not uncommon for individuals to lie. However, sometimes they believe their own lies, and this can be the basis for self-deception. In the extreme, however, some individuals following cerebral injury, make up lies that are so bizarre it takes on the form of confabulation.
In contrast to left frontal convexity lesions which can result in speech arrest (Broca's expressive aphasia) and/or significant reductions in verbal fluency, right frontal damage sometimes has been observed to result in speech release, excessive verbosity, tangentiality, and in the extreme, confabulation (Fischer et al. 1995; Joseph, 1986a, 1988a, 1999a).
When secondary to frontal damage, conflabulation seems to be due to disinhibition, difficulty monitoring responses, withholding answers, utilizing external or internal cues to make corrections, or suppressing the flow of tangential and circumstantial ideas (Shapiro et al. 1981; Stuss et al. 1978). When this occurs, the language axis of the left hemisphere becomes overwhelmed and flooded by irrelevant associations (Joseph, 1986a, 1988a, 1999a). In some cases the content of the confabulation may border on the bizarre and fantastical as loosely associated ideas become organized and anchored around fragments of current experience.
For example, one 24-year-old individual who received a gunshot wound that resulted in destruction of the right inferior convexity and orbital areas attributed his hospitalization to a plot by the government to steal his inventions and ideas--the patient had been a grocery store clerk. When it was pointed out that he had undergone surgery for removal of bone fragments and the bullet, he pointed to his head and replied, "That's how they're stealing my ideas." Another patient with a degenerative disturbance that involved predominantly the right frontal lobe, at times claimed to be a police officer, a doctor, or married to various members of the staff. When it was pointed out repeatedly that he was a patient, he at one point replied, "I'm a doctor. I'm here to protect people."
As detailed in chapters 10, 19, confablation is associated with right frontal lesions in part because of flooding of the speech areas with irrelevant associations. However, yet another factor is loss of memory--or rather, an inability to retrieval autobiographical and episodic details; even those stored using language. Indeed, the right fontal lobe is directly implicated in episodic and autobiographical memory retrieval--as also recently demonstrated using functional imaging (see chapter 19).
Specifically, episodic memory memories are perceptual and are stored in an autobiographical context, and when engaged in episodic retrieval, there is a significant activation of the right frontal lobe, (Brewer et al., 1998; Dolan et al., 1997; Tulving et al., 1994; Kapur et al., 1995), right thalamus, and right medial temporal lobe (Dolan et al., 1997), even when the tasks requiring verbal processing. For example, in a test of unconscious memory, subjects were presented with word stems of complete words were previously presented there was increased blood flow in the right hippocampus and right frontal lobe (Squire, et al., 1992). Right frontal activation was also seen in a recognition tasks involving sentences viewed the day before (Tulving et al., 1994). Presumably, activity increases in the right frontal lobe as a function of retrieval effort (Kapur et al., 1995), whereas injury to the right frontal lobe results in retrieval failure and thus a gap in the information and memories access, coupled with disinhibition and a flooding of the language axis with irrelevant associations.
GAP-FILLING
Confabulation also can result from lesions that involve the posterior portions of the right hemisphere, immaturity or surgical section of the corpus callosum, or destruction of fiber tracts that lead to the left hemisphere (Joseph, 1982, 1986ab, 1988ab; Joseph et al. 1984). This results in incomplete information transfer and reception within discrete brain regions, so that one area of the brain and mind are disconnected from another.
As a consequence, because the language axis of the left hemisphere is unable to gain access to needed information, it attempts to fill the gap with information that is related in some manner to the fragments received. However, because the language areas are disconnected from the source of needed information, it cannot be informed that what it is saying (or, rather, making up) is erroneous, at least insofar as the damaged modality is concerned.
For example, in cases presented by Redlich and Dorsey (1945), individuals who were suffering from blindness or gross visual disturbances due to injuries in the visual cortex continued to claim that they could see even when they bumped into objects and tripped over furniture. Apparently, they maintained these claims because the areas of the brain that normally would alert them to their blindness (i.e. visual cortex) were no longer functioning.
Confabulation and delusional denial also often accompany neglect and body-image disturbances secondary to right cerebral (parietal) damage (Joseph 1982, 1986a, 1988a). For example, the left hemisphere may claim that a paralyzed left leg or arm is normal or that it belongs to someone other than the patient. This occurs in many cases because somesthetic body information no longer is being processed or transferred by the damaged right hemisphere; the body image and the memory of the left half of the body have been deleted. In all these instances, however, although the damage may be in the right hemisphere, it is the speaking half of the brain that confabulates.
On the other hand, there is some evidence to suggest that when information flow from the left to the right hemisphere is reduced, a visual-imaginal -hypnogic form of confabulation may result, i.e., dreaming (Joseph, 1988a). Dreaming is possibly one form of right hemisphere confabulation. Of course, many other factors are also involved (see below and chapters 13, 17). We will return to this issue.MUSIC AND NON-VERBAL ENVIRONMENTAL AND ANIMAL SOUNDS If we may assume that long before man sang his first song, the first songs and musical compositions were created by our fine feathered friends (sounds that inspired mimicry by woman and man) then it appears that musical production was first and foremost emotional and motivational, and directly related to the geometry of space; the demarcation of one's territory. Emotion and geometry are characteristics that music still retains today, they are linked neurologically. This is also why training in music can improve visual-spatial (as well as mathematical) skills and vice-versa.CONSTRUCTIONAL AND SPATIAL PERCEPTUAL SKILLS These same musical ratios, the Pythagorians discovered, also were found to have the capability of reproducing themselves. That is, the ratio can reproduce itself within itself and form a unique geometrical configuration which Pythagoras and the ancient Greeks referred as the the "golden ratio" or "golden rectangle." The gold rectangle was postulated to have devine inspirational origins. Indeed, music itself was thought by early man to be magical, whereas musicians were believed by the ancient Greeks to be "prophets favored by the Gods" (Worner, 1973). Long before the advent of digital recordings, the Babylonians and Hindus, and then Pythagoras and his followers translated music into number and geometric proportions (Durant 1939). For example, by dividing a vibrating string into various ratios they discovered that several very pleasing musical intervals could be produced. Hence, the ratio 1:2 was found to yield an octave, 2:3 a fifth, and 3:4 a fourth, 4:5 a major third, and 5:6 a minor third (McClain 1978). The harmonic system utilized in the nineteenth century by various composers was based on these same ratios. Indeed, Bartok utilized these ratios in his musical compositions. However, even in non-musicians the left hemisphere typically displays if not dominance, then an equal capability in regard to the production of rhythm. In this regard, just as the right hemisphere makes important contributions to the perception and expression of language, it also takes both halves of the brain to make music. Music and vocal emotional nuances also share certain features, such as melody, intonation., etc., all of which are predominantly processed and mediated by the right cerebrum. Thus, the right hemisphere has been found to be superior to the left in identifying the emotional tone of musical passages and, in fact, judges music to be more emotional as compared to the left cerebrum (Bryden et al. 1982). Hence, perhaps our musical nature is related to our original relationship with nature and resulted from the tendency of humans to mimic sounds that arise from the environment --such as those which conveyed certain feeling states and emotions. Perhaps this is also why certain acoustical naunces, such as those employed in classical music, can affect us emotionally and make us visualize scenes from nature (e.g., an early spring morning, a raging storm, bees in flight). The possibility has been raised that music, verbal emotion, and nonverbal environmental-living sounds are, in some manner, phylogenetically linked (Joseph, 1982, 1988a, 1993). For example, it is possible that right hemisphere dominance for music may be a limbic outgrowth and/or strongly related to its capacity to discern and recognize environmental acoustics as well as its ability to mimic these and other nonverbal and emotional nuances. That is, music may have been invented as a form of mimicry, and/or as a natural modification of what has been described as "limbic language" -(a term coined by Joseph 1982). In addition, Penfield and Perot (1963) report that musical hallucinations most frequently result from electrical stimulation of the right superior and lateral surface of the temporal lobe. Berrios (1990) also concluded from a review of lesions studies that musical hallucinations were far more likely following right cerebral dysfunction; whereas conversely destruction of this tissue disrupt the ability to conjure up musical imagery (Zatorre & Halpen, 1993). Findings such as these have added greatly to the conviction that the right cerebral hemisphere is dominant in regard to the non-temporal sequential aspects of musical perception and expression. Conversely, it has been reported that musicians who are suffering from right hemisphere damage (e.g., right temporal-parietal stroke) have major difficulties recognizing familiar melodies and suffer from expressive instrumental amusia (Luria, 1973; McFarland & Fortin, 1982). Even among nonmusicians, right hemisphere damage (e.g. right temporal lobectomy) disrupts time sense, rhythm, and the ability to perceive, recognize or recall tones, loudness, timbre, and melody (Chase, 1967; Gates & Bradshaw, 1977; Milner, 1962; Samsom & Zattore, 1988; Yamadori et al., 1977). In fact, right temporal injuries can disrupt the ability to remember musical tunes or to create musical imagery (Zatorre & Halpen, 1993). The right hemisphere is dominant for the perception and comprehension of non-verbal, environmental and animals sounds, including the melody of music. Likewise, the right half of the brain is dominant for expressing and even mimicking environmental and animal sounds, including the sounds of music.Individuals with extensive left-hemisphere damage and/or severe forms of expressive aphasia, although unable to discourse fluently, may be capable of swearing, singing, praying or making statements of self-pity (Gardner, 1975; Goldstein, 1942; Smith, 1966; Smith & Burklund, 1966; Yamadori et al., 1977). Even when the entire left hemisphere has been removed completely, the ability to sing familiar songs or even learn new ones may be preserved (Smith, 1966; Smith & Burklund, 1966) --although in the absence of music the patient would be unable to say the very words that he or she had just sung (Goldstein, 1942). The preservation of the ability to sing has, in fact, been utilized to promote linguistic recovery in aphasic patients, i.e., melodic-intonation therapy (Albert et al. 1973; Helm-Estabrooks, 1983). The right hemisphere perceives the left half of space. When damaged, patients neglect the left half of space. In this example, patients were instructed to "draw the face of a clock, put all the numbers in, and make it say 10 after 11." Based on studies of brain injured, neurosurgical (e.g., temporal lobectomy, split-brain), and normal populations, the right cerebral hemisphere has been found to be dominant over the left in the analysis of geometric and visual-space, the perception of depth, distance, direction, shape, orientation, position, perspective, and figure-ground, the detection of complex and hidden figures, the performance of visual closure, and the ability to infer the total stimulus configuration from incomplete information, route finding and maze learning, localizing targets in space, the performance of reversible operations, stereopsis, and the determination of the directional orientation of the body as well as body-part positional relationships (Benton 1993; Butters & Barton, 1970; Carmon & Bechtoldt, 1969; DeRenzi & Scotti, 1969; DeRenzi et al. 1969; Ettlinger, 1960; Fontenot, 1973; Franco & Sperry, 1977; Fried et al. 1982; Hannay et al., 1987; Kimura, 1966; 1969, 1993; Landis et al. 1986; Lansdell, 1968, 1970; Levy, 1974; Milner, 1968; Nebes, 1971; Sperry, 1982). Hence, if the right hemisphere is injured, visual-spatial perceptual functioning is negatively impacted. VISUAL-PERCEPTUAL ABNORMALITIES Not surprisingly, males are far superior to females in regard to visual-spatial functioning and analysis (Broverman, et al. 1968; Dawson et al. 1978; Harris, 1978; Joseph, 1999e; Kimura, 1993; Levy and Heller, 1992). This includes a male superiority in the recall and detection of geometric shapes, detecting figures that are hidden and embedded in an array of other stimuli, constructing 3-dimensional figures from 2-dimensional patterns, visually rotating or recognizing the number of objects in a 3-dimensional array, playing and winning at chess (which requires superior spatial abilities). Males also possess a superior geometric awareness, directional sense and greater geographic knowledge, are better at solving tactual and visual mazes, and are far superior to females in aiming, throwing, and tracking such as in coordinating one's movements in relationship to a moving target (reviewed in Broverman, et al. 1968; Harris, 1978; Joseph, 1999e; Kimura, 1993; Levy and Heller, 1992). In contrast, only about 25% of females in general exceed the average performance of males on tests of such abilities (Harris, 1978). DRAWING AND CONSTRUCTIONAL DEFICITS Patient with right cerebral injury was told to copy the star and the cross When the male or female right hemisphere is damaged, most aspects of visual-spatial and perceptual functioning can become altered, including nonlingusitic memory. For example, right temporal lobe damage impairs memory for abstract designs, tonal melodies, objects, positions, and visual mazes (Kimura, 1963; Milner, 1968; Nunn et al., 1999). Deficits in left sided attention, the ability to make judgments which involve visual-figural relationships, in detecting hidden, embedded, and overlapping nonsense figures, recognizing or recalling recurring shapes, and disturbances in the capacity to perceive spatial wholes and achieving visual closure can result (Bartolomeo et al. 1994; Benton, 1993; Binder et al. 1992; DeRenzi, 1982; DeRenzi et al., 1969; Ettlinger, 1960; Gardner, 1975; Kimura, 1963, 1966, 1969; Landis et al., 1986; Lansdell, 1968; 1970; Levy, 1974). INATTENTION AND VISUAL-SPATIAL NEGLECT The left hemisphere also contributes to visual-spatial processing and expression such that when damaged drawing ability can be affected (Kimura, 1993), albeit in a manner different from that of the right (Mehta et al. 1987). For example, because the left is concerned with the analysis of parts or details lesions result in sequencing errors, oversimplification and a lack of detail in drawings such that details may be ignored, although the general outline or shape may be retained (Bradshaw & Mattingly, 1995; Gardner, 1975; Joseph, 1988a; Kimura, 1993; Levy, 1974). THE RIGHT FRONTAL LOBE: AROUSAL & NEGLECT Moreover, some authors have argued that letter cancellation tests appear to be more sensitive than line bisection tasks when testing for (right cerebral) neglect (Binder et al. 1992). Moreover, with the possible exception of letter cancellation, when the task is normally performed best by the damaged hemisphere (that is, before it was damaged) the neglect may be more pronounced (Leicester et al. 1969). Unilateral inattention and neglect are associated most commonly with right hemisphere (parietal, frontal, thalamic, basal ganglia) damage, particularly following lesions located in the temporal-parietal and occipital junction (Bartolomeo et al. 1994; Binder et al. 1992; Bisiach et al.1983; Bisiach & Luzzatti, 1978; Bradshaw & Mattingly, 1995; Brain, 1941; Calvanio et al. 1987; Critchely,. 1953; De Renzi, 1982; Ferro, Kertesz & Black, 1987; Gainotti, et. al.1986; Heilman, 1993; Heilman et al. 1983; Joseph, 1986a; Motomura et al. 1986; Nielsen, 1937; M. Roth, 1949; N. Roth, 1944; Sterzi et al., 1993; Watson et al. 1981). Such patients initially may fail to respond, recall, or perceive left-sided auditory, visual, or tactile stimulation, fail to comb, wash, or dress the left half of their head, face, and body, only eat food on the right half of their plate, write only on the right half of a paper, fail to read the left half of words or sentences (e.g., if presented with "toothbrush" they may see only the word "brush"), or on drawing tasks, distort, leave out details, or fail to draw the left half of various figures, e.g., a clock or daisy (Binder et al. 1992; Bisiach et al., 1983; Calvanio et al., 1987; Critchley, 1953; DeRenzi, 1982; Gainotti et al.,1972, 1986; Hecaen & Albert, 1978; Umilta 1995; Young et al. 1992). Moreover, they show a greater degree of hemiplegia and hemianesthesia as compared to left hemisphere lesions (Sterzi et al., 1993). In addition, frontal injuries may also result in disconnection such that sensory arriving in the posterior regions of the cerbrum are prevented from being transferred to the right hemisphere. Thus, input from the undamaged hemisphere continues to be processed (via the assistance of frontal lobe steering and activating influences) to the exclusion of data normally processed by the other half of the brain.DISTURBANCS OF THE BODY IMAGE In general, there is some evidence to suggest that the right cerebral hemisphere may be involved more greatly in attention and arousal (Beck et al. 1969; Dimond & Beaumont, 1974; Heilman, 1993; Joseph, 1986a, 1999a; Posner & Raichle, 1994; Tucker, 1981), such that it may exert bilateral influences on cerebral and limbic activation (see chapter 19) as well as memory (Brewer et al., 1998). In consequence, right frontal damage can produce mixed extremes in arousal, such that with massive damage there results hypoarousal, bilateral reductions in reaction time and thus diminished attentional functioning (DeRenzi & Faglioni, 1965; Heilman et al. 1978; Heilman & Van Den Abell, 1979; Howes & Boller, 1975; S. Weinstein, 1978). PAIN AND HYSTERIA When the right hemisphere is damaged, somesthetic functioning can become grossly abnormal, and patients may experience peculiar disturbances which involve the body image (Critchley, 1953; Gerstmann, 1942; Gold et al. 1994; Hillbom, 1960; Joseph, 1986a; Miller, 1984; Nathanson et al. 1952; M. Roth, 1949; N. Roth, 1944; Sandifer, 1946; E. Weinstein & Kahn, 1950, 1952). These patients may fail to perceive stimuli applied to the left side; wash, dress, or groom only the right side of the body; confuse body-positional and spatial relationships; misperceive left sided stimulation as occurring on the right; fail to realize that their extremities or other body organs are in some manner compromised; and/or literally deny that their left arm or leg is truly their own. In addition to nonlinguistic, prosodic, melodic, emotional and visual-spatial dominance, the right cerebrum has been shown to be superior to the left in processing various forms of somesthetic and tactile-spatial- positional information, including geometric, tactile-form and Braille-like pattern recognition (Bradshaw et al. 1982; Carmon & Benton, 1969; Corkin, Milner, & Rasmussen, 1970; Desmedt, 1977; Dodds, 1978; Fontenot & Benton, 1971; Franco & Sperry, 1977; Hatta, 1978a; Hermelin & O'Connor, 1971; Hom & Reitan, 1982; Pardo et al. 1991; E. Weinstein & Sersen, 1961).The right cerebrum is also dominant for two point discrimination (S. Weinstein, 1978) pressure sensitivity (Semmes et al. 1960; S. Weinstein, 1978; E. Weinstein & Sersen, 1961) and processing tactual-directional information (Carmon & Benton, 1969; Fontenot & Benton, 1971). The right hemisphere may be more involved than the left in the perception of somesthetically mediated pain (Cubelli et al. 1984; Haslam, 1970; Murray & Hagan, 1973). FACIAL-EMOTIONAL RECOGNITION AND PROSOPAGNOSIA In addition to body image distortions parietal lobe injuries (particularly when secondary to tumor or seizure activity) also can give rise to sensory misperceptions such as pain (Davidson & Schick, 1935; Hernandez-Peon et al. 1963; Ruff, 1980; Wilkinson, 1973; York et al. 1979). That is, in the less extreme cases, rather than failing to perceive (i.e. neglecting ) the left half of the body, patients may experience sensory distortions that concern various body parts due to abnormal activation of the right hemisphere and parietal lobe. AGNOSIA AND TEMPORAL LOBE FUNCTIONAL LATERALITY Bill and Hillary Clinton. Tom CruiseConversely, when the right hemisphere is damaged, particularly the occipital-temporal region, there can result a severe disturbance not just in the capacity to perceive facial emotion, but in the ability to recognize the faces of friends, loved ones, or pets (DeRenzi, 1986; DeRenzi et al., 1968; DeRenzi & Spinnler, 1966; Evans et al. 1995; Hecaen & Angelergues, 1962; Landis et al., 1986; Levine, 1978; Whiteley & Warrington, 1977; Young et al. 1995); i.e. prosopagnosia. Some patients may be unable to recognize their own face in the mirror. Possibly due in part to the visual-spatial complexity as well as the social-emotional significance of the human face, the right hemisphere has been shown to be dominant in the perception and recognition of familiar and unfamiliar faces (Alvarez & Fuentes, 1994; Bradshaw et al. 1980; DeRenzi, 1982; DeRenzi et al. 1968; DeRenzi & Spinnler, 1966; Deruelle & de Schonen, 1991; Evans et al. 1995; Geffen et al. 1971; Hecaen & Angelergues, 1962; Levy et al. 1972; Ley & Bryden, 1979; Moreno, et al. 1990; Rizzolatti et al. 1971; Sergent et al. 1992) and to become more greatly activated when viewing faces as measured by positron emission tomography and regional cerebral blow flow (Sergent, et al. 1992).There is some indication, however, that the left hemisphere is involved in the recognition of famous faces (Marzi & Berlucchi, 1977; Rizzolatti, et al. 1971) and the differentiation of highly similar faces (presented in outline form) when analysis of fine detail is necessitated (Patterson & Bradshaw, 1975). "POSITIVE" EMOTIONS & THE LEFT HALF OF THE BRAIN Abnormalities affecting the middle temporal lobe (area 37) can result in agnosic disturbances (Giannokapoulos et al., 1999). Patients have difficulty correctly naming and identifying visual percepts. However, depending on the laterality and location of the injury, e.g., right vs left inferior/medial vs superior temporal lobe, patients may display category specific agnosias. For example, a 27-year old man I examined who had sustained a massive right inferior-posterior temporal lobe injury that also involved surgical removal, was able to recognize and name pictures of tools--or at least demonstrate their use (he had been a carpenter) but could not recognize or correctly name pictures of animals and he could not correctly remember facial stimuli that he had been shown five minutes earlier and could not differentiate them from faces he had not seen. By contrast, a 43 year old woman who had been a waitress, and had developed a left inferior temporal lobe glioma that required surgical removal (coupled with chemotherapy) was able to recognize and name pictures of animals and could remember different pictures of faces, but had considerable difficulty recognizing and naming common household objects. DISTURBANCES OF EMOTION AND PERSONALITY Almost all other studies demonstrate increased right frontal activity in response to positive (Teasdale, et al., 1999) and negative stimuli or mental imagery (Rauch et al., 1996; Shin et al., 1997, 1999; Teasdale et al., 1999; however, see Mayberg et al., 1999 for contrary results). For example, in a recent functional MRI study (Teasdale et al., 1999), increases in right frontal (and right cingulate) activity was demonstrated when subjects were shown pairs of pictures and captions evoking negative feelings or positive feelings; a finding which is consistent with most all other reports which indicate that the right hemisphere is dominant for almost all aspects of emotion whereas the left hemisphere is less well endowed in this regard. MANIA AND EMOTIONAL INCONTINENCE The right cerebral hemisphere appears to be dominant in regard to most aspects of somesthesis, including the maintanance of the body-image, visual-spatial-geometric analysis, facial expression and perception, and musical and paralinguistic, melodic-intonational processing. The right hemisphere also predominates in regard to almost all aspects of emotional functioning and exerts bilateral influences on autonomic nervous system functioning. Moreover, norepinephrine (NE) concentrations are higher in the right thalamus (Oke et al. 1978), whereas conversely, damage to the right hemisphere disrupts NE levels on both sides of the brain, whereas similar damage to the left hemisphere only effects local NE levels (Robinson 1979). This is highly significant given the role and importance of NE in emotional and arousal. CONSCIOUSNESS, AWARNESS, MEMORY AND DREAMING Since the right hemisphere is dominant in the perception and expression of facial, somesthetic and auditory emotionality, damage to this half of the brain can result in a variety of affective and social-emotional abnormalities including indifference, lability, hysteria, florid manic excitement, pressured speech, ideas of reference, bizzare confabulatory responding, childishness, irritability, euphoria, impulsivity, promiscuity and abnormal sexual behavior (Bear, 1977, 1983; Bear & Fedio, 1977; Clark & Davison, 1987; M. Cohen & Niska, 1980; Cummings & Mendez, 1984; Erickson, 1945; Forrest, 1982; Gardner et al., 1983; Gruzelier & Manchanda, 1982; House et al. 1990; Jamieson & Wells, 1979; Jampala & Abrams, 1983; Joseph, 1986a,1999a; Lishman, 1968; Offen et al. 1976; Rosenbaum & Berry, 1975; Spencer et al. 1983; Spreen et al., 1965; Starkstein et al. 1987; Stern & Dancy, 1942). For example, seven of 10 patients with sexual seizures described by Remillard, et al. (1983) had right hemisphere foci. Similar findings were reported by Freemon and Nevis (1969), Penfield and Rasmussen (1950), and Spencer et al. (1983). In December of 1974, associate Supreme Court Justice William O. Douglas suffered a massive infarct in the right cerebral hemisphere that left him paralyzed and in pain for many years. As reviewed by Gardner et al., (1983): "For all public purposes, Douglas acted as if he were fine, as if he could soon assume full work on the Court. He insisted on checking himself out of the hospital where he was receiving rehabilitation and then refused to return. He responded to seriously phrased queries about his condition with off handed quips: Walking has very little to do with the work of the Court; If George Blanda can play, why not me? He insisted in a press release that his left arm had been injured in a fall, thereby baldly denying the neurological cause of his paralysis. Occasionally, he acted in a paranoid fashion, claiming, for example, that the Chief Justice's quarters were his and that he was the Chief Justice. During sessions of the Court, he asked irrelevant questions, and sometimes rambled on. Finally, after considerable pressure, Douglas did resign. But the Justice refused to accept that he was no longer a member of the Court. He came back, buzzed for his clerks and tried to inject himself into the flow of business. He took aggressive steps to assign cases to himself, asked to participate in, author, and even publish separately his own opinions, and he requested that a tenth seat be placed at the Justices' bench" (p. 170). RIGHT BRAIN PERVERSITY That the right half of the brain is capable of conscious experience has now been well demonstrated in studies of patients who have undergone complete corpus callosotomies (i.e. split-brain operations) for the purposes of controlling intractable epilepsy. As described by Nobel Lauriate Roger Sperry (1966, p. 299), "Everything we have seen indicates that the surgery has left these people with two separate minds, that is, two separate spheres of consciousness. What is experienced in the right hemisphere seems to lie entirely outside the realm of awareness of the left hemisphere. This mental division has been demonstrated in regard to perception, cognition, volition, learning and memory." LATERALIZED MEMORY FUNCTIONING In that the brain of the normal as well as "split-brain" patient maintains the neuroanatomy to support the presence of two psychic realms, it is surprising that a considerable degree of conflict does not arise during the course of everyday activity. Frequently (such as in the case of the "split-brain" patient, LB, described below), although isolated the right half of the brain is fully willing to assist the left in a myriad of activities. Presumably such difficulties do not occur because both minds, having once been joined, share the same goals and interests. However, common experience seems to argue otherwise, for even in the intact individual, psychic functioning often is plagued by conflict. DREAMING AND HEMISPHERIC OSCILLATION Although a variety of neurochemical and neuroanatomical regions are involved in the formulation of memory (Brewer et al., 1998; Gloor, 1997; Graff-Radford et al.1990; Halgren, 1992; Murray, 1992; Rolls, 1992; Sarter & Markovitch, 1985; Squire, 1992; Wagner et al., 1998; Victor et al 1989), functional specialization greatly determines what type of material can be memorized or even recognized by each half of the cerebrum. This is because the code or form in which a stimulus is represented in the brain and memory is largely determined by the manner in which it is processed and the transformations that take place. Because the right and left cerebral hemispheres differentially process information, the manner in which this information is represented also will be lateralized (Bradshaw & Mattingly, 1997). Hence, some types of information only can be processed or stored by the right vs. the left cerebrum. IMAGERY Although up to five stages of sleep have been identified in humans, for our purposes we will be concerned only with two distinct sleep states. These are the REM (rapid eye movement) and non-REM (N-REM) periods. N-REM occurs during a stage referred to as "slow-wave" or synchronized sleep. In contrast, REM occurs during a sleep stage referred to as "paradoxical sleep." It is called paradoxical, for electrophysiologically the brain seems quite active and alert, similar to its condition during waking. However, the body musculature is paralyzed, and the ability to perceive outside sensory events is greatly attenuated (reviewed in Hobson et al. 1986; Steriade & McCarley 1990; Vertes 1990). LONG LOST CHILDHOOD MEMORIES It is important to note that some investigators believe the left hemisphere is responsible for dreaming and the production of images (see Greenberg & Farah, 1986; Miller, 1990 for a detailed review). In fact, some investigators have claimed that the left (posterior) hemisphere is "dominant" for the production of imagery (Farah, 1989; Trojano & Grossi, 1994), and/or that it is faster at generating images from categorically stored (language related) information (Findlay et al. 1994). FUNCTIONAL COMMISSUROTOMIES AND LIMITIED INTERHEMISPHERIC TRANSFER For most individuals it is extremely difficult if not impossible to verbally recall events which occurred before the age of three and a half (Dudycha & Dudycha, 1933; Gordon, 1928; Joseph, 2000; Waldvogel, 1948; White & Pillemer,1979). . There are several reasons for this (see chapter 29). THE ONTOLOGY OF EMOTIONAL CONFLICT The corpus callosum is the gateway via which information may travel from one brain half to the other. However, it also acts to limit information exchange since almost 40% of the adult callosum lacks myelin (Selnes, 1974). Since mylein acts to insulate and, thus, preserve information transmission by minimizing leakage and increasingly conduction velocity and integrity (Konner, 1991; Rogart & Ritchi, 1977; Ritchie, 1984), some information is lost and degraded even when transfer is possible. (Berlucchi & Rizzolatti, 1968; Hicks 1974; Joseph et al. 1984; Marzi, 1986; Merriam & Gardner, 1987; Myers, 1959, 1962; Rizzolatti et al. 1971; Taylor & Heilman 1980). OVERVIEW AND CONCLUDING COMMENTS Thus, due in part to the slow pace of corpus callosum myelination, coupled with differential right and left cerebral specialization, the left hemisphere of a young child has at best incomplete knowledge of the contents and activity that are occurring within the right. This sets the stage for differential memory storage and a later inability to transfer this information between the cerebral hemispheres once the child reaches adulthood. Overall, based on numerous studies conducted on normal, brain-injured and neurosurgical patients, the right cerebral hemisphere has been shown to dominate in the perception and identification of environmental and nonverbal sounds (e.g., wind, rain, thunder, birds singing); somesthesis; stereognosis; the maintanance of the body image; and the comprehension and expression of prosodic, melodic, and emotional features of speech; as well as the perception of most aspects of musical stimuli, i.e., chords, timbre, tone, pitch, loudness, melody, intensity (except in trained musicians, e.g., Evers et al., 1999). Moroever, the right predominates in the analysis of geometric and visual-space, including depth perception, orientation, position, distance, figure-ground, perspective, visual closure, and stereopsis.
