Exploring the Brain: Emotion Theories - Essay Example

Exploring the Brain- Emotion Theories People's emotional encounters capture the interest of all mental health professionals. Emotion originates from fundamental drives, such as eating, pleasure, pain, fear and aggression. Further, specific human emotions, such as anger, disgust, sadness, happiness, pride, are largely discovered and learned and most likely are represented by the cortex. The complex relationship of emotions, however is far beyond the understanding of neuropsychology -- a challenge that brought about the collaboration of psychologists, psychiatrists and neurologists. How are our human emotions represented in our brain Which of the brain systems produce these emotions These interesting questions signify a true boundary of human discovery. Over the years of research, several theories regarding how the neuroanatomy of emotion functions scientifically extend from right hemisphere hypothesis, which suggests that same neural systems causes all emotions, specifically with the right hemisphere of the brain as responsible in processing emotions (Wager, Phan & Liberzon, et al., 1998; Killgore and Yurgelun-Todd, 2007). Regardless of the strong data supporting the major role for the right hemisphere on emotions, a number of substantial evidence from research revealed a new pattern of brain asymmetry. The second theory such as the Valence Model proposes a combination of some brain systems (Elfenbein, Mandal, Ambady, et al., 2004). According to the theorists supporting this hypothesis, the right hemisphere of the brain processes negative emotions, while the left hemisphere, for positive emotions (Killgore and Yurgelun-Todd, 2007). The purpose of this paper is to discuss and compare the two different theories of brain and emotion and establish evidence from empirical research in favor of the alternative Valence hypothesis. The Right Hemisphere Hypothesis The pioneering theory about brain and emotion states that the left hemisphere is related with cognitive processes, whereas the right hemisphere is engaged with the interpretation and processing of emotion (Wager, Phan & Liberzon, et al., 1998). The relationship between emotion and right hemisphere was established very early in the neurological research. In 1912, Mills found that impairment to the right side of the head resulted to a decline of emotional expression. Correspondingly, two years after, Babinsky (1914) confirmed that patients with injury on the right hemisphere became manic or emotionally indifferent (as cited on Dameree, Everhart & Youngstorm, et al., 2005). The two early studies directed to the development of the "right hemisphere hypothesis", which asserts the most important role for the right hemisphere in the processing of all human emotions. Many studies have provided support for this hypothesis. For example, a recent research conducted on recognition of emotion in facial expression among thirty seven brain-damaged subjects (Adolphs, Damasio and Tranel, et al., 1996) noted significant results. First, that participants with lesions on the left hemisphere showed no malfunction in the facial expressions of emotion, whereas, subjects with damage on the right hemisphere displayed such impairment. Further, the research suggests that impairment of the processing of facial expressions of emotion is attributed to lesions of two discrete regions in the right neocortex such as the right inferior parietal cortex and the anterior infracalcarine cortex. Intimately associated with this research is the hypothesis that people with damage to the left hemisphere produces intellectual disorders. Damage to the right hemisphere however produces affective disorders and failure to respond to humor (Wager, Phan & Liberzon, et al., 1998). Sackiem, Gur and Saucy (1978), confirmed that facial expressions are more intensely expressed in the left side of the face, suggesting a greater involvement of the right hemisphere in the production of emotional displays. Research in schizophrenia also noted that these particular patients who are well known to have impairment in the right middle temporal gyrus may have difficulty with comprehension of emotional prosody in external speech. This finding suggests that the processing of emotional prosody is realized by the right hemisphere (Mitchell and Crow, 2005). Despite the studies that prove the right hemisphere theory, certain discrepancies of results are noted. For example, a quantitative meta-analysis on 65 neuroimaging studies of emotion showed more activation peaks for emotional activation in the left hemisphere than the right hemisphere, opposing the study's earlier hypothesis that the emotion is dominantly processed in the right rather than the left hemisphere (Wager, Phan & Liberzon, et al., 1998). The Valence Hypothesis A more recent theory existing in literature is that both the right and left hemispheres process emotions, but each hemisphere fulfills a particular function. The left hemisphere facilitates the processing of positive emotions, whereas the right hemisphere for processing negative emotions (Wager, Phan & Liberzon, et al., 1998). Theorists of the Valence Hypothesis strongly agree that at least two dimensions are required to describe an affective experience. These two dimensions range from negative to positive (Dameree, Everhart & Youngstorm, et al., 2005). Research works have examined the lateralized brain activity (Killgore and Yurgelun-Todd, 2007) and verifies that the right hemisphere is specifically dominant for processing negative affect. A study exploring the cortical theories of hostility made by Everhart and Harrison (1998) used the brain mapping procedure to examine the specific regions of cortical activity. According to the authors, the neuropsychological explanation of hostility would suggest that the inhibition or regulation of autonomic functioning as well as the expression of heightened hostility can be attributed to anterior right cerebrum. Findings of the study show that greater activation and arousal was displayed on the right anterior temporal region than the left temporal region confirming the theory that the right cerebral hemisphere is specialized for the experience of negative emotions. A similar study conducted by Simon-Thomas, Role, and Knight (2005) suggested that during higher cognitive task performance, the right hemisphere processes emotional responses to aversive stimuli. Further, other research on psychiatric patients shows that impairment to the left hemisphere tends to produce depressive mood compared to damage to the right hemisphere. On the contrary, impairment to the right hemisphere more often arouses euphoric condition (Goldstein as cited on Chemerinski and Levine, 2006). In studies of epilepsy, abnormal brain activation is analyzed. A proposed temporal lobe epilepsy is characterized by emotional intensity. Patients with left temporal lobe epilepsy may generate references to personal destiny and philosophical themes and may display a humorless and depressive approach to life. In contrast, patients with right temporal lobe epilepsy may display excessive emotionality, such as elation (Kenworthy, 2005). The prefrontal cortices influence mood in a complementary way. Whereas activation of the left prefrontal cortex appears to lift the mood, activation of the right prefrontal cortex causes depression. A lesion to the left prefrontal area abolishes the normal mood-elevating influences and produces depression and uncontrollable crying. In contrast, a comparable lesion to the right prefrontal area may produce laughter and euphoria (Fowler, Baker and Tipples, et al., 2006). In a research that examined the asymmetrical brain activity that discriminates between positive and negative affective stimuli in human infants (Fox and Davidson, 1986), electroencephalogram responses from two day old infants were recorded. Infants were given sugar water and citric acid. Observation has shown that after the subjects tasted sugar water, more activity of the left hemisphere of the brain was evident compared after they tasted citric acid. These results confirm the Valence model hypothesis that the left hemisphere is engaged in the processing of positive emotions while the right hemisphere is engaged in processing negative emotions. To argue whether that the right hemisphere alone as being accountable for all human emotions or if parts of both left and right hemispheres are differently specialized with facilitating emotions has challenged many theorists. Despite various studies confirming the right hemisphere hypothesis in the occurrence of emotion; at present there is more data supporting the Valence Model. Initial theories of brain and emotion ended to consider emotional functions as facilitated absolutely in one hemisphere alone. Research has now moved from relative dominance as opposed to the absolute dominance. Reference Adolphs, R., Damasio, H., Tranel, D., and Damasio, A. (1996). Cortical systems for the recognition of emotion in facial expressions. The Journal of Neuroscience, 16 (23), 7678-7687. 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Behavioral and electrophysiological evidence of a right hemisphere bias for the influence of negative emotion on higher cognition. Journal of Cognitive Neuroscience, 17 (3), 518-529. Wager, T., Phan, K., Liberzon, I., and Taylor, S. (1998). Valence, gender, lateralization of functional brain anatomy: A meta-analysis if findings from neuroimaging. A Manuscript. Retrieved from http://www.columbia.edu/cu/psychology/tor/Papers/Wager_NIMG90_inpress.pdf Read More