In Search for Etiology of Cerebral Lateralization for Emotional Recognition
An increasing amount of research has investigated how emotion processing is lateralized in the human brain (Bourne & Gray, 2009; Bourne 2008; Burt et al., 2009; Workman, Chilvers, Yeomans & Tylor, 2006; Balconi & Mazza, 2006). Recent research suggests two different hypotheses to elucidate the brain asymmetry in response to emotional stimuli.
The right hemisphere hypothesis supposes that the right hemisphere is specialized for the perception, expression, and experience of emotion, regardless of the valance (negative to positive) and intensity of the emotional content (Davidson & Schwartz, 1976; Bourne 2010). A study examined the development of cerebral lateralization for recognition of emotion by chimeric face(a face composed by different emotions in each side) tests in different age period, 5-6years old, 7-8 years old and 10-11 years old.
This research demonstrated that there was observed right hemispheric biases for every emotion such as, anger, happy, sad, disgust, surprise and fear in 10-11years old children, which is consistent with the adult subjects.
On the other hand, there was observed right hemisphere bias for only happy emotion in 5-6 years old children. Moreover, 7-8 year old subjects showed more adult-like tendency than 5-6 subjects, but less than 10-11 year old subjects (Workman, Chilvers, Yeomans & Tylor, 2006). The results of this study are consistent with right hemisphere hypothesis in 10-11 children because they showed strong left visual field bias (right hemisphere bias) regardless of the valence of emotion.
Moreover, they also find interesting differences in lateralization based on valence. Positive emotion recognition is more lateralized than negative emotion recognition regardless of the age.
Furthermore, there are individual differences in lateralization to emotional stimuli. These results suggest two implications. First, cerebral lateralization of emotional recognition is developing between 5 and 11 years old. Second, there is strong right hemisphere bias for emotional recognition after 11 years old. They, however, did not research what factors are correlated with the development of the lateralization of emotional recognition.
Aljuhanay et al., (2009) investigated the emotional recognition process between adults and children because this strategy difference might cause different lateralization effects for emotional recognition. Prior research suggested that children would use “featural processing”, that is initially recognizing facial features such as distinctive eyes or noses.
On the other hand, adults would tend to use a “configural processing” strategy to recognize emotion. A “Configural processing” strategy is focusing on spatial relationships between the individual features of the faces.
This is two-step process. First, a face was defined as a different category from other stimuli. Second, the spatial information was utilized for identifying individual faces. In this study, they found consistent result with the prior study that children and adults recognized facial emotion differently, although regardless of the age, right hemispheric bias was found. This is inconsistent with the result of Workman and colleagues (2006) who found that age difference is associated with lateralization for emotional recognition.
Bourne and Gray (2009) examined the possible factor which is correlated with hemispheric lateralization. They measured 2D:4D ratio which indicates the influence of prenatal exposure of testosterone and estrogen. Comparative length of the second and the fourth digit (2D:4D) is associated with higher levels of prenatal testosterone and lower levels of prenatal estrogen. This relationship was initially suggested by Manning et al. (1998) and several studies support their suggestion.
Children with congenital adrenal hyperplasia tend to have lower 2D:4D ratios (Mathews et al., 2004). Lutchmaya et al., (2004) directly measured the testosterone level in the amniotic fluid and found an association with 2D:4D ratio. Bourne and Gray (2009) found an association between 2D:4D ratio and right hemispheric lateralization. The lower the 2D:4D ratio is the stronger the right hemispheric lateralization.
However, alternative hypotheses were also formulated on the lateralization effect of facial emotional recognition. The valance hypothesis is one of them. This hypothesis supposes that the cortical functional differences encoding emotional information are based on the valance of emotion: right hemisphere is specialized for negative emotions and left hemisphere is specialized for positive emotions (Everhart, Carpenter, Carmona, Ethridge, & Demure, 2003; Silberman & Weingartner, 1986).
This hypothesis is also supported by several studies. Everhart and Harrison (2000) demonstrated that negative faces were more rapidly identified if the stimuli were placed in the right visual field. Some EEG research has revealed that relative increase of left hemisphere activity was found with positive emotional stimuli (Davidson & Henriques, 2000)
Although several studies have examined the process of the lateralization of emotional recognition, two fundamental issues remained. First, there is not enough evidence about which hypothesis―right hemisphere hypothesis and valence hypothesis― can be correct. Second, regardless of the hypothesis, it is unknown what kind of social and/or personal factors might contribute to influencing individual differences in the lateralization for emotional recognition other than hormone.
Political attitude, personal, social and environmental factors can also contribute to developing cerebral hemispheric lateralization. Oxley et al., (2008) demonstrated the correlation between conservatism and sensitivity to emotional stimuli. This could have associations with lateralization for emotional recognition. The direct relationship is unknown; however, personal trait may have association with cerebral lateralization.
One study revealed that openness is negatively correlated with conservatism, and conscientiousness is positively correlated with conservatism. The correlation between other personal traits and conservatism are inconsistent (Vecchione, 2011). These results indicated that personal traits are correlated with political attitude, and political attitude may be correlated with cerebral lateralization.
Wong, Fung, Chua, and McAlonan (2008) demonstrated that people with autism displayed reduced right hemisphere activity in comparison to normal controls when viewing emotional faces. Nevertheless, Harris and Lindell (2008) found that people with high autistic-like traits showed right hemispheric lateralization bias when viewing emotional faces. This tendency showed the same result when people with low autistic-like traits were viewing happy faces. This result indicates that people with high autistic-like traits but not autistic disorder have an intact facial recognition processing system.
Social anhedonia personality trait which is characterized by a reduced desire for social affiliation and reduced pleasure derived from interpersonal interactions (Germine, Garrido, Bruce and Hooker, 2011). The high SA group showed reduced activity in the anterior rostal medial frontal cortex, right superior temporal gyrus, and somatosensory cortex in comparison to the low SA group when viewing emotional stimuli(Germine, Garrido, Bruce and hooker, 2011).These three areas are the part of the neural network to process emotional recognition.
The arMFC activity is associated with mentalizing, and other aspects of social cognition. This area is associated with abnormal emotional recognition process in schizophrenic individuals (Brunet-Gouet and Decety, 2006).
The superior temporal gyrus and sulcus are involved in perceptual processing of dynamic social stimuli including facial expressions of emotion, eye gaze and movement of lips(Haxby et al., 2000; Hooker et al., 2003, 2008, 2010). Moreover STS is involved in processing complex social emotion recognition processes including recognizing appraisal of intention or context of facial expression (Pourtois et al., 2004).
The somatosensory cortex are thought to contribute to emotional processing by allowing facial expressions to be understood using an internal representation of a facial expression maintained in one’s own somatosensory cortex (Adolphs et al., 2000; Heberliein et al., 2008; Hooker et al., 2008). The somatosensory cortex have dissociable role with superior gyrus and sulcus in emotional processing. Lesion of somatosensory cortex leads to impairment in emotional discrimination of the same facial expression.
Although these deactivation areas were found in high SA subjects, it was unclear whether this is a cause or consequence. People with schizophrenic personality traits showed poor emotional recognition response including sensitivity for detecting emotional prosody. This, however, cannot be attributed to abnormal activation of right hemisphere (Castro and Pearson, 2011).
Socioeconomic status was also thought to be the factor which may contribute to developing cerebral lateralization. High socioeconomic status may positively correlate with cerebral lateralization and low socioeconomic status may negatively correlate with cerebral lateralization (Boles, 2011).
Although cerebral lateralization for emotional recognition has been induced since 5 years old, there is no compelling evidence about what factor would cause this phenomena and how it would be develop. Further researches is needed to shed light on the processes of emotional recognition which is necessary process of acquiring social information and to find out etiology of the lateralization to treatment for the individuals with poor emotional recognition ability.
References
Adolphs,R.,Damasio,H.,Tranel,D.,Cooper,G.,Damasio,A.R.(2000).
A role for somatosensory cortices in the visual recognition of emotional as revealed by three dimensional lesion mapping. Journal of Neuroscience, 20, 2683-2690.
Aljuhanay, A., Milene, E., Burt, M.D., Pasalis, O.(2009).Asymmetry in face processing during childhood measure with chimeric faces. Psychology Press, 440-450.
Balconi, M., & Mazza, G. (2010). Lateralisation effect in comprehension of emotional facial expression: A comparison between EEG alpha band power and behavioral inhibition (BIS) and activation (BAS) system. Laterality, 15,361-384.
Boles, D. (2011).Socioeconomic status, a forgotten variable in lateralization development. Brain and Cogntion, 76, 52-57.
Bourne, V.J. (2010). How are emotions lateralized in the brain? Contrasting existing hypotheses using Chimeric Face Test. Brain and Cognition, 24,903-911.
Bourne, V.J., &Gray, D.L. (2009).Hormone exposure and functional lateralization: Examining the contributions of prenatal and later life hormonal exposure. Psychoneuroendocrinology, 34, 1214-1221.
Bourne, V.J. (2008).Examining the relationship between degree of handed ness and degree of cerebral lateralization for processing emotional facial emotion. Neuropsychology, 22,350-356.
Brunet-Gouet, E., Decety, J., (2006).Social Brain dysfunctions in schizophrenia: a review of neuroimaging studies. Psychiatry Res, 148, 75-92.
Castro, A., & Pearson, R. (2011).Lateralization of language and emotion in schizotypal personality: evidence from dichotic listening. Personality and Individual Differences, 51, 726-731.
Davidson, R.J., &Schwartz, G.E. (1976). Patterns of cerebral lateralization during cardiac biofeedback versus the self-regulation of emotion: Sex differences. Psychophysiology, 13(1), 62-68.
Davidson, R.J., &Henriques, J. (2000).Regional brain function of sadness and depression.
New York, Oxford University Press.
Everhart, E., Carpenter, M.D., Carmona, J.E., Ethridge, A.J., Demaree, H.A. (2003). Adult sex-related P300 differences during the perception of emotional prosody and facial affect. Psychophysiology, 40(S1), S39.
Everhart, E., & Harrison, D.W. (2000). Facial affect perceptions anxious and nonanxious men with depression. Psychobiology, 28(1), 90-98.
Germine, L.T., Garrido, L.B., Hooker, C. (2011).Social anhedonia is associated with neural abnormalities during face emotion processing. NeuroImage, 58, 935-945.
Haxby J.V., Hoffman, E.A., Gobbini, M.I. (2000).The distributed human neural system for face perception. Trends of Cognitive Science, 4, 223-233.
Harris, C.D., & Lindell, A.K.(2011). The influence of autism-like traits on cheek biases for the expression and perception of happiness. Brain and Cognition, 77, 11-16.
Hooker, C.Paller, K., Gitelman, D., Parrish, T., Mesulam, M, Reber, P. (2003). Brain network analyzing eye gazing. Brain Response, 17, 406-418.
Hooker, C.,Verosky, S., Germine, L.,Knight, R.,D’Esposite, M.(2008).Mentalizing emotion and its relationship and empathy.Soc.Cogn.Affect.Neurosci,3, 204-217.
Hooker, C., Verosky, S., Germine, L., Knight, R., D’Esposite, M. (2010).Neural activity during social signal perception correlates with self-reported empathy. Brain Res, 1308, 100-113.
Lutchmaya, S., Baron-Cohen, S., Raggatt, P., Knickmeyer, R., Manning, J.T. (2004).
2nd to 4th digit ratios, fetal testosterone and estradiol. Early human Development, 77, 23-28.
Manning, J.T.,Scutt, D., Willson, J., Lewis-Jones, D.I.(1998).The ratio of 2nd to 4th digit length: a predictor of sperm numbers and concentrations of testosterone, luteinizing hormone and oestrogen. Human Reproduction, 13, 3000-3004.
Mathews, G.A., Fane, B.A., Pasterski, V.L., Conway, G.S., Brook, C., Hines, M. (2004).
Androgenic influences on neural asymmetry: Handedness and language lateralization in individuals with congenital adrenal hyperplasia. PNEC, 29,810-829.
Silberman, K., & Weingartner, H. (1986). Hemispheric lateralization of functions related to emotion. Brain and Cognition, 5(3), 322-353.
Oxley, D., R., Smith, K., B., Alford, J., R., Hibbing, M., V., Miller, J., L., Scalora, M., Hatemi, P., K., Hibbing, J., R. (2008).Political Attitudes Vary with Physiological Traits. Science, 321, 1667-1670.
Poutois, G., Sander, D., Andres, M., Grandjean, D., Reveret L., Olivier, E.,
Vuilleumier, P. (2004). Dissociable roles of the human somatosensory and superior temporal cortices for processing social face signals. European Journal of Neuroscience, 20, 3507-3515.
Vecchione, M., Schoen, H., Gonzalez Castro, J., L., Cieciuch, J., Pavlopoulos, V.,
Caprara G., V. (2011).Personality correlates of party preference: The Big Five in five big European countries. Personality and Individual Differences, 51, 737-742.
Wang,T.K.W.,Fung,P.C.W.,Cula,S.E.,McAlonan, G.M. (2008).Abnormal spatiotemporal processing of emotional facial expression in childhood autism: dipole source analysis of event-related potentials. European Journal of Neuroscience, 28, 407-416.
Workman, L., Chilvers, L., and Yeomans, H. (2006).
Development of cerebral lateralization for recognition of emotions in chimeric faces in children aged 5 to 11. LATERALITY, 11,493-507.