外倾性在人脑功能和结构上的反映:基于MRI研究的回顾
Brain Functional and Structural Changes of Extraversion: Review of the MRI Researches of Extraversion

作者: 杨志林 , 邹枝玲 :西南大学心理学部,认知与人格教育部重点实验室,重庆; 张 雪 :陕西师范大学心理学院,西安;

关键词: 外倾性fMRI脑岛前扣带杏仁核社会脑网络 Extroversion fMRI Insula Anterior Cingulated Cortex Amygdale Social Brain Network

摘要: 随着脑成像技术的不断发展,研究者试图通过脑成像技术研究人格特质的内在神经生理机制。本文对人格的核心特质——外倾性的MRI研究(包括任务态的、静息的、结构的)进行回顾和总结,以期更好地理解外倾性特质的神经机制。研究发现,外倾性与脑岛、腹侧纹状体、杏仁核、眶额叶、楔前叶、前扣带等社会脑网络脑区功能或结构的改变有关。未来的研究需要综合考虑测量手段、选择恰当研究范式,并尽可能考虑年龄、性别、实验刺激类型、被试类型、样本数量等一些因素的影响。
With the development of brain imaging technology, the brain mechanism of personality has captured the attention of researchers for several years. In the present review, MRI researches (including task- fMRI, resting-fMRI, and structural MRI) of extroversion were summarized in order to help understand the neural mechanism of extraversion traits. In summary, extraversion was found to be highly correlated to the functional and structural changes in insula, ventral striatum, amygdala, the medial prefrontal cortex, precu- neate cortex, and anterior cingulated cortex, which were referred to as the social brain network. Future researchers had better choose multiple measurements of extraversion, flexible study design with better ecological validity, and control other extra factors, such as age, gender, stimulus type, subjects’ type and sample size.

文章引用: 杨志林 , 张 雪 , 邹枝玲 (2014) 外倾性在人脑功能和结构上的反映:基于MRI研究的回顾。 心理学进展, 4, 110-122. doi: 10.12677/AP.2014.41019

参考文献

[1] De Young, C. G., & Gray, J. R. (2009). Personality neuroscience: Explaining individual differences in affect, behavior, and cognition. The Cambridge Handbook of Personality Psychology, 323-346.

[2] De Young, C. G., Hirsh, J. B., Shane, M. S., Papademetris, X., Rajeevan, N., & Gray, J. R. (2010b). Testing predictions from personality neuroscience brain structure and the big five. Psychological Science, 21, 820-828.

[3] Drabant, E. M., Kuo, J. R., Ramel, W., Blechert, J., Edge, M. D., Cooper, J. R., Goldin, P. R., Hariri, A. R., & Gross, J. J. (2011). Experiential, autonomic, and neural responses during threat anticipation vary as a function of threat intensity and neuroticism. Neuroimage, 55, 401410.

[4] Egloff, B., & Schmukle, S. C. (2002). Predictive validity of an Implicit Association Test for assessing anxiety. Journal of Personality and Social Psychology, 83, 1441-1455.

[5] Eisenberger, N. I., Lieberman, M. D., & Satpute, A. B. (2005). Personality from a controlled processing perspective: An fMRI study of neuroticism, extraversion, and self-consciousness. Cognitive, Affective, & Behavioral Neuroscience, 5, 169-181.

[6] Frühholz, S., Prinz, M., & Herrmann, M. (2010). Affect-related personality traits and con-textual interference processing during perception of facial affect. Neuroscience Letters, 469, 260-264.

[7] Fujiwara, J., Tobler, P. N., Taira, M., Iijima, T., & Tsutsui, K. (2008). Personality-dependent dissociation of absolute and relative loss processing in orbitofrontal cortex. European Journal of Neuroscience, 27, 1547-1552.

[8] Gao, Q., Xu, J. S., Duan, X. J., Liao, W., Ding, J. R., Zhang, W. H., Li, Y., Lu, G. M., & Chen, H. F. (2013). Extraversion and neuroticism relate to topological properties of resting-state brain networks. Frontiers in Human Neuroscience, 7, 1-14.

[9] Gioia, M. C., Cerasa, A., Valentino, P., Fera, F., Nisticò, R., Liguori, M., Lanza, P., & Quattrone, A. (2009). Neurofunctional correlates of personality traits in relapsing-remitting multiple sclerosis: An fMRI study. Brain and Cognition, 71, 320-327.

[10] Grafton, S. T. (2009). Embodied cognition and the simulation of action to understand others. Annals of the New York Academy of Sciences, 1156, 97-117.

[11] Gray, J. R., Burgess, G. C., Schaefer, A., Yarkoni, T., Larsen, R. J., & Braver, T. S. (2005). Affective personality differences in neural processing efficiency confirmed using fMRI. Cognitive, Affective, & Behavioral Neuroscience, 5, 182-190.

[12] Greenwald, A. G., & Nosek, B. A. (2001). Health of the implicit association test at age 3. Zeitschrift für Experimentelle Psychologie, 48, 85-93.

[13] Haas, B. W., Constable, R. T., & Canli, T. (2008). Stop the sadness: Neuroticism is associated with sustained medial prefrontal cortex response to emotional facial expressions. Neuroimage, 42, 385.

[14] Haas, B. W., Omura, K., Amin, Z., Constable, R. T., & Canli, T. (2006). Functional connectivity with the anterior cingulate is associated with extraversion during the emotional Stroop task. Social Neuroscience, 1, 16-24.

[15] Hahn, T., Dresler, T., Pyka, M., Notebaert, K., & Fallgatter, A. J. (2013). Local synchronization of resting-state dynamics encodes gray’s trait anxiety. PloS One, 8, e58336.

[16] Harenski, C. L., Kim, S. H., & Hamann, S. (2009). Neuroticism and psychopathy predict brain activation during moral and nonmoral emotion regulation. Cognitive, Affective, & Behavioral Neuroscience, 9, 1-15.

[17] Hayano, F., Nakamura, M., Asami, T., Uehara, K., Yoshida, T., Roppongi, T., Otsuka, T., Inoue, T., & Hirayasu, Y. (2009). Smaller amygdala is associated with anxiety in patients with panic disorder. Psychiatry and Clinical Neurosciences, 63, 266-276.

[18] Hooker, C. I., Verosky, S. C., Miyakawa, A., Knight, R. T., & D’Esposito, M. (2008). The influence of personality on neural mechanisms of observational fear and reward learning. Neuropsychologia, 46, 2709-2724.

[19] Hutcherson, C. A., Goldin, P. R., Ramel, W., McRae, K., & Gross, J. J. (2008). Attention and emotion influence the relationship between extraversion and neural response. Social Cognitive and Affective Neuroscience, 3, 71-79.

[20] Gazzaniga, M. S., Ivry, R. B., & Mangun, G. R., 著, 周晓林, 高定国等, 译(2011). 认知神经科学——关于心智的生物学 (3 Ed.). 北京: 中国轻工业出版社.

[21] Jackson, J., Balota, D. A., & Head, D. (2011). Exploring the relationship between personality and regional brain volume in healthy aging. Neurobiology of Aging, 32, 2162-2171.

[22] Jimura, K., Konishi, S., Asari, T., & Miyashita, Y. (2010). Temporal pole activity during understanding other persons’ mental states correlates with neuroticism trait. Brain Research, 1328, 104-112.

[23] Jimura, K., Konishi, S., & Miyashita, Y. (2009). Temporal pole activity during perception of sad faces, but not happy faces, correlates with neuroticism trait. Neuroscience Letters, 453, 45-48.

[24] Juan, E., Frum, C., Bianchi-Demicheli, F., Wang, Y.-W., Lewis, J. W., & Cacioppo, S. (2013). Beyond human intentions and emotions. Frontiers in Human Neuroscience, 7, 1-14.

[25] Kanske, P., & Kotz, S. A. (2011). Emotion triggers executive attention: Anterior cingulate cortex and amygdala responses to emotional words in a conflict task. Human Brain Mapping, 32, 198-208.

[26] Kehoe, E. G., Toomey, J. M., Balsters, J. H., & Bokde, A. L. W. (2012). Personality modulates the effects of emotional arousal and valence on brain activation. Social Cognitive and Affective Neuroscience, 7, 858-870.

[27] Keightley, M.L., Seminowicz, D.A., Bagby, R.M., Costa, P.T., Fossati, P., & Mayberg, H.S. (2003). Personality influences limbic-cortical interactions during sad mood induction. Neuroimage, 20(4), 2031-2039.

[28] Kennis, M., Rademaker, A. R., & Geuze, E. (2013). Neural correlates of personality: An integrative review. Neuroscience & Biobehavioral Reviews, 37, 73-95.

[29] Kotov, R., Gamez, W., Schmidt, F., & Watson, D. (2010). Linking “big” personality traits to anxiety, depressive, and substance use disorders: A meta-analysis. Psychological Bulletin, 136, 768-821.

[30] Kumari, V., Das, M., Wilson, G. D., Goswami, S., & Sharma, T. (2007). Neuroticism and brain responses to anticipatory fear. Behavioral Neuroscience, 121, 643-652.

[31] Kumari, V., ffytche, D. H., Williams, S. C. R., & Gray, J. A. (2004). Personality predicts brain responses to cognitive demands. The Journal of Neuroscience, 24, 10636-10641.

[32] Kunisato, Y., Okamoto, Y., Okada, G., Aoyama, S., Nishiyama, Y., Onoda, K., & Yamawaki, S. (2011). Personality traits and the amplitude of spontaneous low-frequency oscillations during resting state. Neuroscience Letters, 492, 109-113.

[33] Lei, X., Zhao, Z. Y., & Chen, H. (2013). Extraversion is encoded by scale-free dynamics of default mode network. NeuroImage, 74, 52-57.

[34] Liu, W.-Y., Weber, B., Reuter, M., Markett, S., Chu, W.-C., & Montag, C. (2013). The big five of personality and structural imaging revi-sited: A VBM-DARTEL study. Neuroreport, 24, 375-380.

[35] Lucas, R. E., Diener, Ed., Grob, A., Suh, E. M., & Shao, L. (2000). Cross-cultural evidence for the fundamental features of extraversion. Journal of Personality and Social Psychology, 79, 452-468.

[36] Mahoney, C. J., Rohrer, J. D., Omar, R., Rossor, M. N., & Warren, J. D. (2011). Neuroanatomical profiles of personality change in frontotemporal lobar degeneration. The British Journal of Psychiatry, 198, 365-372.

[37] McCrae, R. R., & Costa, P. T. (1987). Validation of the five-factor model of personality across instruments and observers. Journal of Personality and Social Psychology, 52, 81-90.

[38] McIntosh, A. M., Bastin, M. E., Luciano, M., Maniega, S. M., Hernandez, M. del C. V., Royle, N. A., Hall, J., Murray, C., Lawrie, S. M., Starr, J. M., Wardlaw, J. M., & Deary, I. J. (2013). Neuroticism, depressive symptoms and white-matter integrity in the Lothian Birth Cohort 1936. Psychological Medicine, 43, 1197-1206.

[39] Moayedi, M., Weissman-Fogel, I., Crawley, A. P., Goldberg, M. B., Freeman, B. V., Tenenbaum, H. C., & Davis, K. D. (2011). Contribution of chronic pain and neuroticism to abnormal forebrain gray matter in patients with temporomandibular disorder. NeuroImage, 55, 277-286.

[40] Mobbs, D., Hagan, C. C., Azim, E., Menon, V., & Reiss, A. L. (2005). Personality predicts activity in reward and emotional regions associated with humor. Proceedings of the National Academy of Sciences of the United States of America, 102, 16502-16506.

[41] Montag, C., Schoene-Bake, J.-C., Wagner, J., Reuter, M., Markett, S., Weber, B., & Quesada, C. M. (2013). Volumetric hemispheric ratio as a useful tool in personality psychology. Neuroscience Research, 75, 157-159.

[42] Moriguchi, Y., Ohnishi, T., Decety, J., Hirakata, M., Maeda, M., Matsuda, H., & Komaki, G. (2009). The human mirror neuron system in a population with deficient self-awareness: An fMRI study in alexithymia. Human Brain Mapping, 30, 2063-2076.

[43] Morrisj, J. S. (2002). How do you feel? Trends in Cognitive Sciences, 6, 317-319.

[44] Munafó, M. R., & Black, S. (2007). Personality and smoking status: A longitudinal analysis. Nicotine & Tobacco Research, 9, 397-404.

[45] Munafò, M. R., Clark, T. G., Moore, L. R., Payne, E., Walton, R., & Flint, J. (2003). Genetic polymorphisms and personality in healthy adults: A systematic review and meta-analysis. Molecular Psychiatry, 8, 471-484.

[46] Munafó, M. R., Zetteler, J. I., & Clark, T. G. (2007). Personality and smoking status: A meta-analysis. Nicotine & Tobacco Research, 9, 405-413.

[47] Omura, K., Todd Constable, R., & Canli, T. (2005). Amygdala gray matter concentration is associated with extraversion and neuroticism. Neuroreport, 16, 1905-1908.

[48] Onitsuka, T., Nestor, P. G., Gurrera, R. J., Shenton, M. E., Kasai, K., Frumin, M., Niznikiewicz, M. A., & McCarley, R. W. (2005). Association between reduced extraversion and right posterior fusiform gyrus gray matter reduction in chronic schizophrenia. The American Journal of Psychiatry, 162, 599-601.

[49] 林崇德(1995). 发展心理学. 北京: 人民教育出版社.

[50] 郑雪(2007). 人格心理学. 广州: 暨南大学出版社.

[51] Park, M., Hennig-Fast, K., Bao, Y., Carl, P., Pöppel, E., Welker, L., Reiser, M., Meindl, T., & Gutyrchik, E. (2013). Personality traits modulate neural responses to emotions expressed in music. Brain Research, 1523, 68-76.

[52] Rauch, S. L., Milad, M. R., Orr, S. P., Quinn, B. T., Fischl, B., & Pitman, R. K. (2005). Orbitofrontal thickness, retention of fear extinction, and extraversion. Neuroreport, 16, 1909-1912.

[53] Rusting, C. L., & Larsen, R. J. (1998). Personality and cognitive processing of affective information. Personality and Social Psychology Bulletin, 24, 200-213.

[54] Adelstein, J. S., Shehzad, Z., Mennes, M., De Young, C. G., Zuo, X.-N., Kelly, C., Margulies, D. S., Bloomfield, A., Gray, J. R., & Castellanos, F. X. (2011). Personality is reflected in the brain’s intrinsic functional architecture. PloS One, 6, e27633.

[55] Schaefer, M., Knuth, M., & Rumper, F. (2011). Striatal response to favorite brands as a function of neuroticism and extraversion. Brain Research, 1425, 83-89.

[56] Bienvenu, O., Hettema, J., Neale, M., Prescott, C., & Kendler, K. (2007). Low extraversion and high neuroticism as indices of genetic and environmental risk for social phobia, agoraphobia, and animal phobia. American Journal of Psychiatry, 164, 1714-1721.

[57] Schutter, D. J. L. G., Koolschijn, P., Cédric, M. P., Peper, J. S., & Crone, E. A. (2012). The cerebellum link to neuroticism: A volumetric MRI association study in healthy volunteers. PloS One, 7, e37252.

[58] Schuyler, B. S., Kral, T. R. A., Jacquart, J., Burghy, C. A., Weng, H. Y., Perlman, D. M., Bachhuber, D. R. W., Rosenkranz, M. A., MacCoon, D. G., & van Reekum, C. M. (2012). Temporal dynamics of emotional res-ponding: Amygdala recovery predicts emotional traits. Social Cognitive and Affective Neuroscience, 1-6.

[59] Bjørnebekk, A., Fjell, A. M., Walhovd, K. B., Grydeland, H., Torgersen, S., & Westlye, L. T. (2013). Neuronal correlates of the five factor model (FFM) of human personality: Multimodal imaging in a large healthy sample. NeuroImage, 65, 194-208.

[60] Sollberger, M., Stanley, C. M., Wilson, S. M., Gyurak, A., Beckman, V., Growdon, M., Jang, J., Weiner, M. W., Miller, B. L., & Rankin, K. P. (2009). Neural basis of interpersonal traits in neurodegenerative diseases. Neuropsychologia, 47, 2812-2827.

[61] Blankstein, U., Chen, J. Y. W., Mincic, A. M., McGrath, P. A., & Davis, K. D. (2009). The complex minds of teenagers: Neuroanatomy of personality differs between sexes. Neuropsychologia, 47, 599-603.

[62] Sosic-Vasic, Z., Ulrich, M., Ruchsow, M., Vasic, N., & Groen, G. (2012). The modulating effect of perso-nality traits on neural error monitoring: Evidence from event-related fMRI. Plos One, 7, e42930.

[63] Steffens, M. C., & Schulze König, S. (2006). Predicting spontaneous big five behavior with implicit association tests. European Journal of Psychological Assessment, 22, 13-20.

[64] Brück, C., Kreifelts, B., Kaza, E., Lotze, M., & Wildgruber, D. (2011). Impact of personality on the cerebral processing of emotional prosody. Neuroimage, 58, 259-268.

[65] Stein, M. B., Simmons, A. N., Feinstein, J. S., & Paulus, M. P. (2007). Increased amygdala and insula activation during emotion processing in anxiety-prone subjects. American Journal of Psychiatry, 164, 318327.

[66] Brassen, S., Gamer, M., & Büchel, C. (2011). Anterior cingulate activation is related to a positivity bias and emotional stability in successful aging. Biological Psychiatry, 70, 131-137.

[67] Britton, J. C., Ho, S.-H., Taylor, S. F., & Liberzon, I. (2007). Neuroticism associated with neural activation patterns to positive stimuli. Psychiatry Research: Neuroimaging, 156, 263-267.

[68] Brühl, A. B., Viebke, M.-C., Baumgartner, T., Kaffenberger, T., & Herwig, U. (2011). Neural correlates of personality dimensions and affective measures during the anticipation of emotional stimuli. Brain Imaging and Behavior, 5, 86-96.

[69] Bush, G., Luu, P., & Posner, M. I. (2000). Cognitive and emotional influences in anterior cingulate cortex. Trends in Cognitive Sciences, 4, 215-222.

[70] Canli, T., Amin, Z., Haas, B., & Omura, K. (2004). A double dissociation between mood states and personality traits in the anterior cingulate. Behavior Neurosciencce, 118, 897-904.

[71] Canli, T., Sivers, H., Whitfield, S. L., Gotlib, I. H., & Gabrieli, J. D. E. (2002). Amygdala response to happy faces as a function of extraversion. Science, 296, 2191.

[72] Canli, T., Zhao, Z., Desmond, J. E., & Kang, E. (2001). An fMRI study of personality influences on brain reactivity to emotional stimuli. Behavioral Neuroscience, 115, 33-42.

[73] Carver, C. S., & Connor-Smith, J. (2010). Personality and coping. Annual Review of Psychology, 61, 679-704.

[74] Chan, S. W. Y., Norbury, R., Goodwin, G. M., & Harmer, C. J. (2009). Risk for depression and neural responses to fearful facial expressions of emotion. The British Journal of Psychiatry, 194, 139-145.

[75] Chen, J. Y.-W., Blankstein, U., Diamant, N. E., & Davis, K. D. (2011). White matter abnormalities in irritable bowel syndrome and relation to individual factors. Brain Research, 1392, 121-131.

[76] Coen, S. J., Kano, M., Farmer, A. D., Kumari, V., Giampietro, V., Brammer, M., Williams, S. C. R., & Aziz, Q. (2011). Neuroticism influences brain activity during the experience of visceral pain. Gastroenterology, 141, 909-917.

[77] Cohen, M. X., Young, J., Baek, J.-M., Kessler, C., & Ranganath, C. (2005). Individual differences in extraversion and dopamine genetics predict neural reward responses. Cognitive Brain Research, 25, 851-861.

[78] Cremers, H. R., Demenescu, L. R., Aleman, A., Renken, R., Van Tol, M.-J., Van Der Wee, N. J. A., Veltman, D. J., & Roelofs, K. (2010). Neuroticism modulates amygdala-prefrontal connectivity in response to negative emotional facial expressions. Neuroimage, 49, 963-970.

[79] Cremers, H., van Tol, M.-J., Roelofs, K., Aleman, A., Zitman, F. G., van Buchem, M. A., Veltman, D. J., & van der Wee, N. J. A. (2011). Extraversion is linked to volume of the orbitofrontal cortex and amygdala. PloS One, 6, e28421.

[80] Cunningham, W. A., Arbuckle, N. L., Jahn, A., Mowrer, S. M., & Abduljalil, A. M. (2011). Reprint of aspects of neuroticism and the amygdala: Chronic tuning from motivational styles. Neuropsychologia, 49, 657-662.

[81] Davis, M., & Whalen, P. J. (2001). The amygdala: Vigilance and emotion. Molecular Psychiatry, 6, 13-34.

[82] Suslow, T., Kugel, H., Reber, H., Bauer, J., Dannlowski, U., Kersting, A., Arolt, V., Heindel, W., Ohrmann, P., & Egloff, B. (2010). Automatic brain response to facial emotion as a function of implicitly and explicitly measured extraversion. Neuroscience, 167, 111-123.

[83] Tafarodi, R. W. (1998). Paradoxical self-esteem and selectivity in the processing of social information. Journal of Personality and Social Psychology, 74, 1181-1196.

[84] Tafarodi, R. W., Marshall, T. C., & Milne, A. B. (2003). Self-esteem and memory. Journal of Personality and Social Psychology, 84, 2945.

[85] Tamura, M., Moriguchi, Y., Higuchi, S., Hida, A., Enomoto, M., Umezawa, J., & Mishima, K. (2012). Neural network development in late adolescents during observation of risk-taking action. Plos One, 7, e39527.

[86] Terasawa, Y., Shibata, M., Moriguchi, Y., & Umeda, S. (2013). Anterior insular cortex mediates bodily sensibility and social anxiety. Social Cognitive and Affective Neuroscience, 8, 259-266.

[87] Wager, T. D., Davidson, M. L., Hughes, B. L., Lindquist, M. A., & Ochsner, K. N. (2008). Pre-frontal-subcortical pathways mediating successful emotion regulation. Neuron, 59, 1037-1050.

[88] Wei, L. Q., Duan, X. J., Yang, Y., Liao, W., Gao, Q., Ding, J.-R., Zhang, Z. Q., Zeng, W. X., Li, Y., Lu, G. M., & Chen, H. F. (2011). The synchronization of spontaneous BOLD activity predicts extraversion and neuroticism. Brain Research, 1419, 68-75.

[89] Wei, L. Q., Duan, X. J., Zheng, C. Y., Wang, S. S., Gao, Q., Zhang, Z. Q., Lu, G. M., & Chen, H. F. (2012). Specific frequency bands of amplitude low-frequency oscillation encodes personality. Human Brain Mapping, Early View (Online Version of Record Published before Inclusion in an Issue).

[90] Westmaas, J. L., Ferrence, R., & Wild, T. C. (2006). Autonomy (vs. sociotropy) and depressive symptoms in quitting smoking: Evidence for trait-congruence and the role of gender. Addictive Behaviors, 31, 1744-1760.

[91] Wheatley, T., Milleville, S. C., & Martin, A. (2007). Understanding animate agents distinct roles for the social network and mirror system. Psychological Science, 18, 469-474.

[92] Williams, L. M., Brown, K. J., Palmer, D., Liddell, B. J., Kemp, A. H., Olivieri, G., Peduto, A., & Gordon, E. (2006). The mellow years? Neural basis of improving emotional stability over age. The Journal of Neuroscience, 26, 6422-6430.

[93] Wright, C. I., Feczko, E., Dickerson, B., & Williams, D. (2007). Neuroanatomical correlates of personality in the elderly. Neuroimage, 35, 263-272.

[94] Wright, C. I., Williams, D., Feczko, E., Barrett, L. F., Dickerson, B. C., Schwartz, C. E., & Wedig, M. M. (2006). Neuroanatomical correlates of extraversion and neuroticism. Cerebral Cortex, 16, 18091819.

[95] Xu, J. S., & Potenza, M. N. (2012). White matter integrity and fivefactor personality measures in healthy adults. NeuroImage, 59, 800807.

[96] Yamasue, H., Abe, O., Suga, M., Yamada, H., Inoue, H., Tochigi, M., Rogers, M., Aoki, S., Kato, N., & Kasai, K. (2008). Gender-common and-specific neuroanatomical basis of human anxiety-related personality traits. Cerebral Cortex, 18, 46-52.

[97] Zelazo, P. D., Müller, U., Frye, D., Marcovitch, S., Argitis, G., Boseovski, J., Chiang, J. K., Hongwanishkul, D., Schuster, B. V., & Sutherland, A. (2003). The development of executive function in early childhood. Monographs of the Society for Research in Child Development, 68, 93-136.

[98] De Young, C. G. (2010). Personality neuroscience and the biology of traits. Social and Personality Psychology Compass, 4, 1165-1180.

分享
Top