Dimorphic Behavior

https://auctoresonline.org/article/dimorphic-behavior-and-cognition

Maria Dalamagka 

Sexual differences in the structure and functions of the human brain have been the subject of much speculation ever since the time of Greek antiquity. Aristotle, designated the moment at which the male fetus receives its soul at the 40^th day of gestation, whereas the female fetus was supposed to become antimated only six weeks later, around the 80^th day of pregnancy. In the course of 19^th century the interest in the sexual dimorphism of the human brain grew rapidly. The first studies reported that the male brains were larger and more asymmetrical than the female brains and that men had relatively more brain substance in front of the central sulcus than behind (Swaab and Hofman 1984). The existence of these comparatively minor nad seemingly random morphological sex differences in the human brain were often used in support of the biological view of that era, that men were intellectually superior to women nad that white upperclass people were superior to the other races and lower classes.

Sex differences in behavior are the result of natural and sexual selection. The dimorphic classes of behavior described here, courtship, copulatory, and parental behaviors, reflect both kinds of evolutionary selective pressures. The term dimorphism refers to the existence of two distinct forms within a single species. The term sexually dimorphic behavior, by extension, implies two different forms of behavior exhibited by the male and the female. To describe these behavioral differences between the sexes as sexual dimorphisms does not violate common usage of the term by the morphological sciences. Among mammalian forms, both sexes have a pelvis. The difference between the sexes is not in the presence or absence of a pelvis or pelvic outlet , but in its size, girth , or other quantitative  measure. Countless examples exist in morphology of sexual dimorphisms based only on quantitative differences, differences in intensity, or in response of a specific structure to hormonal stimulation. Current concepts of morphogenesis hold that the genetic sex of all vertebrates determines whether the embryonic genital ridge develops into a testis or an ovary. The means of action by which chromosomes direct the differentiation of the embryonic gonad are unknown; but it is known that the type of gonad differentiated determines by its secretory  products whether male or female secondary reproductive organs develop. According to the organizational hypothesis (Phoenix et al., 1959), not only the reproductive organs but also the neural processes mediating sexual behavior in mammals have the intrinsic tendency to develop according to a female pattern of body structure and behavior.

Sex steroids can be regarded as master regulators of sex- specific behaviors ( Morris et al., 2004; Baum, 2003 ). The devel- opmental influence (organizational role) of sex hormones can lead to enduring effects on brain and behavior. By contrast, in adults sex steroids elicit reversible changes (activational role) in neural circuits and behavior. Gonadal hormones bind to distinct nuclear hormone receptors that are essential for sex- typical displays ( Scordalakes and Rissman, 2003; Raskin et al., 2009; Kudwa and Rissman, 2003; Wersinger et al., 1997; Juntti et al., 2010; Ogawa et al., 2000; Lydon et al., 1995 ). These receptors directly regulate gene expression by binding DNA ( Mangels- dorf et al., 1995 ), and they can initiate nontranscriptional signaling via mechanisms such as interactions with intracellular kinases and transmembrane receptors ( Foradori et al., 2008; Lishko et al., 2011; Micevych and Dominguez, 2009; Revankar et al., 2005; Vasudevan and Pfaff, 2008; McDevitt et al., 2008 ). Sex hormones or their metabolites can also bind to neurotrans- mitter receptors to gate their activity (Henderson, 2007). Such nontranscriptional signaling can control neural function at time scales that allow real time modulation of behavior.

Prior work has identified genes downstream of sex hormones that regulate sexually dimorphic behaviors ( Kayasuga et al., 2007; Wersinger et al., 2002; Nelson et al., 1995; Winslow and Insel, 2002 ). The relative paucity of such genes is in contrast to the diversity of these behaviors, and suggests that the underlying neural circuits may be regulated largely by nontranscriptional hormone signaling.

Sexually dimorphic influences on human cognition and behaviour may affect the phenotypic expression of ‘disorders’ and ‘traits’. ‘Disorders’ are sporadic/heritable abnormalities due to non-functional or otherwise mutated genes. ‘Traits’ represent normal variation in sexually dimorphic characteristics. X-linked disorders, such as fragile X syndrome or Rett syndrome, are sexually dimorphic in their expression but they represent extreme cases – dysfunction of a critical gene, even though expression of that gene might be neither dominant nor recessive in the conventional Mendelian sense. X-linked behavioural traits, quantitative variants, include male aggression and parental behaviour. Sexually dimorphic cognitive traits include spatial orientation; in rodents, male spatial learning advantages observed in the radial or water maze are caused by male–female differences in strategy selection. Females (rats and humans) navigate preferentially using landmarks, but males rely on a broader set of spatial representations. These traits are probably influenced by a Y-linked locus , although an X-linked locus may play a contributory role . During evolution, could X-linked genes for specific cognitive abilities, and a female preference for males who demonstrate those traits, have become closely linked, and hence jointly inherited ? Owing to the obligatory expression of all X-linked genes in males, any X-linked trait that is advantageous to males (or to females) would spread rapidly in the population. If higher cognitive abilities were a critical step in our own evolution, it makes sense that you might find those functions on the X-chromosome.

Studies on human facial sexual dimorphism have yielded intriguing insights into perceptions of other characteristics, such as attractiveness or trustworthiness, based on facial masculinity or femininity. Specifically, by manipulating the degree of sexually dimorphic facial traits in computerized faces, scientists have been able to study what judgmental differences arise as a result of physical alterations. What is significant about these findings is their evolutionary implications, in particular the facial cues that trigger innate judgments in reaction to a masculine or feminine face. Multiple studies have confirmed the correlations between sexually dimorphic faces and ratings of attractiveness (Smith et al. 2008; Lee et al. 1998; Welling et al. 2008), and many psychologists theorize that such judgments are evolutionarily based. Sexual selection in humans is largely based upon facial cues and their reflection of an individual’s reproductive quality. In a recent study, Little et al. (2008) found that symmetry and sexual dimorphism in faces are both judged as more attractive to the opposite sex, leading the researchers to conclude that both qualities are reflective of biological quality, and that such judgments are likely to be the result of sexual selective pressures and mate choice preferences. Much research has been conducted on external judgments of personality as they relate to facial asymmetry and neuroticism (Stackelford & Larsen, 1997), facial symmetry and personality (Fink et al., 2006), facial attractiveness and narcissism (Holtzman and Strube, 2009) and judgment accuracy differences between the sexes (Penton-Voak et al, 2006).

References

Akesson, T.R., Mantyh, P.W., Mantyh, C.R., Matt, D.W., and Micevych, P.E. (1987). Estrous cyclicity of 125I-cholecystokinin octapeptide binding in the ventromedial hypothalamic nucleus. Evidence for downmodulation by estrogen. Neuroendocrinology 45 , 257–262.

Arnold, A.P., Rissman, E.F., andDe Vries, G.J. (2003). Two perspectivesonthe origin of sex differences in the brain. Ann. N Y Acad. Sci. 1007 , 176–188.

Baum, M.J. (2003). Activational and organizational effects of estradiol on male behavioral neuroendocrine function. Scand. J. Psychol. 44 , 213–220.

Bendesky, A., Tsunozaki, M., Rockman, M.V., Kruglyak, L., and Bargmann, C.I. (2011). Catecholamine receptor polymorphisms affect decision-making in C. elegans. Nature. Available at:

http://www.ncbi.nlm.nih.gov/pubmed/ 21412235 [Accessed April 17, 2011].

Blaustein, J.D. (2008). Neuroendocrine regulation of feminine sexual behavior: lessons from rodent models and thoughts about humans. Annu. Rev. Psychol. 59 , 93–118.

de Bono, M., and Bargmann, C.I. (1998). Natural variation in a neuropeptide Y receptor homolog modifies social behavior and food response in C. elegans. Cell 94 , 679–689.

Cahill, L. (2006). Why sex matters for neuroscience. Nat. Rev. Neurosci. 7 , 477–484.

Canteras, N.S., Simerly, R.B., and Swanson, L.W. (1995). Organization of projections from the medial nucleus of the amygdala: a PHAL study in the rat. J. Comp. Neurol. 360 , 213–245.

Carroll, J.S., Meyer, C.A., Song, J., Li, W., Geistlinger, T.R., Eeckhoute, J., Brodsky, A.S., Keeton, E.K., Fertuck, K.C., Hall, G.F., et al. (2006). Genome- wide analysis of estrogen receptor binding sites. Nat. Genet. 38 , 1289–1297.

Clodfelter, K.H., Holloway, M.G., Hodor, P., Park, S.-H., Ray, W.J., and Waxman, D.J. (2006). Sex-dependent liver gene expression is extensive and largely dependent upon signal transducer and activator of transcription 5b (STAT5b): STAT5b-dependent activation of male genes and repression of female genes revealed by microarray analysis. Mol. Endocrinol,  20 , 1333– 1351.

Cooke, B.M. (2006). Steroid-dependent plasticity in the medial amygdala. Neuroscience

138 , 997–1005

Cooke, B., Hegstrom, C.D., Villeneuve, L.S., and Breedlove, S.M. (1998). Sexual differentiation of the vertebrate brain: principles and mechanisms. Front. Neuroendocrinol. 19 , 323–362.

Dugger,B.N.,Morris,J.A., Jordan,C.L.,andBreedlove,S.M.(2007).Androgen receptors are required for full masculinization of the ventromedial hypothal- amus (VMH) in rats. Horm. Behav. 51 , 195–201.

Dulac, C., and Wagner, S. (2006). Genetic analysis of brain circuits underlying pheromone signaling. Annu. Rev. Genet. 40 , 449–467.

Enoch, M.-A., Hodgkinson, C.A., Yuan, Q., Albaugh, B., Virkkunen, M., and Goldman, D. (2009). GABRG1 and GABRA2 as independent predictors for alcoholism in two populations. Neuropsychopharmacology 34 , 1245–1254.

Foradori, C.D., Weiser, M.J., and Handa, R.J. (2008). Non-genomic actions of androgens. Front. Neuroendocrinol. 29 , 169–181

Gagnidze, K., Pfaff, D.W., and Mong, J.A. (2010). Gene expression in neuroen- docrine cells during the critical period for sexual differentiation of the brain. Prog. Brain Res. 186 , 97–111.

Garcia, L.R., Mehta, P., and Sternberg, P.W. (2001). Regulation of distinct muscle behaviors controls the C. elegans male’s copulatory spicules during mating. Cell 107 , 777–788.

Henderson, L.P. (2007). Steroid modulation of GABAA receptor-mediated  transmission in the hypothalamus: effects on reproductive function. Neuro- pharmacology 52 , 1439–1453

Barrett, L. F., & Pietromonaco, P. R. (1997). Accuracy of the five–factor model in predicting perceptions of daily social interactions. Personality and Social Psychology Bulletin, Volume 23, 1173–1187.

Bronstad, M., Langlois, J., Russell, R (2008). Computational models of facial attractiveness judgments. Perception, Volume 37, 126-142.

Carré, J., McCormick, C., Mondloch, C. (2009). Facial Structure Is a Reliable Cue of Aggressive Behavior. Psychological Science, Volume 20, 1194-1198.

Fink, B., Neave N., Manning J., Grammer K. (2006). Facial symmetry and judgements of attractiveness, health and personality. Personality and Individual Differences, Volume 41, 491-499.

Fink, B., Neave N., Manning J., Grammer K. (2005). Facial symmetry and the ‘big-five’ personality factors. Personality and Individual Differences, Volume 39, 523-529.

Holtzman, N.S., Strube, M.J. (2009). Holtzman, N.S., Strube, M.J., Narcissism and Attractiveness, Journal of Research in Personality, doi: 10.1016/j.jrp.2009.10.004.

Noor, F., Evans, D.C. (2003). The effect of facial symmetry on perceptions of personality and attractiveness. Journal of Research in Personality, Volume 37, 339–347.

Penton-Voak, I.S., Pound, N., Little, A.C., & Perrett, D.I. (2006). Personality judgments from natural and composite facial images: More evidence for a “kernel of truth” in social perception. Social Cognition, Volume 24, 490-524.

Smith, F., Jones, B., DeBruine, L., Little, A. (2008). Interactions between masculinity–femininity and apparent health in face preferences. Behavioral Ecology, Volume 20, 441-445.

Watson, D. (1989). Strangers’ ratings of the five robust personality factors: Evidence of a surprising convergence with self-report. Journal of Personality and Social Psychology, 57, 120-128.

Khaitovich P, Hellmann I, Enard W, Nowick K, Leinweber M, Franz H, Weiss G, Lachmann M & Paabo S. Parallel patterns of evolution in the genomes and transcriptomes of humans and chimpanzees.

Science 2005 309 1850–1854.

Preuss TM, Caceres M, Oldham MC & Geschwind DH. Human brain evolution: insights from microarrays. NatureReviewsGenetics 2004 5 850–860.

 Hurst LD. Evolutionary genomics. Sex and the X. Nature 2001 411 149–150.

Caceres M, Lachuer J, Zapala MA, Redmond JC, Kudo L, Geschwind DH, Lockhart DJ, Preuss TM & Barlow C. Elevated gene expression levels distinguish human from non-human primate brains. PNAS

2003 100 13030–13035.

 Gu J & Gu X. Further statistical analysis for genome-wide expression evolution in primate brain/liver/fibroblast tissues. Human Genomics 2004 1 247–254.

Dorus S, Vallender EJ, Evans PD, Anderson JR, Gilbert SL, Mahowald M, Wyckoff GJ, Malcom CM & Lahn BT. Accelerated evolution of nervous system genes in the origin of Homo sapiens. Cell

2004 119 1027–1040.

Check E. Genetics: the X factor. Nature 2005 434 266–267.

Khil PP & Camerini-Otero RD. Molecular features and functional constraints in the evolution of the mammalian X chromosome. Critical Reviews in Biochemistry and Molecular Biology 2005

40 313–330.

Charlesworth D & Charlesworth B. Sex chromosomes: evolution of the weird and wonderful. Current Biology 2005 15 R129–R131.

Arnold AP. Sex chromosomes and brain gender. Nature Reviews Neuroscience 2004 5 701–708.

Dobyns WB, Filauro A, Tomson BN, Chan AS, Ho AW, Ting NT, Oosterwijk JC & Ober C. Inheritance of most X-linked traits is not dominant or recessive, just X-linked. American Journal of Medical Genetics. Part A 2004 129 136–143

Jonasson Z. Meta-analysis of sex differences in rodent models of learning and memory: a review of behavioral and biological data. Neuroscience and Biobehavioral Reviews 2005 28 811–825.

Stavnezer AJ, McDowell CS, Hyde LA, Bimonte HA, Balogh SA, Hoplight BJ & Denenberg VH. Spatial ability of XY sex-reversed female mice. Behavioural Brain Research 2000 112 135–143.

Ross J, Roeltgen D & Zinn A. Cognition and the sex chromosomes: studies in Turner syndrome.

Hormone Research 2006 65 47–56.

Zechner U, Wilda M, Kehrer-Sawatzki H, Vogel W, Fundele R & Hameister H. A high density of X-linked genes for general cognitive ability: a run-away process shaping human evolution? Trends in Genetics 2001 17 697–701.

.