Exploring the Biological Contributions to Human Health Does Sex Matter? (2001) / Chapter Skim
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4 Sex Affects Behavior and Perception
4 Sex Affects Behavior and Perception
Pages 79-116
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From page 79... ...
SEX DIFFERENCES IN BEHAVIOR AND COGNITIVE ABILITIES Behavioral sex differences may originate in events that begin in the womb. The fetal environment, particularly hormones present during development, affects aspects of later behavioral and cognitive sex differences.
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From page 80... ...
Psychosexual Differentiation Studies with nonhuman vertebrate species suggest that the sexual role adopted at maturity is determined by the hormonal environment in early life. As for other aspects of sex differentiation, there appears to be a predisposition for individuals to develop female sexual postures.
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From page 81... ...
Another important principle that has emerged from studies with animals and that has been confirmed in humans is that the central nervous system remains plastic throughout the life span. Finally, former notions that discrete brain regions have specific and static functions have been modified by work on
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From page 82... ...
Throughout life, there are profound sex differences in the brain's responsiveness to sex hormones, some of which are established early in development and which have implications for later behavior, including cognitive function. The brain is also involved in the regulation of other hormones that show sex differences and that are involved in both reproductive and nonreproductive behaviors.
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From page 83... ...
Sex-Typed Behavior and Gender Identity Discussions about the determinants of human sex-typed behavior, especially gender identity, have recently become highly visible because of scientific and popular accounts of a prominent case (Colapinto, 2000; Diamond and Sigmundson, 1997~. The case challenged the established belief that individuals are born with the potential to develop male or female gender identity and that the specific gender identity can be determined exclusively by sex of rearing (Hampson and Hampson 1961; Money and Ehrhardt, 1996; Money et al., 1955; reviewed in Grumbach and Conte, 1998~.
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From page 84... ...
Again, the goal of this chapter is not to provide an exhaustive review of behavioral sex differences but to illustrate some of the differences and to indicate how they might be influenced in part by sex hormones. There are also sex differences in health-related behaviors, such as frequency of visits to health professionals and use of complementary medicine, but these have not been well studied.
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From page 85... ...
A more probing question asks if there are particular areas of thinking or problem solving in which males and females differ; such cognitive abilities are referred to as "sexually dimorphic behaviors." Before reviewing the research findings, it is important to bear in mind several factors.
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From page 86... ...
Furthermore, the specific cognitive processes of interest may be assessed quite differently, often leading to conflicting results. Despite these caveats, it should be noted that a reasonable consensus has emerged relating sex differences to specific patterns of cognitive function: in general, women most often demonstrate an advantage in verbal abilities particularly verbal fluency, speech production, the ability to decode a language, and spelling; perceptual speed and accuracy; and fine motor skills whereas men frequently show an advantage on tests of spatial abilities, quantitative abilities, and gross motor strength (Hampson, in press; Hampson and Kimura, 1992~.
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From page 87... ...
, a measure, as discussed later, that is closely related to both reading and reading disability. Reliable sex differences have also been reported for spelling, another verbal ability closely related to reading; however, reports of sex differences in other areas of verbal ability such as vocabulary or reading comprehension have been inconsistent and are not considered reliable (Hampson and Kimura, 1992~.
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From page 88... ...
In particular, the mental rotation task has demonstrated the most sensitivity at detecting sex differences in spatial ability (Sanders et al., 1982~; here, a subject is asked to imagine how a figure would appear if it were rotated in a two- or three-dimensional space. Sex differences in quantitative abilities have also been reported.
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From page 89... ...
Reviews of the relationship between quantitative skills and spatial ability find that spatial ability is an important factor in predicting performance on advanced mathematics tests and that this relationship is especially strong at the highest levels of mathematics performance (Halpern, 2000~. EFFECTS OF HORMONES ON BEHAVIOR AND COGNITION Prenatal Androgens and Sex Differentiation of Human Behavior There is now good evidence that human behavioral sex differences are influenced by sex hormones present during prenatal development, confirming findings from studies with other mammalian species (described in Chapter 3~.
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From page 90... ...
, although some do prefer boy playmates and some have bisexual fantasy and arousal characteristics. The differences are even smaller for gender identity: only a very small minority of females with CAH have male-typical gender identity or are gender dysphoric (Ehrhardt and Baker, ~ Masculine and feminine are empirically defined and refer to a person's relative position on traits that show sex differences.
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From page 91... ...
have lower levels of spatial ability than controls; within the group of men with IHH, spatial ability correlated with testicular volume and did not improve with androgen replacement therapy (indications that the low level of spatial ability was associated with low levels of androgen early in development and not at the time of testing) (Hier and Crowley, 1982~.
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From page 92... ...
Gender-specific behavior in young adult women has been suggested to be related to their exposure to sex hormones during the second trimester of fetal development (Udry et al., 1995~. Although some of these studies are imperfect, the limitations are different from those of studies of individuals with CAH.
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From page 93... ...
Third, the effects of specific hormones may be modified by other hormones (Goy and McEwen, 1980~. There is increasing recognition of the importance of ovarian estrogens for both physical and behavioral sexual differentiation, and it seems likely that androgens are modified by the effects of ovarian estrogens.
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From page 94... ...
Recent studies of gender development in typical children suggest that the social environment is actively constructed and interpreted in ways that reinforce sex differences through the use of gender identity and gender labels (for a review, see Ruble and Martin [1998~. Similar studies with children with variations in sexual differentiation (Table 3-2)
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From page 95... ...
Two members of the committee, however, raised concerns about the use of the term organizational effect. Although is clear that the organizational effects of prenatal hormones on the later development of particular behaviors is mediated and affected by a large number of organismal factors and postnatal effects, it is often not clear what such an effect is or might mean at the cellular level.
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From page 96... ...
Attest site structure attest duration/frequency Observe in wild or semi-wild conditions? FIGURE 4-2 Behavioral development in rodents.
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From page 97... ...
In addition, as noted below, sex hormones affect neural systems in adult women during their active reproductive years and postmenopausal years. During adult life, women's hormone levels fluctuate monthly with the menstrual cycle, and some studies have shown that these variations to some degree affect performance on certain tests of cognitive abilities (although the sizes of the effects were quite small)
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From page 98... ...
Hormonal levels in women also change during menopause, when the levels of the hormone estrogen undergo dramatic declines after the cessation of cyclic ovarian function. Given the demonstrated sex differences in cognitive function that favor verbal abilities in females and the association of better performance of these skills during phases of the menstrual cycle when estrogen levels are high, there has been great interest in the effects of hormone replacement therapy (exogenous estrogen)
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From page 99... ...
and that within language the reading process is related to phonological processing. Interestingly, the key cognitive functions affected by estrogen (verbal fluency, verbal memory, and articulation)
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From page 100... ...
Deficits in phonological processing have been intimately related to reading disability, and a large body of literature now indicates that a phonological core deficit is responsible for the difficulties that dyslexic children have in learning to read. Areas of impaired phonological processing consistently related to reading disability represent the same areas of language most sensitive to the actions of estrogen, that is, word fluency (e.g., naming)
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From page 101... ...
Together, these findings suggest that the deficit in reading ability and the action of estrogen on specific verbal skills may have a common base: phonological processing. These findings are exciting because they represent a link between studies of the influence of sex hormones on cognitive function and studies relating specific cognitive subskills to the reading process.
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From page 102... ...
This explanation is appealing because it is parsimonious, accounting both for the observed difference in prevalence ratios for children compared with those for adults and for the known positive effects of female sex hormones on the cognitive and linguistic skills that underlie reading. More recent studies, using sophisticated imaging technology, demonstrate sex differences for language, specifically for phonological processing, and add further evidence that supports the notion that estrogen may exert its effects on cognitive function through its actions on phonological processing (Shaywitz et al., 1995~.
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From page 103... ...
In females, phonological processing activates both the left and right inferior frontal gyri. (Color dots represent pixels for which the mean value for the split t statistic from the average for the 19 subjects was greater than 0.4.
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From page 104... ...
The investigators noted sex differences in the regions of the brain activated; males activated the left hippocampus but females activated the right parietal cortex and right prefrontal cortex during the same navigational task. Similar to the findings of sex differences in brain organization for observed differences in language skills, specifically, phonological processing, these findings now provide a neural basis for observed sex differences in spatial performance.
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From page 105... ...
Whether it be humans or nonhuman animals, the existence or even the direction of sex-related differences in pain have been shown to vary with different situations, for example, as one ages, by testing paradigm or setting, by type or location of pain, by subject demographics, by reproductive status, by genetic profile, by treatment utilization behavior, by the way in which pain is measured (and by whom) , by analgesic, and by responses to different treatments.
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From page 106... ...
106 EXPLORING THE BIOLOGICAL CONTRIBUTIONS TO HUMAN HEALTH TABLE 4-1 Sex Prevalences of Some Common Painful Syndromes and Potential Contributing Causes Female Prevalence Male Prevalence Head and Neck Migraine headache with aura Chronic tension headache Postdural puncture headache Cervicogenic headache Tic douloureux Temporomandibular disorder Occipital neuralgia Atypical odontalgia Burning tongue Carotodynia Temporal arteritis Chronic paroxysmal hemicrania Carpal tunnel syndrome Raynaud's disease Chilblains Reflex sympathetic dystrophy Chronic venous insufficiency Piriformis syndrome Peroneal muscular atrophyC, d Esophagitis Gallbladder diseased Irritable bowel syndrome Interstitial cystitis Proctalgia fugax Chronic constipation Fibromyalgia syndrome Multiple sclerosis,Tg Rheumatoid arthritis, T Acute intermittent porphyriaC Lupus erythematosus, T Migraine without aura Cluster headache Posttraumatic headache Paratrigeminal syndromes Limbs Internal Organs General Thromboangiitis obliteransb Hemophilic arthropathyC Brachial plexus neuropathy Pancoast tumbrel Pancreatic disease Duodenal ulcer Postherpetic neuralgia a Raeder's syndrome. b Buerger's disease.
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From page 107... ...
In other words, it may be that there are more potent sex differences in mechanisms of pain and analgesia than in measured pain behaviors. The differences seem to lie in how sex steroid hormones exert their effects (Aloisi, 2000; Gintzler and Liu, 2000; Sternberg and Wachterman, 2000~.
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From page 108... ...
On the other hand, before concluding that a specific drug may eventually be prescribed on the basis of the sex of the individual or the reproductive or hormonal status of the patient, it also seems important to consider how stress exerts its cumulative effects over the life span of an individual. Of relevance here is the plasticity of neural function: the ability of neural elements to change their phenotype, to "learn." Considerable research on these changes in the context of pain has led to the discovery of what is called "central sensitization," which is an enhanced responsiveness of central nervous system neurons induced by intense stimulation or injury or by a stressor that, importantly, continues long after the initial noxious event has resolved (Dubner and Ruda, 1992; McMahon et al., 1993~.
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From page 109... ...
Impact of Menstrual Cycle on Pain Along with genetic and developmentally programmed sex differences in neural organization and physiology, the entire nervous system is potently influenced by the hormonal milieu of the individual (McEwen, 1999; McEwen and Alves, 1999~. One arena in which this influence becomes evident is the ovarian cycle (one should keep in mind, however, that the basis for ovarian cyclicity in any realm of physiology or behavior may not necessarily be entirely due to the hormonal milieu)
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From page 110... ...
110 EXPLORING THE BIOLOGICAL CONTRIBUTIONS TO HUMAN HEALTH TABLE 4-2 Growing List of Therapies for Pain Somatic Interventions Drugs Situational Approaches Primary analgesics Nonsteroidal antiinflammatory agents A cet amin op hen Opioids Other analgesics a2 Agonists p-Adrenergic antagonists Antidepressants Antic onvuls ants Antiarrhythmics Calcium channel blockers Cannabinoids Corticosteroids Cox-2 inhibitors y-Aminobutyric acid type B agonists Serotonin agonists Adjuvants Antihistamines Laxatives Neuroleptics Routes Topical, transdermal, oral Buccal, sublingual, intranasal Vaginal, rectal Inhalation Intramuscular, intraperitoneal Intravenous Epidural, intrathecal In tr av e nt ri cu. l a r Simple Heat or cold Exercise Massage Vibration Relaxation Minimally invasive Physical therapy Traction Manipulation Ultrasound Transcutaneous electrical nerve stimulation Acupuncture Local anesthetics Invasive Radiation therapy Dorsal column stimulation Nerve blocks Neurectomy Local ganglion blocks Sympathectomy Rhizotomy Dorsal root entry zone lesions Punctate midline myelotomy Limited myelotomy Commissural myelotomy Cordotomy Brain stimulation Brain lesions Clinician Education Attitude Clinical setting and arrangement Self Education Meditation Diet Art, music, poetry, performing arts Sports, gardening, hobbies Humor Aroma therapy Religion Pets Interactive Hypnosis Biofeedback Support groups Advocacy groups Networking Self-help groups Structured settings Group therapy Family counseling Job counseling Cognitive therapy Behavioral therapy Psychotherapy Multidisciplinary clinic Hospice SOURCE: Berkley (2000~.
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From page 111... ...
Part of the inconsistency across studies may be due to technical factors, such as how different parts of the menstrual cycle are classified and the manner in which the analysis has been made. Given that brain imaging studies, however, are beginning to show that the brain regions engaged while an individual is under painful conditions vary with the individual (Davis et al., 1998; Gelnar et al., 1999)
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From page 112... ...
So far the results show significant interactions between the two conditions that have implications for diagnosis and treatment in both females and males (Giamberardino, 2000; Giamberardino et al., 1999~. Second, a number of painful clinical disorders vary significantly with the menstrual cycle in some women but not others, such as certain types of headache, irritable bowel syndrome, interstitial cystitis, temporomandibular disorder, and fibromyalgia (Bradley and Alarcon, 2000; Fillingim and Maixner, 2000; Holroyd and Lipchik, 2000; Mayer et al., 1999; Naliboff et al., 2000~.
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From page 113... ...
MCAO, estrogen treatment of M Prognosis improves in estrogen-treated MCAO, estrogen receptor antagonist Mice Unilateral carotid occlusion Unilateral carotid occlusion in SOD overexpressers M (Toting et al., 1998) Ischemia increases in F but not in M (Sawada et al., 2000)
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From page 114... ...
The mechanisms by which female sex or by which estrogen or progesterone attenuates brain damage are complex. Estrogen could preserve autoregulation or antioxidant activity, affect leukocyte adhesion, or upregulate nitric oxide synthase.
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From page 115... ...
Furthermore, the inclusion of female animals in preclinical studies increases the complexity of a study because of the female estrous cycle and the need to control for the associated hormonal fluctuations (Panetta and Srinivasan, 1998~. Thus, the roles of sex and sex hormones in mechanisms of disease outcome have not been routinely studied in animal models.
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From page 116... ...
116 EXPLORING THE BIOLOGICAL CONTRIBUTIONS TO HUMAN HEALTH to recognize modulators of brain organization and function. Explore innovative ways to expand the availability of and reduce the cost of new technologies.
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