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Chapter 10

PSYB64 CHAPS 10, 11, 12, 14, 15 from 2ND EDITION

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Janelle Leboutillier

CHAPTER 10: SEXUAL BEHAVIOUR Introduction - Children begin to prefer sex-typed toys between ages 12 and 18 months - At the same age, children are unable to match sex-typed toys (vehicles and dolls) with male or female voices, suggesting they have not yet been socialized to think of toys as “male” or “female” - Bruce Reimer o During circumcision in 1965, Bruce’s penis so badly damaged that John Money thought he should be raised as a girl o Bruce’s genitals were surgically altered, became known as Brenda o As a kid he always dreamed of growing up to be a man o At 14, while on female hormone therapy, Brenda was informed of his medical history o He wanted to be male so began male hormone therapy, changed name to David o Lived as a man, married, adopted wife’s children o Commit suicide in 2004 (age 39) - Reimer’s story suggests our biological sex may influence our ultimate sense of being a man or woman more strongly than how we are raised Sexual Development - 355 B.C., Aristotle argued sex of a child was result of temperature of semen at conception o Hot semen – male, cool semen – female - Individual’s genetic sex begins with sex chromosomes inherited from two parents - Mother provides X chromosome: one of two types of sex chromosomes; individuals with two X chromosomes will usually develop into females - Fathers determine offspring’s sex by providing either another X or Y chromosome: one of two types of sex chromosomes; individuals with a Y chromosome will usually develop into males - Without exposure to male hormones, all babies would be born with outwardly female physical appearance and female behaviour Sex Chromosome Abnormalities - Turner syndrome: a condition caused by an XO genotype, characterized by frequent abnormalities of the ovaries and fertility o First described by Henry Turner o Lack a second X chromosome or Y chromosome o Occurs in 1 out of 2500 births o Have normal female external genitalia, but ovaries develop abnormally o Women are relatively short (4”8), have skin folds at the neck, deficits in spatial relation tasks and memory - Klinefelter syndrome: a condition in males caused by an XXY genotype, characterized by frequent problems with fertility, secondary sex characteristics and verbal skills o Identified by Harry Klinefelter o One of most common genetic abnormalities related to sex chromosomes, 1.79/1000 male births o Individuals are male but experience reduced fertility and require hormone treatment at puberty to promote secondary male sex characteristics and to inhibit female characteristics like breast development o Lefthandedness more common, suggesting Klinefelter syndrome might affect brain lateralization or localization of specific functions - Existence of XYY genotype first reported by Sandberg, Koepf, Ishiara, Haushcka o Relationship between XYY genotype and higher likelihood of antisocial behaviour under considerable debate o “super male” o Richard Speck – serial murderer of 8 nurses in Chicago, falsely claimed to have XYY genotype for more lenient sentencing o Gotz, Johnstone, Ratcliffe – followed progress of 17 men with XYY genotype, these men did show significantly; higher rate of antisocial and criminal behaviour than control participants, mostly property crimes rather than violent crimes - Nielson, Wohlert – study of 13,000 + newborns over 13 years, found that none of the children with 3 sex chromosomes were mentally retarded and that all were in regular public school; no increases in criminal activity, mental disorders, physical disorders relative to population with normal sex chromosomes Three Stages of Prenatal Development - Gonads: the internal organs, ovaries in females, and testes in males, that produce reproductive cells and secrete sex hormones - External genitalia: the external sexual organs, including the penis and scrotum in males and labia, clitoris, and lower third of the vagina in females - Intersex: a condition in which elements of both male and female development occur in the same fetus The Development of the Gonads - Both male and female foetuses are identical until 6 week after conception - Ovaries: female gonads; the source of ova and sex hormones - Testes: male gonads; source of sperm and sex hormones - After 6 weeks, the sex-determining region of the Y chromosome: a gene located on the short arm of the Y chromosome that encodes for testis-determining factor, is expressed in male embryos - Testis-determining factor: a protein encoded by the SRY gene on the Y chromosome that turns the primordial gonads into testes - Chromosomally male mice genetically modified to lack the SRY gene develop ovaries, whereas female mice in which the SRY gene has been inserted develop testes Differentiation of the Internal Organ - Until about third month of development in humans, both male and female foetuses possess a male Wolffian system and male Müllerian system - Wolffian system: the internal system that develops into seminal vesicles, vas deferens, and the prostate gland in males - Müllerian system: the internal system that develops into a uterus, fallopian tubes, and the upper two thirds of the vagina in the absence of anti-Müllerian system - During third month, male’s new testes will begin to secrete two hormones: o Testosterone: an androgen produced primarily in the testes o Anti-Müllerian hormone: a hormone secreted by the fetal testes that causes the degeneration of the Müllerian system - Androgen: a steroid hormone that develops and maintains typically masculine characteristics - Testosterone promotes development of the Wolffian system - Anti-Müllerian hormone initiates degeneration of Mullerian system - In female fetus, no additional hormones are needed for development, non-functional remnants of the Wolffian system remain throughout a woman’s life - Androgen insensitivity syndrome (AIS): a condition in which a genetic male fetus lacks androgen receptors, which leads to the development of female external genitalia and typically female gender identity and sexual behaviour o No androgen receptors mean the Wolffian system will not develop o However, anti-Müllerian hormone still works normally, so the Müllerian system will not develop either o No ovaries, fallopian tubes, uterus o Individual’s external appearance is quite typically female o Genetically male - Gender identity: the sense of being male or female, independent of genetic sex or physical appearance - Estimated 1/60 000 males are born with AIS, and estimated 1/500 women competing at international levels of sport have AIS Development of the External Genitalia - Male external genitalia include penis and scrotum - Female external genitalia include labia, clitoris, and outer part of vagina - No hormonal activity required to develop female external genitalia - A particular androgen, 5-alpha-dihydrotestosterone, must be recognized by receptor sites for male external genitalia to develop normally - 5-alpha-dihydrotestosterone: an androgen secreted by the testes that masculinizes the external genitalia - If genetic females are exposed prenatally to excess androgens, their external genitalia become masculinized - Congenital adrenal hyperplasia (CAH): a condition in which a fetus is exposed to higher-than-normal androgens, resulting in masculinization of external genitalia and some cognitive behaviours in affected females o Recessive heritable condition o Males with CAH show few observable traits because they are already typically exposed to high levels of androgens o Females with CAH are exposed to about half the amount of androgens of a typical male and are born with ambiguous external genitalia o Females with CAH more frequently describe themselves as tomboys, more likely than other women in engage in bisexual/lesbian behaviour o Note: majority of CAH women are heterosexual, majority of lesbian/bisexual women do not have CAH Development at Puberty - Puberty leads to maturation of the genitals and the development of secondary sex characteristics: characteristics related to sex that appear at puberty, including deepening voice and facial hair growth in males and widening hips and breast development in females - Average age of puberty has dropped over past century from 16 to 12 o Due to increased rates of obesity - All edible tissues from animals contain a type of estrogen (a steroid hormone that develops and maintains typically female characteristics), called estradiol: an estrogen hormone synthesized primarily in the ovaries - Many nations permit use of sex hormones to promote growth in cattle production - Consumption of treated meat can increase exposure to estrogens by 40% - At onset of puberty, gonadotropin-releasing hormone (GnRH) is released by hypothalamus - GnRH: a hormone released by the hypothalamus that stimulates the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) by the anterior pituitary gland - FSH: a hormone released by the anterior pituitary gland that stimulates the development of eggs in the ovaries and sperm in the testes - LH: a hormone released by the anterior pituitary gland that signals the male testes to produce testosterone and that regulates the menstrual cycle in females - Testes also produce small amounts of estrogens, including estradiol, and ovaries produce small amounts of androgens, including testosterone - Testosterone regulates production of sperm and affects a male’s hairline and can result in baldness later in adulthood - In both sexes, estradiol slows down skeletal growth, individuals who experience early sexual maturation stop growing at earlier stages - 5-alpha-reductase deficiency: a rare condition in which a child is born with ambiguous genitalia but develops male secondary sex characteristics at puberty o Condition first observed in Dominican Republic o Affects a male’s ability to produce the enzyme 5-alpha-reductase which converts testosterone into 5- alpha-dihydrotestosterone o In Dominican Republic these kids are known as “guevedoces” or “eggs (testes) at 12” Summary Table: Steps in Sexual Development Chromosomes XX XY (determined at conception) Gonads (6-8 At 6 weeks, gonads are developed but are At 6 weeks, gonads are developed but are weeks undifferentiated in male or female structures. undifferentiated in male or female structures. postconception) At 8 weeks, testes-determining factor encoded by the SRY gene on the Y chromosome stimulates the development of primordial gonads, leading to testes. Internal Müllerian system develops in the absence of Testosterone stimulates development of the Structures (9- androgens and anti-Müllerian hormone. Wolffian system. 12 weeks Primitive, non-functional Wolffian system is Anti-Müllerian hormone stimulates the postconception) retained. deterioration of the Müllerian system. External In the absence of androgens such as 5-alpha-reductase converts testosterone to 5- Structures (6- testosterone, female external structures develop alpha-dihydrotestosterone, which in turn 12 weeks (labia, clitoris, outer vagina). masculinizes the external structures into penis and postconception) scrotum. Puberty (8-16 Gonadotropin-releasing hormone stimulates the Gonadotropin-releasing hormone stimulates the years) release of LH and FSH by the pituitary gland. release of LH and FSH by the pituitary gland. LH and FSH signal the ovaries to begin releasing LH and FSH stimulate the release of additional estradiol. testosterone by the testes. Sex Differences in the Nervous System - Sexually dimorphic: displaying structural differences between the sexes - Sexually dimorphic nucleus of the preoptic area (SDN-POA): a nucleus in the preoptic area of the hypothalamus that is larger in male rats than in female rats - Development of SDN-POA reflects the early organizing effects of hormone exposure - At birth, the SDN-POA of rats is approximately the same size in males and females - The SDN-POA of the male grows rapidly during the newborn period, however if a male is castrated than the SDN-POA is much smaller than normal - If a newborn female rat is injected with testosterone, the SDN-POA will be much larger than normal - Castration or injection of older animals does not change the size of the SDN-POA - Human beings do not have an SDN-POA - Humans have the interstitial nuclei of the anterior hypothalamus (INAH): a collection of four small nuclei in the anterior hypothalamus, two of which (INAH-2 and INAH-3) appear to be sexually dimorphic. The size of INAH-3 might be associated with male sexual orientation - INAH2 and INAH3 are twice as large in males than females - Sexual dimorphism also observed in spinal cords of animals o Male rats have more motor neurons in the spinal nucleus of the bulbocavernosus (SNB): motor neurons in the spinal cord that innervate the male rat’s bulbocavernosus muscles in the penis  These muscles are missing in the female rat, originally they are there and the same size as males but during the critical period the low levels of androgens causes the muscles and SNB neurons to die - Aromatization: a chemical reaction resulting in an aromatic compound, characterized by a six-carbon ring; for example, the enzyme aromatase transforms testosterone into estradiol - Alpha fetoprotein: a substance circulated by rats that deactivates estradiol and prevents maternal estradiol from masculinizing female pups - In many other animals, the mother’s estradiol is blocked by the placenta o Hyenas do not have this capacity, so females are born rather masculine looking and acting, they have an enlarged clitoris that looks like a penis and urinate and give birth thru the clitoris - Why aromatization may not be responsible for the masculinization of the human brain: o Ppl with AIS, who have male genetic sex but inactive androgen receptors, are still overwhelmingly feminine in their behaviour o If aromatization of testosterone to estradiol masculinized the human brain, we would expect these individuals to show more typical male brain structure and behaviour, but this doesn’t occur o In addition, males with inactive aromatase enzyme have typical male brain structure and behaviour o Androgens appear to play a direct role in the masculinization of the human brain that is not dependent on aromatization into estradiol - High levels of maternal testosterone have been correlated with daughters’ more masculine play behaviour, prenatal exposure to many other substance like barbiturates and DDT also masculinizes the brains of females Sexual Orientation - Sexual orientation refers to stable pattern of attraction to members of particular sex, not synonymous with sexual behaviour - Stroller and Herdt – described a tribal culture in which all adolescent males are expected to engage in same-sex behaviour until they are married to women Hormones, Sexual Behaviour, and Sexual Orientation - Early exposure to androgens influences adult sexual behaviour - Exposure to testosterone during critical period accounts for sexual dimorphism in SDN-POA in rats - In humans, high levels of prenatal androgens typical of males have an impact on the development of the inner ear o Inner ear produces otoacoustic emissions, as it processes sound into neural impulses o These emissions are stronger in women than in men o Strength of emissions of lesbians/bisexual women fell below normal levels of heterosexual men and women o McFadden and Pasanen – suggested that exposure to prenatal androgens may have influence both the ear structure and sexual orientation of the lesbian and bisexual women - Another possible indicator of prenatal exposure to androgens, and the resulting influence on sexual orientation is the so called 2D:4D ratio o In heterosexual women, the index finger and ring finger are typically the same length o In men, the index finger is usually shorter than the ring finger o Lesbians show more masculine patter of finger length, suggesting they might have experienced prenatal exposure to androgens - What could cause the difference in prenatal hormonal environments associated with homosexuality? o Men who have older brothers are slightly more likely to be gay than men who have no siblings, younger siblings only, or older sisters o Protein products of 3 genes located on the Y chromosome are believed to provoke the mother’s immune response, which should become greater with each successive pregnancy with a male fetus Brain Structure and Sexual Orientation - Simon LeVay – found that INAH-3 was two to three times larger in heterosexual men than in homosexual men - The size of INAH-3 among LeVay’s homosexual subjects was not significantly different from the size observed in female subjects - LeVay studied autopsied brains because INAH-3 too small to observe with current imaging technologies o Prevented from obtaining detailed history of subject’s sexual behaviour, gay men’s medical records documented their sexual behaviour, but not straight men o Study couldn’t be extended to women o LeVay raised possibility that AIDS caused shrinkage of INAH-3 - Kay Larkin et al – studied the sheep equivalent of SDN-POA in rams who engaged in same-sex behaviour, rams who mated with ewes, and ewes o Results parallel to LeVay’s findings in INAH-3 - Laura Allen and Roger Gorski – reported that the size of the anterior commissure varies reliably between homosexual and heterosexual males o Anterior commissure has no direct role in sexual behaviour Genes and Sexual Orientation - Chances of a homosexual male win have a homosexual brother are twenty to twenty-five percent for fraternal twins and about fifty percent for identical twins - Mothers of homosexual sons showed more extreme skewing, in which one X chromosome is more likely to be inactivated than the other Attraction - Viewing faces of beautiful women activated areas of the brain involved in pleasure and reward, including the nucleus accumbens, which participates in addictive behaviour - men participants given opportunity to press a lever to see pictures of beautiful woman, participants were willing to press the lever 6000 times in an interval of 40 minutes, analogous to the amount of work rats are willing to do to obtain cocaine - Judith Langlois et al – 3 and 6 month old infants spend more time staring at faces adults had judged to be attractive than at faces judged to be unattractive The Importance of Symmetry - Degree of similarity of one side of the face or body to the other - Highly symmetrical bodies are generally healthier and we are programmed to select healthy mates - According to researchers, symmetrical men became sexually active at earlier ages than less symmetrical men - Symmetrical men less attentive to their partners and much more likely to cheat on them The Beauty of Fertility and a Good Immune System - Victor Johnston – preferred female face is youthful, with delicate jaw, full lips, wide set eyes - Women seem to find masculine men, with square jaws and other testosterone-related facial features, more attractive as “one night stands” than their less macho counterparts o Ability of women to recognize good genes - Women believe men with very masculine faces would be more dominant, less faithful, worse fathers, colder personalities compared to the less masculine men - Women were able to anticipate how a man would score on the infant interest questionnaire, a measure of how involved a father a man is likely to be, just by looking at photos of men’s faces - Women might prefer less masculine looking men for the long term - Men pay more attention to women’s figures than women do to men - Devendra Singh – men prefer women whose waist measurements are approximately 70% of their hip measurements - Tovee et al – men consistently preferred women with a BMI of 20, regardless of waist-hip ratio - Norma McCoy and Lisa Pintinto – investigated the effects of underarm secretions of fertile, sexually active, heterosexual females o Compared with women wearing placebo scents, women who were wearing the underarm secretions reported significantly increased sexual activity - Clause Wederkind and Sandra Füri – women showed distinct preferences for certain odours, especially those that reminded them of past lovers, and smelled distinctly different from brothers and father - Major histocompatibility complex: a gene that encodes our immune system’s ability to recognize intruders; might account for female human preferences for male odours Romantic Love, Sexual Desire, and Parenting - Romantic love and the bonding of parent and child both involve the establishment and maintenance of long- term relationships - Sexual desire promotes mating and reproduction - Can experience one without the other - Bartels and Zeki – compared ppl’s responses to photos of friends and photos of lovers o When viewing lovers, areas of the brain associated with rewards and activity of oxytocin and vasopressin showed increased activity o Love is a push-pull mechanism in which bonding activates the reward system, and social distance is reduced by silencing social judgement - Oxytocin: a hormone, released by the posterior pituitary gland that simulates uterine contractions, releases milk, and participates in social bonding, including romantic love and parenting behaviour - Oxytocin released in both sexes during orgasm - Approximately 16 million men living today, are closely related to Genghis Khan (Mongol emperor) - Only 3% of mammals practice monogamy: the custom of having one mate at a time or for life - Prairie vole is exclusively monogamous, males participate in raising of young - Montane vole is promiscuous, males do not interact with offspring at all, montane females abandon their pups at a very early age (not nurturing) - Young, Wang, Insel – receptor locations for oxytocin and vasopressin were different in prairie and montane voles o Vasopressin increases paternal behaviours o Oxytocin increases maternal behaviours Sexual Dysfunction and Treatment - Erectile dysfunction: the inability to get and maintain an erection long enough for satisfactory sexual activity - Erections occur as a result of either direct stimulation of cognitive factors o Parasympathetic neurons respond to direct stimulation and cognitive factors Summary Table: Hormones Associated with Parenting Behaviour Hormone Effects Observed in Humans Effects Observed in Animals Oxytocin Released during orgasm. Increases parenting behaviour in Released during nursing; produces calming, pleasant effect. male prairie voles. Promotes uterine contractions during childbirth. Predicts maternal bonding behaviours. Predicts bonding to parents among young adults not currently in romantic relationships. Vasopressin Regulates body fluid levels. Increases parenting behaviour in male prairie voles. CHAPTER 11: SLEEP AND WAKING - 1969 DJ Peter Tripp stayed awake for more than 8 days for a publicity stunt - 1955 Randy Garnder stayed awake for 11 days to make it into the Guiness world book of records - 2007 Tony Wright went 266 hours without sleep to break Randy’s record - Sleepiness contributed to 1979 Three Mile Island nuclear meltdown, 1986 Challenger space shuttle explosion, 1989 grounding of the oil tanker Exxon Valdez, 1984 chemical leak at a factory in India - American adults average only 6 hours 55 minutes of sleep per night Circadian Rhythms - Circadian rhythm: a repeating cycle of about 24 hours - Circadian = Latin for “about a day” - Internal biological clocks interact with stimuli known as zeitgebers: external cues for setting biological rhythms - Light is most important zeitgeber for humans - Free-running circadian rhythm: a rhythm that is not synchronized to environmental time cues - Entrainment: the resetting of internal biological clocks to the 24-hour cycle of the earth’s rotation; sunlight helps entrain the biological clock - other zeitgebers include physical activity, feeding, body temperature, sleep=related hormones Variations in Sleep Patterns - individual sleep patterns result from different versions of the genes responsible for our internal clocks - Larks – ppl who are most alert and productive in the mornings - Night owls – ppl alert at night - Melatonin drops dramatically at onset of puberty, contributing to age-related changes in sleep habits - Following adolescence, many night owls revert back to previous state, due to the maturation of neural systems that regulate sleep Shift Work, Jet Lag, and Daylight Saving Time - Between 40-80% of workers on night shift experience disturbed sleep and cluster of symptoms known as shift maladaptation syndrome o These workers receive 1.5 hours less sleep than workers on other shifts - Accident rates in afternoon shift are higher than in day and night shift - Night shift workers more likely to develop breast cancer - Jet lag: fatigue, irritability, and sleepiness resulting from travel across time zones - North-south travel of equal distance doesn’t produce jet lag - It is easier to adjust to a phase-delay of our cycle than to a phase-advance - Traveling eastward is more disruptive than traveling westward - Daylight saving time requires the setting of clocks forward on hour in spring (phase advance) and one hour back in fall (phase delay) o Fall shift equivalent to westward travel and spring shift equal to eastward travel - Coren: correlated Canadian traffic accident data with daylight saving time shifts o 7% decrease in traffic accidents on following Monday after fall shift o 7% increase in traffic accidents following spring shift Internal Clocks - Body’s master clock is suprachiasmatic nucleus (SCN): an area of the hypothalamus located above the optic chiasm; responsible for maintaining circadian rhythm - Retinohypothalamic pathway: a pathway leading from the retina of the eye to the hypothalamus; provides light info necessary for the maintenance of circadian rhythms - Melanospin: a photopigment used by non-image-forming retinal cells - SCN only active during day, whether species is diurnal or nocturnal - SCN is independent from other structures  when SCN tissue from a short-period hamster is transplanted into a normal hamster, the normal hamster shows the short free-running cycle - SCN coordinates the activities of other internal, peripheral clocks that exist in most body cells - Rhythms of SCN more influenced by presence of light, peripheral clocks more influenced by daily feeding cycles The Cellular Basis of Circadian Rhythms - Research with fruit flies allowed researchers to identify three separate genes and their protein products that are involved with cellular circadian rhythms: o Per (for period), tim (for timeless), clock (for Circadian Locomotor Output Cycles Kaput) o Per and tim proteins inhibit the clock protein, the clock protein promotes the production of more per and tim proteins Biochemistry and Circadian Rhythms - SCN regulates and responds to hormone melatonin: an indoleamine secreted by the pineal gland that participates in the regulation of circadian rhythms - Lesions of SCN abolish circadian release of melatonin - Melatonin levels low during the day and rise in hours before sleep, peak at about 4 am - Melatonin release suppressed by light - Levels of hormone cortisol (a hormone released by the adrenal gland that promotes arousal) also fluctuate with patterns of waking and sleeping - Cortisol levels high during the morning and lower at night Seasonal Affective Disorder - During winter the reduction in daylight hours can interfere with circadian rhythms - Seasonal affective disorder: a type of depression that results from insufficient amounts of daylight during the winter months - Serotonin levels drop during fall and winter - SAD might also be influenced by disruptions in melatonin release caused by uneven patterns of daily light - SAD treated by exposure to bright lights - Magnusson et al: Icelanders experience no more frequency or severe symptoms of depression during winter than during summer o Icelanders might enjoy protective genetic influences o Compared to Canadians living at same altitude, Icelanders experience lower rates of SAD Stages of Wakefulness and Sleep - Desynchronous: having different period and phases; in EEG, represents high levels of brain activity - Synchronous: having identical periods and phases; in EEG, represents relatively low levels of brain activity Wakefulness - EEG recordings alternate between beta wave (a brain waveform having 15-20 cycles per second, associated with high levels of alertness during wakefulness) and alpha wave (a brain waveform having 9-12 cycles per second, associated with less alertness and more relaxation than beta activity during wakefulness) - Ultradian cycle: a cycle that occurs several times in a single day - Alpha and beta activity alternate throughout periods of wakefulness Brain Activity During Sleep - Volunteers must sleep with scalp electrodes for EEG recordings - They are observed and filmed thru two way mirror - Sleep consists of alternating periods of REM and non-REM sleep - Rapid eye movement sleep: a period of sleep characterized by desynchronous brain activity, muscle paralysis, eye movement, and storylike dream behaviour - Non-REM sleep: a period of sleep characterized by slow, synchronous brain activity, reductions in heart rate, and muscle relaxation - Sleep begins at Stage 1 of NREM – some theta wave (a brain waveform having 4-7 cycles per second found primarily in lighter stages of NREM sleep) activity now occurs and hear rate and muscle tension relaxes o This stage usually disturbed by myoclonia: a muscle jerk occurring in early stages of sleep - Stage 2 NREM starts after 15 mins, accounts for 50% of night’s entire sleep o EEG begins to show sleep spindles: a short burst of 12-14 cycle-per-second waves observed during NREM sleep (generated by interactions between thalamus and cortex) o K-complex: a brief burst of brain activity occurring during Stage 2 NREM only o K-complex reflects brain’s efforts to keep us asleep while continuing to monitor external environment - Enter Stage 3 and 4 NREM after 15 mins of Stage 2 o Body temp, breathing, blood pressure, heart rate are at very low levels due to parasympathetic nervous system o Delta wave: a brain waveform having 1-4 cycles per second that occurs during Stages 3 and 4 of NREM sleep - First period of REM sleep occurs after 90 minutes of NREM (also known as paradoxical sleep) o Vivid dreaming occurs at this stage o In 8 hours of sleep, person experiences 5 periods of REM sleep o EEG shows activity similar to beta activity observed during wakefulness o Eyes move back and forth o Sympathetic nervous system becomes very active Sleep Throughout the Life Span - Half of newborn’s sleeping time is spent in REM compared to adults which is 20% - The more prematurely the child is born, the greater percentage of his or her sleep time is spend in REM - By age 1, babies sleep 13 hours, including 1-2 hours of naps - Between ages 1-5 infants sleep 8.7 hours - Delta wave activity highest between ages 3-6 - At puberty there is slight decrease in REM and decreases in Stages 3 and 4 sleep (teens feel like sleeping more) - NREM sleep declines further as ppl approach midlife - Around age 50, total sleep time decreases by 27mins per decade - Women approaching menopause have disruptions in sleep Dreaming During REM and NREM - Dreams occur during both REM and NREM sleep but more likely to be reported if awaked during REM sleep - REM dream are storylike, lengthy, vivid, complicated - NREM dreams are short episodes characterized logical single images and a relative lack of emotion - Calvin Hall: most dreams occur in familiar places and involve routine activities, imaginary strangers more likely to appear in our dreams than familiar ppl, participate in our dreams as characters 15% of the time - Alley Hobson and Robert McCarley: proposed activation-synthesis theory of dreaming o Content of dreams reflect ongoing neural activity (sprinkling water on sleeping volunteers made them dream of rain) - Francis Crick and Graeme Mitchison: computerized neural network model that sees dreaming as a way for brain to forget irrelevant and unnecessary info - Jonathan Winson: animals evolved ability to integrate sensory experience with stored memories during REM sleep rather than while awake; dreaming is just a window into brain’s processing of the day’s events - 70% of our dreams have negative emotional content - Nightmare: a REM dream with frightening content - Lucid dreaming: thoughtful dreaming; the dreamer is aware that he or she is dreaming and can manipulate the experience - Night terror: an NREM episode in which the individual is partially aroused, disoriented, frightened, and inconsolable o Most episodes begin with an abrupt scream, followed by sweating and accelerated heartbeat o Mental imagery during night terrors is rare; feelings of pressure on the chest The Functions of Sleep - Fatal familial insomnia – middle aged ppl gradually lose the ability to sleep and eventually die Sleep Keeps Us Safe - Prevents some animals from being active during parts of the day when they are least safe from predation - Allison and Cicchetti: able to predict a species’ sleep habits quire accurately on the basis of the animals’ risk of predation and their access to shelter o Horses live in the open wild, so sleep about 1-2 hours a day o Rabbits have burrows to hide in so sleep more than the horse o Lions sleep a lot and wherever/whenever because they don’t have predators Sleep Restores Our Bodies - NREM sleep helps us restore our bodies and conserve energy - Sleep deprivation leads to reduced immune system function, inability to heal, inhibition of adult neurogenesis in hippocampus - During NREM sleep, lower body temps and rates of metabolism might provide ideal environment for repairing damage produced by free radicals during wakefulness - Growth hormone: a hormone released during Stages 3 and 4 of slow-wave sleep that promotes growth, increases in bone and muscle mass, and immune system function - Release of GH peaks at puberty and drops by age 21 Sleep Helps Us Remember - Researchers believe that sleep plays more active role in consolidation of memories - Staying up all night resulted in poor memory retention for a visual task, and two addition nights of sleep didn’t compensate for the initial deprivation - Sleep-related changes in memory might be different form the changes that occur when we learn something while awake - Memories for word pairs stronger following period of NREM than following a period of wakefulness Benefits of NREM Sleep - Involved with restorative functions of sleep - After deprivation of NREM sleep, volunteers complain of muscle and joint pain - Increased physical demands during the day correlated with a need for increased amounts of sleep the following night, reinforcing the role of NREM in restoration of the body Benefits of REM Sleep - Only birds and mammals show true REM sleep - REM sleep increases after learning has taken place, due to participation of sleep in consolidation of memory - But individuals in whom REM sleep is regularly suppressed retain an ability to learn - Changes in REM sleep over lifespan suggest REM sleep plays role in brain development - Dement: REM deprivation caused phenomenon REM rebound: the increased amount of REM sleep following a period of REM deprivation - REM deprivation causes irritability, difficulty concentrating, too much REM sleep not good either (seen in depression) Brain Mechanisms of Wakefulness and Sleep The Control of Wakefulness - Two pathways originating in reticular formation of medulla are essential to wakefulness - One pathway proceeds from medulla to posterior hypothalamus and on to the basal forebrain - Other pathway projects to a group of cells known as the cholinergic mesopontine nuclei: a group of cells located at the border of the pons and midbrain that use acetylcholine as their major neurotransmitter and participate in the maintenance of wakefulness - Locus coeruleus of the pons also participates in wakefulness thru its rich connections to the thalamus, hippocampus, cortex - Locus coeruleus most active when ppl are alert, less active when person is relaxed The Initiation and Control of NREM Sleep - How do we make a transition from wakefulness to NREM sleep? - Sleep debt: the homeostatic control of sleep, in which sleep promotion is related to the preceding duration and intensity of wakefulness o Preoptic area of hypothalamus - Continued activation of preoptic area by input from serotonergic raphe nuclei will lead to inhibition of the circuits promoting wakefulness, allowing sleep to occur - These preoptic cells are referred to as NREM-on cells because electrical stimulation of these cells produces immediate NREM sleep, and lesions result in insomnia - As NREM begins, activity of locus coeruleus and raphe nuclei gradually declines Initiation and Control of REM Sleep - REM-on areas are active during REM sleep but not during wakefulness, and REM-off areas are active during wakefulness but not during REM sleep - Most of key REM-on areas located on pons - Parts of rostral pontine reticular formation near border of midbrain are important because lesions of this area abolish REM sleep o This area inactive during wakefulness and NREM sleep but active during REM sleep - Critical REM-off components are locus coeruleus and raphe nuclei o As they reduce their activity in NREM sleep, they disinhibit the activity of rostral pontine reticular formation - PGO spike: an electrical waveform observed during REM sleep, originating in the pons and traveling to the thalamus and occipital cortex; each PGO wave is associated with an eye movement o P – pontine reticular formation, G – lateral geniculate nucleus, O – occipital cortex - Paralysis during REM results from inhibitory messages traveling from pontine reticular formation to medulla and, from there, to the motor systems of spinal cord - Only muscles able to respond during REM sleep are eye muscles, ear muscles, muscles involved in breathing - Hippocampus is active, so is secondary visual cortex The Biochemistry of Wakefulness and Sleep - Loss of cholinergic neurons in Alzheimer’s disease might account for lack of attention and sleep probs that accompany the condition - Cholinergic agonists like nicotine produce a high level of mental alertness - Histamine activity high during wakefulness but low during REM and NREM sleep - Antihistamines produce drowsiness if they cross the blood-brain barrier - Serotonin and norepinephrine highest during wakefulness, drop off during NREM sleep, very low during REM - Ppl with major depressive disorder initiate REM too early and too frequently due to low serotonin activity - Caffeine blocks receptors for adenosine, an ATP byproduct that has inhibitory effect on many brain systems - When adenosine is inhibited, alertness is maintained - Adenosine inhibits acetylcholine, serotonin, norepinephrine Sleep Disorders - Parasomnia: a sleep disorder that involves the intrusion of unusual behaviours into sleep - Dyssomnia: a sleep disorder that involves difficulty initiating or maintaining sleep Dyssomnias - Insomnia: the inability to sleep a normal amount of time - “Healthy insomnia” – female lady slept only one hour per night w/o any detrimental effects - Onset insomnia: insomnia in which the individual has difficulty getting to sleep at bedtime - Maintenance insomnia: insomnia in which the individual cannot stay asleep during the night o Frequently interrupted or wakes up early - Pseudoinsomnia – ppl dream that they are awake - Benzodiazepines prescribed for insomnia and other sedatives - Sleep apnea: a sleep disorder in which the person temporarily stops breathing, then awakens gasping for air o Often occurs in obese individuals who snore  airway obstructions o Abnormalities in brainstem neurons responsible for maintenance of breathing during sleep - Narcolepsy: a sleep disorder characterized by the intrusion of REM sleep, and occasionally REM paralysis, into the waking state o Last from 10-20mins o Sleep attacks may have affected Harriet Tubman - Cataplexy: a feature of narcolepsy in which REM muscle paralysis intrudes into the waking state o Does not cause loss of consciousness o Nearly always preceded by strong emotional reaction or stress - Sleep paralysis: a feature of narcolepsy in which REM muscle paralysis intrudes into the waking state - Hypnogogic hallucination: a REM type dream that intrudes into the waking state prior to the onset of sleep - Hypnopompic hallucination: a REM type dream that intrudes into the waking state upon awakening - Narcolepsy results from disruptions in synthesis of orexins or in their receptors - Orexins typically found in cerebrospinal fluid of ppl without narcolepsy but are absent or greatly reduced in patients with the disorder o Cells in hypothalamus that secrete orexins are missing/damage in brains of patients w/narcolepsy Parasomnias - Nightmares and night terrors - Sudden infant death syndrome: a syndrome in which an otherwise healthy infant stops breathing and dies during sleep - Filiano and Kinney: argue SIDS involves a vulnerable infant in critical period of development exposed to external stressor - Sleep talking – most common in young people, diminishes with age - Somnambulism: sleepwalking o Much more common in children, between ages 4-12 o Probably a deep NREM phenomenon cause of paralysis during REM - REM behaviour disorder: a sleep disorder in which the normal REM paralysis is absent o Ppl act out their dreams, appears to be inherited but can also result from brain damage in pons o Pons are responsible for inhibiting motor movement during REM o Accompanies Parkinson’s disease o Treated with benzodiazepines (sedatives) - Restless leg syndrome: a sleep disorder in which a limb, usually a leg, moves at regular intervals during sleep o Occurs in children/adults with ADHD o Kidney disease, pregnancy, anemia might be at fault o Treatment is massage, applying heat/cold, avoiding caffeine, medication Table 11.2 Comparison of Night Terrors and Nightmares Night Terrors Nightmares Time of night Within 4 hours of bedtime Late in sleep cycle State on waking Disoriented, confused Upset, scared Response to caregivers Unaware of presence, not consolable Comforted Memory of events None unless fully awakened Vivid recall of dream Return to sleep Usually rapid unless fully awakened Often delayed by fear Sleep stage during which even occurs Partial arousal from deep NREM sleep REM sleep Summary Table: Stages of Waking and Sleep Stage of Waking or Brain Activity Related Phenomena Sleep Recorded by EEG Wakefulness Alpha/beta Alternation of period of alertness (beta waves) with period of relaxation (alpha waves). Logical thought. Continuous voluntary movement. Highly responsive to external stimuli. NREM sleep 1 Some theta Logical thought. Periodic involuntary movement. Continued responsiveness to external stimuli. Reduced heart rate and muscle tension. 2 Larger proportion of Reductions in responsiveness to external stimuli. Further reductions in theta heart rate and muscle tension. Sleep spindles appear. K-complexes appear. 3 Some delta Further reductions in heart rate and muscle tension. 4 Larger proportion of Profound reductions in heart rate and muscle tension. delta Very low responsiveness to external stimuli. REM sleep Similar to beta, some PGO spike correspond to eye movements. Paralysis of major muscle theta groups in the limbs and torso. Irregular autonomic activity. Sexual arousal. Vivid dreaming. Table 11.3 Role of Neurochemicals in the Control of Wakefulness, NREM, REM Neurochemical Locations at Which Relation of Activity to Sleep Effects of Agonists Effect of Antagonists Neurochemical is and Walking for Neurochemical for Neurochemical Active Acetylcholine Pons High during wakefulness and Increased arousal. Decreased arousal. Basal forebrain REM. Low during NREM Increased REM sleep. Decreased REM sleep. Histamine Thalamus High during wakefulness. Low Increased drowsiness Hypothalamus during NREM and REM and sleep. Norepinephrine Locus coeruleus High during wakefulness. Low Increased arousal. Increased REM sleep. during NREM. No activity Decreased REM. during REM Serotonin Raphe nuclei High during wakefulness. Low Increased sleep time. Increased REM sleep. during NREM. No activity Decreased REM. Increased arousal. during REM Adenosine Widely distributed Accumulates in the brain Possibly promotes Inhibits sleep. areas in the brain during wakefulness; probably sleep. helps induce sleep. Summary Table: Brain Mechanisms of Sleep and Arousal Wakefulness NREM REM Reticular Formation: Midbrain Active Inactive Inactive Pons Inactive Inactive Active Medulla Active Inactive Inactive Basal Forebrain Active Inactive Inactive Locus coeruleus Active Less active Inactive Raphe nuclei Active Less active Inactive Preoptic area of the Less active Active Inactive hypothalamus Summary Table: Sleep Disorders Type of Disorder Name of Disorder Major Features Treatment (if any) Dyssomnias Insomnia Difficulty initiating or maintaining Avoidance of stimulants. sleep Regular sleep schedules. Treatment of underlying psychopathology. Medication. Sleep Apnea Failure to maintain normal breathing Weight loss. Surgical patterns during sleep. correction of airways. Mechanical regulation of airflow during sleep. Narcolepsy Inappropriate intrusions of sleep Medication. Stress phenomena into normal waking management. Parasomnias SIDS Unexplained death of otherwise Avoiding smoking in healthy infant during sleep. household with infants. Avoiding putting infant to sleep on stomach or with blankets or stuffed animals. Sleep talking Speech during early stages of NREM None. Appears to diminish and REM with age. Somnambulism Sleep walking None. Appears to diminish with age. REM behaviour Lack of normal muscle paralysis Medication. disorder during REM sleep. Restless leg Regular movements of limbs during Correction of any syndrome sleep underlying medical conditions. Massage. Application of heat/hold. Medication CHAPTER 12: LEARNING AND MEMORY Introduction - Patient S had synaesthesia - Experience of a sensation in multiple sensory modalities, S’s memory was extraordinary - He was unable to organize his knowledge using concepts, categories, and generalization Learning - Behaviour or organisms can be separated into 3 major categories: o Reflexes: involuntary responses to stimuli o Instinct: a stereotyped pattern of behaviour elicited by particular environmental stimuli  Most instinctive behaviours involve parenting or mating behaviour o Learning: a relatively permanent change in behaviour or the capacity for behaviour due to experience Types of Learning - Associative learning: a type of learning that involves the formation of a connection between two elements or events - Non-associative learning: a type of learning that involves a change in the magnitude of responses to stimuli rather than the formation of connections between elements or events; habituation and sensitization Habituation and Sensitization - Habituation: a type of learning in which the response to a repeated, harmless stimulus becomes progressively weaker - Sensitization: a type of learning in which the experience of one stimulus heightens response to subsequent stimuli o Increasing overall level of responsiveness as a result of detecting one type of harmful stimulus makes us able to react more quickly to other sources of potential harm Classical Conditioning - Classical conditioning: a type of associative learning in which a neutral stimulus acquires the ability to signal the occurrence of a second, biologically significant event - Conditioned stimulus: an initially neutral event that takes on the ability to signal other biologically significant events - Unconditioned stimulus: an event that elicits a response without prior experience - Conditioned response: a learned reaction to the conditioned stimulus - Unconditioned response: a spontaneous unlearned reaction to a stimulus without prior experience Using Invertebrates to Study Learning - Their large-celled, simple, and easily observed nervous systems make them ideal subject - G.A. Horridge’s demonstration that of headless cockroaches learning classically conditioned responses - Aplysia californica: an invertebrate sea slug frequently used as a subject of experiments on learning and memory - Gill-withdrawal reflex: in Aplysia, a protective reflex in which the gill is retracted in resp
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