Introduction
- Einstein's brain contained unusually many glial cells
- Jacob Moleschott: Just as kidneys produce urine, the brain produces mind.
1. Development, Birth, and Parental Care
- Labor is trigger when the child accounts for around 15% of the mother's metabolism.
- While still in the womb, the brain cells in the child's hypothalamus respond to a drop in blood sugar level in the same way that they later respond to a lack of food in adulthood, by stimulating the stress axis. This induces a series of hormonal changes, making the uterus contract. The contractions, stimulated by oxytocin, make the baby's head press against the cervix. This in turn triggers a reflex, via the mother's spinal cord, which causes the release of yet more oxytocin. The baby's head then exerts more pressure, triggering the same reflex. The child can only escape from this chain reaction by being born.
- We now know that schizophrenia is an early developmental brain disorder largely caused by genetic factors. So a difficult birth can be seen as a failure of interaction between the brains of mother and child.
- A difficult labor or premature or delayed labor tends to be the consequence of a problem in fetal brain development.
Maternal Behavior
- During pregnancy, the pituitary gland secretes the hormone prolactin, which prompts nesting behavior.Oxytocin, the "bonding hormone" - It's the messenger of affection, generosity, tranquility, trust, and attachment, and has been found to suppress fear by affecting the amygdala, the center of fear and aggression.Vasopressin makes men hostile but women more likely to approach strangers, because they are better at distinguishing friendly features.Society could be improved by giving men a whiff of oxytocin and women a whiff of vasopressin.Abnormal blood levels of vasopressin and oxytocin have been found in people with autism, who also display small genetic variations in the proteins that are the brain's vasopressin and oxytocin receptors.
Paternal Behavior
- Patriarchy is though to have developed when our ancestors had to exchange the protection of the jungle for a more vulnerable life in the savanna.
- The male's protection of the female and her child had an evolutionary advantage: Humans were able to reproduce every two to three years, while female chimpanzees, who were solely responsible for their young and therefore had to look after them and feed them for much longer, could reproduce only every six years.
- Scents given off by the pregnant female may cause the behavioral changes in expectant fathers.
- Fatherhood induces changes in the prefrontal cortex. The number of synapses in this area increases suggesting a reorganization of the local network. It also becomes more sensitive to vasopressin, the chemical messanger that promotes social behavior and aids fathers in their new tasks.
Early Brain Development
- Children who are seriously neglected during their early development also have smaller brains, their intelligence and linguistic and fine motor control are permanently impaired, and they are impulsive and hyperactive. Their prefrontal cortices can be particularly undersized. Studies have shown that orphans adopted before the age of two go on to develop normal IQs of 100, while those not adopted until 2-6, attain average IQs of 80.
- The frontal cortex is the site of Broca's area, which is crucial for language. When adults learn a second language, another sub-area of this region is involved. But if children are brought up bilingually from an early age, both languages use the same frontal areas and the left caudate nucleus check which language system is being used.
- When doing mental arithmetic, the Chinese use different parts of the brain than Western Anglophones.
- The bond between mother and child is first established during pregnancy through the mother's voice.
2. Threats to the Fetal Brain in the "Safety" of the Womb
- Thyroid hormones are necessary for normal brain development but can only function if sufficient iodine is incorporated into the hormone.
- Exposure to lead, mercury, DDT, PCBs, dioxins and many other substances can disrupt fetal brain development, as can ingestion of nicotine, alcohol, cocaine, and other addictive substances.
- Our levels of aggression and stress are set before birth for the rest of our lives.
- Body Integrity Identity Disorder (BIID) - Patients can want to have limbs amputated because they feel they don't belong to them. Scans show that their frontal and parietal cortices respond differently to a touch on the leg according to whether it's the accepted or the rejected leg.
3. Sexual Differentiation of the Brain in the Womb
- The brain differentiates along male or female lines in the second half of pregnancy, due to a male baby producing a peak of testosterone or a female baby not doing so. It's in this period that the feeling of being a man or woman - our gender identity - is fixed in our brains for the rest of our lives.
- Gender-base behavioral differences are fixed in our brains before birth.
- In Western culture women use eye contact to understand other women better while men experience eye contact as testing their place in the hierarchy and can feel threatened by it.
- Development after birth seems to have little impact on our sexual orientation.
- Homosexual behavior has now been observed in around 1,500 animal species from insects to mammals.
- Male-to-female transexuality (MtF) occurs in 1 in 10k individuals while FtM occurs in 1 in 30k.
- The differentiation of our sex organs takes place in the first months of pregnancy, while the sexual differentiation of the brain occurs in the second half. In the case of transsexuality we expect to find female structures in the brains of MtF transsexuals and vice versa in FtM and this has been the case.
- it may be that the neural body map of MtFs lacks a penis and FtMs lack breasts and so the individuals don't recognize these organs as their own and want to get rid of them.
- The smaller the amygdala, the more likely an individual was to commit pedophilic crimes.
4. Puberty, Love, and Sexual Behavior
Puberty
- In puberty, the pituitary gland starts to produce sex hormones. The craving for new experiences, the readiness to take great risks, and the impulsive behavior are all part of preparations to leave the nest.
- People with a mutation in the KISS1 system never enter puberty.
- Melatonin, a hormone produced by the pineal gland, is one of the substances that prevent the onset of puberty in children.
- Normally, the brain cells that stimulate the sex hormones develop at the place where a fetus's nose develops. The cells then migrate along the olfactory nerve to the hypothalamus. This process is distruped in patients with Kallmann syndrome, so that not only do they not enter puberty, they also lack a sense of smell.
- A youngster's parents function as his or her temporary prefrontal cortex.
- Adults distribute assignments across different brain areas. Adolescent PFCs can sometimes function at an adult level but need to work much harder to do so, as they fail to outsource tasks to other brain areas. As a result, a teenager's PFC reaches the ceiling of its capacity earlier, and distractions can undermine the performance of assigned tasks.
- After the age of seventeen, young people commit fewer crimes. It seems logical to assume that this curve reflects the gradual development of the PFC, which inhibits impulsiveness and promotes moral behavior.
Love and Sex
- People who are in love also have raised levels of the stress hormone cortisol.
- Our partners are determined initially by our ancient reward circuitry. Only when the most intense period of infatuation has passed does the cerebral cortex take over.
- Many areas of the brain are constantly busy inhibiting our sexual urges. This is usually effective for around 23 hours a day.
- Electrically stimulating the amygdala has been shown to induce pleasant sexual sensations.
- To encourage us to truly commit to reproduction, the brain provides orgasm as a reward. It releases dopamine into the nucleus accumbens and oxytocin in the hypothalamus.
- The thalamus is the central structure for all erotic sensory information.
- DNA polymorphisms, tiny differences in the gene for the protein that receives dopamine's chemical message are correlated to the degree of sexual desire, arousal, and activity.
- In brain scans, brain activity during orgasm is similar to the response to a heroin injection.
- Activity in the female brain is concentrated in the motor and sensory areas of the cerebral cortex; in the male brain it's mainly in the occipito-temporal cortex and the claustrum.
- In both sexes, the cerebellum regulates muscle contractions during orgasm.
- Without being aware of it, American female students dress more fashionably around the time of ovulation.
- Strippers tips are also much higher around ovulation.
- Erotic images provoke greater arousal and brain activity in men than in women.
- In men aged 46-55 brain areas like the thalamus and hypothalamus cease to display activity, a sign that aging reduces arousal in response to erotic stimuli
- Lesions in the temporal lobe can cause people to develop Klüver-Bucy syndrome with symptoms of hypersexuality and hyperorality. Loss of inhibition has also been reported in individuals with lesions of the thalamus or the subthalamic nucleus.
- Depression is associated with higher levels of cortisol, the stress hormone, which can deprive patients of all the pleasure in life (anhedonia).
- In able-bodied men, psychogenic erections start in the brain and erotic impulses in the sex organs travel up the spinal cord.
- Epileptics whose condition is sparked by a focus in the cerebral cortex sometimes feel as if they are having an orgasm just before a seizure, due to electrical stimulation of the brain cells in that area.
5. Hypothalamus: Survival, Hormones, and Emotions
- The idea that brain cells could produce hormones was first suggested in the 1940s by the Scharrers. "Nerve gland cells" proved to be a universal cell type that regulates many bodily processes throughout the animal kingdom by means of hormones. The Scharrers' observations founded the discipline of neuroendocrinology.
- The hypothalamus:
- Memory information is transmitted from the hippocampus via the fornix to the mammillary bodies, and the routed to the thalamus.
- The suprachiasmatic nucleus is the biological clock.
- Thermoregulation and sexual activity are governed by the preoptic region, while the tuberomammillary nucleus, the only place where histamine is produced in the brain, is important for focusing our attention.
- The areas that regulate appetite and metabolism are the infundibular (arcuate) nucleus and the paraventricular nucleus.
- The paraventricular nucleus and the suproptic nucleus send fibers to the posterior pituitary, where oxytocin and vasopressin are released.
- The infundibular nucleus sends fibers to the capillaries of the hypophyseal portal system, where neuropeptides are released that regulate the anterior pituitary.
Depression
- All forms of depression feature overreaction of the stress axis. We respond to stress by activating nerve cells in the hypothalamus, which send a substance called corticotropin-releasing hormone (CRH) to the pituitary gland and the brain. The pituitary gland in turn stimulates the adrenal gland to produce the stress hormone cortisol. CRH and cortisol equip our brains and bodies to cope with stressful situations. But if th stress axis becomes overactive, a stressful event can lead to the overproduction of both CRH and cortisol, and these substances can affect the brain so strongly that depression results.
- Seasonal affective disorder.
- Various cell groups become hyperactive in the hypothalamus of depressive patients. In many cases the stress axis (the hypothalamus-pituitary-adrenal axis) is strongly activated.
Obesity, Anorexia and Narcolepsy
- In the Western world, around 60% of adults are overweight and 30% are obese.
- The leptin hormone is produced by fat tissue and helps the hypothalamus know how full we are, but if there are mutations in the leptin gene or receptor the hypothalamus will conclude that there's no fat tissue and continually prompt you to eat, resulting in morbid obesity.
- The symptoms of narcolepsy are cause by the absence of hypocretin (or orexin) in the hypothalamus.
- All the symptoms of anorexia nervosa can also be caused by a cyst, a small tumor, or some other abnormal process in the hypothalamus.
- Anorexia sufferers may maintain the process of voluntary starvation because they become addicted to the diet-triggered opiates released by their brains, which activate the reward center at the base of the striatum.
6. Addictive Substances
7. The Brain and Consciousness
8. Aggression
9. Autism
10. Schizophrenia and Other Reasons for Hallucinations
11. Repair and Electric Stimulation
12. The Brain and Sports
13. Moral Behavior
14. Memory
15. Neurotheology: The Brain and Religion
16. There Isn't More Between Heaven and Earth
17. Free Will, a Pleasant Illusion
18. Alzheimer's Disease
19. Death
20. Evolution
21. Conclusions
