Creation Date: 7 May 2014 | Review Date: 7 May 2014
His and Hers: Sex Differences in the Brain
Source: Society for Neuroscience
For years before the U.S. Food and Drug Administration (FDA) came out with its recent recommendation that women cut the dose of Ambien and related sleeping medicines in half, there were reports of patients engaging in strange, sleepy next-day behaviors. However, it wasn’t until scientists took a closer look at the data showing the amount of the drug still in the blood of male and female users when they awoke the next day that they recognized one reason why.
MRI studies of healthy people (How is “healthy” determined? Who is excluded?) suggest there are sex differences in the size of regions throughout the brain. This image highlights regions that were larger in women (pink) and men (blue) relative to the total volume of the cerebrum. Courtesy, with permission: Cahill. Nature Reviews Neuroscience, 2006.
The “point is” that 2,000+ years of relentless prejudice against the female sex cannot be “undone” by mere statements of “reform“. The very foundation of social and cultural beliefs is involved, and in fact, still guides and informs “scientific” research; the intent, design and results of “studies” – and the conclusions and claims about how humans (and animals LOL) are “supposed to” think, behave and feel. And the “body of knowledge” based on prejudice remains active in academic belief systems. That includes women in academic systems…
As it turns out, (a weasel phrase meant to “sweep away” any questions as to what all this means, implying that the “sciences elves” have definitively and objectively applied their magic and have “discovered” some ultimate truth about “reality” – in this case – a revealing conclusion) women break the drug’s active ingredient zolpidem down slower than men do. Since they were taking the same dose of the drug as men, they were waking up with more of the drug still in their bodies. Studies would later reveal that these elevated levels increased their risk of adverse events, like car accidents.
Why did it take years to recognize sex matters when it comes to sleep medication doses? Because many (male authorities) assumed “sex cannot matter that much,” explains Larry Cahill, a neuroscientist at the University of California, Irvine who studies sex differences in the brain. (Sex DOES matter though when innate skill, intelligence, rationality, judgement, logic, leadership, or other “performance” ability is being discussed.)
Traditionally, in both human and animal research, males have been the research subject of choice because their hormone levels do not vary cyclically the way that they do in females. (The “females are crazy by default” myth) Many researchers assumed that fluctuating hormone levels in females would make it more difficult to draw conclusions from their findings (Because the conclusion has already been made that women are hormonally defective “crazy people”), and any findings in male study subjects translated to females. (That is, almost all conclusions about “human – ness are strictly male-based human-ness. Only female reproductive physiology is of interest – ) However, recent analysis of numerous studies comparing male and female mice show studies with females show no greater variability than those with males.
Additionally, as the sleep medication study suggests, “The assumption that you can safely ignore sex [when developing treatments] is wrong,” Cahill says. In fact, a growing number of studies highlighting sex differences in the brain are beginning to turn this concept on its head.
Sex differences start early
Early research on sex differences in the brain began with animal studies of the hypothalamus, the brain area involved in feeding, stress, and mating behaviors. Just as early exposure to the sex hormone testosterone guides the “masculinization” of the body — including the development of the male reproductive tract and external genitals — scientists discovered it also influences the development of the brain and behavior. When researchers exposed female guinea pigs to testosterone while still in the womb, they found that the animals displayed mating behaviors more similar to males later on in life. In contrast, female guinea pigs exposed to testosterone later in life showed typical female mating behaviors.
Comment: How fraught with misinterpretation are these parameters: “typical male mating behaviors” and “typical female mating behaviors”? And in Guinea pigs? Guinea pig “mating behavior” translates to human mating behavior? Really? Human mating behavior is socially determined, regardless of biology! No human is free from the dictates of culture in “mating” behavior.
Researchers have since identified structural differences in male and female brains in animals. In rats, the volume of a large cluster of cells in the preoptic area of the hypothalamus is greater in males. In contrast, the anteroventral periventricular nucleus — a section of the hypothalamus that helps to regulate the ovulatory cycle — is larger in females. Other studies have found that the length and complexity of dendrites (the branch-like structures neurons use to receive information) in the ventromedial nucleus of the hypothalamus also differs between males and female rats, suggesting there may be sex differences in brain circuitry (in rats!) Sex and memory Scientists (those busy unidentified elves who always seem to agree with whomever is writing the article or paper) are now learning sex differences are present beyond the regions of the brain that are involved in mating. Animal research indicates the presence of sex differences in the hippocampus — an area involved in storing memories and the spatial mapping of an environment. In addition, magnetic resonance imaging (MRI) studies of people have found that, when compared to the total volume of the brain, the hippocampus is larger in women than men. In contrast, the amygdala — an area crucial to the formation of emotionally charged memories (and much more) — tends to be larger in men. (Wouldn’t this “suggest” that men are more emotionally reactive than women?) Other studies suggest that there are differences in how these brain regions function in men and women, perhaps affecting how they respond to stress (Stress=watching violent movies?) For instance, when researchers asked men and women to watch violent films, they discovered that women display greater activity in the amygdala on the left hemisphere of the brain while men show greater activity on the right. Regardless of sex, the more active the amygdala, the more the participant remembered when asked about the violent film a few weeks later.
When scientists gave participants a drug that dampens amygdala activity before presenting them with an emotional story, they found that men had a more difficult time remembering information central to the emotional story line, while women had a harder time recalling peripheral story details one week later. (Did anyone take into consideration the dosage of whichever drug was used, as per the warning at the beginning of the article?)
What does all this crude tinkering actually prove?
These hemispheric activity differences may explain why men tend to recall the gist of an emotional event, while women tend to remember the specific details. (So – from this “fragment of brain activity” “gist vs. detail” we can legitimately “confirm” a pre-conceived cliche about “gist vs. detail”? Is there any possibility that the “focus” of males and females has been socially and culturally directed from birth? Ie, there are “environmental reasons” for females to pay attention to detailsvs. “the gist” (if they actually do). What about male “focus” when males are trained to be “unemotional”? What is the “gist” of an event anyway, in scientific terms?)
Sex matters for understanding disease
Generalizing animal research findings on sex differences to humans remains a significant challenge, (but we’re over-generalizing anyway) as does determining the ways in which the varying life experiences of men and women affect the brain, says Michigan State University neuroscientist Cheryl Sisk, who studies the role of hormones on adolescent brain development. Still, many researchers believe that studying sex differences in the brain will one day uncover new information about brain illnesses that affect the sexes differently. (Autism is not an “illness” – there is no medical diagnosis!)
For example, boys are nearly four times as likely as girls to be diagnosed with autism and attention deficit hyperactivity disorder (ADHD) early in life. In contrast, depression and anxiety, which are more commonly diagnosed after puberty, occur almost twice as frequently in women as men. A recent study also suggests that APOE4 — a gene variant commonly associated with heightened risk of developing Alzheimer’s disease — confers greater disease risk to women. (So depression=Alzheimer’s?)
The article is mixing-conflating – “illness” as a disease process with “mental states” in women (depression). Given the inferior status of women – the constant “stress” of social inequality and misogynist dogma present in most cultures, and the pervasive physical and mental abuse – which are environmentally present and active from birth – and add to these social indoctrination which is intended to change female human beings into subservient objects, NONE OF THESE factors can be considered to be the source of “disruption” in brain functioning that is “labeled” depression!)
According to Margaret McCarthy, who studies the effects of hormones on brain development at the University of Maryland School of Medicine, sex differences in the prevalence of these and other brain illnesses suggest “something is different in the way the brain is developing that is making it more vulnerable at different times for males versus females.” In cases where a disease is affecting one sex more than the other, “one sex is protected from disease more than the other,” McCarthy explained in a 2012 article in The Journal of Neuroscience. “Thus, identifying the sex-specific protective agents could lead to better understanding of potential therapies, or identification of new drug targets,” she wrote.
WOW! It’s a huge leap to assume some “protective agent” lurks within “female brains” or “male brains” when the “differences” that are being discussed may (logically) be the result – consequence of factors in the environment that (literally) shape the child’s brain post-birth, in addition to whatever anatomical differences may exist between “male and female” fetus-infants-children. This identification of “biology” and “culture” as one and the same, or the equally egregious dismissal of either as determinants in human experience and behavior is simply a disaster.
The tendency is to (erroneously) “confirm” social concepts about “being human” by appropriating “biology” as the causal factor in what is SOCIALLY PRESCRIBED and ENFORCED human behavior: “proof” of prejudice is coerced from supposedly scientific investigations, but what is ”going on” is not science: it’s pseudoscientific feedback that supports myths about laboratory animals being sufficient “stand-ins” for humans – while perpetuating archaic religious beliefs about human nature.
Isn’t it a bit contradictory to claim that Homo sapiens, the most complex, intelligent, creative, sensitive, technology-producing “uber-species” on planet earth (males only, of course) is “explainable” by the “primitive” brains of rats, mice, monkeys, rabbits dogs – even invertebrates?