Implications of Sex Differences in the Human Brain

The biological differences between female and male brains have been a topic of research for hundreds of years. Debates over brain differences have gone back to the Ancient Greeks, but it was around the 17th century when significant empirical evidence first began. In 1854, German anatomist Emil Huschke discovered that male frontal lobes were 1% larger than female frontal lobes. Through more recent research, scientists have found that men have around 8%-13% larger brain size than females, and the sexes have different activation patterns due to their differences. However, this Huschke’s research began a revolution of new research specific to the question: does sex impact how humans behave or perform daily tasks?

It was once thought that problem solving and cognitive task differences between sexes weren’t prominent until puberty, but evidence has suggested that these differences present themselves earlier in development. Research has found that pre-pubescent old boys are better at tasks including manipulating an object and motor skills, such as video games or mental rotation and are also faster on reaction time and finger tapping tests. On the contrary, pre-pubescent girls are better at memorizing, recalling, and identifying patterns. Females tend to have an advantage in performing tasks involving verbal learning/memory, object location memory, matching, and precision tasks. In laboratory-created scenarios by the National Institute of Health, in maze and path completion tasks, males learned the goal route at a quicker rate, while females remembered the routes/landmarks at quicker speeds.

The difference in grey matter levels between sexes is critical in understanding the neurological and psychiatric conditions between males and females. A 2014 meta-analysis found that males had more grey matter in their amygdala (structure involved with emotion), hippocampus (structure involved with memory), and other limbic regions while females had more grey matter in their frontal lobe regions (structure involved with personality/thinking), occipital cortex (structure involved with vision), and other cerebral cortex regions. Additionally, males tended to have a denser left amygdala, hippocampus, and cerebellum (structure involved with balance and coordination). These are due to men obtaining more rightward lateralization and women having leftward lateralization, which signifies that males have more volume in their left hemisphere and females have more volume in the right hemisphere. Lateralization is the tendency for some cognitive functions/neural processes to be specialized in one side of the brain. Essentially, we have “left-brain functions”, which are associated with logic, critical thinking, language, math/science, etc., and “right-brain functions”, which are associated with creativity and art. This can be connected back to the idea of women being more language and artistic inclined while men are more logically and motor inclined. Though scientists are still figuring out exactly what this implies, it’s important to note these biological differences and what they might relate to neurological conditions/functions.

One interesting neurological difference is the difference between brain networks in males and females. Humans have an active working memory network that works in the cerebral cortex area. Although everyone uses the same brain networks, certain regions of the brain are sex-specific. Females have more activity in the limbic regions and prefrontal regions, while males have a distributed network spread out throughout the cerebral cortex. There has been a study on how the susceptibility of women getting stress-prone diseases such as major depressive disorder or posttraumatic stress disorder increases when a woman’s brain activity is centralized around the prefrontal cortex due to their overactive networks around the prefrontal regions. As a result, stressors that contribute to such conditions could be increased.

Lastly, the neurochemical differences between males and females is significant in understanding the implication of sex differences in the brain. The pituitary gland is a gland in the brain that produces and regulates hormones. From this gland, hormones like testosterone, estrogen, progesterone, and more are all secreted. Estradiol is a hormone taken to reduce the symptoms of menopause, and this hormone influences cognitive function. Studies have shown that it enhances learning and memory relating to the doses one takes. Additionally, too much estrogen in females can weaken the performance of learned tasks and memory tasks. While estrogen levels mainly affect females, the steroid hormone progesterone affects both males and females. In women, increased progesterone is mainly linked to the menstrual cycle; In males, increased progesterone has been linked to high suicide risked adolescent males.