No Differences Between Men and Women in Memory Region of the Brain

 

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Have you ever felt that your girlfriends get where you’re coming from while your guy friends are clueless? Stereotypes about men and women have been around for centuries and many theories have circulated about the differences between the brains of women and men covering everything from emotion processing, to memory, to social interactions. While small studies have noted brain differences that appear to be linked to gender, larger studies have called those links into question. A new study released this week has studied a specific region of the brain long said to differ between men and women and has found the discrepancies to be smaller than previously thought.

What differences exist between the male and female brain?

While many new studies have found that the brain differences between genders are small, there are some that seem to reliably show up. Male brains seem to be larger overall than female brains, but that increase in size applies to all structures of the brain including the ventricles or spaces in the brain present in all people. Male brains also seem to have relatively more white matter in their brains compared to the total weight of the brain. White matter is brain tissue that generally serves to connect different parts of the brain and transfer information between them. These pathways act as the superhighways of communication between different parts of the brain. Finally, male brains grow for a longer period of time during the teenage years than female brains. The significance, if any, of these differences is still unknown.

Do these differences make any difference?

While it’s tempting to point to these differences and say that they must in some way explain the differences you see between men and women, few studies have shown that to be the case. When it comes to brain size, the male brain seems to be scaled up in size rather than actually being more complex, perhaps because of the body size difference between most men and women. The increases in white matter make it tempting to think that men might be able to get information around the brain more quickly, perhaps allowing them to process information more quickly. But studies looking at processing of language and emotion, areas where men and women are often thought to differ, haven’t shown major gender disparities. Time and again, the minor differences seen in the brains of men and women haven’t worked as an explanation for the stereotypes we hold about the way men and women act.

What part of the brain did this team study and why?

Past studies had indicated that a part of the brain called the hippocampus involved in memory was different between men and women. This was based on a few observations. First, studies done in mice and voles had found indications that males might be better with navigation through space, assisted by spatial memory in this region. It was thought this might because the nerve cells in this part of the brain respond to testosterone, a typically male hormone. But the contrary line of thought was also found to be true. When researchers have looked at the effects of estrogen, a typically female hormone, on this area of the brain, it also seems to bump up connections and nerve growth.

Other researchers have hypothesized differences between female and male brains in the hippocampus because diseases that tend to target this area affect women and men differently. Depression, PTSD, schizophrenia, and Alzheimer’s disease all affect the hippocampus and also tend to affect women more often than men. Some have hypothesized that to be the case because women have a smaller or less resilient hippocampus that caves more easily when the ravages of disease take hold. Some have also wondered if changes in hippocampus over a lifetime may play a role. These researchers wanted to figure out exactly what was going on.

How did these researchers study the size of the hippocampus?

The team used what’s called a meta-analysis to figure out just how different the region was between men and women. That meant scanning the research for past studies that had looked at the size of the hippocampus in men and women of different ages and pooling that data together to reanalyze it. In total, the team gathered data from 76 studies that included men and women of all ages.

What did the researchers find?

The team found that there were indeed differences between the brains of men and women, namely in the size of the brain as noted by past studies. But when the researchers compared the scale of the hippocampus with the scale of the brain, they found that there was no real difference in size between men and women. Proportionally, the hippocampus of men and women was about the same. The size of the hippocampus also didn’t change much with age between men and women. Any changes in size over a person’s lifetime occurred regardless of whether they were male or female in line with past research that had found similar effects of age on the brain between men and women.