Part 4: Self-Perception and the Default Mode Network

If you’ve made it to part 4 well done. I hope that it’s made you think a little more about the whole concept of gender and identity. For the last part I wanted to focus on the science and see whether that has any insights to offer us.

There are many papers that look at brain differences between males and females and compare them to the trans population. These often give the impression that there are significant differences between the male brains and female brains. Whilst there are some anatomical differences it’s unclear how significant they are. Other papers focus on the hormonal influences on different parts of the brain or how different genes are expressed by different brains. it is a matter of hot debate as to whether these differences play a significant role in sexed behaviours and as such I don't think this is a good avenue at present to argue that gender identity exists. For what it's worth anatomically trans people have variable anatomical changes compared to their cisgender counterparts. Some areas are in line with natal sex others in line with gender identity.

For me it is much more interesting to look at how we see ourselves. For me gender incongruence has always been a disconnect between what I expect to see in the mirror and what I actually see. To put it another way how I perceive myself is not how I actually see myself. So, what does science say about self-perception? Do we know where that comes from in the brain and do trans people show something different in this area? This work will likely develop over the coming years but our self perception and perception of others most likely comes from some specific areas of the brain collectively known as the Default Mode Network (DMN).

Excuse my terrible drawing but the areas of the brain that make up the DMN are sh

own in the picture here. These areas are active when we are awake but not engaged in a task. When we're daydreaming, considering the future, thinking about ourselves or the intention of others i.e. it's active when we're just thinking. This is where general thought arises. It's also where we consider ourselves.

A recent study published in Nature Scientific reports looked the default mode network of trans people pre and post treatment with cross sex hormones. Firstly, it showed that both trans men and women pre treatment we're much less likely to say a picture of them was how they saw themselves. whereas cisgender counterparts would. Following cross-sex hormone treatment they began seeing themselves the same as the picture they were presented with I.e. Treatment with hormones made trans peoples physical appearance align much more closely with their perceived sense of self.

To me this is a nice functional demonstration of the paradox of truths I described in part 3. 'I see this image as me, but I know it's not who I am' When you reduce that tension the conflict resolves and you simply rate the image as 'this is me'

It then looked at what was going on in the brain of these participants and what it showed was there are significantly weaker connections in the parts of the DMN for trans women and men when compared to cisgender controls. The connections between the different areas of the brain that perceive self are much lower for trans people than for cisgender controls. Even more interestingly when scanned again after cross sex hormones this reduction in connectivity disappeared. So the areas of the brain that perceive self became like everyone else when trans people appeared more like who they say they are.

In summary trans peoples outward self-rating of their perception of themselves was more accurate AND their brains became aligned with their cisgender counterparts when given cross sex hormones.

For me this is pretty strong evidence that there is something inherently biological going on here. We seem to have an innate sense of our gender and sometimes that doesn't match what we see reflected in the mirror.

Is this absolutely proof gender identity exists? No. I don't think anyone can say that but what I hope it does show is that this is clearly something fundamental and biological and much much more than a feeling in my head or a philosophical construct.

I know no level of evidence would be enough to convince some people, but I hope some of you found this interesting. Please feel free to ask any questions as long as they're in good faith and thank you for reading.