The brain within the brain

Fractals are fascinating because no matter how close you zoom in, you find a crystal clear picture just as complex as the original – often sharing the same structure as the original. Look closely at the brain fractal below, and you will see many smaller brains inside it; if not for the limits of JPEG compression, you might not know you were zoomed in at all.

Fractal brain, by Cory Ench. http://www.enchgallery.com/

Fractal brain, by Cory Ench. http://www.enchgallery.com/

The more I learn about the brain, the more it puts me in mind of a fractal. The zoomed image may not be identical to the whole, but each region we have identified reveals itself to have far more complexity than first thought, itself composed of distinct regions working together in unbearably intricate fashion.

Take the  hypothalamus. My Intro Psych students grow to know and love-hate this brain region, nestled at the center of the brain with very fuzzy boundaries, because it appears in so many chapters. The hypothalamus regulates hunger and thirst, produces some vital  emotional responses – including love – regulates reactions to stress,  and it helps start puberty. Some of them have probably done quite well for themselves on multiple choice questions by just defaulting to “hypothalamus”.

The hypothalamus, one small piece of a complex brain. From http://www.organsofthebody.com/

The hypothalamus, in purple, one small piece of a complex brain. From http://www.organsofthebody.com/

The reason the hypothalamus plays so many different roles, though, is that when you look closer, the hypothalamus is not just one thing. Look closely, and you will see more component regions – just like the hypothalamus itself is one component of your brain.

The anterior (closer to the forehead) region of the hypothalamus is named the medial preoptic area (mPOA), rich in receptors for: oxytocin, widely known as the “love drug” (although not everyone thinks it deserves that reputation); vasopressin, which will turn promiscuous voles monogamousprogesterone, also known as the “pregnancy hormone”;  and prolactin, named for its role in producing breast milk. Small wonder, then, that the mPOA is thought to be the origin of mothering behavior; among other findings, damage to this region will reduce mothering behavior – including a mother rat’s willingness to to press a bar to have a rat pup delivered to her side via slide.

The brown semi-circles (mPOA) are a key player in mothering. Image originally from http://www.simonlevay.com

The mPOA is not a one-trick pony, though, and not just for mothers. In males, the mPOA seems to play major roles in sexual behavior; injecting oxytocin in this region in male rats will give them a performance boost in the rat bedroom, while damage to that area would quickly curb the rat population.

The multiple roles of the mPOA may again be explained by looking even closer, and seeing that it too is a complex structure composed of multiple regions working together. These component regions are so small we call them “nuclei”. There’s the interstitial nucleus (INAH-3, for short), known for being dramatically different in size between men and women, and linked to both sexual orientation and gender identity.

The next step will be to zoom in to these nuclei, and who knows what we’ll find then? Perhaps we should start getting ready to see neurological names ending in “nucleolus” as we zoom into the next layer that is our fractal of a brain.

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