random stuff i've learned: your brain!!! and limbic system (mental health 101)

   Evolutionarily - emotions have had more of a place than you may think. Mating, sensing danger, memories, everything. Emotions aren't such an abstract concept as it may seem, though - our brain's limbic system is to thank. This blog will serve as a brief intro to the limbic system, its function, and diseases linked. 

   For disclaimer: I took a psych course and currently study biology & sociology - but am still at a high-school level and mostly referencing from memory and internet references. Take my info with a grain of salt; this "random stuff i've learned" series is more passion project than textbook, and aims for a more humanistic approach than academic. Enjoy!

   First: What is the limbic system?

   Structures within our brain that regulate emotion, memory, reproduction, and our automatic brain function. Basically everything you feel or have felt the result of - love, sadness, yearning, fear - all are results of our limbic system, alongside any sensory issues you may have. 

  Second: What structures make up the limbic system?

   -The amygdala processes emotions, feelings, memory of trauma, and intensity of all of the above. The amygdala is like a volume-wheel on a voice recorder - it decides the intensity of your emotions and remembers the intensity of others around you to store in your memory.

- The thalamus processes senses like touch, hearing, vision and aids memory + emotions. 

- The hippocampus which controls the formation of new memories.

-Finally, the hypothalamus: which controls hormones, manages your autonomic nervous system (therefore your pulse, breathing, hunger, etc), and everything connected to hormones: that's to say a lot. 

-Important note here: although it's not part of the limbic system, your prefrontal cortex regulates your reasoning and regulation of emotions and intensity - it works in tandem with the amygdala to regulate your emotions. As teenagers, our less developed pre-frontal cortex is what can make us more likely to fall victim to peer pressure or have emotional outbursts - it acts as another regulator of intensity, among other things.

   Summary: any anxiety, fear, anger, or intense emotion that you have felt was processed via your amygdala. If you've ever had sensory overload, that was your thalamus acting up - it aids in processing most of your senses. Any new memory you've ever made was thanks to your hippocampus. Your hypothalamus is what's made your heart rate jump while running - what made you feel less hungry after eating ice despite the lack of nutrition. 

   Each organ replies to one another and works together with your brain -  sensory overload from your thalamus' processes can make your amygdala flare up in frustration, creating a new memory of your overload in the hippocampus, and your hypothalamus detecting this all - making your heart rate shoot up and signaling release of cortisol (stress hormone). It's important to note: all of our brains are different, both from genetics and from our environment and development. I'll delve more into that in the disease bit - but it's important to note now, as each structure presented is that of a neurotypical brain. Neurodivergent brains have the same organs - but they diverge from typical ones in the underuse or overuse of certain organs over others.

Third: Diseases/Disorders related to limbic system (MENTAL HEALTH 101)

   As we've learned - each act within the orchestra is essential to the song which results. That is no different from our function as humans. Here's some common disorders and their associated organs within the limbic system, and a brief summary of each:

Autism Spectrum Disorder / Neurodevelopmental Disorders & Dysautonomia
-These three are linked together more for their impact upon the hypothalamus and thalamus, the organs which regulate your autonomic nervous system and sensory perception. The sensory overload and issues associated with ASD and other developmental disorders aren't just "complaining" as some insensitive old people may have you believe. An overactive or sensitive thalamus creates those sensory issues - and your hypothalamus (which processes information from your thalamus and other glands) can therefore become overactive or dysfunctional as a result.

-That's where dysautonomia comes in: dysfunction of your autonomic nervous system. While the big words make it sound bad - dysautonomia can be as simple as your heart having a slight stutter in opening its atrium, or as advanced as syndromes like POTs or orthostatic hypotension. Both of those affect your body's regulation of blood pressure and pulse - which is why people with ASD, ADHD etc., can be more likely to have either syndrome. Your brain can be just worse at regulating its pulse and blood pressure as a result of different development - though science hasn't figured out the mechanism of that, so take it with a grain of salt. I've experienced orthostatic hypotension before (standing up too fast, your body drops in blood pressure - which makes you faint or lose vision & balance) from my own ASD - I'm sure some of you reading this have too.


Alzheimer's: 
-The hippocampus is the prime suspect in many memory-related diseases - this one is fairly clear-cut to understand. Hippocampus controls the formation of new memories - an underactive hippocampus brought on via age, genetics, etc., create that textbook forgetfulness associated with Alzheimer's and other diseases in the dementia sphere.

Borderline Personality Disorder and other mood / depressive disorders:
-Can be linked to an overactive amygdala, being the organ most responsible for emotions, an overactive amygdala typically manifests with the symptoms of BPD, and other personality disorders. Also linked to an under-active pre-frontal cortex , which adds up - if your amygdala perceives things very intensely, but your pre-frontal cortex can't filter and balance that with reason - leading to that intensity of emotion and rapid changing of opinions. As much as some think personality is a controllable thing - the tools which control it must be developed enough to do so.

-Your environment helps shape your amygdala - a more malleable organ when it comes to what your emotions, etc. will be - that's why many personality disorders have environmental causes. Think about it - your first shaping of emotion in your amygdala is developed when you're a baby, replicating and inferring your parents' emotions. If your environment demands too much of your amygdala (abusive parents, etc.) - then it only makes sense your body adapts, but in that adaptation to an atypical lifestyle in youth, you can lose your ability to navigate a more typical lifestyle later on. An under-active amygdala, (and pre-frontal cortex) by contrast - would look like psychopathy. A lack of fear and general emotional processing - studies have even shown a 17-19% shrinkage in the amygdala for those with psychopathy - but of course, it's not just the amygdala. That pre-frontal cortex plays a role too - as it regulates the emotion from your amygdala -studies simultaneously show pre-frontal cortex being under-used and under-linked with the amygdala for those with psychopathy.

Conclusion:

  I hope these nerdy ramblings were able to kickstart or give some of you guys a working knowledge of the limbic system - or at very minimum an interesting read. The best takeaway I can give here: each system and organ within the brain develops in its own way - not only can our personality and general affect and response to others be decided by this - it can pay to be somewhat educated upon the emotional center within our brain - helps to avoid ignorance towards certain disorders & diseases. Education is the best tool in eliminating stigma - especially so in the case of mental health - so I hope this gave some of you a decent understanding for what can make certain people how they are. 

Sources (besides my own memory)
-clevelandclinic.org. link 1, link 2
-NIH.org. link
-med.wisc.edu. link