#gaba

Dopamine (Ne) is all about exploration, novelty, and active engagement with the world. It’s testing, experimenting, seeing what works, and staying open to multiple perspectives in real time. It’s "what if" thinking, bouncing between ideas, trying them out, and learning through trial and error. This is why the dopamine pathway is short and reactive, driving people to act quickly and be highly responsive to stimuli.

Acetylcholine (Ni) is much more about conception, depth, and refinement. It’s about filtering through possibilities, refining, and finding the most efficient path. This is more about a long-term vision, where you discount distractions and focus on what’s likely to work based on deep internal understanding. Like Ni, acetylcholine works with refined material, builds on past knowledge, and strives for clarity over time. Quality control over quantity. The pathway is longer, as it requires more time for reflection and synthesis.

Norepinephrine (Se) = Sensory Engagement / External Stimulation: Norepinephrine is often about stimulation, arousal, and action in the present moment, which matches Se's focus on immediate sensory input and the world outside. Se engages directly with external stimuli, maximizing the sensory experience—seeing, hearing, touching, and reacting to what's right in front of them, seeking novel or impactful experiences. Norepinephrine similarly drives people to engage with their surroundings, often seeking intensity and excitement. Both want to be in the moment and responsive to the environment.

GABA = Si (Introverted Sensing): GABA is an inhibitory neurotransmitter, meaning it calms down neural activity and contributes to a sense of stability, relaxation, and grounding. This is highly similar to Si, which is about internal sensory recall, stability, and creating a grounded mental state based on past experiences. Just like Si helps us process and stabilize memories and experiences, GABA contributes to calmness and internal balance.

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Ooops. Clickbait. Only the perceiving functions can be directly associated with neurotransmitters but here is why:

Perceiving functions (Ne, Ni, Se, Si) are more fundamental in terms of information gathering and conceptualizing because they deal with raw data, sensory input, and ongoing experience. These are processes that happen almost automatically and are more closely tied to the REACTIONS of the brain to immediate stimuli, which is where neurotransmitters like dopamine, norepinephrine, GABA, and serotonin come into play.

Judging functions, on the other hand, are higher-order, more abstract, and deal with organizing, categorizing, and deciding how to act on the information the perceiving functions gather. These processes tend to be more cognitive, involving more logical, computational thinking (yes, fi too!), which requires less direct chemical input and is mediated by higher-level brain areas like the prefrontal cortex. They are more internalized, less reactive to real-time input, and more about evaluating and controlling the data.

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But hey! If you really twist my arm, I could associate Fi with serotonin and Fe with oxytocin.

Today's paper is all about the mesopontine tegmental anesthesia area in the brainstem (the MPTA), which seems to be the key to understanding how anesthesia works. Adding tiny amounts of general anesthetic (like what they would usually use on your whole body in the hospital) to JUST this area will make you lose consciousness. Since we don't yet fully understand how anesthesia works, this is a big deal.

Specifically, the authors are looking for brain regions that are physically connected to the MPTA through synapses to find out who, what, and where is influencing this spot. They hypothesize that these communications could be for the purposes of phasing in and out of regular losses of consciousness, like sleeping or fainting, as well as anesthesia, seizures, concussion, etc.

The way to find regions that are communicating with a region you're interested in is to use a retrograde tracer. Neurons communicate by firing electrical signals down the length of their axons, which are basically a long pool noodle that you shoot water through. These electrical signals are designed to only go one direction, from Neuron A to Neuron B. However, Neuron A has a lot of subcellular structures in the axon and at the end of the axon that still need to be supported by the main cell, despite the fact that axons can be super long.

So axons send electrical signals, but they are ALSO full of transportation mechanisms that carry molecules to and from the end of the axon. Retrograde tracers hijack these transportation mechanisms by hopping on the route leading backwards from the end of the axon back to the body of Neuron A. Inject a retrograde tracer into a brain area and any neurons with axons there will pick up the tracer and carry it back to the brain region they came from. Stick your brain under a special microscope and bada bing bada boom, you can now see what brain regions were influencing the region you injected.

To make a long paper short: a LOT of areas have synapses in the MPTA. Cortical areas, subcortical areas, brainstem, cerebellum, you name it. There are a ton of detailed figures and explanations here so I encourage you to explore it more deeply.

This paper was largely exploratory, meaning it was just curious what the circuitry is like in this area of the brain. They also talk a lot about GABA, the neurotransmitter that they believe plays a big role in anesthesia, but I wanted to focus on retrograde tracers for this post so you can have fun with that on your own.

Ciao!

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