Author: Choi Jang-hyeok · Korean Medicine Doctor · Director, Dongjedang Korean Medicine Clinic
Medical Review: Director Choi Jang-hyeok
Program: Dongjedang Korean Medicine Clinic Sasang Constitution Clinic
Research Method: DJD Multi-Literature Cross-Research

1. Core Summary (Abstract)

Attempts to reduce Sasang constitutional types to neurotransmitter profiles — yangyin as dopaminergic type and eumyin as GABAergic type — have shown pilot-level statistical correlations, but remain at the level of superficial correspondence between behavioral phenotypes. A 2024 study published in Cell Reports on dopamine-GABA co-release demonstrated that these two substances are released simultaneously from the same synaptic vesicles, thereby undermining the neurobiological basis of the very dichotomy of "dopaminergic humans" versus "GABAergic humans." Recognizing this limitation, this study argues that the seongjeong (性情) structure of Sasang Simhak describes not a question of total neurotransmitter volume, but of circuit selection — whether the same neurochemical energy takes a subcortical or cortical pathway. Furthermore, we propose a framework for reinterpreting Sasang constitution as four attractor basins with different state space structures, on the grounds that hard-coded neurotransmitter biases constrain not only subcortical function but also the range of cortical plasticity.

2. Context of the Question (Introduction)

Attempts to translate Sasang medicine into modern biological language have a long history. Research using autonomic nervous system activity, HRV (heart rate variability), and genetic polymorphisms has accumulated, and among these, the correlation between neurotransmitters and Sasang constitution is a frame with strong intuitive appeal. The active, extroverted temperament of soyangin overlaps with the reward-seeking behavior of dopamine, and the anxious, withdrawn tendency of soeumin resembles reduced GABA function.
The pilot study by Lee et al. (2015), using the Braverman Nature Assessment (BNA), was the first to report a correlation between Sasang constitution and neurotransmitter temperament types. Dopaminergic type was found in 43.2% of soyangin, GABAergic type in 50.0% of taeumin, and GABAergic type in 57.1% of soeumin; the yangyin-dopamine and eumyin-GABA correspondence was statistically significant (P = 0.017). — Lee et al., 2015, 『Journal of Pharmacopuncture』 (DOI)

However, this frame has fundamental limitations. First, the BNA itself is not a validated tool in mainstream neuroscience, and the classification of "dopaminergic human types" carries the character of pop neuroscience. Second, recent neuroscience has revealed that dopamine and GABA are co-released from the same axons rather than being separate systems, shaking the foundations of typologies based on a single neurotransmitter. Third, the camouflage structure of motivation described in the seongjeong theory of Sasang Simhak — the insight that seong (性) may appear outwardly as virtue but may actually be a camouflage for self-preserving jeong (情) — cannot in principle be captured at the neurotransmitter level.

What the clinician can gain from this study is not an answer to "which neurotransmitter can explain Sasang constitution," but rather a topographic map of at which levels of modern neuroscience the seongjeong theory of Sasang Simhak corresponds, and at which levels it transcends them.

3. What the Literature Says (Results)

3-1. Dopamine-GABA Co-Release: The Collapse of the "Two Separate Systems" Premise

The "yangyin = dopamine, eumyin = GABA" frame relies on the implicit assumption that dopamine and GABA are independent systems secreted separately from different neurons. However, Patel et al. (2024) demonstrated that dopamine axons in the mouse striatum co-release dopamine and GABA from the same vesicles, and that this co-released GABA autoinhibits dopamine release itself via GABAA receptors (α3 subunit) on the axons. Notably, this GABA autoinhibition operates more strongly during phasic bursts (explosive firing associated with reward signals) than during tonic single firing, functioning to reduce the phasic-to-tonic dopamine signal contrast. Because ionotropic GABAA receptors have faster kinetics than G-protein-coupled D2 autoreceptors, co-released GABA functions as the "first responder." — Patel et al., 2024, 『Cell Reports』 (DOI)

The implication of this finding is clear. Since dopamine neurons themselves co-secrete GABA, classifying an individual as "dopaminergic type" or "GABAergic type" is a categorical error akin to separating cardiac contraction and dilation to distinguish "contracting humans" from "dilating humans."

3-2. VTA GABA-Dopamine Antagonism: The Switch Between Reward and Aversion

The GABA-dopamine interaction in the ventral tegmental area (VTA) presents a more complex picture. GABA neurons, which constitute approximately 30% of the VTA, are divided into two subtypes — projection neurons (inhibiting multiple brain regions including NAc) and local interneurons (inhibiting adjacent dopamine neurons). In mouse studies, activation of VTA GABA neurons strongly suppressed the firing rate of adjacent dopamine neurons, and conversely, inhibition of GABA neurons produced disinhibition of dopamine — i.e., increased dopamine. Aversive stimuli (foot shock) transiently increased VTA GABA neuron activity while simultaneously decreasing dopamine neuron activity, and this effect was blocked by GABAA receptor antagonists.

Translated into Sasang medicine terms, the fear (恐)/anxiety tendency of soeumin overlaps with the pattern of VTA GABA neuron overactivation → dopamine suppression, and the anger (怒)/hastiness of soyangin overlaps with the pattern of dopamine overactivation + insufficient GABA suppression. Up to this level, the "yangyin = dopamine, eumyin = GABA" frame appears to hold approximately.

3-3. Dopamine and Personality Temperament: Dopamine as an Exploration System

Cornell University's Depue reported that individual differences in extraversion arise from functional variation in the VTA projection system that codes the intensity of incentive motivation, and that the higher the reactivity of the dopamine system, the more sensitive to reward incentives, and the higher the positive emotionality score. — Depue & Collins, 1999, 『Behavioral and Brain Sciences』
DeYoung (2013) further elaborated that the comprehensive function of the dopamine system is **"exploration,"** with salience-coding dopamine neurons driving cognitive exploration (openness/intellect) and value-coding dopamine neurons driving behavioral exploration (extraversion). In Fisher et al.'s FTI (Fisher Temperament Inventory) fMRI study, the curiosity/energy dimension correlated with substantia nigra activity, confirming that this dimension reflects the activity of the dopamine system.
These studies support the connection of "high dopamine reactivity = extroverted/exploratory," which superficially corresponds to the yangyin temperament in Sasang medicine.

3-4. The Seongjeong Theory of Sasang Simhak: Levels That Neurotransmitters Cannot Capture

In Sasang Simhak, each constitution has an antagonistic structure of seong (性) and jeong (情). Seong (性) refers to mibaljiSeong (未發之性) — the essence of human existence meaning "the will to live, the drive to live" — and jeong (情) refers to ibaljijeong (已發之情), the actual driving force that emerges from seong. These are called hoseongjiSeong (好善之性) and oakjijeong (惡惡之情): seong is the superior function that loves goodness, and jeong is the secondary function that manifests defensively, hating evil. — Taeyul (Kim Do-sun), 『Sasang Simhak: Commentary on the Theory of Expansion』

The seongjeong arrangement by constitution is as follows. Taeyangin: ae-seong (哀性) - no-jeong (怒情); soyangin: no-seong (怒性) - ae-jeong (哀情); taeumin: hui-seong (喜性) - nak-jeong (樂情); soeumin: nak-seong (樂性) - hui-jeong (喜情). In each constitution, the innate superior function (seong) and the defensive secondary function (jeong) antagonize. — Taeyul (Kim Do-sun), 『Sasang Simhak Jeonmun: 四象心學』

Here a critical problem arises. The no-seong (怒性) of soyangin — the tendency to step forward when seeing injustice — overlaps with the salience detection of the dopaminergic system. Yet ae-jeong (哀情) as jeong can also be translated as a state where dopamine prediction error is chronically negative — frustration where expectations are high but reward is insufficient. Taeumin's nak-jeong (樂情, greed/accumulation) directly conflicts with the underlying "GABA-type" framing. Behavior involving gluttony, material accumulation, and wanting to eat and possess more is a typical pattern of the nucleus accumbens dopamine reward circuit.

More fundamentally, from the perspective of the dopamine reward circuit, the "warm glow" when helping others and receiving praise, and the pleasure when displaying oneself and receiving recognition, are the same dopamine release. At the molecular level, altruistic motivation and self-aggrandizing motivation are indistinguishable. The phenomenon Jema Yi captured — "what seemed like virtue turned out to be a camouflage of jeong" — cannot be explained by neurotransmitters, since both involve the same dopamine, making explanation itself impossible.

3-5. The Dual-Pathway Model of Olfaction: Circuit Selection as the Solution

An analogy that can resolve this deadlock lies in the olfactory system. Even when the same odor molecule binds to olfactory receptors, it splits into two pathways. One is the subcortical pathway that goes directly from the olfactory bulb to the amygdala-hypothalamus, where smelling a rotten odor triggers nausea without conscious judgment. The other is the cortical pathway via the orbitofrontal cortex and hippocampus, where contextual memory and cognitive evaluation occur — such as "this smell resembles my grandmother's house." Same molecule, same receptor, but completely different pathway and function.

The seongjeong structure of Sasang Simhak is isomorphic to this. When soyangin reacts in the face of injustice, taking the amygdala-hypothalamus direct pathway is no (怒) — threat detection, sympathetic activation, aggressive behavior. When the same stimulus takes the prefrontal-temporal lobe-mediated pathway, it reads the context, considers the other party's perspective, and judges how it is right to act in this situation — this is ui (義). Dopamine is released in both pathways. At the molecular level, they are the same. But which circuit is taken determines whether one is instinct (jeong) or virtue (seong).

Therefore, Jema Yi's statement that "seong must control jeong" is structurally equivalent to saying that the cortical pathway must regulate (top-down regulation) the subcortical pathway, which is exactly the same frame as cognitive reappraisal in modern emotion regulation research.

3-6. The Range That Hard-Coding Penetrates: Constraints on Plasticity and the Attractor Basin

The cortex's acquired plasticity does not have infinite degrees of freedom. The structure of the prefrontal cortex, cortical thickness, synaptic density, and myelination speed themselves have genetic biases, and these biases determine which direction of learning is easy and which direction is difficult. The strength of prefrontal-amygdala connectivity correlates with individual differences in emotion regulation capacity, and while this connectivity is influenced by both genetics and experience, the variable range itself differs by individual.

This is the neuroscientific basis for why Jema Yi considered constitution to be "immutable." Since hard-coding exists not only at the subcortical level but also constrains the range of plasticity at the cortical level, no matter how much one changes postnatally, those changes occur within certain boundaries. Dynamic changes occur innumerably, but the space of possible changes (state space) itself has a different shape for each constitution.

Mathematically expressed, each Sasang constitution forms a different **attractor basin**. The state space of soyangin and the state space of soeumin differ in the range of trajectories they permit, and no matter how complex the dynamic changes within each basin, they do not leave the basin. This is the logical basis for Jema Yi's constitutional classification — that all people differ yet converge to four types.

4. Cross Reading (Discussion)

Comparing the explanatory power of neurotransmitter typology and the seongjeong theory of Sasang Simhak:

Category	Neurotransmitter Typology (WM)	Sasang Simhak Seongjeong Theory (KM)
Core mechanism	Individual differences in dopamine/GABA reactivity	Seong(性)-jeong(情) antagonistic structure + circuit selection
Explanatory range	Behavioral phenotype (temperament, reward sensitivity)	Behavioral phenotype + camouflage structure of motivation + cultivation theory
Limitation	Cannot distinguish motivational self-deception	Does not present molecular-level mechanisms
Corresponding level	Subcortical hard-coding	Subcortical + entire range of cortical plasticity
Constitutional immutability	Genetic neurotransmitter bias	Structural constraints of state space
Postnatal change	Limited (centered on drug intervention)	Changing circuit selection habits through cultivation (修養)

The key intersection is this. Neurotransmitter typology partially captures the hard-coding level (subcortical temperamental bias) of Sasang constitution, and at this level, "yangyin = dopamine, eumyin = GABA" holds approximately.

However, what Sasang Simhak is truly interested in is not this hard-coding.
Which circuit is selected from the same hardware — that is the core of the seongjeong theory, and it is entirely the postnatal work of the cortex.

This is precisely the point at which Jema Yi emphasized cultivation (修養). Hard-coding (neurotransmitter bias) cannot be changed, but the habit of circuit selection can be changed. One cannot lower soyangin's dopamine reactivity itself, but cultivation (수양) is the training that increases the probability of taking the cortical route (ui, 義) rather than the subcortical direct route (no, 怒) when that reactivity flares up.

Therefore, to translate Sasang constitution into modern science, one must shift from typology at the neurotransmitter level to the frame of dynamic regulation between cortical and subcortical circuits and individual differences in its plasticity.

5. What Is Not Yet Known (Limitations & Future)

The limitations of this study are as follows.
First, the Sasang constitution-Braverman correlation study by Lee et al. (2015) is a pilot study of 142 subjects, and independent validation of the construct validity of the BNA itself is lacking.

Second, the translation from the seongjeong theory of Sasang Simhak to the circuit selection model is a theoretical frame proposed in this study, and direct experimental data supporting this does not yet exist.

Third, the attractor basin model remains at the metaphorical level, and to define it mathematically, variable selection and dynamical modeling quantitatively describing the state space of each constitution would be required.

Fourth, the dopamine-GABA co-release study (Patel et al., 2024) was conducted in mouse striatum, and direct confirmation in humans has not yet been achieved due to technical constraints.

Fifth, it is in principle extremely difficult to neuroscientiifically verify Sasang Simhak's problem of "motivational self-deception" — the observation that seong (性) may be a camouflage of jeong (情).
Additional Research Questions:

Are there significant differences in resting-state functional connectivity by Sasang constitution, particularly in prefrontal-amygdala connectivity patterns?
When dopamine synthesis capacity and GABA concentration by Sasang constitution are directly measured via PET/MRS, do the correlations of the BNA-based pilot study replicate?
Are differences in prefrontal-subcortical circuit regulation (top-down regulation) efficiency observed between individuals of the same constitution who differ in cultivation level?
When tracking the "immutability" of Sasang constitution in a longitudinal study, do individual state changes remain within the boundaries predicted by the attractor basin model?
Do individual differences exist in the ratio of dopamine-GABA co-release and the efficiency of the autoinhibition mechanism, and do these correlate with temperamental bias?

6. Source Citation Cards (References)

Source 1 [WM]

Source: GABA co-released from striatal dopamine axons dampens phasic dopamine release through autoregulatory GABAA receptors
Author/Year: Patel JC et al., 2024, 『Cell Reports』
DOI: 10.1016/j.celrep.2024.113834 | PMID: 38431842
Reliability: high
Key point: Striatal dopamine axons co-release GABA, which acts as a first responder autoinhibiting phasic dopamine release through GABAA receptors

Source 2 [WM]

Source: Neurobiology of the structure of personality: dopamine, facilitation of incentive motivation, and extraversion
Author/Year: Depue RA, Collins PF, 1999, 『Behavioral and Brain Sciences』
PMID: 11301519
Reliability: high
Key point: Dopamine codes the intensity of incentive motivation, and functional variation in VTA dopamine projections determines individual differences in extraversion

Source 3 [WM]

Source: Dopaminergic foundations of personality and individual differences (Special Issue Editorial)
Author/Year: Wacker J, Smillie LD, 2015, 『Frontiers in Human Neuroscience』
Reliability: high
Key point: The comprehensive function of the dopamine system is "exploration," with cognitive and behavioral exploration driven by different dopamine neurons

Source 4 [KM]

Source: A Pilot Study of Psychological Traits in the Sasang Constitution According to the Braverman Nature Assessment
Author/Year: Lee S, Yu JS, Lee S, 2015, 『Journal of Pharmacopuncture』
DOI: 10.3831/KPI.2015.18.035 | PMID: 27547483
Reliability: medium (pilot study, 142 subjects, BNA validity unverified)
Key point: Soyangin-dopaminergic type (43.2%), taeumin-GABAergic type (50.0%), soeumin-GABAergic type (57.1%) correlation. Yangyin-dopamine, eumyin-GABA correspondence P=0.017

Source 5 [KM]

Source: Sasang Simhak Jeonmun (四象心學)
Author/Era: Taeyul (Kim Do-sun), modern interpretation
Reliability: high (primary text of Sasang Simhak original interpretation)
Key point: Seong(性) = mibaljiSeong (好善之性), jeong(情) = ibaljijeong (惡惡之情). Constitutional seongjeong antagonistic structure: taeyangin ae-seong-no-jeong, soyangin no-seong-ae-jeong, taeumin hui-seong-nak-jeong, soeumin nak-seong-hui-jeong

Source 6 [KM]

Source: Commentary on Expansion Theory: Roles of Seong, Jeong, Sim, Gi, and Hui-No-Ae-Nak
Author/Era: Taeyul (Kim Do-sun), modern interpretation
Reliability: high
Key point: Structure of hoseongjiSeong and oakjijeong. Seong is the superior function of innate character traits; jeong is the defensive secondary function. The core of constitutional diagnosis is the observation of "which function one relies on to respond to situations"

Research Information: DJD Korean Medicine Research System | 6 Sub-Questions | 8 Searches/Queries | 2026-03-26

From Neurotransmitters to Circuit Selection: Modern Neuroscientific Reinterpretation of Sasang-Simhak Seongjeongnon

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