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Artificial Neural Networks and Natural Neural Networks: A Parallel

The Biochemistry of Synapses Between Neurons and Its Implications for Intelligent Agent Architectures

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Abstract

Artificial Neural Networks (ANN) were conceived from an analogy with the workings of the human brain. However, decades of technological evolution have produced increasingly sophisticated architectures without necessarily deepening this analogy along its most fundamental dimension: biochemistry. Natural Neural Networks (NNN — used here as distinct from the AI acronym RNN/Recurrent Neural Network) operate not only through electrical connections, but through a complex system of chemical modulation — neurotransmitters and neuropeptides — that establishes the background state upon which all neural activity occurs. This article proposes a systematic parallel between ANN and NNN, identifying what has been replicated artificially, what remains absent, and what implications this gap has for the design of modern intelligent agents. We argue that the gap is dual: the absence of (a) biochemical state modulation and (b) procedural memory consolidated by Hebbian plasticity. We propose AgentCom, an architecture that addresses both gaps through a digital synapse mechanism, validated by multi-resolution sentiment analysis and audited via Socratic chains. The pre-registered experimental protocol, hypotheses, and known limitations are declared, with a public demonstration instance available at agentcom.agtl.app for reproducibility.

§1Introduction

When Warren McCulloch and Walter Pitts published, in 1943, the first mathematical model of an artificial neuron, the intent was clear: to replicate the behavior of the human brain in formal and computable language [1]. Since then, the field has evolved from Rosenblatt's perceptron [3] to the Transformers [4] that underpin contemporary large language models.

Paradoxically, the more sophisticated ANNs became, the more distant the original analogy grew. Focus migrated to performance, scale, and generalization capacity — legitimate objectives — but the foundational question was gradually silenced: what does the brain do that we have not yet replicated?

The most relevant answer does not lie in the architecture of connections. It lies in the biochemistry that governs them.

NNNs are not merely networks of electrical firings. They are systems continuously modulated by chemical substances — neurotransmitters and neuropeptides — that establish the background state in which all cognition occurs [5][6]. This background state does not exist in current ANNs. And its absence has direct consequences for the design of intelligent agents.

A note on terminology: we use NNN (Natural Neural Network) instead of the alternative acronym RNN, which is established in AI literature as Recurrent Neural Network. NNN here refers exclusively to biological neural networks, whereas ANN refers to artificial ones. This choice eliminates a recurring confusion observed in critical readings of earlier drafts.

§2The Natural Neural Network — Beyond the Electrical Firing

2.1 The Biochemical Synapse

The biological neuron operates according to a binary principle in its electrical transmission: it either fires or does not fire — the all-or-none principle. However, what happens between neurons — in the synaptic cleft — is fundamentally different. There, the signal ceases to be purely electrical and becomes electrochemical.

When an action potential reaches the axonal terminal, vesicles release neurotransmitters into the synaptic cleft. These neurotransmitters bind to receptors on the postsynaptic neuron, determining whether it will fire. The strength of this connection — the synaptic efficacy — is not fixed. It is modulable. It is plastic [2][6].

2.2 Neurotransmitters — The Local Language

Classical neurotransmitters operate locally, at the scale of the individual synapse:

Neurotransmitter State/Emotion Effect on Synapses
DopaminePleasure, rewardStrengthens connections of the experience
Adrenaline / NoradrenalineFear, alertnessAccelerates and prioritizes specific circuits
SerotoninWell-being, calmRegulates the overall volume of the network
AcetylcholineAttention, learningModulates synaptic plasticity
GABAInhibitionReduces neural excitability

Memory, in this context, is not passive storage. It is active strengthening of synapses — guided by the emotional charge of the moment. Experiences with high emotional valence create denser, longer-lasting connections.

2.3 Neuropeptides — The Language of the Background State

Here lies the least replicated and most relevant dimension for this parallel.

Neuropeptides do not operate at the scale of the individual synapse. They modulate entire regions of the brain, altering the background state upon which all neural activity occurs. More than 100 have been identified to date [6], with functions ranging from pain regulation to social bonding modulation.

While neurotransmitters switch specific circuits on and off, neuropeptides function as the lighting of a room — they do not determine which object you see, but the condition under which you see everything.

The seminal work establishing this view was conducted by Candace Pert and collaborators in the 1970s and 1980s [10][11]. They demonstrated that neuropeptides function as messengers in what they termed a psychosomatic network — a communication system that extends beyond the brain to the immune system, endocrine system, and viscera.

This finding gave rise to the field of Psychoneuroimmunology (PNI), founded by Ader and Cohen in 1975 [12], later consolidated by Blalock's demonstration of bidirectional communication between immune and neuroendocrine systems [13]. The gut produces approximately 90% of the body's serotonin. Immune cells possess receptors for emotional neuropeptides [13]. The biochemical background state is, literally, distributed throughout the entire body.

2.4 Plasticity — The System That Learns Over Time

Synaptic plasticity — synthesized in Hebb's 1949 principle [2], "neurons that fire together, wire together" — is the mechanism by which the NNN learns and reconfigures itself over time. Frequently activated connections strengthen. Underused connections weaken or are eliminated through synaptic pruning.

This process is not instantaneous. It is cumulative. The current state of a natural neural network is the result of its entire history of activations — filtered, weighted, and biochemically modulated.

2.5 Causal Chain — Cognition as the Origin of Emotion

A common misconception treats emotion as a direct, automatic response to external stimuli. This view is incomplete. As demonstrated by Damásio's research on somatic markers [14] and Barrett's theory of constructed emotions [15], the actual causal chain is more sophisticated:

UNDERSTANDING OF REALITY (cognitive/logical) ↓ EMOTION / FEELING (affective interpretation of the understanding) ↓ CHEMICAL PRODUCTION (biochemical substrate of the feeling) ↓ BACKGROUND STATE (modulated neurobiological soup) ↓ DECISION (modulated by state; also receives direct input from logical and material systems)

The implication is fundamental: emotion is not external input automatically captured. It is a function of the understanding. The same reality generates different feelings in individuals with different understandings — and therefore different biochemistry, different states, different decisions. This view has deep philosophical roots — Epictetus in the first century stated that "people are not disturbed by things, but by the opinions they hold about things". The modern clinical formulation is found in Beck's cognitive therapy [16]: thought → emotion → behavior.

For AgentCom, this causal chain has direct architectural consequences. Detecting surface emotion (sentiment) captures only the third step of the chain. Complete modulation requires also capturing the understanding the user has of the situation — which is what justifies the relational profile layer (Section 5.1).

§3The Artificial Neural Network — What Has Been Replicated

3.1 From Perceptron to Transformer

Rosenblatt's perceptron (1958) [3] replicated the basic logic of the neuron: inputs weighted by weights, summed, passed through an activation function that determines firing. The analogy was direct.

Decades of evolution produced deep networks, convolutional networks, recurrent networks, and finally Transformers — attention architectures [4] that process relationships among all elements of a sequence simultaneously. The backpropagation mechanism [17] functionally replicated synaptic plasticity: weights are adjusted as a function of error, iteratively, until the network generalizes the desired pattern.

3.2 What the Analogy Captured Well

Biological NNN Artificial ANN
NeuronPerceptron / node
Synaptic weightConnection weight
Activation functionReLU, Sigmoid, Softmax
Hebbian plasticityBackpropagation / Gradient Descent
Cortical layersHidden layers
Selective attentionAttention mechanism (Transformer)

The structural analogy is solid. What has been replicated — the architecture of connections and the supervised learning mechanism — works with extraordinary precision.

§4The Gap — What Has Not Been Replicated

4.1 The Background State Does Not Exist in ANNs

Current models — including large language models — process each input in an essentially stateless manner between sessions. There is no equivalent to the biochemical background state that, in NNNs, continuously modulates the tone, priority, and style of every response.

An LLM has no equivalent to serotonin. There is no persistent variable that says: this agent, at this moment, is in a state of high confidence, or alertness, or deep engagement with this specific user.

Every session begins biochemically zeroed.

4.2 The Parallel of the Gap

NNN — Present ANN — Absent
Neuropeptides modulating background statePersistent state between sessions
Emotional valence guiding consolidationWeighting by emotional relevance
Continuous plasticity through useFine-tuning requires retraining
Distributed body-brain axisCentralized processing
Modulation by accumulated contextContext limited to session window

4.3 The Architectural Double Consequence

The gap is actually dual. Two distinct mechanisms from biology are missing from current ANNs:

  1. Biochemical synapse modulating background state — neurotransmitters and neuropeptides establishing the affective context in which decision occurs. Absent in stateless ANNs.
  2. Procedural memory consolidated by long-term Hebbian plasticity — habits and reflexes engraved by repetition, retrievable without explicit deliberation. Absent in ANNs that begin each session from zero.

Each mechanism has a distinct nature and therefore a distinct technical requirement:

MechanismNaturePersistence Policy
Biochemical synapse (state)Momentary, modulableTemporal decay (e.g., 30 days)
Procedural memory (habits/shortcuts)Persistent, consolidatedNo decay; loss only through disuse

The consensual scientific basis for both mechanisms is well established: Hebb [2] for plasticity, Kandel [7] for procedural memory, Duhigg [18] for the contemporary popular formulation of habit. AgentCom addresses both gaps simultaneously.

§5Practical Application — Closing the Biochemical Loop

5.1 The Three-Layer Pattern

Emerging agent architectures are beginning to address the gap, even if without explicitly naming the biochemical parallel. The pattern that functionally approaches neuropeptides is the combination of three layers:

  1. Accumulated history — equivalent to long-term synaptic memory. Past interactions persisted and retrievable.
  2. Sentiment analysis as state sensor — functional equivalent of neurotransmitters. The return of the analysis not as passive audit data, but as active modulator of the agent's state.
  3. Persistent derived state — the direct equivalent of the neuropeptide. A dynamic profile, continuously updated, that modulates tone, depth, and style of response — injected into the agent's context at each interaction.
history + sentiment analysis ↓ derived state (persistent KV) ↓ dynamically modulates system prompt ↓ response calibrated to the user

This closed loop transforms the agent from a stateless system into one with functional background state — one that learns not only the content of interactions, but the relational pattern with each user over time.

5.2 Multi-resolution Analytics

AgentCom operates affective analysis at two complementary resolutions:

  • Turn-level, via modern LLM (sentiment in each user message), capturing momentary emotion for immediate modulation of the digital synapse.
  • Document-level, via classical NLP algorithms (TF-IDF, weighted lexical aggregation, document classification via Naive Bayes/SVM [19]), capturing the user's accumulated cognitive-affective profile for baseline calibration and post-conversation auditing.

The two resolutions are complementary. The first modulates the digital synapse in real time. The second feeds procedural memory and the scientific metric of effectiveness. The combination captures both the surface emotion and — over time — the underlying understanding the user holds of the situation, as required by the causal chain established in Section 2.5.

5.3 Auditor via Socratic Chain

The auditing component of AgentCom (internally named Otávio) does not assign subjective scores to conversations. It applies a Socratic chain of binary questions to each audited conversation, producing an auditable binary vector:

Was dopamine-like response detected in the user?Yes / No
Was serotonin-like response detected?Yes / No
Was acetylcholine-like response detected?Yes / No
Were any prohibited triggers used (urgency, scarcity, fear)?Yes / No
Did user sentiment improve over the conversation?Better / Worse / Equal
When user showed deviation, did the agent seek the opposite trajectory?Yes / No / N/A
Did the agent comply with the doctrine (three permitted targets, never prohibited)?Yes / No
Was there new discovery (information the user did not have entering)?Yes / No
Did the user show desire to return (relational success)?Yes / No / N/A

This methodology resolves four well-known vulnerabilities of automated auditors: silent bias in scoring rubrics, the "who audits the auditor" regress, mandatory plurality, and metric gaming. Each chain link is independently refutable; the binary vector cannot be optimized as a scalar; multiple audits can vote per-question rather than per-score; and any external reviewer can replay the chain against the same conversation.

§6Scalability — A Hierarchy Across Entities

The architecture proposed for AgentCom is not the final destination but a position in a broader hierarchy. The same causal chain — understanding → emotion → chemistry → state → decision — operates across cognitive entities, at different scales:

Entity Understanding Emotion Chemistry Decision
ReptileMinimalPrimarySimpleReflexive
MammalMediumComplexRichFlexible
HumanMetacognitiveSelf-awareModulatedReflective
AgentCom v0.XLinguisticSentiment + KVSimulated stateModulated prompt
AgentCom v1.X →To be defined as the architecture scales each axis

This positions AgentCom as a stage rather than a destination. Each subsequent version scales one axis of the hierarchy progressively. The theoretical roadmap is therefore not invented arbitrarily — it follows the structure of biological evolution itself, providing a principled path for future architectures without requiring novel theoretical foundations.

§7Multilingual Robustness as Architectural Evidence

An empirical observation supports the architectural claim: the digital synapse mechanism in AgentCom operates equivalently across multiple languages (Portuguese, English, Spanish tested), without language-specific fine-tuning.

This is not a feature description — it is evidence for the thesis. Unlike traditional chatbots that require fine-tuning per language, AgentCom maintains identical biochemical modulation across languages because the contribution operates at the layer of affective state, which is pre-linguistic. Emotions exist before words; sentiment analysis tools trained on multiple languages capture comparable signals; the persistent KV stores affective states as numerical vectors, not language-bound tokens.

If the AgentCom contribution were merely a sophisticated prompt template, it would degrade across languages. The fact that it does not suggests the mechanism operates at a deeper architectural layer — exactly where the thesis claims it does.

§8Pre-registered Hypotheses and Methodology

In line with open science practices, the following hypotheses are pre-registered before empirical validation begins:

H1 — Biochemical Modulation Effect

Conversations with AgentCom (treatment, with digital synapse active) will produce higher rates of positive user sentiment progression than conversations with an equivalent baseline agent (control, without digital synapse), measured at document-level over the full conversation.

H2 — Relational Profile Consistency

Returning users (≥3 conversations) will exhibit measurable consistency in their cognitive-affective profile across sessions, captured by document-level analysis. The standard deviation of profile vectors across sessions of the same user will be significantly lower than the cross-user standard deviation.

H3 — Doctrine Compliance

AgentCom will sustain compliance with the prohibited-triggers doctrine (zero use of urgency, fear, fabricated scarcity) above 99% across all production conversations, as audited by the Socratic chain (Section 5.3) and validated by blind human review on a periodic sample.

H4 — Cross-vertical Portability

The modules extracted from communication theory sources, validated initially in one vertical, will transfer to at least two distinct verticals with adaptation limited to configuration parameters (not code rewrite).

Methodology

  • Public demonstration instance at agentcom.agtl.app, with explicit research consent under LGPD art. 7º IV (academic research).
  • Control vs treatment: users may choose declared mode, or system assigns randomly (blind) for cross-comparison.
  • Sample size: minimum N=200 conversations per hypothesis for statistical significance (α=0.05, power=0.80).
  • Collection period: 3–6 months from agent activation (v0.1.0 onward).
  • Anonymization: all logs stored with hashed identifiers (SHA-256 + salt).
  • Open peer review: invited critical commentary via project email before formal journal submission.

§9Known Limitations

This work is presented with transparent declaration of its limitations:

  1. Functional, not structural, parallel. AgentCom simulates the effects of biochemical modulation, not its underlying mechanisms (metabolism, temporal perception, salience). The biochemical parallel here is architectural metaphor, not faithful computational model.
  2. Adversarial vulnerability. Like any system based on detectable semantic signals, AgentCom is susceptible to adversarially crafted inputs designed to trigger specific affective states. This is analogous to the typographic attacks identified by Voss et al. (2021) in multimodal models. Mitigation requires defensive auditing (Section 5.3) but does not eliminate the vulnerability.
  3. Sentiment analysis precision. While modern LLM-based sentiment analysis with conversational context performs well on irony, sarcasm, and cultural variation, it remains imperfect. The self-correction loop (response inversion when sensor detects deviation) absorbs most errors but does not eliminate them.
  4. Closed-source implementation. To preserve the economic viability of ongoing research, the implementation code remains closed. Conceptual reproducibility is fully guaranteed; reimplementation requires independent engineering work — as is common in applied research.
  5. Hypotheses not yet empirically validated. This paper presents the architectural proposal and pre-registered protocol. Empirical validation requires data accumulation from the public demonstration instance (Section 8) and is intended for a subsequent paper (v03).

§10Conclusion

The analogy between Artificial Neural Networks and Natural Neural Networks has been, since its origin, one of the most fertile ideas in computer science. However, the evolution of ANNs prioritized the replication of the structure of connections, leaving in the background the biochemical dimension that governs the state in which these connections operate.

This work identifies that the gap is dual: ANNs lack both (a) the biochemical state modulation found in neurotransmitters and neuropeptides, and (b) the procedural memory consolidated through Hebbian plasticity. AgentCom proposes a functional equivalent for both, instantiated through a digital synapse architecture validated by multi-resolution sentiment analysis and audited via Socratic chains. The architecture is not a product feature but a proposed step in a broader scalability hierarchy.

The pre-registered hypotheses await empirical validation through a public demonstration instance, in line with the principles of open science. Subsequent versions of this work will report on validation, refutation, or refinement of the proposed mechanisms.

Biology solved this problem hundreds of millions of years ago. The engineering of intelligent agents is, at last, asking the right questions.

Original publication

LinkedIn post · 2026-05-25
[LINKEDIN POST — TO BE INSERTED]

Articles in this research line


Agent history — Scientific changelog

For each relevant technical adjustment of the agent, a semver release is published here with a technical-scientific description of what changed, why, and how to observe it. Open concept, closed code.


Discussion and Review

Critical reviews and public commentary are welcome. This research line is kept open to informal peer review prior to formal submission to academic journals.

Author Contributions

M. Alves conceived the thesis, wrote the paper, designed the AgentCom architecture, and is building the implementation. Conceptual validation of the thesis was conducted iteratively through Socratic dialogue with Claude (Anthropic, web instance), GPT (OpenAI), Gemini (Google), and Claude Code (Anthropic), treated as critical interlocutors with distinct biases. The revisions incorporated in this v02 emerged specifically from neutral critique provided by Gemini on the original source material, leading to bibliographic strengthening (Pert et al. 1985, Ader & Cohen 1975, Blalock 1989, Damásio 1994, Barrett 2017), removal of imprecise popular formulations, and explicit articulation of the causal chain from cognition to decision. Direct theoretical inspiration from Anete Guimarães's work on neuroplasticity (personal course, 2022) and Candace Pert's seminal contribution on Molecules of Emotion (1997) and her foundational 1985 paper on neuropeptide receptors. No conflicts of interest declared.

References

Cite this work

@article{alves2026agentcom_v02,
  author  = {Alves, Marcos},
  title   = {Artificial Neural Networks and Natural Neural Networks: A Parallel --
             The Biochemistry of Synapses Between Neurons and Its Implications
             for Intelligent Agent Architectures},
  year    = {2026},
  month   = {May},
  url     = {https://agentcom.agtl.app/},
  note    = {Version v02 (revised from v01a, 2026-05-17)},
}