THE CORTEX: NEUROBIOLOGICAL STRUCTURE AND THE DUAL NATURE OF THE PERCEPTUAL BRAIN

 THE CORTEX: NEUROBIOLOGICAL STRUCTURE AND THE DUAL NATURE OF THE PERCEPTUAL BRAIN

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Abstract

​The cortical structure is not merely a biological data processor; it is a unique system bearing the individual's perceptual signature. This article analyzes the six-layered structure of the cortex, its neuronal function, and its connection to person-specific synaptic patterns, supported by scientific literature. Furthermore, it argues that the cortical function, built upon a biological foundation, must also be evaluated on the conscious plane within the framework of predictive perception and embodied cognition.

​1. Introduction: Neuronal Patterns, Neuroplasticity, and Individual Differences

​The human cortex contains approximately 16 billion neurons, with trillions of synaptic connections established between them [1]. Each individual's cortical structure is formed by the combination of a genetic basis and environmental experiences. These trillions of connections are continuously reshaped through the dynamic process known as neuroplasticity.

​This synaptic variety ensures that every individual carries a unique neuronal signature [2]. Repeated experiences and learning processes strengthen specific synaptic pathways according to the Hebb's rule ("Neurons that fire together, wire together"). This leads each person to develop a unique neuronal connectome (connection map), creating a perceptual system that is unique at both structural and functional levels.

​2. Structural Layers and Functional Organization of the Cortex

​The histological structure of the cortex consists of six layers (laminae). This horizontal stratification is integrated through cortical columns, which are vertically organized and considered the fundamental unit of information processing:

​Lamina I (Molecular Layer): Contains few cells; provides the high-level connections for cortical integration.

​Laminae II and III (External Granular and External Pyramidal): Responsible for cortico-cortical information flow and higher-order cognitive processes (memory, integration).

​Lamina IV (Internal Granular): Dense in the primary sensory cortex, it directly receives excitatory thalamocortical inputs (sensory information) [3].

​Lamina V (Internal Pyramidal): The main output layer of the motor cortex; houses large pyramidal cells and transmits motor commands to subcortical regions.

​Lamina VI (Multiform): Establishes bidirectional connections with the thalamus and other cortical areas, managing feedback loops.

​This hierarchical structure indicates that the cortex is linked to both lower-level processing (sensory input) and higher-level cognitive functions (decision-making, language, attention) [4].

​3. The Biological Brain and the Perceptual Brain: Duality and Prediction

​In explaining brain functions, neuroscience focuses on chemical and electrical transmission mechanisms (The Biological Brain). However, the brain also functions as a generator of perception, integrating experience, expectation, and structures of meaning (The Perceptual Brain) [5].

​Theoretical Framework: The Perceptual Brain does not passively record the world as a receiver; instead, it constantly attempts to predict sensory inputs and minimize prediction error. This dynamic is strongly associated with Karl Friston's Free Energy Principle (FEP). The cortex strives to build internal models that best predict the external world.

​This interpretive role supports Varela and Thompson's theory of "The Embodied Mind" [6]. Cognition is not solely shaped by neuronal activity but by the continuous interaction of the body-mind-environment whole; the Perceptual Brain is an expectation-driven interpreter built upon a biological foundation.

​4. The Cortical Signature: Uniqueness of Neuronal Identity

​Epigenetic interactions and environmental factors enable the cortical structure to be reshaped over time through synaptic plasticity [7]. This dynamic leads to differences in the neuronal connection map between individuals, causing each cortex to carry a person-specific "neuronal identity."

​Functional magnetic resonance imaging (fMRI) studies have shown that functions like language processing, empathy, and memory activate different cortical regions in different individuals [8]. More importantly, this person-specific neuronal identity is observed not only when performing a specific task but also during the resting state.

​Individual differences in Default Mode Network (DMN) connectivity prove the uniqueness and continuity of the individual's self-referential cognitive processes (i.e., the perception of "self") at the cortical level.

​5. Perception of Time and Structuring of Information

​The brain does not merely receive incoming information passively; it processes, formats, and records it instantly into the past. Therefore, time, from a neuroscientific perspective, is not linear but a dynamic phenomenon structured by the cortex [9].

​This is closely related to the prefrontal cortex's function of sequencing events and its ability for proactive coding of future events. Immediately after new information is processed in the cortex, it begins to be integrated into long-term memory via long-term potentiation (LTP) mechanisms, instantly becoming the "past." This phenomenon demonstrates that the cortex actively structures time itself [10].

​6. Artificial Systems and the Human Cortex: Simulation or Replication?

​Neural tissue simulations developed through nanobiological engineering are currently being attempted to be mimicked by "neural networks" (Artificial Neural Networks - ANNs). However, these systems are far from being a complete replication of the human brain.

​Current artificial intelligence models (especially deep learning) cannot mimic the dynamics of differential plasticity caused by synaptic plasticity and complex neurochemical modulation (e.g., by neurotransmitters like dopamine and serotonin). Even more advanced approaches like Spiking Neural Networks (SNN) fall short of replicating the cortex's ability for continuous self-organization and unsupervised learning [11]. Artificial systems simulate the human brain but cannot perceive or create an experience-based structure of meaning like it does.

​7. Conclusion: The Brain is a Universal Mapper

​The cortex is not just an area through which neural transmissions pass; it is the prediction-driven structural center where the individual's entire perceptual, emotional, and temporal life is shaped. The cortex of every individual is a center of consciousness that remaps the universe with its unique history, experience, and neurochemical structure. This center functions as a biological algorithm that shapes the flow of time and the meaning of life, making every individual both biologically similar and perceptually unique.

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​References

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