The Harmonics of the Brain: A symphony of Electrical Activity

Cortico-Columnar Brain Waves

David Slater

Abstract

The human brain is an incredibly complex organ capable of processing vast amounts of information simultaneously. One way to conceptualize the brain’s function is by considering it as a series of layers, each of which processes neural signals at different frequencies. This layered approach, synchronized through harmonic oscillations, offers an intriguing framework for understanding how the brain integrates and responds to both internal and external stimuli.

The layers

At the base of the brain’s layered architecture is the brain stem, which is responsible for regulating autonomic functions such as heart rate, breathing, and digestion. These functions are fundamental to survival and are managed without conscious effort. The electrical activity in the brain stem primarily operates at a low base frequency, around 3 Hz, corresponding to delta waves. These delta waves represent slow, rhythmic oscillations that are essential for maintaining the body’s homeostasis.

Delta waves are not only present in the brain stem but also dominate during deep, restorative sleep, where the brain and body undergo critical maintenance and repair processes. The rhythmic oscillations at this level provide a stable foundation upon which more complex brain functions are built.

The next layer of brain function involves the processing of sensory signals from the external world. This layer operates at the next harmonic frequency, approximately 6 Hz, associated with theta waves. Theta waves are often observed during light sleep, relaxation, and the initial stages of memory encoding. They are particularly prevalent in regions like the hippocampus and are crucial for processing sensory input and navigating the environment.

The thalamus, a central relay station for sensory information, plays a key role in this layer. It receives sensory signals from the outside world—such as visual, auditory, and tactile stimuli—and relays them to the appropriate cortical areas for further processing. The rhythmic activity of theta waves ensures that sensory information is sampled and integrated in a synchronized manner, allowing the brain to construct a coherent representation of the external environment.

As sensory information ascends through the brain’s hierarchy, it reaches the deeper layers of the cortical columns and structures such as the hippocampus and amygdala. These areas operate at a frequency of around 12 Hz, corresponding to alpha waves. Alpha waves are commonly associated with relaxed wakefulness and play a significant role in integrating sensory input with past experiences stored in memory.

The hippocampus and amygdala, both part of the limbic system, are essential for memory formation and emotional processing. The rhythmic oscillations of alpha waves allow these regions to effectively coordinate their activities, linking sensory information to emotional states and memories. For instance, the hippocampus can process spatial and contextual information, while the amygdala attaches emotional significance to this information. Together, these processes can trigger responses, such as the release of neurotransmitters by the hypothalamus to regulate mood, stress, and arousal.

Moving further up the hierarchy, the cortical columns—particularly those in the frontal and prefrontal cortex—operate at around 24 Hz, corresponding to beta waves. Beta waves are associated with active thinking, attention, and cognitive tasks. At this level, the brain constructs perceptual “pictures” from the processed sensory data, integrating information across different modalities and forming a conscious experience.

The frontal cortex is responsible for higher-order functions, such as decision-making, planning, and problem-solving. The beta wave activity in these cortical columns facilitates rapid communication between neurons, allowing the brain to quickly synthesize sensory input, retrieve relevant memories, and generate appropriate responses. This synchronized activity is crucial for maintaining focus and executing complex cognitive tasks that require precise timing and coordination.

Finally, the outer layers of the cerebrum are involved in executing decisions and sending motor commands. These regions operate at the highest harmonic frequency, around 48 Hz, corresponding to gamma waves. Gamma waves are associated with high-level cognitive functions, such as consciousness, perception, and motor coordination.

The rapid oscillations of gamma waves enable the brain to send quick and precise motor commands to the body, allowing for fast reactions to environmental changes. This high-frequency activity is essential for tasks that require immediate responses, such as catching a ball or navigating a complex environment. Additionally, gamma waves are involved in synchronizing activity across different brain regions, ensuring that sensory processing, decision-making, and motor output are tightly coordinated.

The Cortical Columns of the Cerebrum

The human brain is thus a centre of dynamic electrical activity. At the heart of this phenomenon are the cortical columns—the basic functional units of the cerebral cortex.(Figure 1). These columns are the key players in how the brain processes information, from the sensory perception of the world around us to the execution of precise motor commands and the orchestration of complex cognitive functions like reasoning and conscious thought.

Figure 1 – The neurons of the cortex, stacked in columns

Cortical Columns: The Building Blocks of Brain Function

Imagine the cerebral cortex, the brain’s outer layer, as a vast forest where each tree represents a cortical column. These columns are arranged perpendicularly to the surface of the cortex and stretch across all six layers, much like trees rising from the forest floor to the canopy. Each column contains around 80,000 to 100,000 neurons, tightly packed and interconnected, working together to process specific types of sensory input or motor output.

The structure of these columns allows for specialized processing. For example, in the visual cortex, certain columns are dedicated to detecting specific features such as the orientation of lines or the direction of motion. This specialization extends across various sensory modalities, with columns in different regions of the cortex tuned to different types of input, creating a finely tuned network capable of high-level processing.

The Rhythm of Neural Activity: Neuronal Firing and Oscillations

At the core of the cortical columns’ function is neuronal firing—the rapid electrical impulses known as action potentials that neurons use to communicate. These impulses represent sudden changes in voltage across the neuron’s membrane, triggered by synaptic inputs that can excite or inhibit the neuron. When a neuron fires, it releases neurotransmitters at synapses, which are the points of connection between neurons, further modulating the electrical activity within the column.

But neuronal firing is not random. The brain’s activity is organized into oscillations or brain waves, which are rhythmic patterns of electrical activity that occur at various frequencies, such as alpha, beta, gamma, theta, and delta waves. These oscillations are not just background noise; they play a crucial role in coordinating the brain’s functions, much like a conductor synchronizes the musicians in an orchestra. Local field potentials (LFPs), which reflect the summed electrical activity of a group of neurons, provide a window into this synchronized activity, revealing how different regions of the cortex communicate with each other.

The cerebral cortex is also layered, and each layer contributes to different aspects of sensory processing and cognition. In the sensory cortices, such as the visual, auditory, and somatosensory cortices, columns in the deeper layers (e.g., layers 5 and 6) primarily receive input from the thalamus—a relay station for sensory information. As sensory information ascends through the cortical layers, it reaches the middle layers (e.g., layers 2 and 3), where it is integrated and processed further.

Inter-Columnar Communication and Synchronization

Figure 3 – Intercolumnar Connections (http://blog.agi.io/2015/12/

Moreover, the thalamocortical connections—projections from the thalamus to the cortex—play a vital role in synchronizing oscillations across cortical columns. This synchronization is essential for binding together different aspects of sensory input into a unified perception and for coordinating motor actions in response to sensory stimuli. The rhythmic activity of brain waves helps to synchronize these processes, ensuring that information is processed efficiently and effectively across the brain.

Harmonic Oscillations in the Brain: Layer-Specific Neural Activity and Synchronization

The human brain then operates as a sophisticated network of neural circuits, each functioning at different frequencies to manage a vast array of sensory, cognitive, and motor tasks. These networks are organized in layers, each characterized by distinct patterns of electrical activity, often referred to as brain waves. These brain waves represent oscillatory electrical activity that plays a vital role in how the brain processes information, integrates sensory inputs, forms perceptions, and executes actions. Understanding the organization of these brain waves in relation to the layers of the cerebral cortex can provide profound insights into the mechanisms of brain function and synchronization.

Layer-Specific Brain Wave Activity: A Spectrum of Frequencies

Delta Waves and the Deeper Cortical Layers

Delta waves (1-4 Hz) are the slowest brain waves and are primarily associated with deep sleep and states of unconsciousness. In the cerebral cortex, delta waves are often observed in the deeper layers, such as layers 5 and 6. These layers are heavily involved in the brain’s output functions, projecting signals to subcortical regions and the spinal cord. During states of reduced cortical excitability, such as sleep, the neurons in these deeper layers tend to exhibit lower frequency oscillations, like delta waves, which are crucial for restorative processes and maintaining the body’s autonomic functions.

Theta Waves: Bridging Sensory Input and Memory

Moving up the frequency spectrum, theta waves (4-8 Hz) are typically seen in the context of light sleep, drowsiness, and specific cognitive processes, such as memory encoding and retrieval. Theta rhythms can also be generated in the deeper cortical layers (5 and 6) but are not exclusive to these layers. These waves play a critical role in processing sensory inputs and integrating them with past experiences, aiding in spatial navigation and memory consolidation. The hippocampus, a key structure for memory formation, exhibits prominent theta wave activity, which reflects its role in bridging sensory inputs from the cortex with stored memories.

Alpha Waves and Relaxed Wakefulness

Alpha waves (8-12 Hz) are most commonly associated with relaxed wakefulness and are often observed in the occipital cortex, which is involved in visual processing. These waves can involve multiple cortical layers, particularly layers 2 through 4, which are rich in horizontal connections that facilitate the integration of sensory information. Alpha waves play a crucial role in modulating attention and preparing the brain for active processing, serving as a sort of “idling” rhythm that allows for quick shifts to more engaged states of cognition.

Beta Waves: Active Processing and Cognitive Engagement

Beta waves (13-30 Hz) are faster oscillations linked to active thinking, attention, and motor activity. These waves are not confined to a specific cortical layer but are frequently observed in the motor cortex and other regions involved in high-level cognitive tasks. Beta oscillations often involve both superficial and deep cortical layers, depending on the task at hand. For instance, during motor planning and execution, beta waves help coordinate the activity of neurons across different cortical regions, facilitating precise motor control and cognitive engagement.

Gamma Waves: High-Frequency Synchronization for Complex Processing

At the highest frequency range, gamma waves (30-80 Hz or higher) are associated with high-level cognitive functions, such as attention, perception, and consciousness. Gamma oscillations often involve layers 2 and 3 of the cortical columns, which are crucial for local processing and integration within and between cortical areas. These waves are essential for tasks that require the synchronization of activity across different parts of the brain, such as integrating sensory inputs into a unified perceptual experience or maintaining working memory during complex problem-solving.

Figure 5 – The Functions of the Brain in their  Layers (Slater)

Interactions Between Layers and Frequencies: A Dynamic Network

The brain’s electrical activity is not confined to discrete layers or frequencies; instead, it involves dynamic interactions across multiple layers and regions. This interplay is facilitated by several mechanisms:

• Multi-layer Interactions: Neurons within a cortical column are interconnected across layers, allowing for communication between deeper and superficial layers. For example, gamma oscillations in the upper layers can influence beta or theta rhythms in the deeper layers, creating a coordinated response across the cortical column.
• Oscillatory Coupling: Different frequency bands often interact in a phenomenon known as cross-frequency coupling. This interaction is particularly evident in the hippocampus and cortex during learning and memory tasks, where theta-gamma coupling helps synchronize neuronal activity for effective encoding and retrieval of information.
• Thalamocortical and Corticocortical Interactions: Brain waves also involve interactions with subcortical structures, such as the thalamus, which plays a crucial role in synchronizing oscillations across different frequency bands. The thalamus acts as a relay station, coordinating sensory inputs and sending them to the appropriate cortical areas for further processing.

The Brain as an Harmonic Oscillator: Synchronization and Information Processing

The brain can be thought of as a harmonic oscillator, where different layers operate at various harmonics of a base frequency. For example, autonomic functions regulated by the brain stem might operate at a low delta frequency (around 3 Hz), sensory processing in the deeper cortical layers could occur at a theta frequency (around 6 Hz), and higher cognitive functions in the superficial layers could engage at higher frequencies such as alpha (12 Hz), beta (24 Hz), and gamma (48 Hz).

Figure 6 – These frequencies are essentially the natural harmonics of the base Delta waves (A. F. Rocha)

This hierarchical organization allows the brain to process information efficiently and adaptively:

1. Base Rhythms for Basic Functions: At the foundational level, delta rhythms manage essential autonomic functions, maintaining a stable internal environment. This slow rhythm ensures that basic life-support functions such as heart rate and breathing are reliably maintained without conscious effort.
2. Sensory Sampling and Integration: As the frequency increases to the theta range, the brain samples sensory inputs more frequently, allowing for the integration of information across different sensory modalities. Theta rhythms facilitate the initial stages of processing, particularly in areas like the hippocampus, where sensory inputs are matched with existing memories and context, allowing for a continuous update of the brain’s internal model of the external world.
3. Intermediate Processing and Relaxed Focus: Alpha waves provide a rhythm for relaxed wakefulness and general vigilance, enabling the brain to remain ready for more focused activity. This frequency band supports an optimal state of readiness, balancing between idling and intense focus, making it easier for the brain to shift into higher frequencies as needed.
4. Active Cognitive Processing and Attention: At the beta frequency, the brain engages in more active cognitive processes. Beta waves are essential for tasks that require sustained attention, motor planning, and precise cognitive control. These waves support rapid, flexible processing, enabling quick decision-making and coordination across different regions of the brain.
5. High-Frequency Synchronization for Complex Cognitive Tasks: Gamma waves represent the highest frequency range and are critical for tasks that require high-level cognitive functioning, such as perception, consciousness, and complex problem-solving. Gamma rhythms synchronize the activity of neurons across distant brain regions, integrating diverse types of information to produce coherent thoughts and actions.
6. Transmission and amplification of the oscillations as harmonics of resonant frequencies. These oscillations or fluctuating ion currents in the cortical neurons can induce resonating ion currents in neighbouring neurons if suitable structures. This could explain the waves of activity across multiple centres in the cortex. The neurons of the cortex stacked in columns

Figure 7 – Signal transmission by induced electrical oscillations (Dario Dematties)

Synchronization and Signal Processing: A Bayesian Predictor-Corrector Mechanism

The brain’s layered and harmonic structure is not just a passive framework but a dynamic, predictive system. It operates much like a Bayesian predictor-corrector mechanism, where it continuously generates predictions about incoming sensory information and adjusts these predictions based on real-time sensory input. Otherwise, we would be continually working in the past by the length of time the brain takes to receive and process the sensory signals from its environment.

• Prediction: Each layer of the brain generates predictions about the information it expects to receive, based on past experiences and the current context. For example, the thalamus may predict certain sensory inputs based on ongoing stimuli and relay this information to the cortical columns.
• Correction: As new sensory information is received, these predictions are updated. The deeper cortical layers may process discrepancies between expected and actual sensory inputs at lower frequencies (theta waves), while superficial layers might quickly adjust motor responses or attention at higher frequencies (gamma waves).

This continuous feedback loop allows the brain to remain flexible and adaptive, quickly adjusting to new information and optimizing its responses based on both historical and current data. The harmonically structured oscillations enable rapid communication and integration across different brain regions, ensuring that the brain operates as a cohesive whole, even as it processes vast amounts of diverse information.

Figure 8 – The Bayesian Predictor Mechanism for the columns (Marianna Brienza)

Conclusion

Understanding the brain as a series of harmonically synchronized layers reveals a remarkable mechanism of neural processing. From the slow, steady rhythms that maintain our basic physiological functions to the rapid, high-frequency oscillations that underpin our most sophisticated cognitive abilities, the brain’s oscillatory dynamics are key to its incredible versatility and efficiency. By functioning across multiple frequencies and layers, the brain achieves a seamless integration of sensory processing, cognitive function, and motor control, allowing us to navigate and respond to an ever-changing world with precision and agility. This harmonic model not only enhances our understanding of brain function but also offers new perspectives on how different types of brain activity are synchronized to produce coherent thoughts, actions, and experiences.

Post modern brain waves, sampling, synchronicity and synthesis?

So, we are seeing more and more devices which attempt to tune into these transmitters and receivers?  And gradually we are learning  what are the correct frequencies and locations for tapping into these signals.

Implanted receivers on the neocortex are being increasingly utilised for outputs. For example, tapping into the motor cortex can animate prosthetics and bypass spinal injuries.

But shouldn’t we be exploring how to engineer inputs also – into the Thalamus?

But apart from connecting us directly to the internet (as yet another thing?), this opens up a whole area of ethics and social issues on mind control, rehabilitation, applications (drugs, crime, etc.).

So, the more we think we understand, the more responsible we have to be with how we utilise the benefits and avoid the potential harms. This is currently true of so-called artificial intelligence; it must be doubly true for manipulating and exploiting real human intelligence.

References

Priyanka A. Abhang, et al, (2016)  Technological Basics of EEG Recording and Operation of Apparatus, , in Introduction to EEG- and Speech-Based Emotion Recognition

https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/brain-waves