The First Discoveries: How Scientists Learned About Brain Electricity
Since antiquity, the brain has been recognized as the seat of thought and consciousness, yet its operational mechanisms remained shrouded in mystery. The story of how we came to understand the brain’s electrical nature is a journey from philosophical speculation to rigorous scientific investigation. The realization that electricity plays a vital role in the nervous system, particularly the brain, emerged gradually through centuries of exploration, starting with observations of electrical phenomena and culminating in the experimental validation of ‘animal electricity.’ These initial discoveries laid the groundwork for the invention of electroencephalography (EEG) and the subsequent revolution in neuroscience. Understanding this historical trajectory is crucial to appreciate the significance of EEG as a tool that has bridged ancient mysteries with modern scientific understanding.
Electricity in the Ancient World and Early Enlightenment
While the precise nature of electricity was unknown, phenomena associated with it were observed in ancient civilizations. The Greeks, as early as 600 BCE, noted that amber, when rubbed, could attract light objects, a basic manifestation of static electricity. However, these observations remained largely isolated and did not translate into a deeper scientific inquiry. Electricity remained an unexplained natural curiosity for millennia. The real impetus for understanding electricity began to gather momentum during the Enlightenment period of the 17th and 18th centuries. Significant milestones during this era included Otto von Guericke’s invention of a sulfur globe that could generate static electricity through friction and Francis Hauksbee’s experiments with vacuum tubes that produced light when electricity was discharged within them. Stephen Gray’s identification of materials as conductors and insulators of electricity was another crucial step, differentiating substances based on their electrical properties. These advancements provided a more tangible and experimental approach to studying electricity, moving beyond mere observation and laying the groundwork for more profound discoveries. A pivotal invention during this time was the Leyden jar in 1745, independently by Pieter van Musschenbroek and Ewald Georg von Kleist. The Leyden jar, the first capacitor, could store electrical charge, allowing for more controlled and powerful electrical experiments. This invention facilitated the study of electrical phenomena in a more systematic way and allowed for demonstrations that captivated public and scientific interest alike. Benjamin Franklin’s work in the mid-18th century further revolutionized the understanding of electricity. Franklin proposed the concept of positive and negative electrical charges and famously demonstrated that lightning was electrical in nature through his kite experiment. His work not only demystified lightning but also provided a conceptual framework for understanding electrical phenomena, shifting the understanding from mere static curiosities to a force governed by laws and principles. Charles-Augustin de Coulomb later quantified the force between electric charges with Coulomb’s Law, and Alessandro Volta’s invention of the voltaic pile in 1800—the first true battery—provided a continuous and reliable source of electric current. These cumulative discoveries transformed electricity from a poorly understood natural phenomenon into a measurable and manipulable force, setting the stage for its application to biological systems and the eventual discovery of ‘animal electricity’.
Luigi Galvani and the Discovery of Animal Electricity
The late 18th century witnessed a groundbreaking shift towards understanding the role of electricity in living organisms, primarily through the work of Italian anatomist and physiologist Luigi Galvani. In the 1780s, Galvani conducted a series of experiments on dissected frogs that would lead to the concept of ‘animal electricity’. Galvani observed that frog legs, when touched by two different metals (such as copper and iron), twitched even in the absence of any external electrical source. Initially, he believed that this phenomenon was due to ‘animal electricity’, a vital force intrinsic to living tissues, particularly nerves and muscles. One of Galvani’s most famous experiments, the ‘frog leg experiment,’ involved hanging frog legs with copper hooks on an iron railing. He noted that the legs contracted whenever they made contact with the iron. Galvani meticulously documented these observations, proposing that animal tissues themselves generated electricity. He postulated that this ‘animal electricity’ was a unique vital force, distinct from the ‘artificial electricity’ produced by machines like Leyden jars or voltaic piles. Galvani’s theory of ‘animal electricity’ sparked considerable interest and debate within the scientific community. While his interpretation of a unique vital electricity was eventually challenged, his experiments were crucial in directing scientific attention to the electrical properties of biological tissues. Galvani’s work, although not entirely correct in its theoretical underpinnings, was pivotal in establishing the idea that biological processes, particularly in nerves and muscles, were fundamentally electrical. His experiments compellingly demonstrated that living tissues could respond to electrical stimuli, suggesting an intrinsic electrical component in their function. The very notion of ‘animal electricity’, even if later refined, was a revolutionary departure from purely mechanistic or vitalistic views of life, indicating that the physical principles governing inanimate matter, like electricity, could also be at play in living systems. Galvani’s legacy lies not in the accuracy of his ‘animal electricity’ theory, but in his empirical demonstration of bioelectricity and its implications for understanding life. His work directly inspired further research, notably by Alessandro Volta, which would ultimately refine and correct the understanding of bioelectricity and its sources.
Emil du Bois-Reymond and the Nerve Impulse as Electrical
Building upon the foundational work of Galvani and Volta, the mid-19th century saw significant advancements in understanding the electrical nature of nerve function, largely due to the pioneering work of German physiologist Emil du Bois-Reymond. Du Bois-Reymond, often considered the founder of electrophysiology, rigorously investigated the electrical activity of nerves and muscles, moving beyond the concept of ‘animal electricity’ towards a more mechanistic and accurate understanding of nerve impulses. In the 1840s, using sophisticated instruments of his own design, du Bois-Reymond successfully detected and measured electrical currents in living nerves and muscles. He provided definitive experimental evidence that nerve impulses are indeed electrical signals. His most significant contribution was the discovery of the ‘action potential,’ which he termed ‘negative variation.’ Du Bois-Reymond demonstrated that when a nerve is stimulated, a transient change in electrical potential, a brief negativity, propagates along the nerve fiber. This ‘negative variation’ was, in fact, the nerve impulse itself—a wave of electrical depolarization traveling along the nerve axon, carrying information. His experiments meticulously characterized the properties of the action potential, including its velocity, duration, and the factors influencing its propagation. Du Bois-Reymond’s findings decisively refuted vitalistic theories that posited nerve function as something beyond ordinary physical laws and firmly established nerve conduction as an electrochemical phenomenon. He showed that nerves transmitted signals not through some mysterious ‘vital spirit’ but through measurable electrical events. His work provided the crucial link between electricity and nerve function, demonstrating that nerves operate on principles analogous to electrical circuits. This understanding was paradigm-shifting, transforming the field of physiology and opening new avenues for studying the nervous system. Du Bois-Reymond’s work had a profound impact, not only by confirming the electrical nature of nerve impulses but also by pioneering the techniques of electrophysiology. He developed specialized electrodes and galvanometers sensitive enough to detect the minute electrical currents generated by nerves and muscles. His experimental methodologies and rigorous approach set a new standard for physiological research, influencing generations of scientists and paving the way for future developments in neurophysiology, including the invention of EEG. His research underscored that the language of the nervous system was, fundamentally, electrical, directly leading to the pursuit of methods to record and interpret the electrical activity of the brain, thus setting the stage for Richard Caton’s and subsequently Hans Berger’s groundbreaking work on brain electricity and EEG.
Richard Caton’s Discovery of Electrical Activity in Animal Brains
The late 19th century marked a pivotal transition from understanding nerve electricity to investigating brain electricity, with Richard Caton, a British physiologist, playing a pioneering role. In 1875, Caton published findings that for the first time demonstrated the presence of electrical activity in the brains of animals. He placed electrodes on the exposed cerebral cortex of rabbits and monkeys and, using a galvanometer, recorded fluctuating electrical currents emanating from the brain. Caton’s experiments were remarkably insightful for his time. He not only confirmed that the brain produced electrical phenomena but also observed that this activity was spontaneous and ongoing, not merely reactive to external stimuli. He noted that these electrical currents varied in strength and pattern and were not constant, indicating dynamic electrical processes within the brain. Furthermore, Caton observed that brain electrical activity changed in response to sensory stimulation. For instance, he noted alterations in brain currents when the animals were exposed to light or sounds. This was a crucial early indication that brain electrical activity was not random noise but correlated with brain function and sensory processing. Caton’s findings, published in the British Medical Journal, were initially met with limited attention, perhaps because his primary publication venue was not specialized in physiology or neuroscience. Despite this initial underappreciation, Caton’s work was groundbreaking. He was the first to experimentally demonstrate that the brain, like nerves and muscles, was electrically active. His use of electrodes placed directly on the cerebral cortex to record brain electricity was a significant methodological advancement, foreshadowing the techniques that would later be refined and applied in human EEG. Richard Caton’s discovery of brain electricity was a critical step towards EEG. It provided empirical evidence that the brain was not just a complex biological organ but also an electrical organ, capable of generating and responding to electrical signals. His work validated the idea that brain function could be studied by measuring its electrical activity, paving the path for Hans Berger’s successful recording of human EEG and the development of a technology that would transform neurology and neuroscience. Caton’s experiments bridged the gap between the established understanding of nerve electricity and the emerging concept of brain electricity, making the invention of EEG a logical next step in the scientific exploration of the brain.
The Invention of the EEG Machine: Who Created It and Why?
Following the crucial discoveries of brain electricity in animals, the quest to extend these findings to humans and develop a practical tool for studying human brain activity intensified. This endeavor culminated in the groundbreaking invention of the electroencephalograph (EEG) by German psychiatrist Hans Berger in the early 20th century. Berger’s invention was not just a technological achievement but a paradigm shift, creating a non-invasive method to observe and record the electrical dynamics of the human brain. Understanding who created the EEG machine and the motivations behind its creation is essential to appreciate its transformative impact on neuroscience and medicine.
Hans Berger’s Motivation and Background
Hans Berger, born in Germany in 1873, was a psychiatrist deeply committed to understanding the physiological basis of mental phenomena. Trained in medicine at the University of Jena, Berger became fascinated by the objective study of the brain and mind, seeking to move beyond purely subjective clinical observations in psychiatry. His motivation to invent the EEG machine was multifaceted, stemming from both scientific curiosity and personal experiences. One of the significant personal events that profoundly influenced Berger’s research direction was a near-death experience during his military service. While stationed as a psychiatrist, he fell from a horse and narrowly escaped being crushed by a cannon. Remarkably, on the same day, his sister, living miles away, had a strong premonition that Berger was in danger and insisted their father send a telegram to check on him. This event, which Berger interpreted as a form of telepathic communication, deeply intrigued him and spurred his lifelong quest to find a physiological basis for psychic phenomena and thought transmission. While his belief in telepathy and psychic energy is not scientifically validated today, it served as a powerful personal impetus for his scientific endeavors. Berger hypothesized that if psychic energy or thought transmission were real, they might have a detectable physiological correlate in the brain, possibly electrical in nature. This led him to explore the possibility of recording and analyzing the electrical activity of the human brain. Beyond personal motivations, Berger was driven by a strong scientific desire to objectify psychiatric diagnosis and research. In the early 20th century, psychiatry was largely based on subjective clinical assessments. Berger sought a more objective, physiological measure of brain function that could aid in diagnosing and understanding mental disorders. He believed that by recording and analyzing brain electrical activity, he could uncover objective markers of mental states and pathologies, thereby transforming psychiatry into a more empirically grounded and scientifically rigorous discipline. Furthermore, Berger was aware of the earlier work on animal brain electricity, particularly Richard Caton’s findings. He was inspired by the potential of extending Caton’s animal experiments to humans in a non-invasive manner. He aimed to develop a technique that could safely and repeatedly record brain activity from the human scalp, making it clinically applicable and useful for continuous monitoring of brain function. Hans Berger’s unique combination of personal curiosity, scientific ambition to objectify psychiatry, and inspiration from prior research on brain electricity drove him to invent the EEG machine. His vision was to create a tool that could unlock the physiological secrets of the human mind, bridging the gap between subjective mental experience and objective brain activity.
Berger’s Experimental Setup and First Human EEG Recordings
Hans Berger embarked on developing his electroencephalograph in the early 1920s, facing significant technological challenges for his time. The amplification and recording of minute electrical signals from the human scalp required innovative instrumentation. Berger meticulously constructed his EEG apparatus, employing then-contemporary technologies to meet these demands. Berger’s EEG machine essentially comprised several key components: electrodes to pick up electrical signals from the scalp, an amplifier to boost the weak brain signals to a recordable level, and a recording device to visualize these amplified signals. For electrodes, Berger initially used simple silver wires applied to the scalp using a saline solution as a conductive medium. Later, he refined his electrodes to include silver foil electrodes held in place with rubber bandages or caps, improving consistency and reducing movement artifacts. The amplifier was a critical component. Berger used a sensitive galvanometer, an instrument designed to detect and measure small electrical currents. However, the brain’s electrical signals are extremely weak, in the microvolt range. To amplify these signals sufficiently for recording, Berger employed vacuum tube amplifiers, a relatively new technology at the time that could provide the necessary signal amplification. The recording device was another crucial aspect. Berger used a string galvanometer, a modification of the standard galvanometer, which could inscribe the amplified electrical signals onto photographic paper. The string galvanometer used a thin silvered quartz fiber suspended in a magnetic field. When an electric current passed through the fiber, it moved, and this movement was recorded photographically, producing a visual trace of the electrical signal over time. With his prototype EEG apparatus assembled, Berger began conducting experiments on human subjects, including himself, his son Klaus Berger, and his laboratory assistant, Heinrich Dietsch. His first human EEG recordings, achieved in 1924, were a monumental achievement. These initial recordings were technically challenging and often contaminated with artifacts, but Berger persevered, refining his technique and improving signal quality over time. In his pioneering EEG recordings, Berger identified and described distinct types of brainwaves, which he named alpha and beta rhythms. Alpha waves, around 10 Hz, were observed when subjects were awake but relaxed, with eyes closed, and were prominently seen in the posterior regions of the scalp. Beta waves, faster and of lower amplitude, were noted during states of alertness and mental activity. These initial findings were described in his seminal 1929 paper, “Über das Elektrenkephalogramm des Menschen” (“On the Electroencephalogram of Man”), marking the formal introduction of EEG to the scientific world. Berger’s early human EEG recordings were not just a technical feat; they were a demonstration that it was indeed possible to non-invasively capture and record the electrical activity of the human brain. His invention of the EEG machine and the successful recording of human brainwaves opened up an entirely new field of neurophysiological investigation, providing a direct window into the dynamic electrical workings of the human brain and paving the way for clinical and research applications that would transform neuroscience.
Initial Skepticism and Eventual Acceptance of EEG
Hans Berger’s groundbreaking publication on human EEG in 1929 was met with considerable skepticism and initial disbelief within the scientific community. The idea that such minute electrical signals recorded from the scalp could meaningfully reflect brain activity was novel and challenging for many of his contemporaries to accept. Many scientists doubted the validity of Berger’s findings, questioning whether the recorded signals were genuine brain activity or merely artifacts from muscle activity, eye movements, or electrical interference. One of the primary reasons for skepticism was the rudimentary nature of EEG technology at the time and the subtle nature of the EEG signals. Berger’s early EEG recordings were technically crude compared to modern standards. The signal amplification was limited, and the recordings were susceptible to various artifacts, making it difficult for others to replicate his results reliably at first. Furthermore, Berger’s initial interpretations of EEG rhythms and their correlations with mental states were somewhat speculative and lacked robust experimental validation that is expected by modern standards. His claims regarding alpha and beta waves and their relation to relaxation and alertness were initially seen as preliminary and needing further rigorous confirmation. The scientific community at the time was also generally cautious about accepting new and radical ideas, particularly in the relatively young field of neuroscience. The notion of recording brain activity from the intact human scalp was a conceptual leap that required strong empirical validation before widespread acceptance. The initial skepticism towards EEG began to wane in the early 1930s, largely due to independent confirmations and validations of Berger’s findings by other researchers. Key figures like Edgar Douglas Adrian and B.H.C. Matthews at Cambridge University played a crucial role in scientifically validating EEG. In 1934, Adrian and Matthews replicated Berger’s EEG recordings using more sophisticated amplification techniques, obtaining clearer and more robust EEG signals. They independently confirmed the existence of alpha and beta rhythms and verified their modulation with changes in mental state, such as eye opening and mental arithmetic, lending strong support to Berger’s initial observations. Adrian and Matthews published their confirmatory findings in the journal Brain, which was widely respected in the neurological community, significantly enhancing the credibility of EEG. Their validation was critical in converting initial skepticism into scientific acceptance. Further validation came from American neurophysiologist Hallowell Davis and his wife, Pauline Davis, who also independently confirmed Berger’s EEG findings in the United States during the 1930s. As more researchers successfully replicated Berger’s work and began to explore its clinical and research applications, EEG gradually gained acceptance within the scientific and medical communities. By the late 1930s and early 1940s, EEG was increasingly recognized as a valuable tool, particularly in clinical neurology, especially for the diagnosis of epilepsy and brain tumors. The initial skepticism surrounding EEG eventually gave way to widespread recognition of its scientific and clinical value, marking a turning point in the history of neuroscience and firmly establishing EEG as a foundational neurophysiological technique.
How EEG Has Evolved: From Simple Signals to Modern Neuroscience
Once validated and accepted, electroencephalography began a period of rapid evolution, both technologically and in its applications. From its humble beginnings as a simple recording of brainwaves, EEG has transformed into a sophisticated tool in modern neuroscience. The journey of EEG’s evolution is marked by advancements in technology, refined methodologies, and expanded applications across clinical and research domains. Tracing this evolution reveals how EEG has become an indispensable technique, continually adapting and contributing to our deepening understanding of the brain.
Technological Advancements in EEG Recording and Analysis
The evolution of EEG technology has been continuous and transformative, driven by advancements in electronics, computing, and signal processing. Early EEG machines, like Berger’s prototype, were rudimentary, using vacuum tube amplifiers and string galvanometers. Signal quality was limited, and analysis was primarily visual and qualitative. The mid-20th century saw significant improvements in EEG recording technology with the introduction of transistor-based amplifiers. Transistors replaced bulky vacuum tubes, making EEG machines more compact, reliable, and sensitive. This transition to solid-state electronics greatly enhanced signal amplification and reduced noise, improving the overall quality of EEG recordings. The late 20th century witnessed the advent of digital EEG systems. Digital EEG revolutionized data acquisition, storage, and analysis. Analog EEG signals were converted to digital data, allowing for computer-based signal processing, quantitative analysis, and digital storage of EEG records. Digital EEG systems enabled sophisticated signal filtering, artifact reduction, and automated analysis algorithms that were not feasible with analog systems. The introduction of computerized EEG analysis software further transformed EEG interpretation. Quantitative EEG (qEEG) emerged as a prominent approach, using computer algorithms to quantify EEG features such as frequency bands, amplitude, and coherence. qEEG provided objective and statistically analyzable measures of brain electrical activity, complementing traditional visual EEG interpretation. Modern EEG systems are characterized by high channel counts, improved electrode technology, and advanced digital signal processing capabilities. High-density EEG (hd-EEG) systems with 64, 128, 256, or more electrodes provide enhanced spatial resolution, allowing for more detailed mapping of brain electrical activity across the scalp. Electrode technology has also advanced significantly, with the development of more conductive and less artifact-prone electrodes, as well as user-friendly electrode caps that simplify electrode placement and improve recording consistency. Signal processing techniques have become increasingly sophisticated. Advanced filtering algorithms, independent component analysis (ICA), and wavelet transforms are routinely used to remove artifacts and extract meaningful brain signals from EEG data. Machine learning and artificial intelligence (AI) are now being integrated into EEG analysis, enabling automated detection of epileptic seizures, sleep staging, cognitive state classification, and even prediction of clinical outcomes. These technological advancements have collectively enhanced the sensitivity, spatial resolution, and analytical power of EEG, transforming it from a basic diagnostic tool into a sophisticated instrument for both clinical and neuroscientific applications.
Refinement of EEG Methodologies and Protocols
Alongside technological advancements, the methodologies and protocols for EEG recording and interpretation have also been refined and standardized over decades, ensuring reliability, comparability, and clinical utility. The standardization of electrode placement with the International 10-20 system, developed in the 1940s and refined subsequently, was a crucial methodological advancement. The 10-20 system provided a consistent and anatomically-referenced method for electrode positioning, allowing for comparable EEG recordings across different laboratories and clinics worldwide. This standardization is fundamental for clinical EEG practice and research, ensuring that EEG findings are reproducible and interpretable across diverse settings. Clinical EEG protocols have been meticulously developed and refined for various applications, such as epilepsy diagnosis, sleep studies, and brain death determination. Specific EEG montages, activation procedures (like hyperventilation and photic stimulation), and reporting guidelines have been established to optimize EEG recordings for specific clinical indications and to ensure consistent and clinically meaningful interpretations. Sleep polysomnography protocols, incorporating EEG along with other physiological measures, have become highly standardized for the diagnosis and classification of sleep disorders. These protocols specify electrode placements, recording durations, scoring criteria for sleep stages, and guidelines for reporting sleep EEG findings, ensuring diagnostic reliability and comparability across sleep laboratories. Quantitative EEG (qEEG) methodologies have also been increasingly standardized, with consensus guidelines developed for data acquisition, preprocessing, feature extraction, and statistical analysis. Standardization in qEEG promotes rigor and reproducibility in quantitative EEG research and clinical applications, facilitating the translation of qEEG findings into clinical practice. Furthermore, guidelines for EEG interpretation and reporting have been developed by professional organizations, such as the American Clinical Neurophysiology Society (ACNS) and the International Federation of Clinical Neurophysiology (IFCN). These guidelines provide standards for EEG reading, terminology, and reporting formats, ensuring that clinical EEG reports are clear, comprehensive, and clinically actionable. Continuous EEG monitoring (cEEG) protocols, particularly in intensive care units (ICUs), have also been refined to optimize the detection of non-convulsive seizures and other critical neurological events in critically ill patients. Standardized cEEG montages, acquisition settings, and interpretation criteria have been established to guide the use of cEEG in neurocritical care and improve patient outcomes. The ongoing refinement and standardization of EEG methodologies and protocols have been essential for ensuring the reliability, validity, and clinical utility of EEG, making it a robust and widely accepted neurophysiological technique in both research and clinical practice.
Expansion of EEG Applications in Modern Neuroscience
The evolution of EEG technology and methodologies has been accompanied by a remarkable expansion in its applications across diverse domains of modern neuroscience and clinical medicine. From its initial use in epilepsy diagnosis, EEG has found applications in cognitive neuroscience, psychology, brain-computer interfaces, neurofeedback, and neuromarketing, among others. In cognitive neuroscience, EEG has become a cornerstone for studying the neural basis of cognition, perception, attention, memory, language, emotions, and consciousness. Event-related potentials (ERPs), derived from EEG, are extensively used to investigate the timing and neural correlates of cognitive processes with millisecond temporal resolution. EEG-based studies have provided invaluable insights into the neural dynamics of cognitive operations, brain network activity underlying cognitive functions, and the effects of cognitive training and interventions. Psychology research extensively utilizes EEG to explore various psychological phenomena, including sleep, emotions, stress, attention-deficit hyperactivity disorder (ADHD), anxiety, depression, and other mental health conditions. EEG measures, such as brainwave frequencies, coherence, and event-related potentials, are used to investigate the neurophysiological underpinnings of psychological states, traits, and disorders, contributing to a better understanding and potential biomarkers for mental health. Brain-computer interfaces (BCIs) represent a transformative application of EEG technology. EEG-based BCIs enable direct communication and control between the brain and external devices, translating brain signals into control commands. BCIs hold immense potential for assisting individuals with paralysis, amyotrophic lateral sclerosis (ALS), stroke, and other motor disabilities, providing them with means to communicate, control prosthetic limbs, and interact with their environment through their brain activity. Neurofeedback, or EEG biofeedback, has emerged as a therapeutic application of EEG. Neurofeedback uses real-time EEG displays to train individuals to self-regulate their brainwave patterns. It has shown promise as a non-pharmacological intervention for ADHD, epilepsy, anxiety disorders, and other conditions, helping individuals learn to modulate their brain activity to improve cognitive function and emotional regulation. Neuromarketing and consumer neuroscience are emerging fields that apply EEG to study consumer responses to marketing stimuli, advertisements, and product designs. EEG measures of attention, emotional engagement, and cognitive processing are used to gain insights into consumer preferences, decision-making, and the effectiveness of marketing campaigns, providing neurophysiological metrics for marketing research. The expansion of EEG applications across these diverse fields underscores its versatility and enduring value as a neuroscientific tool. From fundamental research into brain function to innovative clinical and commercial applications, EEG continues to evolve and contribute significantly to our understanding of the brain and its myriad complexities, bridging the gap from ancient mysteries to modern neuroscientific insights.
Conclusion: EEG as a Cornerstone of Modern Neuroscience
From its origins in the quest to understand the ancient mysteries of the brain and mind, electroencephalography has evolved into a cornerstone of modern neuroscience. The journey from early observations of electrical phenomena to the sophisticated EEG technologies of today is a testament to scientific curiosity, technological innovation, and the relentless pursuit of knowledge about the human brain. EEG, invented by Hans Berger and validated by subsequent generations of scientists, has not only revolutionized our understanding of brain function but has also become an indispensable clinical tool and a powerful research method across diverse fields. From diagnosing neurological disorders like epilepsy and sleep disorders to exploring the neural basis of cognition, emotions, and consciousness, EEG provides a unique window into the dynamic electrical activity of the brain in real-time and in a non-invasive manner. The continuous advancements in EEG technology, methodologies, and data analysis techniques promise an even more exciting future for EEG in neuroscience. High-density EEG, multimodal brain imaging, brain-computer interfaces, and AI-driven EEG analysis are expanding the frontiers of EEG research and applications, pushing the boundaries of our ability to decode brain signals, understand brain networks, and develop innovative neurotechnologies. As we move further into the 21st century, EEG remains a vital and evolving tool, bridging the gap between ancient inquiries about the brain and the cutting-edge of modern neuroscience. Its enduring legacy is not only as a diagnostic and research instrument but also as a symbol of human ingenuity in unraveling the complexities of the most enigmatic organ—the human brain.