Celebrating five decades of discoveries that revealed the chemical basis of thought, memory, and consciousness
Think of the most complex object in the known universe. It's not a distant galaxy or a supercomputer; it's the three-pound mass of tissue inside your head.
Your brain is a bustling metropolis of nearly 100 billion neurons, each communicating in a silent, electrochemical language that dictates everything from your memories to your movements. For the past 50 years, The Japanese Society for Neurochemistry (JSN) has been at the forefront of deciphering this language, moving beyond the simple "spark" of electricity to understand the intricate chemistry that makes thought, feeling, and consciousness possible.
This anniversary isn't just a celebration of a scientific society; it's a tribute to five decades of peering into the very essence of what makes us human.
Neurons in the human brain
Of neurochemistry research
Synaptic connections
For a long time, brain science focused on electricity—the rapid-fire impulses that travel along neurons. But neurochemistry reveals a far richer story. It explores the symphony of chemical messengers that allow one neuron to whisper, shout, or even change the very structure of its neighbors.
The chemical molecules released from one neuron to deliver a message to the next. Think of them as the vocabulary of the brain.
The tiny gap between neurons where communication happens. This is not a static wire but a dynamic, ever-changing interface.
Once considered mere "glue," these cells are now known as active participants in brain chemistry, helping control the synaptic environment.
The fundamental chemical basis of learning and memory, where synaptic connections are strengthened or weakened.
The main "accelerator," exciting neurons to fire.
The main "brake," calming neuronal activity.
The "reward and motivation" molecule.
The "mood and stability" regulator.
One of the most elegant experiments in modern neurochemistry provided direct visual proof that memories have a physical, chemical form. This groundbreaking work, heavily influenced by techniques refined in Japan, aimed to pinpoint where and how a memory is stored in the brain.
"The artificial reactivation of that specific chemical and physical network was the memory."
The formation of a specific memory (e.g., a fear of a particular sound) strengthens specific synaptic connections in a specific brain region (the amygdala).
Optogenetics – Controlling Neurons with Light. Researchers used a virus to deliver two special genes into neurons in the mouse amygdala.
A mouse was placed in a novel chamber and given a mild, harmless foot shock paired with a sound. This created a fear memory. The neurons active during this memory formation were genetically "tagged" with the light-sensitive protein and the fluorescent marker.
Under a microscope, researchers could later see a cluster of fluorescent neurons in the amygdala—the putative "fear memory engram."
Days later, the mouse was placed in a completely different, safe chamber. It behaved normally.
Researchers then delivered a pulse of blue light directly into the amygdala, specifically activating only the neurons that were tagged during the initial fear learning.
The moment the light was turned on, the mouse immediately froze in fear, despite being in a safe environment and hearing no sound. The artificial reactivation of that specific chemical and physical network was the memory.
This experiment was a landmark because it moved memory from an abstract concept to a tangible, manipulable chemical and physical entity. It demonstrated that:
| Experimental Group | Context (Chamber) | Light Stimulation? | Behavioral Response (Freezing %) |
|---|---|---|---|
| Memory-Tagged | Novel (Safe) | No | < 10% |
| Memory-Tagged | Novel (Safe) | Yes | > 70% |
| Control (No Tag) | Novel (Safe) | Yes | < 15% |
| Mouse ID | % of Tagged Neurons in Amygdala | Freezing % upon Light Stimulation |
|---|---|---|
| 1 | 0.8% | 65% |
| 2 | 1.2% | 78% |
| 3 | 0.5% | 45% |
| 4 | 1.5% | 82% |
| Molecule | Function | Change in Engram Neurons vs. Non-Engram |
|---|---|---|
| AMPA Receptors | Primary receiver for glutamate (excitation) | Significantly Increased |
| CREB Protein | A master genetic switch for memory formation | Highly Activated |
| Synaptophysin | A marker for synaptic vesicles | Increased Density |
The revolution in neurochemistry has been powered by a toolkit of sophisticated reagents and techniques, many of which have been pioneered or perfected by JSN researchers.
| Reagent / Tool | Function | Why It's Indispensable |
|---|---|---|
| Green Fluorescent Protein (GFP) & Variants | A natural jellyfish protein that glows green. Can be genetically fused to other proteins. | Allows scientists to "see" specific neurons, synapses, or molecules in real-time within living brain tissue. |
| Optogenetic Tools (e.g., Channelrhodopsin) | Light-sensitive proteins that can activate or silence neurons with millisecond precision. | Enables precise control of neural circuits to establish direct cause-and-effect relationships, as in the memory experiment. |
| Patch-Clamp Electrophysiology | A fine glass electrode that forms a tight seal with a neuron's membrane. | The gold standard for measuring the minute electrical currents and voltage changes produced by individual ion channels and neurotransmitters. |
| Monoclonal Antibodies | Highly specific proteins designed to bind to a single target molecule. | Used to label, isolate, and quantify specific brain proteins (e.g., receptors, tau) with incredible precision, crucial for diagnosing and studying disease. |
| LC-MS/MS (Liquid Chromatography-Mass Spectrometry) | A powerful machine that separates and identifies thousands of different molecules in a sample. | Allows for the comprehensive profiling of neurotransmitters, lipids, and metabolites, giving a complete "chemical snapshot" of the brain's state. |
Modern neurochemistry relies on highly specific reagents that target individual molecules with incredible accuracy.
Fluorescent proteins and advanced microscopy allow researchers to watch neural processes in real time.
Genetic tools enable precise manipulation of specific neuron types to understand their functions.
The journey of The Japanese Society for Neurochemistry over the past 50 years mirrors the journey of the field itself—from understanding basic chemical transmission to manipulating the complex code of memory and emotion.
The fundamental knowledge unlocked by neurochemistry is the bedrock for the next great leap: tackling the chemical roots of Alzheimer's, Parkinson's, depression, and autism. As we celebrate this golden anniversary, we look forward to a future where decoding the brain's secret language leads to healing its most profound disorders, a future that the JSN will undoubtedly help to write.
"The next 50 years of neurochemistry will transform how we treat brain disorders and understand the very nature of human thought and identity."