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Adult Neurogenesis: Generation of New Neurons in Mature Brain

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Neuronal Compartments: Soma, Dendrite, and Axon→→Critical Periods and Neural Plasticity Hippocampus: Memory Consolidation and Spatial Representation +2 more

Core Idea

Contrary to classical dogma, neural stem cells in the adult hippocampus (and olfactory bulb) generate new neurons throughout life. These newborn neurons integrate into existing circuits and contribute to learning and memory; disrupting neurogenesis impairs cognitive performance. Activity, enrichment, and learning promote neurogenesis, while aging and stress suppress it.

Explainer

For most of the 20th century, neuroscience operated under an axiom: the adult brain does not produce new neurons. Santiago Ramón y Cajal wrote in 1928 that nerve paths are "fixed, ended, immutable" — and this dogma held for decades. It was wrong. Beginning with studies in songbirds in the 1980s and confirmed in rodents and humans through the 1990s and 2000s, we now know that adult neurogenesis — the birth, maturation, and functional integration of new neurons in the adult brain — occurs in at least two regions, and it plays a meaningful role in cognition.

The best-characterized site is the subgranular zone (SGZ) of the hippocampal dentate gyrus. Neural stem cells here divide to produce progenitor cells that differentiate into granule neurons — the principal excitatory cells of the dentate gyrus. These newborn neurons go through a maturation process lasting several weeks: they extend dendrites into the molecular layer, send axons along the mossy fiber pathway to CA3, and gradually develop mature electrophysiological properties. Crucially, during a window of about 4–6 weeks after birth, these young neurons are hyperexcitable and have enhanced synaptic plasticity compared to mature granule cells, making them especially responsive to new experiences. The second site is the subventricular zone (SVZ) lining the lateral ventricles, where new neurons are born and migrate along the rostral migratory stream to the olfactory bulb, becoming interneurons involved in odor discrimination.

What controls the rate of neurogenesis is as important as the fact that it occurs. Physical exercise — particularly aerobic running — is one of the most robust promoters of hippocampal neurogenesis in animal models, increasing both the proliferation of progenitor cells and the survival of newborn neurons. Environmental enrichment (novel objects, social interaction, complex housing) has similar effects. Learning itself, particularly tasks that depend on the hippocampus like spatial navigation and pattern separation, promotes the survival of neurons that were born shortly before the learning experience. Conversely, chronic stress and elevated glucocorticoids suppress neurogenesis dramatically, and age-related decline in neurogenesis parallels age-related decline in memory performance.

The functional significance of adult neurogenesis centers on pattern separation — the ability to distinguish between similar but distinct memories. The hippocampal dentate gyrus is thought to perform this computation, and the continuous addition of new, hyperplastic neurons may refresh the circuit's capacity to encode new memories without interfering with old ones. When neurogenesis is experimentally blocked in rodents (through irradiation or genetic tools), animals show specific deficits in distinguishing between similar contexts or overlapping memories, while performance on simpler memory tasks remains intact. This suggests that adult-born neurons are not required for memory in general, but for the fine-grained discrimination that prevents your memory of today's parking spot from blurring with yesterday's.

Practice Questions 5 questions

Prerequisite Chain

Understanding Zero → The Number Zero → Counting to Five → Counting to 10 → Counting to 20 → Counting a Set of Objects Up to 20 → Cardinality: The Last Number Counted → Matching Numerals to Quantities → Subitizing Small Quantities → Addition Within 10 → Number Bonds to 10 → Addition Within 20 → Doubles and Near Doubles → Doubles Facts Within 10 → Near Doubles Facts Within 20 → Mental Math Strategies for Addition → Mental Math: Adding and Subtracting Tens → Addition Within 100 → Repeated Addition as Multiplication → Multiplication as Equal Groups → Multiplication: Arrays → Basic Multiplication Facts (0s, 1s, 2s, 5s, 10s) → Multiplication Facts Within 100 → Division as Equal Sharing → Division as Grouping (Measurement Division) → Division: Grouping (Repeated Subtraction) Model → Division: Fair Sharing Model → Division as Equal Sharing → Division as Grouping → Basic Division Facts → Division Facts Within 100 → Multiplication and Division Fact Families → Relationship Between Multiplication and Division → Division Facts as Inverse of Multiplication → Remainders and Quotients in Division → Division Word Problems → Multi-Step Word Problems → Solving Multi-Step Word Problems → Multiplication Word Problems → Division Word Problems → Introduction to Long Division → Factors and Multiples → Prime and Composite Numbers → Equivalent Fractions → Relating Fractions and Decimals → Decimal Place Value → Integers and the Number Line → Comparing and Ordering Integers → Absolute Value → Adding Integers → Subtracting Integers → Multiplying Integers → Dividing Integers → Unit Rates → Proportions → Percent Concept → Converting Between Fractions, Decimals, and Percents → Operations with Rational Numbers → Two-Step Equations → Solving Multi-Step Equations → Equations with Variables on Both Sides → Angle Pairs: Complementary, Supplementary, and Vertical → Parallel Lines and Transversals → Corresponding Angles → Alternate Interior Angles → Triangle Angle Sum Theorem → Exterior Angle Theorem → Triangle Inequality Theorem → Similar Triangles: AA Similarity → Similar Triangles: SSS and SAS Similarity → Proportions in Similar Triangles → Right Triangle Trigonometry Introduction → Sine, Cosine, and Tangent Ratios → Trigonometric Ratios Review → Radian Measure → Converting Between Degrees and Radians → The Unit Circle → Graphing Sine and Cosine → Graphing Tangent and Reciprocal Trigonometric Functions → Derivatives of Trigonometric Functions → Antiderivatives → Indefinite Integrals → Basic Integration Rules → Riemann Sums → Definite Integral Definition → Double Integrals: Definition and Setup → Iterated Integrals and Fubini's Theorem → Double Integrals over Rectangular Regions → Double Integrals over General Regions → Applications of Double Integrals: Area, Mass, and Moments → Triple Integrals in Cartesian Coordinates → Triple Integrals in Cylindrical and Spherical Coordinates → Change of Variables and the Jacobian Determinant → Applications of Triple Integrals: Volume and Mass → Vector Fields and Their Representations → Line Integrals of Vector Fields → Work and Circulation → Line Integrals of Scalar and Vector Functions → Fundamental Theorem for Line Integrals → Conservative Vector Fields → Conservative Vector Fields and Potential Functions → Curl and Divergence of Vector Fields → Curl and Divergence → Divergence Theorem → Electric Flux and Divergence Theorem → Gauss's Law: Integral Form and Meaning → Solving Problems with Gauss's Law → Conductors in Electrostatic Equilibrium → Capacitance and Capacitors → Dielectrics → Dielectric Constant and Relative Permittivity → Electric Field Inside Dielectric Materials → Dielectric Materials and Polarization → Dielectric Susceptibility and Permittivity → Energy Density in Electric Fields → Electric Current and Current Density → Electrical Resistance and Resistivity → Ohm's Law and Circuit Elements → Electromotive Force (EMF) and Batteries → Kirchhoff's Circuit Laws: Voltage and Current → DC Circuit Network Analysis Methods → Transient Response in RC Circuits → RC Circuits → LC and RLC Circuits → AC Circuits: Fundamentals → Impedance and Reactance → AC Power and Resonance → Electromagnetic Waves → Postulates of Special Relativity → Time Dilation → Length Contraction → Lorentz Transformation → Relativistic Velocity Addition → Relativistic Momentum and Energy → Mass-Energy Equivalence and E=mc² → Photons as Particles with Energy and Momentum → Planck-Einstein Relation: Energy and Frequency → Photoelectric Effect → The Photon: Light as Quanta → Compton Scattering → Wave-Particle Duality → de Broglie Wavelength → The Schrödinger Equation → State Vectors and Wavefunctions → Quantum Superposition → Quantum Entanglement → Bell Theorem and Bell Inequalities → Postulates of Quantum Mechanics → Observables and Quantum Operators → Commutators and Commutation Relations → Quantum Angular Momentum → Quantum Mechanical Treatment of Hydrogen → Solving the Schrödinger Equation for Hydrogen Atom → Quantum Numbers → Electron Configuration → Periodic Trends → Covalent Bonding → Electronegativity and Bond Polarity → Ionic Bonding → Lewis Structures → VSEPR Theory and Molecular Geometry → Molecular Geometry and Electron Pair Geometry → Molecular Polarity and Dipole Moments → Intermolecular Forces → States of Matter and Phase Changes: Melting, Boiling, and Sublimation → Gas Laws and the Ideal Gas Equation → Gas Stoichiometry and Volume-Volume Calculations → Thermochemistry and Enthalpy → Heat Capacity and Calorimetry → Entropy and Molecular Disorder → Spontaneity and ΔG → Entropy and Gibbs Free Energy → Chemical Equilibrium → Acid-Base Chemistry → Weak Acid Ionization → Weak Base Ionization → Acid and Base Strength: Ka, Kb, and Ionization → Leaving Groups and Nucleofugality → SN2 Substitution Reactions → SN1 Substitution Reactions → E1 Elimination Reactions → Alcohols and Ethers: Structure, Properties, and Nomenclature → Reactions of Alcohols → Aldehydes and Ketones: Structure and Reactivity → Oxidation Reactions in Organic Chemistry → Oxidation of Alcohols to Aldehydes and Ketones → Aldehyde and Ketone Structure and Nomenclature → Nucleophilic Addition to Aldehydes and Ketones → Carboxylic Acids and Their Derivatives → IUPAC Nomenclature of Carbonyls and Carboxylic Acids → IUPAC Nomenclature of Alkenes → Electrophilic Addition to Alkenes → Aromaticity and Benzene → Electrophilic Aromatic Substitution (EAS) → Nucleophilic Aromatic Substitution (SNAr) → Nucleophilic Acyl Substitution → Amines: Structure, Basicity, and Reactions → Amine Reactivity: Nucleophilicity and Basicity → Amino Acid Structure and Properties → Peptide Bonds and Polypeptide Formation → Protein Primary Structure → Protein Secondary Structure → Protein Tertiary Structure → Ion Channels and Selective Permeability Mechanisms → Osmotic Regulation and Cellular Water Balance → Osmosis and Tonicity → Active Transport → Cell Signaling and Signal Transduction → Homeostasis and Feedback Loops → Nervous System Overview → Neuronal Compartments: Soma, Dendrite, and Axon → Adult Neurogenesis: Generation of New Neurons in Mature Brain

Longest path: 212 steps · 1124 total prerequisite topics

Prerequisites (1)

Neuronal Compartments: Soma, Dendrite, and Axonsoft

Leads To (4)

Critical Periods and Neural Plasticitysoft Hippocampus: Memory Consolidation and Spatial Representationsoft Myelination and Brain Maturationsoft Thyroid Hormone and Neural Development and Functionsoft