Chapter 3: Neural Networks & Brain Plasticity

Discover how neurons connect and adapt through experience

How does your brain create networks and adapt?

Your brain contains approximately 86 billion neurons forming trillions of connections. These neural networks process information, store memories, and remarkably, can reorganize themselves throughout your lifetime; A phenomenon called neuroplasticity.

In this exploration, you'll discover:

Start by selecting a tab below to begin your exploration!

Neural Networks: The Brain's Computing Architecture

💡 Click on neurons to activate them and see signal propagation

Network Architecture Types

Different neural network architectures serve specific computational functions in the brain:

Feedforward Networks

Information flows in one direction from input to output. Found in sensory processing pathways like the visual cortex hierarchy (V1 → V2 → V4 → IT).

Recurrent Networks

Contain feedback loops enabling working memory and temporal processing. Essential for the prefrontal cortex and hippocampal circuits.

Small-World Networks

High clustering with short path lengths. Optimizes efficiency vs. cost trade-off. Characteristic of cortical connectivity patterns.

Clinical Relevance

Network disruptions underlie many neurological and psychiatric disorders. Alzheimer's disease affects hub nodes, autism involves connectivity alterations, and schizophrenia shows reduced small-world properties.

Network Statistics:

  • Nodes: 0
  • Connections: 0
  • Active Nodes: 0

Brain Plasticity: How Your Brain Adapts

Synaptic Plasticity Simulation

Long-Term Potentiation (LTP) and Long-Term Depression (LTD) are the cellular basis of learning and memory:

1 Hz (LTD) 10 Hz 100 Hz (LTP)

Plasticity Mechanisms

Long-Term Potentiation (LTP)

  • • High-frequency stimulation (>50 Hz)
  • • Ca²⁺ influx through NMDA receptors
  • • AMPA receptor insertion
  • • Strengthens synaptic connections

Long-Term Depression (LTD)

  • • Low-frequency stimulation (1-5 Hz)
  • • Moderate Ca²⁺ elevation
  • • AMPA receptor endocytosis
  • • Weakens synaptic connections

Homeostatic Plasticity

  • • Synaptic scaling
  • • Intrinsic excitability changes
  • • Maintains network stability
  • • Prevents runaway excitation

Clinical Applications

Understanding plasticity enables therapies for stroke recovery, depression treatment (rTMS), and cognitive enhancement. Critical periods in development guide intervention timing.

Neural Pathways: Information Highways

Neural pathways are anatomically distinct circuits that form the brain's information highways. These pathways connect specific brain regions to process sensory input, control motor output, and integrate cognitive functions. Understanding these circuits is essential for diagnosing and treating neurological conditions.

🧠 Pathway Organization Principles

  • Hierarchical Processing: Information flows from primary to secondary to association areas
  • Parallel Processing: Multiple pathways process different aspects simultaneously
  • Cross-Modal Integration: Higher areas combine information from multiple senses
  • Redundancy: Critical functions have backup pathways for resilience

Visual Pathway

Retina → LGN → V1 → V2 → V4/V5

Dorsal stream: motion & spatial processing
Ventral stream: object recognition & form

Magnocellular Parvocellular

Motor Pathway

M1 → Pyramidal Decussation → Spinal Cord

85% of fibers cross at medulla
Upper motor neurons → Lower motor neurons

Lateral CST Ventral CST

Auditory Pathway

Cochlea → CN VIII → SOC → IC → MGN → A1

Tonotopic organization preserved
Binaural processing for sound localization

Frequency Location

Pain Pathway

Nociceptors → Spinal Cord → Thalamus → S1/S2

Fast (Aδ) and slow (C fiber) pain transmission and modulation

Memory Circuit

Hippocampus ↔ Cortex ↔ PFC

Encodes, consolidates, and retrieves episodic and semantic memories

Reward Pathway

VTA → NAc → PFC

Dopaminergic system for motivation, addiction, and learning

Select a pathway above to see detailed information

Click on any pathway card to explore its anatomy, function, and clinical significance in detail.

Learning & Memory: How Experience Changes Your Brain

Memory Formation Process

Memory formation involves three key stages: encoding, consolidation, and retrieval. Each stage activates different brain regions:

Current Stage: Ready

Active Regions: None

Memory Systems

Working Memory

Temporary storage and manipulation of information

  • • Prefrontal cortex networks
  • • 7±2 item capacity limit
  • • Essential for reasoning and problem-solving

Long-Term Memory

Permanent storage of information and experiences

Declarative:

  • • Episodic (events)
  • • Semantic (facts)

Non-declarative:

  • • Procedural (skills)
  • • Priming

Key Brain Regions

Hippocampus: Encoding and consolidation of episodic memories

Prefrontal Cortex: Working memory and executive control

Amygdala: Emotional memory enhancement

Cerebellum: Motor learning and procedural memory

Memory Disorders

Alzheimer's disease primarily affects hippocampal-dependent memory, while Huntington's disease impairs procedural learning. Understanding these systems guides therapeutic interventions.

Key Concepts Summary

Neural Networks

  • • 86 billion neurons, trillions of connections
  • • Different architectures serve specific functions
  • • Small-world properties optimize efficiency
  • • Network disruptions cause disease

Brain Plasticity

  • • LTP strengthens, LTD weakens synapses
  • • Activity-dependent mechanisms
  • • Critical periods and lifelong adaptation
  • • Foundation of learning and recovery