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Machine Learning Toolkit · 13

Combining Neurons into a Network

Building intermediate representations in hidden layers

A network stacks neurons so that hidden layers build intermediate features and later layers recombine them into an output.

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The essential idea: composition lets simple neurons cooperate to represent patterns no single neuron can express.

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One Concept · One Example

Combining Neurons into a Network video thumbnail▶

Combining Neurons into a Network

Presented by Charlotte Moser

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What to notice

The idea in 30 seconds

From neurons to a layered map

Hidden layer

Each hidden neuron applies its own weighted transformation and activation.

h=f(W1x+b1)

Output layer

The next layer recombines those hidden activations.

y=g(W2h+b2)
Explore

Follow the slides network, edge by edge

Use the one-hidden-layer example from the slides. Nonzero and zero-weight edges reveal exactly how the two inputs become h₁, h₂, and then y.

w₁ = 0w₂ = 1w₃ = 0w₄ = 1w₅ = 0w₆ = 1x₁2x₂3.0h₁0.9526h₂0.9526y0.7216Input layerHidden layerOutput layer
Hidden neuron 1h₁ = σ(0·2 + 1·3.0) = 0.9526
Hidden neuron 2h₂ = σ(0·2 + 1·3.0) = 0.9526
Output neurony = σ(0·h₁ + 1·h₂) = 0.7216
KEY TAKEAWAY

Hidden layers build reusable intermediate features by composing weighted transformations and activations.