1. Where Do We Think?
• Where people thought they thought
• Thinking takes place in the brain
2. The Classical Biological Neuron
• Somma
• Dendrites
• Axon
• Synapses
• Excititory
• Inhibitory
• Synaptic Efficacy
• Strong
• Weak
3. The Ping-Pong Ball Model
• Ideal gas law explained in statistical physics using unrealistic model
• Model breaks down at extremes but extremely useful over large range
• Biologists haven't made headway studying single neurons
• Statistical physics is where a large number of simple units can be analyzed
4. The McCulloch-Pitts Model
• Neuron's state (firing or quiescent) represented by (0,1) or (-1,+1)
• Synaptic efficacies are represented by arbitrary real numbers
• PSP is the weighted sum of inputs
• Decision whether to fire or remain quiet is deterministic (step function)
• Can perform many logical, signal/image processing, computational tasks
5. Comparison Of The Brain And A Computer
• Can only directly compare two computers of identical architecture
• Can indirectly compare computers by cross emulation
• Computer and brain architectures are so radically different that you can't compare them
• Before trying to solve a problem choose correct architecture

Assignment

1. Find the connection between the (0,1) and (-1,+1) representations.
2. Prove that the McCulloch-Pitts formulae for these neurons are equivalent.
   Find formulae for the equivalence of weights and thresholds.
3. Is this equivalence purely mathematical, or biological as well?