1. COMP305
Biology-Inspired Algorithms
Ross McFarlane
Tutorial 1

2. Admin
Monday, 1400–1500
Ashton Lecture Theatre
Friday, 1300–1400
Rendall Building
• Attendance is optional
• Lecture notes: www.csc.liv.ac.uk/~ivb
• Tutorial news: www.csc.liv.ac.uk/~rossmcf/teaching

3. Ion Channel
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Inside

4. Biology
•Natural Biology-Inspired
•Experimental Algorithms
•Computational
•Artificial Neural Networks
•Evolutionary Algorithms
•...
Bioinformatics

5. McCulloch-Pitts Neuron
a0
a1 q X
...
an

6. McCulloch-Pitts Neuron
t Time step
θ Threshold
ai Input from presynaptic neuron i
Wi Weight of input from presynaptic neuron i
X Output

7. McCulloch-Pitts Neuron
n
X t+1
= 1 ⇐⇒ s = t t
Wi ai >θ
i=0
Output is 1 if and only if weighted sum of inputs is
greater than the threshold.
while Wi > 0 ∀ai > 0
So long as no inhibitory inputs are active.

8. McCulloch-Pitts Neuron
Check inputs from ALL inhibitory
connections
Yes
No
=0
All inputs from inhibitory t+1
connections equal to 0? X
Yes
(continued)

9. continued
Calculate the instant state of the neuron
n
st = Wi at
i
i=0
Yes
t
s ≥θ ? No
X t+1
=0
Yes
X t+1
=1