Gain control

Question 1

What is gain control?

Answer 1

Mechanism for neurons to control their sensitivity

Question 2

Why is gain control needed?

Answer 2

As neurons have to code for large dynamic ranges

Question 3

What is contrast?

Answer 3

The average luminance variation in part of the visual field

Question 4

How does contrast model gain control?

Answer 4

neuronal inputs are divided by the sum of the local average response

Question 5

What are the 4 signatures of cortical gain control?

Answer 5

1. Operates over a long range
2. Tuning
3. Slow
4. Complex features

Question 6

What is the dipper function?

Answer 6

Graph of experiment carried out by Nachmias and Sansbury which finds a ‘dip’ at which the visual system is at its most sensitive

Question 7

Where has abnormal gain control been observed?

Answer 7

Autism, schizophrenia, epilepsy and Parkinson’s