Basic principles of sensory processing

Chapter 8

The basic problem

• Imagine that you are trying to convey sensory information someone who is locked in a room with no access to the external world.

• All you can do is knock on the walls.

1. The senses convey specific information about some source of

physical energy

•Muller’s specific nerve energies•we can’t see thunder or hear lightning

•Each sensory modality has a ‘labelled line’•Each sensory modality has specialized receptors for transduction

An example of transduction - The Pacinian corpuscle

2. Each sensory modality responds to a range of stimuli

3. Each sensory modality has evolved to fit an animal’s needs

Pit vipers and thermoreception

Burmese python

Can sense temperature changes of as little as 0.002 C

Insect eyes and UV

Many flowersHave distinctive UV signatures

4. Each sensory modality has a set of codes

• Intensity coding

• Location coding

• Coding of special object properties (colour, pitch)

Coding for intensity

Coding for locationTopography…. …albeit distorted

\Coding for quality

5. Submodalities have separate pathways

Submodality coding is universal

6. Sensory systems are interested in change

Adaptation -temporal change Mach bands - spatial change

Sensory systems provide caricatures

• A vast number of illusions demonstrate that our senses do not convey an exact replica of the external world but instead help us to construct a world that ‘makes sense’ (i.e. allows us to behave adaptively).