Outline 10/20/98

3 Common Principles across sensory systems

Transduction,

Neural Coding

Interaction

Interaction in Time: Adaptation

Interaction in Space: Contrast

Perception

 

 

Common Principle #1--Transduction

 

All of the senses must be able to convert physical stimulus energy (e.g., light waves, chemical molecules, air pressure) into electrical changes in the receptor cells. This process is called "transduction."

 

Transduction and Smell

 

 

Transduction and Taste

 

 

Transduction and Sound

 

 

Common Principle #2-- Neural Coding

 

The stimulus input must be processed and coded for intensity (i.e., strong vs. weak) and qualitative aspects (e.g., red vs. blue, foul vs. pleasant, A flat vs. B sharp).

Typically, much of this coding happens at post-receptor sites.

 

Neural Coding and Sound

 

 

How Pitch and Volume are Coded

 

 

Common Principle #3--Sensory systems interact across time and location

 

PUT SUCCINCTLY... What you sense now in any given place depends upon what you sensed a minute ago and what is happening at other receptor sites.

E.G., Sensory adaptation--The change in sensitivity that occurs when a sensory system is either stimulated or not stimulated for a length of time.

 

Some Examples of Sensory Interaction from Vision

 

 

The Anatomy of the Eye

The Retina

 

Rods and Cones

 

Duplex Theory of Vision

Rods--operate under low illumination and are relatively achromatic. Think of them as night time receptors.

 

Cones--operate under high illumination. Chromatic. Packed around fovea. Think of them as daytime receptors.

 

Interaction in Time: Adaptation

Adaptation--Repeated stimulation of a particular receptor leads to reduced responding.

 

 

A demonstration--peripheral vision, adaptation, and movement.

 

 

Color Afterimage: Another demonstration of interaction across time

 

 

Why does color afterimage work? Adaptation and "Opponent Processes"

Every hue (i.e., color) has a complementary hue. When mixed together, these two hues form gray.

Two pairs are crucial--blue/yellow and red/green.

Why? Because they are antagonists--meaning that when they are balanced, we perceive gray.

 

 

Interaction is Space: Contrast

In vision, the response in one receptor region depends upon how neighboring receptor regions are responding.

 

 

Brightness Contrast

 

Color Contrast--the Chromatic counterpart to brightness contrast.

 

 

From Sensation to Perception Color vs. Movement Afterimage

 

Color Afterimage--Retinal Processing

 

 

Motion Afterimage--Cortical Processing