We have selected material for this presentation by structuring the discussion around a series of critical questions that might be asked with a view toward modelling a biological tactile sensing system.

1. What is touch used for?

2. What are the primary units that are sensitive to mechanical stimulation?

2.1. What are the response characteristics of these tactile units?

2.2. What are the factors that determine a unit's response characteristics?

2.3. Classification of tactile units

3. What are the specific features of the mechanical stimulus to which individual tactile units selectively respond?

3.1. Sustained deformation normal to skin surface

3.2. Spatially patterned deformation (normal to or scanned across fingertip skin)

3.3. Transient deformation, i.e. vibration (normal to skin surface)

3.4. Temporal vs spatial tradeoffs

3.5. Sustained deformation lateral to the skin surface, i.e. skin stretch

4. Other issues/parameters that affect the response of populations of tactile units

4.1. What is known about the population distribution of the four types of tactile units in the

fingertip?

4.2. What is known about convergence in the cutaneous system beyond the first synapse?

4.3. A neural alternative to mechanical edge enhancement

4.4. Which populations of tactile units are involved in coding complex spatial patterns applied

to the fingertip?

4.5. Which mechanoreceptor populations are involved in coding textures moved across the fingertip?

5. What is known about the human response to stimulus properties at the behavioural level?

5.1. Point or unpatterned probes

5.2. Edge properties

5.3. Stimulus Width

5.4. Patterns

5.5. Surface topology

5.6. Detecting Slip for Controlling Precision Grip

6. How is cutaneous information used to understand objects?

6.1. Limitations on cutaneous integration

6.2. The role of hand/arm movements

7. Other issues to consider

7.1. What coordinate system(s) do we use to code the cutaneous/kinesthetic input?

7.2. How does the human system integrate perceptual and manipulative demands during

haptic exploration?

7.3. How do haptic and visual inputs become integrated?

8. References