Neural circuits

Question 1

How are neural circuits studied?

Answer 1

Define the neurons involved
Establish their synaptic connections
Properties of synapses
Properties of neurons

Question 2

Different ways of studying?

Answer 2

Invertebrate preparations allow recordings from semi-intact preparations, giving direct link to behaviour

Invertebrates have “identified neurons” -present in every individual, same size same place, doing the same task

Establishing the link between neurons and behaviour is harder in vertebrate preparations

Vertebrates do not have “identified neurons” (mostly)

More indirect methods are needed to deal with populations of neurons

HRP Back-filling, a way of defining neuronal categories

Immunocytochemistry also helps to categorize neurons: the tadpole has only one class of glycinergic interneuron

The lamprey -a robust, primitive vertebrate preparation for studying spinal CPGs

Question 3

How do you decide membership of a Central Pattern Generator?

Answer 3

Is it active during motor behaviour, with an appropriate pattern? (Necessary but not sufficient)

Can it be used to reset the rhythm?
(Sufficient, but not necessary)

Inactivation/destruction/blocking of activity
–does pattern generation cease?

However resetting experiments are only possible when a central pattern generator consists of relatively few neurons.

This is OK for invertebrate CPG’s but not for those in vertebrates which can consist of 1000’s of neurons –other approaches are needed here…

Question 4

What are the correct uses of models?

Answer 4

Helping us to understand the roles of individual cells and cellular components
Making testable predictions about function
Abstracting general principles of circuit behaviour