14 - CPG (central pattern generators)

Question 1

What is a central pattern generator?

Answer 1

Neural network that produces rhythmic (motor) output endogenously (ie without sensory or central input)

eg: air flow (breathing, coughing, singing)

Feeding (chewing, stomach movement)

Locomotion (walking, swimming, flying)

Question 2

The rhythmic CPG activity can ultimately be generated by how many neurons?

Answer 2

The rhythmic CPG activity can ultimately be generated by one neuron (or by one identical population of cells) with so called intrinsic bursting properties

Question 3

What does it mean when a single (or population of) neurons have intrinsic bursting properties?

Answer 3

This means that this (population of) neuron(s) continues to generate rhythmic depolarization of membrane potential (Vm), and accompanying bursts of action potentials (“spikes”), after isolation from the rest of the CPG

The rate of rhythmic activity in such intrinsic (or conditional) burster neurons (also called “pacemakers”) depends on Vm, with depolarization accelerating the rhythm

Question 4

As opposed to this intrinsic mechanism, rhythm in various other CPGs is due to _________. In most cases, these neurons form inhibitory synapses with each other that typically use ___________ or _________ as the neurotransmitter for activation of receptor-coupled Cl- channels

Answer 4

As opposed to this intrinsic mechanism, rhythm in various other CPGs is due to antagonistic activity of neuron populations. In most cases, these neurons form inhibitory synapses with each other that typically use γ-aminobutyric acid (GABA) or glycine as the neurotransmitter for activation of receptor-coupled Cl- channels

Question 5

Intrinsically bursting CPG neurons show what kind of activity in isolation? When together in petri dish?

What does this mean?

Answer 5

When isolated, these neurons show either no activity or ongoing relatively constant (tonic) discharge as shown here in the middle of the upper part of this slide.

However, when put together in a Petri dish, these neurons form synapses and show rhythmic Vm oscillations with different, often opposite phases.

This means that depolarization in one neuron hyperpolarizes the antagonistic neuron via inhibitory (GABA and/or glycinergic) synapses

Question 6

When isolated, these (neurons with intrinsic bursting properties) neurons show either no activity or ongoing relatively constant (tonic) discharge as shown here in the middle of the upper part of this slide. However, when put together in a Petri dish, these neurons form synapses and show rhythmic Vm oscillations with different, often opposite phases.

What does this suggest about the actions of one neuron and the antagonistic neuron?

Answer 6

This means that depolarization in one neuron hyperpolarizes the antagonistic neuron via inhibitory (GABA and/or glycinergic) synapses

Question 7

The activity of intrinsically activated CPG depends on:

Answer 7

Thus, the activity of this type of CPG depends critically on so-called mutual (or antagonistic) synaptic inhibition.