the intrinsic function of a motor system – from ion channels to networks and behavior

The intrinsic function of a motor system – from ion channels to

networks and behavior

S. Grillner, L. Cangiano, G.-Y. Hu, R. Thompson, R. Hill, P. Wallén

3 types of motion

• Propulsive movements– Leg movements, wing movements, ondulatory

trunk movements

• Postural motor system– Maintain body orientation

• Goal directed movements– Visuomotor coordination

Motor System overview

Part of major interest in thispaper

Oscillatory patterns in propulsive movements

The lamprey model

Forebrain control

• Direct projections from olfactory bulb and optic nerve into ventral thalamus• Basal ganglia control the activity of v. th. by GABAergic inputs (Similar function as in mammals. e.g. MPTP)• Reticulospinal neurons activate the spinal cord locomotor activity

Lamprey brainsteam-spinal cord preparation (in vitro)

Can be maintained in vitro over several days at T=4-7°C

Locomotion can be elicited bystimulation in the brainsteam or by administration of agonists of excitatory amino acids.Spinal cord networks producethe motor pattern. (Ondulations at 0.2-10 Hz)

Brainsteam-spinal cord circuitry

Connectivity is critical for producing the motor pattern.

Goal: isolate the circuitry in the spinal cord and see how it works on a detailed level.

Importance of membrane properties

sAHP regulates the duration of burstsdue to Ca-concentration in the cell Kca-ChannelsCa enters also if the neuron is notspiking (NMDA, LVA-Ca)

A whole series of mechanismsregulate the duration of bursts in the spinal cord pattern generator

Calcium Imaging in dendrites

The calcium signal correlates with the spiking of neurons in the ipsilateral ventral root.

Modulatory effect of metabotropic receptors

Implement the findings in amodel

Questions and next steps

• What is the influence of using T=4°C?

• Why are there stretch receptors, when the model works fine without?

• Include control mechanisms from brain: e.g. how to swim a curve.

• Can all metabotropic effects be included? These are the „interesting“ mechanisms.