Lecture 2 6th February 2017
Neural Circuits
Rhythm generation by Central Pattern Generator (CPG) circuits
The spinal cord can generate complex motor patterns independently of the
brain: the simplest motor system
- E and F is extension and flexion
The cycle of locomotion is organised by central pattern generators (CPGs) that
drive motor neurons
The step cycle.
Leg flexion and extension
Their relation to the swing and stance phase of locomotion.
Transection (cut across) of the spinal cord at the thoracic level isolates the hind
limb segments of the cord
After cord transection
The hind limbs are still able to walk on a treadmill
Reciprocal bursts of electrical activity can be recorded from flexors
during the swing phase and from extensors during the stance
phase of walking
Therefore there must be a central pattern generator present in the
spinal cord and independently of the brain
There are two alternative hypotheses for the generation of rhythmic and
alternating movements
Reflex chain model
Sensory neurons innervating a muscle fire and excite interneurons
that activate motor neurons to the antagonist muscle
No support as of yet
Central pattern generator model
Neural Circuits
Rhythm generation by Central Pattern Generator (CPG) circuits
The spinal cord can generate complex motor patterns independently of the
brain: the simplest motor system
- E and F is extension and flexion
The cycle of locomotion is organised by central pattern generators (CPGs) that
drive motor neurons
The step cycle.
Leg flexion and extension
Their relation to the swing and stance phase of locomotion.
Transection (cut across) of the spinal cord at the thoracic level isolates the hind
limb segments of the cord
After cord transection
The hind limbs are still able to walk on a treadmill
Reciprocal bursts of electrical activity can be recorded from flexors
during the swing phase and from extensors during the stance
phase of walking
Therefore there must be a central pattern generator present in the
spinal cord and independently of the brain
There are two alternative hypotheses for the generation of rhythmic and
alternating movements
Reflex chain model
Sensory neurons innervating a muscle fire and excite interneurons
that activate motor neurons to the antagonist muscle
No support as of yet
Central pattern generator model
