Have you ever heard of the hyperdirect pathway? I hadn't Check out my Basal Ganglia teaching presentation, a review of the pathways and their relation to Parkinson's

1. The Basal Ganglia and
Parkinson’s Disease
Ellena Farrow
April 2018
Band 5 Physiotherapist, Addenbrooke’s Hospital

2. Anatomy
• Caudate and putamen also known as striatum
• https://en.wikipedia.org/wiki/Basal_ganglia

3. Function
• Predominantly involved in movement
• Also roles in cognition and emotions
• Activity of basal ganglia influence activity in other
areas of the brain
• Different circuits (pathways) that promote and inhibit
movement
• Initially thought there were 2 pathways (direct and
indirect).

4. Components and functions
• Striatum: I send inhibitory signals to the globus pallidus
and the substantia nigra.
• Substantia Nigra and Globus Pallidus: We also send
inhibitory messages to the thalamus and the subthalamic
nucleus
• Thalamus: I send messages to the motor cortex to either
initiate or prevent movement, depending on if I’m excited
or inhibited.
• Subthalamic nucleus: The only part of the basal ganglia
with EXCITATORY neurones.

5. • Just remember- The components of the
pathways are inhibitory. They aim to prevent any
unwanted movement.

6. http://www.virtualmedstudent.com/links/anatomy/basal_ganglia_direct_pathway.html

7. Direct Pathway
• When you want to move, you send an excitatory stimulus to the
striatum, increasing it’s activity
• Striatum sends increased inhibitory signals to globus pallidus and
substantia nigra
• Globus pallidus and substantia nigra fire less messages (as they have
been inhibited)
• Less inhibitory messages fired to the thalamus means it is less inhibited,
therefore it sends more stimulatory signals to the motor cortex, which in
turn initiates more movement.

8. http://www.virtualmedstudent.com/links/anatomy/basal_ganglia_direct_pathway.html

9. Indirect Pathway
• Motor correct stimulates the striatum
• Striatum inhibits the external part of the globus pallidus
• Globus pallidus externus (now inhibited) therefore sends less signals to the sub
thalamic nucleus
• The sub thalamic nucleus (normally inhibited) is now inhibited less
• Subthalamic nucleus neurones become more active and stimulate the internal
segment of the globus pallidus
• Globus pallidus internus (normally inhibits the thalamus) is now more active, so
inhibits the thalamus even more.
• Thalamus now sends less stimulatory signals to motor cortex, so less muscle
activation.

10. Direct Pathway simplified
• You want to move
• Your motor cortex gets excited and sends more signals to your striatum
• Your striatum is a negative thinking friend. It’s job is to send out inhibitory
signals. By exciting it, it sends out loads more inhibitory signals.
• Your stn and gp also like to send out inhibitory signals. By pummelling them
with inhibition from the striatum, they become more inhibited, and therefore
send out less signals. (So they send LESS INHIBITORY signals to the
thalamus.
• By sending less inhibitory signals to the thalamus (thanks to the stn and gp) it
becomes more excited and sends more stimulatory signals to the motor cortex.
• Your motor cortex tells your muscles to move!

11. Indirect pathway simplified
• You want to rest
• Your motor cortex needs to stop movement, so it sends lots of signals to your striatum.
• Your striatum is still a negative thinker, so he sends lots of negative thinking inhibitory signals
• These signals reach the external part of the globus pallidus.
• The globus pallidus (external) receives all the negative vibes and becomes inhibited.
• The sub thalamic nucleus is usually lazy
• Lazy sub thalamic nucleus is receiving less lazy vibes from the inhibited globus pallidus, so he becomes
less lazy and more excited.
• The (now excited) sub thalamic nucleus stimulates the internal part of the globus pallidus (which is normally
negative and inhibits the thalamus).
• With more excited signals, the globes pallidus becomes more excited, releasing lots more inhibitory signals
for the thalamus.
• The thalamus receives the negative inhibitory signals, inhibiting it’s output to the motor context and
therefore initiating less movement.

12. The Hyperdirect Pathway: Because when
you’ve already got 2 confusing pathways,
why not add a third?
• The signals from the motor cortex bypass the striatum and head
straight to the sub thalamic nucleus
• Remember the subthalamic nucleus is excitatory.
• All the excited signals reach the internal part of the globus pallidus.
• This stimulates the globus pallidus to release more inhibitory signals
to the thalamus.
• The thalamus is now inhibited much more, sends less signals to the
motor cortex….. Movement stops.

13. Courtesy of http://slideplayer.com/slide/7060336/

14. Clear as mud?

15. Don’t panic
• In the grand scheme of physio, you don’t need to
remember all the nuclei and their functions.
• We just need to know:
• 1 pathway stimulates movement
• 1 pathway inhibits movement
• 1 pathway stops movement
• It is a balance of all of these pathways that enables most
of us to move “normally”

16. Parkinson’s
• What is it?
• Loss of dopamine neurones from the substantia
nigra
• How does it present?
• Tremor, freezing/slowed movement, cognitive
deficits, lewy body dementia.

17. Dopamine?
• Dopamine neurones are present in the
substantia nigra
• The neurones project into the striatum.
• The role of these neurones is to regulate the
pathways- They stop excessive movement in the
direct pathway and they prevent unwanted
cessation of movement in the indirect pathway.

18. Dopamine and Parkinson’s
• In Parkinson’s, the dopamine neurones are
damaged and lost
• In simple terms, without the dopamine the pathways
cannot be regulated correctly.
• Now we cannot initiate more movement in the direct
pathway and we cannot prevent an excessive
reduction in movement in the indirect pathway
• This manifests as tremor and bradykinesia.

19. • Are you still with me?
• To summarise:
• 3 Pathways- Direct, indirect, hyperdirect
• All work together to ensure we elicit the movement we actual
want and need, no more, no less.
• People with Parkinson’s are missing vital neurones that help
regulate the 3 pathways
• This leads to too much movement, too little movement or a bit
of both.

20. Does any of that information have any
relevance to me treating patients?
• Depends….
• Remember the hyperdirect pathway? Remember how it
bypasses the striatum and goes straight to the subthalamic
nucleus?
• Have you ever heard of deep brain stimulation for Parkinson’s
or movement disorders, to stop the unwanted movements?
• The stimulation is often applied direct to the subthalamic
nucleus. Why?
• Well, you now know why….

21. • Thanks for listening
• This presentation could not have been made without the help of the following!
• https://www.youtube.com/watch?v=J56CFExkHgE
• https://www.youtube.com/watch?v=APXYe_P1BLA
• https://www.youtube.com/watch?v=TWAKheHlDHs
• https://www.youtube.com/watch?v=8mvUDiBQbjg