2-Minute Neuroscience: Indirect Pathway of the Basal Ganglia

The indirect pathway is a circuit in the basal ganglia best-known for its hypothesized role in the inhibition of movement. In this video, I discuss how the structures of the indirect pathway are thought to work together to suppress unwanted movements.

TRANSCRIPT:

The indirect pathway is a circuit in the basal ganglia hypothesized to play a role in the inhibition of movement. If you’re not already familiar with the direct pathway of the basal ganglia, you might want to watch my video on the direct pathway before you watch this video.

The indirect pathway model involves GABA neurons that project from the external segment of the globus pallidus to a region called the subthalamic nucleus. These globus pallidus neurons typically exert an inhibitory effect on glutamate neurons in the subthalamic nucleus, but when the indirect pathway is activated by signals from the cerebral cortex, this causes the activation of GABA neurons in the striatum, which project to the globus pallidus external and inhibit the activity of neurons there. This keeps the globus pallidus external neurons from being able to inhibit neurons in the subthalamic nucleus. The subthalamic nucleus neurons are activated by projections from the cortex, and they stimulate GABA neurons in the globus pallidus internal segment and substantia nigra pars reticulata. These GABA neurons in turn project to the thalamus, inhibiting thalamic neurons that travel to motor regions of the cerebral cortex to stimulate movement. The inhibition of these thalamic neurons thus inhibits movement. This activity in the indirect pathway is thought to antagonize the activity of the direct pathway and act to keep unwanted movements from occurring.

Neurons from the substantia nigra pars compacta travel to the striatum via the nigrostriatal pathway, and they can modulate the activity of the indirect pathway through dopamine release in the striatum. One effect of this seems to be the inhibition of activity in the indirect pathway, which leads to the facilitation of movement. This is thought to be one reason why dopamine depletion in disorders like Parkinson’s disease may lead to difficulties initiating movement.

References:

Mink JW. The basal ganglia: focused selection and inhibition of competing motor programs. Prog Neurobiol. 1996 Nov;50(4):381-425.

Purves D, Augustine GJ, Fitzpatrick D, Hall WC, Lamantia AS, Mooney RD, Platt ML, White LE, eds. Neuroscience. 6th ed. New York. Sinauer Associates; 2018.

Special thanks to Nicole Lookfong for help with fact-checking the script for this video.

[chan-lcwi]

Amazing how these videos explain so much better than any uni professors

[manasidevakumar]

This helped so much, thank you! I have an exam tomorrow and you saved my life.

[Nahs_]

شكرا عالشرح الرائع وشكرا كتيير للشخص اللي عمل الترجمة العربية انقذت خمس ساعات من حياتي ❤❤❤❤❤

[tannerjoseph]

the thoughtfulness within the diagram worked really well for me, thank you!

[TEAMPHY]

Neat to watch this video before watching pop and lock dance competitions, knowing all the stuff going on in those people.

[silviakrebesova]

I finally understood this topic, thanks to you! Thank you for making this simple explainatory videos.

[prospertsebam]

Thank you so much!
May God bless you.

[sagbaby]

So we’re saying the speed at which we initiate movements depends on how we balance the excitation and inhibition in our basal ganglia?

[sudhandradevirj]

hi I didn't understand one part u have colored red from substantia nigra pars compacta to striatum is it because it inhibits the indirect pathway as a whole ? cuz dopamine release activates the striatum right ?

[jsedla]

Thank you for this video, it will be helpful to my students. I just had a quick question. If we are speaking to dopamine depletion like in Parkinson Disease. If we are looking at the Indirect Pathway that is involved in preventing unwanted movements. If there is a dopamine depletion impacting the Nigrostriatal pathway which assists the striatum in inhibiting the GP external so that the SN and GPi/SN retic can inhibit initiation of wouldn't the depletion of dopamine more so be the presence of the tremor since the system is not effectively inhibiting movements? I may be looking at it wrong. In my head, a dopamine depletion in the setting of the DIRECT pathway, would demonstrate movement initiation issues, since it is not there to assist the striatum in inhibiting the SN/GPi from inhibiting the thalamus. Thank you so much ahead of time for your assistance and help with this

[valda]

The arrow from the substantia nigra pars compacta to the striatum is drawn in red (inhibitory connection) in the indirect pathway but in green (exciatory connection) in the direct pathway.
Does it mean that the nigrostriatum pathway has opposite roles in indirect and direct pathways?

[infinityandbeyond]

I watched the dirty medicine vid on this and was lowkey still confused... THIS vid helped me soooo much thank you!!

[orca_ah]

Thank you for the good video. Can you please share, where did you find all the motivation to not only study and work with tons of information but also taking your time to share it with people?

[jameel]

You are great. do videos on basic sciences such as biochemistry, biology, microbiology, immunolgy, histology and etc. Thanks

[Lifewithpradip]

I am always thankful to you for clearing concepts through making such awesome videos!!


btw, do u use any special software to make these videos? because I really like your representation...:)

[sem]

Very helpful, thanks for your perfect work

[bhawnavermaverma]

Can u tell me if basal ganglia is not present in left side do wht happen

[jokullsindrigunnarsson]

it's not at all clear how dopaminergic output from the substantia nigra pars compacta could be inhibiting the striatum without there being an additional step inbetween. I don't get it. Is ther a stimulation of another inhibitory neuron in the sstriatum?

[jayakkrishnak]

Anyone explain me about substantia nigra part alone
What is it doing ?