Spinocerebellar and Medial Lemniscus Pathways

[coreytayloris]

Whats the link between these two tracts?

I dont get it, im reading brodal and nolte and they say that medial lemniscus is for proprioception and discriminative touch, but then they say spinocerebellar pathway is also for proprioception

Are the two pathways linked together or whats the story!?
how do they relate to each other??

thanks

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[Justforkicks4]

Whats the link between these two tracts?

I dont get it, im reading brodal and nolte and they say that medial lemniscus is for proprioception and discriminative touch, but then they say spinocerebellar pathway is also for proprioception

Are the two pathways linked together or whats the story!?
how do they relate to each other??

thanks

The main distinction you'll want to keep in mind is that the medial lemniscus is carrying info to the CEREBRAL cortex (spinal cord-->medullary nuclei-->VPL of thalamus-->cortex), whereas spinocerebellar tracts are carrying info to the CEREBELLUM (often directly from spinal cord). But you're totally right in that both inform our higher motor centers about proprioception. The medial lemniscus pathway is probably the more important one to commit to memory. But if you're asked on an exam about a patient with ataxia, you might consider lesions to spinocerebellar tracts as well. Does that kinda make sense?

 

[VisionaryTics]

Think of it as low-road and high-road processing. The medial lemniscus pathway is conscious proprioception processed in the cerebral sensory cortex after thalamic relay (high-road), while the spinocerebellar system feeds into the cerebellar cortex to modulate cerebellar pathways that can directly feedback back to the spinal cord (low-road).

Think of the ML system as you consciously knowing where in space your arms are if your eyes are closed, while the spinocerebellar system is working overtime when Michael Jordan is driving the lane against defense -- he is unconsciously modulating his motor pathways based on proprioceptive information.

In terms of clinical lesions, it's pretty hard to knock out the spinocerebellar system, while the dorsal column-medial lemniscus system has a whole host of lesions that can affect it. In terms of symptoms, they will be similar.

 

[Untraditional]

Spino-cerebellar: unconscious proprioreception for limb position (feedback to your cerebellum about where your foot is currently having received a command to move or having been moved)

There is a Dorsal and a Ventral. Dorsal is joint position and Ventral is whole limb position. These are for the trunk and lower extremity. There is also a Cuneo-cerebellar system for the neck and upper extremity. All go to the cerebellum. The Dorsal and Cuneo systems enter through the inferior cerebellar peduncle. The Ventral enters through the superior. The Ventral tract is double-crossed so input it ultimately ipsi.

The Dorsal Column System is for conscious proprio vibration and 2pt kinesthesia. When someone does the Romberg test or moves your limb with your eyes closed you're evaluating the Dorsal Column / ML system. The DC/ML system crosses in the medulla and lands in VPL thalamus before going to the cortex.

This site got me through my first neuro exam, maybe it will help you:

http://library.med.utah.edu/kw/animations/hyperbrain/pathways/

 

[Dr McSexy]

FWIW, just about about every question that I saw relating to the spinocerebellar tract had to do with knowing that the ventral spinocerebellar tract gets its info via golgi tendon organs (Ib fibers) and the dorsal spinocerebellar tract gets it info via muscle spindles (Ia fibers), and know stuff about Clarke's nucleus as well.

 

[medstud87]

Very simply, the spinocerebellar tract projects ipsilaterally upwards to the cerebellum for non-conscious propioception but also gives off collateral branches to the dorsal column-medial lemniscus pathway to synapse on either cuneate or gracilis nuclei which then cross over towards the contralateral somatosensory cortex for conscious propioception.

 

[coreytayloris]

thanks guys!