17. Motor systems and brain states, part 3

TL;DR

The spatial organization of motor pathways in the central nervous system plays a crucial role in motor control and can lead to paralysis when damaged.

Transcript

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Key Insights

• 🧑‍🦼 Bilateral lesions of the medial pathways impact body axis control and overall motor function.
• 🤗 Selective paralysis can occur when the lateral pathways are cut on one side, leading to a loss of grasping ability in the affected hand.
• 🧑‍🦼 The descending motor pathways control various movements, including locomotion and grasping, and are crucial for motor control.
• 🌸 Central lesions can result in flaccid paralysis or loss of reflex control, highlighting the importance of intact spinal cord connections.
• 🧑‍🦽 The size of the neocortex is correlated with the depth of spinal projections and manual dexterity in animals.
• 🧑‍🦼 In humans, motor cortex dominance may be attributed to its connections with prefrontal areas and the ability to anticipate movements.
• 🪗 Various movement patterns, such as swallowing and locomotion, can be centrally generated by the hindbrain and spinal cord.
• 😟 Feedback circuits and endogenous activity contribute to the generation of temporal patterns in the nervous system.
• 🎮 The overall state of the brain, including feedback loops and endogenous activity, plays a role in motor control and timing.

Questions & Answers

Q: How do bilateral lesions of the medial pathways affect motor control?

Bilateral lesions of the medial pathways impact the control of body axis, making it difficult for individuals to walk straight, orient their heads, or maintain balance.

Q: What happens when the lateral pathways are cut on one side?

Cutting the lateral pathways on one side can lead to selective paralysis in the hand on the opposite side, where individuals are unable to grasp objects but can still control their arm muscles.

Q: What role does the descending pathway play in motor control?

The descending pathway is responsible for controlling various motor functions, including locomotion and grasping, and is critical for coordinated movements.

Q: Can individuals with transected spinal cords still have voluntary movements?

Individuals with transected spinal cords can still have voluntary intention to move, as seen through imaging methods, but the loss of descending pathways prevents the activation of motor neurons and limits their ability to physically move.

Summary & Key Takeaways

• Bilateral lesions of the medial pathways in the motor system can result in a loss of control over body axis, making it difficult to walk straight or even orient the head.

• Lateral lesions of the motor pathways on one side can lead to selective paralysis, where one hand can reach but not grasp objects.

• The descending motor pathways are essential for controlling motor functions, such as locomotion and grasping, and can be impacted by central lesions.