Lecture 23 : Motor circuits – Sensory-motor

Summary

This lecture explores the intricacies of motor circuits in the nervous system, detailing how they control our movements and behaviors. Key components include the motor cortex, which orchestrates actions based on sensory input and decision-making, and the roles of the basal ganglia and cerebellum in learning and coordination. The distinction between visually guided and memory-guided movements is highlighted, emphasizing the importance of sensory feedback for smooth execution. The session underscores the seamless integration of perception, planning, and action in our daily interactions with the environment.

Takeaways

• 🧠 The motor system serves as the output mechanism of the nervous system, controlling behaviors and interactions with the external environment.
• 🔄 Motor movements rely on sensory inputs, with decisions formed based on the information processed through the nervous system.
• 🗣️ The motor cortex, located anterior to the central sulcus, is essential for planning and executing movements.
• ⚙️ Key areas of the motor cortex include the primary motor cortex (M1), pre-motor cortex, and supplementary motor area, each playing specific roles in movement control.
• 📏 Motor control involves feedback mechanisms that help adjust movements in real-time, ensuring stability and precision.
• 👁️ Visually guided movements require real-time sensory feedback and are primarily managed by the pre-motor area.
• 🧩 Memory guided movements are executed based on learned sequences without immediate visual cues, mainly regulated by the supplementary motor area.
• 🔗 There is a continuous feedback loop between motor actions and sensory input, essential for fine-tuning and adapting movements.
• 🗺️ The organization of both the motor and somatosensory cortices reflects a somatotopic mapping, indicating body parts that require greater control are represented more extensively in the brain.
• 🔍 Future discussions will cover sensory-motor systems and executive circuits, further exploring how these systems interact to influence behavior.

Q & A

What role do sensory circuits play in the nervous system?

Sensory circuits serve as the input to the nervous system, providing connections with the external world and enabling the perception of information necessary for decision-making.

What is the function of the motor system?

The motor system controls behavioral outputs, enabling actions such as speech and movement, by translating sensory inputs into motor actions.

How does the motor cortex contribute to movement?

The motor cortex, located anterior to the central sulcus, is responsible for the top-level control of movements, sending signals to spinal motor neurons that activate muscles.

What are the primary areas involved in planning and executing movements?

The primary areas include the primary motor cortex (M1), the premotor cortex, and the supplementary motor area, which work together to plan and execute movements.

What types of motor movements are controlled by the supplementary motor area (SMA) and premotor area?

Visually guided movements are primarily controlled by the premotor area, while memory-guided movements are mainly managed by the supplementary motor area.

What is the importance of feedback in motor control?

Continuous sensory feedback is crucial for adjusting and refining movements, allowing for adaptive changes based on muscle position, force, and movement velocity.

How does the brainstem and cerebellum contribute to motor function?

The brainstem and cerebellum are involved in maintaining postural stability and coordination during movement execution, ensuring smooth and accurate actions.

What is somatotopy, and how is it relevant to the motor cortex?

Somatotopy refers to the mapping of different body parts onto specific areas of the motor cortex, where more complex or fine movements correspond to larger areas of cortical representation.

What happens when the premotor area is damaged?

Damage to the premotor area can impair visually guided movements, while memory-guided movements remain intact, highlighting the area's role in real-time movement planning.

What does the term 'sensory motor system' refer to?

The sensory motor system encompasses the pathways that provide sensory inputs to the motor cortex, influencing behavioral outputs based on sensory information and executive signals.