Locomotion and functions of the cerebellum

Introduction to Locomotion and the Cerebellum

  • Presented by Professor Vincent CK Cheung, School of Biomedical Sciences, The Chinese University of Hong Kong.

  • Date: 7 January 2026, Wednesday.

  • Overview of cyclic nature of locomotion.

Historical Background on Motion Studies

  • Eadweard Muybridge (1830 – 1904)

    • Key contributions to the understanding of movement through photography.

    • Documented various modes of locomotion:

    • Walking

    • Running

    • Crawling

    • Flying

    • Swimming

    • Example: A running bison activates muscle groups in a cyclical form.

Visual Representation of Movement

  • Key works from artists and photographers:

    • "The Horse in Motion" by Eadweard Muybridge (1878)

    • "The Barb" by Richard Wingfield Stuart (1886)

    • "Erlkoenig" by Moritz von Schwind (1860)

Gait Cycle Overview

  • Each gait cycle comprises two primary phases:

    • Stance Phase: When the foot is in contact with the ground.

    • Swing Phase: When the foot is in the air.

  • Example: In walking cats, both flexors and extensors engage in complex patterns during these phases:

    • Hip: Flexion and extension

    • Knee: Flexion and extension

    • Ankle: Controlled extension and flexion.

Neurological Basis of Locomotion

  • The spinal cord’s sufficiency in generating locomotor patterns once locomotion is initiated.

    • In experiments with decerebrate cats (forebrain severed), locomotor rhythm maintained without brain involvement.

  • Sensory feedback from limbs to the spinal cord is critical for coordinating locomotion.

Graham Brown's Experiment (1911)

  • Conducted a deafferentation experiment establishing that:

    • Locomotor rhythmic activities can persist without sensory input to the central nervous system (CNS) once locomotion is triggered.

    • Isolation of the spinal cord from brain control demonstrated sustained locomotor rhythm.

  • Findings indicate that alternating muscle contractions are independent of peripheral sensory feedback.

Central Pattern Generators (CPG)

  • Definition: Neuronal networks within the CNS that generate rhythmic motor activities autonomously, without sensory input coordination.

    • Components include:

    • Half Center Model: Two mutually inhibitory centers that regulate alternate muscle activation.

    • Inhibitory Output: Fatigues over time, triggering activation of the opposite center to create rhythmic motion.

    • Functions facilitated by:

    • Descending modulation

    • Sensory modulation

    • Temporal and spatial specifications.

Modulation of CPG Activities

  • Inputs from the brainstem that can alter CPG activity:

    • Midbrain Locomotor Region (MLR)

    • Subthalamic locomotor region

    • Pontine reticular formation

    • These areas influence speed and facilitate modifications for muscle recruitment patterns.

Effects of Stretching on Locomotion

  • Stretching of hip flexors (iliopsoas) simulates end-of-stance phase conditions.

    • Stretching can induce early initiation of the swing phase.

    • Muscle spindle afferents provide real-time feedback altering phase lengths or timing during locomotion.

Visual and Motor Cortex Interaction

  • Motor Cortex Activity: Engages during locomotion, specifically for obstacle navigation.

    • Requires sensory inputs to guide walking trajectories and obstacle avoidance.

    • Feedback from visual stimuli is integral to modulating locomotor responses.

Role of Neurons in Obstacle Navigation

  • The posterior parietal cortex is critical for processing spatial memory relevant to steady walking on uneven surfaces.

    • Involves working memory to adapt limb movements based on obstacle heights:

    • Demonstrated through comparisons of pause durations before and after lesions impacting this cortical area.

Key Takeaways on Locomotor Patterns

  • Spinal locomotor patterns exhibit adaptability influenced by:

    • Sensory inputs (proprioception and cutaneous signals)

    • Constant regulation by descending commands from higher brain areas.

    • Adjustments in muscle patterns and locomotion speed necessary for various locomotor tasks.

Understanding Human Locomotion

  • Research by Capogrosso et al. (2016) shows that:

    • Direct cortical inputs to the spinal cord are essential for initiating or maintaining CPG activities, especially after spinal cord lesions.

    • Articulating the connection between brain, spinal cord, and sensory feedback during locomotion.

Overview of Cerebellar Function

  • Cerebellum: Located in the hindbrain, plays a critical role in motor output modification, facilitating flexibility and precision.

    • Composed of three layers with specific roles:

    • Purkinje Cells: Receive converging inputs from granule cells, integrating sensory and motor signals for movement coordination.

Cerebellar Structure and Connectivity

  • Inputs:

    • Mossy Fibers: Convey sensory information to granule cells.

    • Climbing Fibers: Provide error signals necessary for refining coordination.

  • Outputs:

    • Purkinje Cells: Each can influence approximately 500 other neurons, creating extensive neural networks for motor regulation.

Motor Control Strategies

  • Two fundamental strategies:

    • Feedforward Motor Control: Involves pre-planned commands that do not adapt to feedback.

    • Feedback Motor Control: Adjusts movements based on real-time sensory input, enhancing accuracy.

Spinocerebellum Functions

  • Acts as a neural substrate for feedback motor control:

    • Generates motor commands for muscle activations based on sensory feedback from ongoing movements.

Cerebrocerebellum Role

  • Responsible for motor planning and anticipation of movement execution:

    • Binds closely with feedforward control alongside the motor cortex.

Effects of Cerebellar Lesions

  • Motor impairments following cerebellar damage include:

    • Inability to coordinate spatially and temporally across multi-joint movements.

    • Dysfunction in motor planning and feedback adjustments that typically ensure accurate motion.

Final Thoughts on Cerebellar and Locomotor Networks

  • The cerebellum modulates and refines activities across the spinal cord and cortex through feedback loops.

  • Highlighting the intricate connections between the cerebellum, cortex, and spinal network for optimal motor control.