Rhythmic motor movements 2 Flashcards
stepping, swing and stance phases, supraspinal control of stepping, spinal rehabilitation
what is the role of basal ganglia
action selection
what is the role of the optic tectum (superior colliculus)
orientation/ avoidance behaviours
what is the role of the cerebellum
control/ coordination
What is the central role of the brainstem in motor control?
The brainstem serves as a main interface between the brain and the spinal cord, facilitating high-level motor control that influences central pattern generators.
It integrates signals from various brain regions involved in movement control
What is the mesencephalic locomotor region (MLR)?
The MLR is a brain region critical for controlling locomotion, discovered through electrical stimulation experiments.
It was first identified in cats, but homologous regions exist in many species.
What happens when the MLR is stimulated at low versus high intensity?
Low intensity stimulation elicits walking, while high intensity stimulation induces running.
This observation was made in cats and replicated in other species.
what does MLR firing rate determine
initiation and speed of locomotion according to frequency of APs of neurons in this region
How does the firing rate of neurons in the MLR relate to locomotion speed?
The firing rate of individual neurons in the MLR is proportional to locomotion speed, although the correlation is not exact.
The relationship varies among different neurons.
What are the two main anatomical subregions of the MLR?
The two main subregions are the peduncolopontine nucleus (PPN) and the cuneiform nucleus (CnF).
what type of neurons do the two subregions contain
Both regions contain excitatory glutamatergic neurons and inhibitory GABAergic neurons.
BUT
PPN also some cholinergic
What is the role of glutamatergic neurons in the MLR?
Glutamatergic neurons in the MLR are primarily involved in initiating and drive locomotion.
what happens if glutamatergic neurons are stimulated
can lead to increased locomotion speed.
What is the effect of stimulating GABAergic neurons in the MLR?
Stimulating GABAergic neurons can terminate locomotion or enhance running speed when the animal is already running.
what do cholinergic neurons in the MLR do
modulate locomotion
What distinct function does the CnF serve in locomotion?
CnF evokes the full range of speed, from slow (walking) to fast locomotion (gallop)
revealed from stimulation of glutamatergic neurons
what is the function of PPN
only evokes slow locomotion
revealed from stimulation of glutamatergic neurons
In the CnF how is the firing rate of glutamatergic neurons related to speed
linearly
the PPN has a more complex relationship
PPN glutamatregic neurons beyond locomotion speed control
- neurons active during rearing and project to SPINAL CORD
- neurons active during grooming and handling and project to BASAL GANGLIA
what si the MAIN brain region of MLR that controls posture
PPN
in posture, what is the role of a small subset of CnF neurons
control body extension
- first principal component of posture
associated with execution and rearing and locomotion
How do the projections to CNF and PPN differ?
afferents / input
PPN receives projections from a wide range of brain regions such as basal ganglia, while CNF receives more localized projections from more specific brain regions such as the colliculi and Periaquiductal Gray
This suggests different functional roles in motor control.
Summary of MLR
where is the medullary reticular formation ?
between MLR and spinal cord
what does the MRF do?
This structure is essential for transmitting signals to spinal cord neurons involved in central pattern generation (CPGs) via the reticulospinal tract
True or False: Locomotion is solely about moving the legs.
False.
Balance and other muscle groups are also crucial for effective locomotion.
What is the significance of the vestibular system in locomotion?
The vestibular system is important for maintaining balance during locomotion.
It processes information critical for postural adjustments.
What behavioral changes occur with different stimulation frequencies of glutamatergic neurons in the MLR?
Different stimulation frequencies lead to variations in locomotion speed and patterns, such as transitioning from a walking gait to a galloping gait.
This indicates that speed and gait pattern are modulated by neuronal activity.
What role do PPN glutamatergic neurons play outside of locomotion?
PPN glutamatergic neurons are active during various motor behaviors, such as grooming and standing, not just locomotion.
This highlights their functional diversity.
Fill in the blank: The _______ is important for controlling body posture during movement.
PPN.
Proper posture is essential for effective locomotion and mobility.
What is the relationship between posture and movement according to Sherrington?
Posture follows movement like a shadow.
This emphasizes the interconnectedness of posture and locomotion.
What is locomotion primarily about?
Locomotion is not just about moving your legs; it involves multiple muscles to maintain balance.
What happens to deserebrated cats in terms of locomotion?
Deserebrated cats can still walk and run on a treadmill but require physical support due to impaired balance.
What is the key player in controlling balance during locomotion?
The vestibular system.
Where is the peripheral organ of the vestibular system located?
In the inner ear.
What are the two main types of vestibular organs?
- Otoliths (utricle and saccule)
- Semicircular canals.
What do otoliths sense?
Linear acceleration and gravity.
What do semicircular canals sense?
Angular acceleration along the yaw, pitch, and roll axis.
3 types
where are vestibular nuclei located and what are they
brain stem
- medial, lateral, superior, inferior
what do vestibular nuclei do
- recieve vestibular information from internal ear
- integrate vestibular, proprioceptive, motor and cerebellum inputs
- some project to SC via vestibulospinal tracts
what do patients with vestibular disorders display
- postural instability
- reduced ability to respond to unexpected pertubations
- increased variability in locomotor pattern (low velocity)
What is the role of the lateral vestibular nucleus?
It controls postures by targeting extensor muscles.
projects to spinal cord via lateral vestibulospinal tract
What are extensor muscles responsible for?
They are anti-gravity muscles that help fight gravity.
What happens to muscle tone in deserebrated cats?
They experience celebrated rigidity due to overly active extensor muscles.
ridigity reduced by lesioning LVN
What is the significance of the firing pattern of neurons in the lateral vestibular nucleus during locomotion?
They fire more during locomotion, particularly during extensor muscle contraction.
What is the effect of ablating neurons in the lateral vestibular nucleus?
It disrupts the early phase of muscle response and reduces the late phase
- increases postural instability
What is the coefficient of variation used to measure?
It measures the variability in the locomotor pattern.
what are vestibular reflexes
oppose movement to maintain stable balance
how is motion enabled by vestibular reflexes
vestibular reflexes are downregulated during initiation and termination of locomotion
True or False: Vestibular reflexes are always beneficial for locomotion.
False; they can be counterproductive when initiating locomotion.
What is required for initiating locomotion regarding vestibular reflexes?
They have to be transiently downregulated.
Fill in the blank: The vestibular system integrates information from the _______ and motor information.
[proprioceptive system].
What is the impact of bilateral vestibular failure on gait?
It leads to postural instability and increased variability in locomotor patterns.
What type of muscles do the lateral vestibular nucleus target?
Extensor muscles.
What happens to tail position during perturbations in balance?
It remains well centered, projecting down on the beam for stability.
What does a high coefficient of variation indicate in gait analysis?
Increased variability in stride duration or working cycle.
