Action part 2 Flashcards
Motor Control System Cerebellum,Basal Ganglia, Motor Cortex (Premotor, SMA, Primary)
Motor Cortex (Premotor, SMA, Primary): Plans, and directs voluntary movements.
Basal Ganglia: Controlling the Start of Movement
Cerebellum: Coordinates sensory-motor function.
Results of damage to cerebellum
B Range of movement errors :motor learning process in which the nervous system adjusts movement to correct predictable errors
C Patterned movement errors: patterns sent from the brain, proprioception issues, and neural or biomechanical damage.
Gross anatomy
of cerebellum( PFCWGF)
Gross anatomy
of cerebellum
1. Pons
2.Fourth ventricle
3.Cerebellum
4.White matter
(Arbor vitae)
5.Grey matter
(Folia)
(Cerebellar cortex)
The Cerebellar Cortex
Granule Cells: ~50 billion (¾ of all brain neurons).
Purkinje Cells: ~200,000 inputs per cell.
Highly regular arrangement.
Cerebellum and Motor Control
Uses a forward model to predict motor outcomes.
Compares actual vs. predicted results for:
Error correction (real-time adjustments).
Motor learning (adapting movements).
Feedback control (refining actions).
Generates an error signal to improve future movements.
Nothing here
Feedback control and Fitts Law
Faster movements allow less time for feedback, increasing errors.
Fitts’s Law explains this tradeoff in pointing motions.
Fitts’s Law ( TDWab
T depends on:
D = Distance to target
W = Target width
a = Initiation time
b = Limb movement speed
Fitts’s Law –
Imagine an experiment where participants point at targets with either their elbow or finger. Participants initiate movements equally fast with their elbow and finger. But their elbow moves slower than their finger. Which constant in Fitts’s Law would represent this difference?
C. Constant b would be larger for elbows.
Fitts’s Law - Speed/accuracy tradeoff
Faster: To reach quicker, increase speed → lower accuracy (wider target).
More Accurate: To hit a smaller target, take more time → slower movement.
Cerebellum and Cognition
cerebellum is involved in cognitive functions. It plays a role in shaping, coordinating, and finessing action, cognition, and thought.
From cortex to
spinal cord
Primary motor cortex sends signals directly to lower motor and local circuit neurons.
Spinal cord circuits can independently control movements.
Patellar reflex circuit.
Motor (Red) Pathway:
Ventral root → Efferent neuron axon → Flexor muscle (muscle contraction)
Sensory (Blue) Pathway:
Extensor muscle & sensory receptor → Afferent neuron axon → Dorsal root → Interneuron (processing in spinal cord).
Withdrawal Reflex
Requires 2 spinal cord synapses to activate the motor neuron.
Involves local circuit neurons and lower motor neurons.
Central
pattern
generators
The details of exactly which muscles need to fire and which sequence to implement for an action that is largely handled in the spinal cord itself.
Local Circuits in Spinal Cord
Control complex movements.
Respond to environmental changes.
Do not require higher-level input.
Motor Units and Muscle Activation
Motor neurons and muscle fibers are the smallest units of force activation.
The nervous system controls muscle activation and its impact on other body parts.
Motor Control and Muscle Activation (Acetylcholine)
Lower motor neurons synapse directly on muscle fibers.
Acetylcholine release causes muscle fibers to contract.
Muscle spindles detect muscle length changes and send information to the spinal cord via dorsal root ganglia.
Finer Motor Control
For finer control in limbs, each motor neuron innervates fewer muscle fibers.
Neuromuscular disorder:
Myasthenia Gravis (MG)
Weakness in voluntary muscles (eyes, face, throat, limbs).
Autoantibodies block acetylcholine
receptors at the neuromuscular junction.
Symptoms include muscle fatigue, drooping eyelids, and difficulty swallowing and speaking.
Brainstem and Spinal Cord
Serve as highways for motor commands from the brain to muscles.
Contain circuits for controlling functions like breathing and posture maintenance.
Intracellular Recording Techniques clamps
Voltage clamp: Measures and controls the membrane potential to study ion flow.
Current clamp: Measures the membrane potential in response to injected current.
Patch clamp: Measures ion currents through individual ion channels.
Types of electrical
recordings ( Extracellular)(SMFIvitIvivA)
Extracellular Recording
Single-unit: Individual neuron activity.
Multi-electrode: Multiple neuron activity.
Field potentials: Group neuron activity
In vitro: Outside organism.
In vivo: Inside organism.
Anaesthetized vs awake: State-dependent activity.
Spatial and Temporal Resolution in Neuron Recording
Great spatial resolution (individual neurons).
Great temporal resolution (precise timing of action potentials).
Ethical concerns with
animal experimentation
Areas of potential concern:
* Care and housing
* Surgical implantation of
electrodes
* Training & performance
* Food/water deprivation
* Physical coercion/restraint
* Sacrifice after experiment
Ethical concerns with
animal experimentation
Larger considerations:
* Pain and suffering
* Lack of consent
* Killing living creatures
* Interspecies differences
* Fruit fly
* Mouse
* Macaque
* Benefit to humanity
* Necessity for knowledge
Ethical concerns
with animal
experimentation ( Against)
Experimenting on animals is always unacceptable because:
- it causes suffering to animals
- the benefits to human beings are not proven
- any benefits to human beings that animal
testing does provide could be produced in other ways
Ethical concerns
with animal
experimentation( Favor)
Experimenting on animals is acceptable if (and only if):
- suffering is minimized in all experiments
- human benefits are gained which could not be
obtained by using other methods
Brain-Computer Interface (BCI)
Enables direct communication between the brain’s electrical activity and external devices (e.g., computer, robotic limb).
Aims to assist, augment, or repair cognitive or sensory-motor functions by bypassing physical movement.
Microelectrode arrays
A very small spiky thing that can go on a neuron
Nothing here
Decoding
primary motor cortex
activity
refers to the process of reading and interpreting the electrical signals in the primary motor cortex of the brain.
Reaching
& grasping
are essential tasks that impact daily life. These activities include self-feeding, using adaptive equipment, and maintaining a safe environment
