Motor control, attention and consciousness Flashcards
What’s the Libet 1983 article about?
Libet (1983) – Cerebral Conscious Volition & Free Will
Question:
Does the brain make decisions before we are consciously aware of them?
Method:
EEG (to measure brain activity), EMG (to measure muscle movement), and CRO timer (to record decision timing).
Participants watched a moving light on a wall and reported when they consciously decided to move their hand.
Readiness potential (RP) was recorded before the reported decision to move.
Findings:
EEG (Readiness Potential) appeared before conscious awareness of movement.
This suggests that the brain initiates movement before we consciously decide.
Implications:
Challenges the idea of free will—are we just executing decisions our brain already made?
Suggests consciousness arises after unconscious neural activity, rather than causing it.
Criticism:
Does readiness potential actually reflect decision-making?
Participants self-reported decision timing, which may be inaccurate.
Later studies using fMRI suggest brain activity predicts movement even earlier.
Key Takeaway:
Free will may be an illusion—our brain acts before we consciously decide.
What’s the Dijksterhuis 2006 article about?
Deliberation Without Attention
Question:
Does unconscious thinking lead to better decision-making than conscious deliberation?
Method:
Participants were shown 4 car options, each with different positive/negative attributes (25%, 50%, 75% favorable).
Two groups:
Conscious Deliberation Group: Thought about the attributes before choosing.
Unconscious Thinking Group: Were distracted before choosing.
Later, participants chose the “best” car and reported satisfaction.
Findings:
Unconscious thinking led to better choices in complex decisions (e.g., when many attributes needed to be weighed).
Conscious thinking worked better for simple decisions (fewer attributes).
People who relied on unconscious thought felt more satisfied and confident in their decision.
Implications:
For complex decisions, stepping away (“letting it simmer”) improves choices.
For simple decisions, deliberate thinking is better.
Overthinking can lead to dissatisfaction and regret.
Criticism:
What defines “complex”?
Cultural & individual differences in decision-making styles.
Ecological validity—real-world decisions may not follow the same patterns.
How do we define the “best” choice objectively?
Key Takeaway:
Conscious thinking is best for simple decisions, but unconscious processing helps in complex choices.
Big decisions? Take a break and let your unconscious mind process it!
What’s the relationship between key motor control structures?
Motor control is a step-by-step process that begins with planning and selection before execution. Each structure plays a role in refining movement.
- Motor cortex - Planning & Sensory Integration
• Premotor Cortex (PMC) & Supplementary Motor Area (SMA) → Plan & organize movement sequences.
• Posterior Parietal Cortex → Integrates sensory input to guide movement. - Basal Ganglia – Movement Selection & Inhibition
• Function: Determines which movement to execute while suppressing unnecessary actions.
• Pathway: Basal Ganglia → Thalamus → M1 → Sends the selected motor plan to the motor cortex. - Cerebellum – Movement Coordination & Correction
• Function: Ensures accuracy, timing, and coordination of movements.
• Pathway: Cerebellum → Thalamus → M1 → Adjusts and refines motor output before execution. - Thalamus – The Relay & Integration Hub
• Function: Filters & integrates motor signals, combining input from the basal ganglia & cerebellum before sending it to M1.
• Pathway: Thalamus → M1 → Delivers final motor instructions. - Primary Motor Cortex (M1) – Movement Execution
• Function: Sends final movement commands to the spinal cord & muscles.
• Pathway: M1 → Brainstem & Spinal Cord → Muscles → Executes voluntary movement.
Final Takeaway – The Flow of Motor Control
1️⃣ Motor planning (PMC, SMA, Posterior Parietal Cortex).
2️⃣ Basal ganglia selects the appropriate movement & inhibits others.
3️⃣ Cerebellum refines the movement for precision & coordination.
4️⃣ Thalamus integrates all motor signals & relays them to M1.
5️⃣ M1 executes the movement by sending commands to the muscles.
🚀 This structured process ensures voluntary movements are well-planned, precisely controlled, and executed smoothly!
What is GABBA, epinephrine and Acetylcholine’s function in motor control?
Motor control relies on neurotransmitters to regulate movement, coordination, and execution.
- GABA (Gamma-Aminobutyric Acid) – Inhibition & Movement Control
• Function: The main inhibitory neurotransmitter in the motor system.
• Role in Motor Control:
• Basal Ganglia → Uses GABA to regulate movement selection.
• The indirect pathway increases GABA activity to suppress unwanted movements.
• The direct pathway reduces GABA inhibition, allowing movement initiation.
• Cerebellum → Uses GABA to fine-tune coordination & balance.
• Spinal Cord → GABAergic interneurons help control reflexes & prevent excessive muscle activity.
✅ Key Takeaway: GABA prevents excessive or unwanted movements, ensuring smooth motor execution.
- Epinephrine (Adrenaline) – Arousal & Motor Readiness
• Function: A stress-related excitatory neurotransmitter & hormone involved in motor readiness & alertness.
• Role in Motor Control:
• Enhances reaction speed & muscle activation in high-stress or emergency situations.
• Increases heart rate & oxygen delivery to muscles during movement.
• Modulates the autonomic nervous system, influencing fight-or-flight responses.
✅ Key Takeaway: Epinephrine boosts motor readiness, speed, and energy levels in response to physical demands.
- Acetylcholine (ACh) – Movement Execution & Neuromuscular Control
• Function: The primary neurotransmitter at the neuromuscular junction (NMJ), linking nervous system signals to muscle contraction.
• Role in Motor Control:
• Motor Cortex → Spinal Cord → Muscles: Acetylcholine triggers muscle contraction by activating motor neurons.
• Basal Ganglia → Striatum: Helps balance excitation & inhibition for movement precision.
• Cerebellum & Brainstem: Plays a role in posture, balance, and motor learning.
✅ Key Takeaway: Acetylcholine is essential for muscle activation and fine-tuned motor control.
Final Takeaway – Neurotransmitters in Motor Control
1️⃣ GABA → Inhibition & smooth movement (Basal Ganglia, Cerebellum, Spinal Cord).
2️⃣ Epinephrine → Arousal & motor readiness (Fight-or-flight, energy boost).
3️⃣ Acetylcholine → Muscle activation & motor precision (Neuromuscular junction, Basal Ganglia, Brainstem).
🚀 Motor control depends on a balance between excitation (Epinephrine, ACh) and inhibition (GABA) for smooth and coordinated movement.
What’s dopamine’s function in movement and voluntary control?
Dopamine’s Role in Movement & Voluntary Control
✅ Dopamine regulates movement initiation & suppression via the basal ganglia.
- Dopamine & Basal Ganglia Pathways
• Direct Pathway (D1 Receptors, Excitatory) → Promotes movement by reducing thalamic inhibition.
• Indirect Pathway (D2 Receptors, Inhibitory) → Suppresses excessive movement by dampening the inhibitory circuit. - Dopamine & Voluntary Movement
• Produced in the Substantia Nigra (SNc), sent to the basal ganglia.
• Deficiency → Parkinson’s Disease (rigidity, slow movement).
• Excess → Hyperkinetic disorders (e.g., Huntington’s, dyskinesia).
Key Takeaway:
Dopamine balances movement activation & inhibition, ensuring smooth voluntary motion. 🚀
What’s the Speed vs. Accuracy Trade-Off in Movement Control?
Overview:
Movement control balances speed and accuracy, which depends on whether feedback is available. There are two main control mechanisms:
Closed-Loop Control (Maximizes Accuracy)
Uses feedback to adjust movement in real time.
Compares actual output to the desired outcome and makes corrections.
Example: Driving—the brain continuously adjusts based on visual feedback to stay in the lane.
Open-Loop Control (Maximizes Speed)
Pre-programmed movements without feedback.
Faster but less precise; once initiated, the movement cannot be adjusted.
Example: Typing or throwing a fastball, where precision is sacrificed for speed.
Key Takeaway:
Closed-loop control prioritizes accuracy (adjustments based on feedback).
Open-loop control prioritizes speed (pre-determined, rapid execution).
The brain selects the control type based on task demands—high precision vs. fast execution.
How do muscle work
Muscles work by contracting individual muscle fibers.
They function in antagonistic pairs, meaning when one muscle contracts, the other relaxes (e.g., biceps and triceps).
Motor neurons control muscle movement by sending signals.
Types of Striated Muscle Fibers:
Fast-twitch fibers:
Contract quickly but fatigue rapidly.
Used for short bursts of strength or speed (e.g., sprinting).
Slow-twitch fibers:
Contract more slowly but resist fatigue.
Used for endurance activities (e.g., maintaining posture or long-distance running).
Illustration Explanation:
The left figure shows extension:
The triceps contract while the biceps relax.
The right figure shows flexion:
The biceps contract while the triceps relax.
What’s motor neuron and muscle
Motor neurons connect to muscle fibers and control movement.
They release acetylcholine (ACh) at the neuromuscular junction (NMJ) to trigger muscle contraction.
The NMJ is a highly effective synapse, meaning almost every action potential (nerve signal) results in a muscle contraction.
Key Takeaways:
Motor neurons branch out to multiple muscle fibers.
Acetylcholine (ACh) is the neurotransmitter responsible for communication between nerves and muscles.
The NMJ ensures strong signal transmission, so muscle contractions occur reliably when needed.
What’s motor unit and innervation ratio
Motor Unit:
A motor unit consists of a single motor neuron and all the muscle fibers it innervates.
When the neuron fires, all its associated muscle fibers contract together.
Motor units vary in size, depending on the muscle’s function.
Innervation Ratio:
The innervation ratio refers to the number of muscle fibers controlled by a single motor neuron.
Low innervation ratio → More control, finer movements (e.g., fingers, eyes).
High innervation ratio → Less precision, larger force production (e.g., legs, back).
Fingers require fine motor control, so they have many small motor units, each controlling only a few muscle fibers. This allows for precise movements (e.g., writing, playing an instrument).
Quadriceps (thigh muscles) require more force but less precision, so they have fewer but larger motor units, each controlling hundreds to thousands of muscle fibers. This enables powerful movements like jumping or squatting but lacks fine control.
Key Takeaway:
👉 More motor units = Greater control (fingers, eyes).
👉 Fewer motor units = More force, less precision (legs, back
What’s Back to Reflexes
Key Concept: Reflexive and Rhythmic Movements Mediated by the Spine
Some movements, such as rhythmic locomotion, are controlled by spinal circuits rather than requiring direct brain input.
These rhythms can persist even when brain control is removed, meaning spinal networks can function independently.
Central Pattern Generator (CPG)
CPG is a neural circuit that generates rhythmic movements, such as walking or swimming (Dogs swim above water when holded by someone, it’s actually automative and initiated by spine).
It allows for automatic, repetitive motor patterns without requiring constant brain input.
Brown’s Experiment (1911)
Tested whether the spinal cord alone could generate rhythmic movement.
Method: Severed the spinal cord of cats at the thoracic level (disconnecting from the brain).
Findings: When placed on a treadmill, the cats still produced stepping movements.
Conclusion: The spinal cord contains the necessary circuitry for basic locomotion (suggesting locomotion can occur without direct brain control).
Key Takeaways:
The spinal cord can generate rhythmic patterns for movement.
CPGs control repetitive, automatic behaviors like walking.
Brown’s experiment demonstrated spinal circuits can independently produce rhythmic movement even after brain disconnection.
👉 Implication: Some movements, such as walking, are pre-programmed in the spinal cord, requiring minimal conscious effort.
what comes after if spinal cord injuried
Spinal cord injuries can result in different types of paralysis, depending on whether the lower motor neurons (LMNs) or upper motor neurons (UMNs) are affected.
Types of Paralysis After Spinal Cord Injury
Flaccid Paralysis (Lower Motor Neuron Injury)
Cause: Damage to a large section of the spinal cord affecting lower motor neurons (LMNs).
Effect: Reflexes below the injury are lost, resulting in muscle weakness, lack of tone, and inability to contract.
Spastic Paralysis (Upper Motor Neuron Injury)
Cause: Injury to upper motor neurons (UMNs) while lower motor neurons remain intact.
Effect: Without brain inhibition, LMNs fire uncontrollably, leading to involuntary muscle contractions, stiffness, and exaggerated reflexes.
Partial Spinal Cord Damage
Reflexes below the injury become excessive because brain inhibition is lost.
This results in overactive reflexes and muscle spasticity.
Key Takeaways
Lower Motor Neuron Damage → Flaccid Paralysis (No Reflexes, No Muscle Activity).
Upper Motor Neuron Damage → Spastic Paralysis (Uncontrolled Reflexes, Muscle Spasms).
Partial Injuries → Reflexes below the injury become hyperactive due to loss of brain inhibition.
👉 Clinical Relevance: Understanding these differences is crucial for diagnosing and treating spinal cord injuries effectively.
What’s the strategy to reconnect the injuried spinal cord
Spinal cord injuries disrupt neural communication, leading to paralysis and sensory loss. Researchers are exploring multiple strategies to promote spinal cord regeneration and restore function.
- Stem Cells for Neuron Regeneration
Stem cells differentiate into new neurons to replace damaged ones.
Research has shown some success in integrating stem cells into injured spinal cords.
Challenges include cell survival and proper connectivity. - Glial Cells for Axon Regrowth
Glial cells play a crucial role in promoting axonal regeneration.
Example: Olfactory ensheathing cells (OECs) have been found to support axon regrowth in the olfactory bulb.
Studies suggest injecting glial cells into spinal cord lesions helps axons reconnect and form new pathways. - Neurotrophic Factors & Adhesion Molecules
Neurotrophic factors (e.g., NGF, BDNF) support neuronal survival and growth.
Adhesion molecules guide axons to form correct connections.
This strategy enhances plasticity and circuit rebuilding after spinal cord injury. - Peripheral Nerve Implants
Peripheral nerves have a higher regeneration capacity than central nerves.
Transplanting these nerves provides a scaffold for axonal regrowth.
This method bridges the damaged spinal region and promotes reconnection. - Electrical Stimulation of the Spinal Cord
Stimulating dorsal roots can activate central pattern generators (CPGs).
CPGs are spinal circuits that control rhythmic movements (e.g., walking).
Example: In animal studies, electrical stimulation restores stepping motions even without brain input.
Key Takeaways
Spinal cord repair is complex due to limited natural regeneration.
Combination approaches (stem cells + glial cells + stimulation) show promise.
CPG activation may help paralyzed patients regain movement via electrical stimulation.
What’s huntington’s disease?
Huntington’s disease is a genetic neurodegenerative disorder caused by CAG repeat expansion in the HTT gene, leading to toxic huntingtin protein and basal ganglia degeneration (It essentially makes an individual to lost basal ganglia and striatum).
Huntington it’s the opposite of Parkinson. It’s uncontrolled, involuntary flailing movement.
Symptoms:
Motor: Chorea (jerky movements), dystonia (rigidity), bradykinesia (slow movement).
Cognitive: Memory loss, impaired decision-making.
Psychiatric: Depression, mood swings, aggression.
Cause & Diagnosis:
Autosomal dominant inheritance (50% chance if a parent has HD).
Neuroimaging: Shows caudate atrophy.
Genetic testing: Confirms CAG repeat expansion.
🗝 Key Takeaway: HD leads to progressive motor, cognitive, and psychiatric decline due to basal ganglia dysfunction. No cure, but symptom management improves quality of life.
What’s the pyramidal system
The pyramidal system (also called the corticospinal system) is responsible for voluntary motor control. It consists of neurons in the cerebral cortex, whose axons travel down to the spinal cord via the pyramidal tract.
Key Features from the Graph:
Neurons in the primary motor cortex send signals for movement.
Pathway Through the Brainstem:
The pyramidal tract passes through the medulla.
At the medullary pyramids, most fibers cross the midline (decussation) before reaching the spinal cord.
Crossed Control:
The right motor cortex controls the left side of the body.
The left motor cortex controls the right side of the body.
Divisions in the Spinal Cord:
Lateral corticospinal tract: Major pathway for voluntary movement.
Ventral corticospinal tract: Controls axial (trunk) muscles.
Key Takeaway:
The pyramidal system is essential for voluntary movement, relaying motor commands from the brain to the spinal cord. The decussation explains why brain injuries often affect movement on the opposite side of the body.
What’s the Motor Cortex Organization and Plasticity
The primary motor cortex (M1) is the main region responsible for voluntary movements. It sends commands through the pyramidal tract to spinal motor neurons.
Key Points from the Slide & Graphs:
Motor Cortex Organization:
M1 is somatotopically organized (mapped to different body parts).
Larger areas in M1 are dedicated to body parts requiring fine motor control (e.g., hands, face).
Motor Homunculus Representation:
The motor homunculus (bottom-right figure) exaggerates the hands and face, showing they have more cortical space due to the need for precise movements.
Plasticity of Motor Cortex:
The motor map is not rigid—it can change with experience and training.
If a body part is used more frequently (e.g., learning to play an instrument), its representation in M1 expands.
If a limb is lost or unused, other areas may take over its cortical space.
Key Takeaway:
The motor cortex is adaptable (plastic), meaning motor representations can reorganize based on experience, injury, or training.
Does cortical activity in M1 represents muscles or movement?
Cortical activity in M1 (Primary Motor Cortex) represents both muscles and movement direction, as shown by experimental findings:
Muscle Representation:
About 1/3 of M1 neurons respond specifically to muscle contractions, regardless of movement direction.
This suggests that some M1 neurons are directly linked to specific muscles, activating them for contraction.
Movement Direction Representation:
Most M1 neurons respond to movement direction, independent of which muscles are used.
This means M1 encodes movement as a coordinated action rather than just individual muscle activations.
Conclusion:
M1 integrates both types of information: some neurons focus on specific muscle contractions, while others prioritize movement direction.
This dual encoding allows for precise motor control, coordinating complex voluntary movements.
Experimental Setup (Monkey Study)
Monkeys were trained to move a cursor based on visual cues while neural activity in M1 was recorded.
Different hand positions were used to assess whether M1 neurons encode specific muscles or movement direction.
Findings showed that M1 controls both aspects, meaning motor commands involve both direct muscle activation and directional planning.
Thus, M1 is crucial for voluntary motor control, integrating muscle and movement signals to execute precise and coordinated actions
what’s the clinical application for M1 study
M1 activity can be used to control robotic arms for individuals with motor impairments. The process involves recording brain signals, decoding motor commands, and using them to guide robotic limb movement.
Step 1: M1 Activity Assessment
Microelectrodes implanted in M1 record neuronal activity.
The participant observes a robotic arm performing repetitive movements and imagines themselves moving it.
M1 neuron patterns are decoded to understand the user’s intended movements.
Step 2: Using M1 Signals to Control the Robot
The decoded M1 signals are translated into commands for the robotic arm.
With visual feedback, the user learns to refine their motor commands, improving control over the robotic limb.
The process allows individuals to mentally guide the robotic arm for tasks like grabbing and drinking from a bottle.
Significance & Next Steps
Demonstrates how brain-machine interfaces (BMIs) enable movement for paralyzed individuals.
Future developments aim to improve feedback mechanisms, allowing for more precise control and sensory integration.
This technology has potential applications in neuroprosthetics and assistive devices for patients with spinal cord injuries or neurodegenerative disorders.
Conclusion
This research showcases how M1 signals can restore motor function by allowing individuals to control external devices using only their thoughts.
What’s mirror neuron
Mirror neurons, located in Area F5 of the premotor cortex, fire both when an individual performs a movement and when they observe someone else performing the same movement. These neurons are thought to be crucial for action understanding, imitation, and social cognition.
Monkey Experiment:
Mirror neurons fire both when a monkey picks up a raisin and when it watches a human pick up the raisin.
Suggests mirror neurons encode actions, not just movements.
Object Grasping:
Mirror neurons are more active when an object is grasped than when the same hand movement occurs without an object.
This implies that mirror neurons are context-sensitive, responding more to meaningful actions than meaningless gestures.
Neural Basis of Empathy:
Mirror neurons may contribute to understanding others’ intentions and empathy.
They allow an individual to simulate another person’s actions internally, forming a neural basis for social learning and interaction.
Autism Spectrum Disorder (ASD):
Individuals with ASD show reduced mirror neuron activation, particularly in brain areas involved in facial expression imitation.
This could explain difficulties in social interaction and empathy in ASD.
Key Takeaways:
Mirror neurons link perception and action, playing a role in imitation, learning, and empathy.
They are more sensitive to goal-directed actions (e.g., grasping an object) than meaningless movements.
What is Extrapyramidal Input?
Extrapyramidal input refers to motor control systems that influence upper motor neurons but do not pass through the pyramids of the medulla. These systems regulate movement by refining and modulating motor commands rather than directly initiating them. The cerebellum and basal ganglia are the main structures involved in extrapyramidal control.
What’s the function of cerebellum and basal ganglia in extrapyramidal input system
The Cerebellum (Extrapyramidal Input)
Function:
Adjusts firing patterns for fine motor control and coordination.
Size of the cerebellum varies across species based on movement complexity.
Inputs:
Sensory systems: Receives information from muscles, joints, vestibular system, somatosensory, visual, and auditory systems.
Brain motor systems: Works with cortical and subcortical motor areas.
Continuous monitoring: Detects and corrects movement errors.
Motor learning: Develops precise movement programs, making frequently performed actions automatic.
Key Role:
Essential for motor precision and coordination.
Learns and refines motor patterns for smooth execution of movements.
Basal Ganglia (Extrapyramidal Input)
Function:
Modulates upper motor neurons to refine voluntary movement.
Integrates cortical activity into a single motor output/behavior.
Structure:
Forebrain nuclei: Includes caudate nucleus, putamen, and globus pallidus.
Connected to: Substantia nigra and subthalamic nucleus.
Striatum = Caudate nucleus + Putamen.
Role:
Procedural memory (learned motor skills).
Determines movement amplitude and direction.
Decides whether to initiate or inhibit movement.
What’s the Basal Ganglia and Thalamus Processing Loop
Processing Pathways:
Cortex → Basal Ganglia → Thalamus → Cortex feedback loop.
Thalamus continuously inhibits the cortex to control movement precision.
Pathways:
Direct pathway: Releases inhibition, allowing targeted movement.
Indirect pathway: Enhances inhibition, preventing unwanted movements.
Key Role:
Balances excitation and inhibition of motor commands.
Deficits in this system lead to movement disorders (e.g., Parkinson’s and Huntington’s disease).
Final Summary:
Cerebellum: Fine-tunes and corrects movements, ensuring smooth coordination.
Basal Ganglia: Decides when and how to move, refining movement amplitude and direction.
Extrapyramidal Input: Indirectly regulates voluntary movement through feedback loops, helping to balance movement execution and inhibition.
What’s the Interactions Between the Cerebellum, Basal Ganglia, and Motor Cortex
Cerebellum: Adjusts movements based on sensory feedback (e.g., correcting errors).
Basal Ganglia: Determines whether a movement should be initiated.
Supplementary Motor Area (SMA): Plans complex movements.
Primary Motor Cortex (M1): Executes movements.
Cerebellum activity peaks after movement starts (error correction).
Basal ganglia activity occurs before movement initiation (decision-making).
Supplementary motor area activates before M1, suggesting movement planning happens before execution.
What’s the specific different betweenn direct and indirect pathway?
he direct and indirect pathways are the two major circuits in the basal ganglia that regulate movement by controlling the thalamus’ influence on the motor cortex.
- Direct Pathway (“Go” Pathway)
Function: Allows movement by disinhibiting the thalamus.
Mechanism: Inhibits the inhibitory output of the globus pallidus interna (GPi), allowing the thalamus to send an excitation signal (“GO”) to the motor cortex.
Result: Promotes voluntary movement. - Indirect Pathway (“No-Go” Pathway)
Function: Prevents unwanted movement by keeping the thalamus inhibited.
Mechanism: Activates the globus pallidus interna (GPi), which strengthens inhibition of the thalamus, preventing movement initiation.
Result: Inhibits unnecessary or competing movements.
Final Takeaway
The direct pathway promotes movement, while the indirect pathway inhibits movement.
Dopamine is critical for balancing these pathways, ensuring smooth and controlled motor output.
Dysfunction in these pathways leads to movement disorders like Parkinson’s and Huntington’s disease.
