Frontal Lobe

 

Put your left foot in. Put your right foot in & shake it all about.

A movement is anything we do. So movement and muscles naturally go together. We need muscles to pull on the bones or stetch and shrink. And we need various areas of the brain to plan and execute movements. That’s where having a frontal lobe comes in handy.

The frontal lobe, basal ganglia, cerebellum and other areas are involved in controlling, planning, regulating and executing movements. What is simple to us as users takes a lot of brain work to accomplish.

• Frontal Lobes
  • What is it?
  • Home to personality?
  • Lesions: wide variety symptoms
    • More than any part of brain
    • Involved in:
      • motor function
      • problem solving
      • spontaneity
      • memory
      • language
      • initiation
  • Extremely vulnerable to injury
    • Large in size
    • Located up front
    • Most common brain injury
    • Mild to moderate trauma
• 1. Primary Motor Cortex
  • M1
    • Pre-central gyrus
    • Directs motor coordination
    • Voluntary movement
    • Input
  • Pre-Motor area
    • Plan and execute movements
  • Posterior Parietal Cortex
    • Visual information
  • Supplementary Motor Area
    • planning & coordinating complex movements
    • (requiring two hands)
  • Cerebellum
    • Balance
  • Output
    • contains Betz cells
    • large neurons
    • long axons down spinal cord
    • synapse directly to motor neurons of muscles
  • Sends info to
    • Cranial nerves
    • Lower motor neurons
  • Functions
    • Elicits movements
    • Not directly connected to muscles
    • Axons go to brainstem & spine
    • Central pattern generators control actual muscle move
  • Homunculus
    • Organized by body region
      • Top-down
      • Toes
      • Knee
      • Hip
      • Trunk
      • Stomach
      • Arm
      • Elbow
      • Wrist
      • Hand
      • Fingers
      • Thumb
  • Important for complex actions
    • Writing
    • Less important for coughing, sneezing, laughing, or crying
  • 2 major actions
    • Elicit complex movement patterns
    • Also $ when imagine movement
  • Note:
    • Causes movements, doesn’t plan them
    • Movement needs Muscles
• *********************
• Muscles
  • 1. Smooth muscles
    • Digestive sys. & internal organs
    • Long, thin cells
  • 2. Striated
    • Skeletal muscles
    • Acetlycholine causes contraction
    • With no acetlycholine, relaxes
  • 3. Cardiac muscles
    • Smooth & skeletal combo
    • Looks striated
    • Acts like smooth
    • Many individual fibers
    • Fibers fuse together at points
    • One axon may innervate more than one muscle fiber
    • Distinctive Firing Rhythm
      • They just beat
• Principles
  • One movement per muscle
  • Contraction; relaxation
  • Antagonistic muscles
    • Two in opposite directions
  • Flexor muscles
    • limbs flexed or raised
  • Extensor muscles
    • extend or straighten limbs
  • Fast and Slow Muscles
    • Contractions are chemical
    • Affected by temperature
    • Fish use more muscles in cold, fewer muscles in warmer water
    • Fish muscles:
      • Red : slow move, no fatigue
      • White : fast move, quick fatigue
    • Pink : intermediate on both
    • Human Muscles
      • Muscle fibers are mixed
      • Fast-twitch fibers: fast contractions, fast fatigue
      • Slow-twitch fibers: slower contraction, less fatigue
    • Aerobic: use oxygen during movement
      • Walking, swimming, running
    • Anaerobic = don’t use oxygen
      • Short burst
      • Less that 2 min.
    • Fast-twitch fibers fatigue quickly
      • oxygen is needed for recovery
      • produce lactate and phosphate
      • give sensation of fatigue
    • People vary in amounts of fast- and slow-twitch
      • can increase one or the other
      • depending on which use
  • Proprioceptors
    • receptor that detects position
    • indicates movement of body part
    • detect stretch & tension of muscle
  • Stretch reflex
    • Also called myotatic reflex
    • Monosynaptic reflex
    • Muscle lengthens, spindle stretches
    • Increases nerve activity
    • Contracts muscle, resist stretch
• Muscle spindle
  • Kind of proprioceptor
  • Inside muscle
  • Detect changes in length
  • Also activates stretch reflex
  • Resist muscle stretch
• Golgi tendon organ
  • Located in tendons
  • At ends of muscles
  • Inhibit contraction when too intense
• Involuntary Movements
  • Reflexes
  • Consistent
  • Automatic responses
    • Not affected by reinforcements, punishments, and motivations
    • Pupil constricting to bright light
  • Infantile Reflexes
    • Infants have more
    • Grasp reflex = put object in hand, grasp tightly
    • Babinski reflex
      • Stroke sole of foot
      • Extend big toe, fan others
    • Rooting Reflex
      • Touch cheek, turn head & suck
      • Not pure reflex
      • Intensity increase when hungry
      • Infantile reflexes fade with time
        • suppressed by maturing brain
        • sometimes reappear when brain damaged
  • Life-long Reflexes
    • Knee jerk reflex
    • Lengthen muscle fibers
    • Monosynaptic reflex
    • Not involve brain
    • When muscles lengthen
      • reflexively contract
    • Helps in posture
    • Sneezing
    • Coughing
• Movements
  • Most behaviors are not purely voluntary or involuntary
  • Most are sensitive to feedback
  • Ballistic movements
  • Once initiated, can’t be altered
  • Completely ballistic are rare
  • Behavior Sequences
  • Central pattern generators
  • Generate rhythmic patterns of motor output
    • wings flapping
    • fin movements
  • Motor programs
    • Fixed sequence of movements
    • Can be learned or built in
• *************
• 1. Primary Motor Cortex (con’t)
  • Posterior parietal cortex
    • Planning a movement
    • Keeps track of body position
    • Intention to move
    • Damage causes
      • trouble converting visual perceptions into actions
      • trouble finding objects in space
  • Supplemental Motor Region
    • Plan-organize rapid sequences
      • pushing, pulling, and then…
    • Mirror Neurons
    • Function
      • Preparing to do movement
      • Watching someone else do it
      • Type of cell or function?
      • Some innate
      • Some acquired by experience
      • Imitating & understanding others
      • Modeling
• 2. Pre-Motor Cortex
  • Preparing for movement
  • Somewhat active during move
  • Receives info about
  • Where target is in space
  • Current position of your body
  • Damage
    • Poorly planned movements
• Cerebellum
  • Balance and coordination
  • More neurons than rest of brain combined
  • Damage
    • Problems making rapid move
    • Anything require aim & timing
    • Point at moving object
    • Clapping hands
    • Writing, typing
    • Not good at discrete tasks
    • Good at continuous tasks
    • Drawing continuous circle
  • Functions
    • Saccades:
      • Ballistic eye movements
      • From one fixed point to next
      • Gaze following moving objects
    • Finger to nose test
      • Alcohol
      • 1st brain area impacted
    • Clumsiness
    • Slurred speech
    • Inaccurate eye move
  • Other Functions
    • Feel things with both hands
    • Decide if two objects same
    • Habit formation
    • Timing
    • Attention
  • Cellular Organization
    • Input from
    • spinal cord
    • sensory systems (eyes, ears…)
    • cerebral cortex
  • Neurons characteristics:
    • Precisely arranged
    • Geometrical patterns
    • Multiple copies of same unit
    • Parallel fibers
    • Parallel to each other
    • Perpendicular to Purkinje cells
  • Purkinje cells
    • Flat cells in sequential planes
    • Inhibit cells in cerebellum nuclei
    • Inhibit vestibular nuclei too
    • Controls timing of movement including onset & offset
  • Motor coordination
    • Integration of auditory-visual info
    • Skilled movements
      • Dancing
      • Throwing
    • Modular structure
    • Coordinates movements, not cause them
    • Regulator or timing mechanism
    • Timing of skilled movements
    • Posture and balance
    • Highly impacted by alcohol
    • Speaking rhythm (slur)
    • Can’t walk straight
    • Finger to nose test
  • Cells highly organized
  • Repeating geometrical patterns
• Basal Ganglia
  • The Basal Ganglia
  • Group of subcortical structures
    • includes caudate nucleus, putamen & globus pallidus
  • Multiple connections
    • with cerebral cortex & thalamus
  • Regulates (inhibits) thalamus
  • Uninhibited movements become actions
  • Important for things can’t put into words
  • Learning movements
  • Movement patterns more consistent from trial to trial
• Inhibition of Movement
  • Antisaccade task
  • Task: Look in opposite direction of moving object on periphery of visual field
  • Very hard to do
  • Very strong tendency to watch moving object
  • Almost impossible for kids 5-7
  • Ability develops slowly
    • prefrontal cortex is one of slowest brain areas to reach maturity
• Conscious Decisions
  • Readiness Potential?
  • Motor cortex activity may proceed decision to move
  • Decisions to make movement unconscious?
• Connects To Spinal Cord
  • Two tracts
    • Lateral corticospinal tract
    • Medial corticospinal tract
• 1. Lateral corticospinal tract
  • Axons from
  • primary motor cortex
  • red nucleus of midbrain
  • Path downward
  • Down thru white matter
  • Get closer together as they go
  • Go to medulla oblongata
  • Medulla Pyramids
  • Lateral tract crosses contralateral
  • Controls move of distal limbs
  • Hands, fingers, feet & toes
  • Dorsolateral (pyramidal tract)
  • Clumsiness of cerebral palsy is from competition of contralateral and ipsilateral paths
  • Controls movement of fingers
  • Controls many cranial nerves
  • Controls facial muscles
• 2. Medial corticospinal tract
  • Axons from
    • primary motor cortex
    • supplementary motor cortex
    • midbrain tectum
    • reticular formation
    • vestibular nucleus
  • Go to both sides of spinal cord
  • Largely responsible for
    • Neck, shoulder & trunk move
    • Control posture
    • Vestibulospinal: vestibular information
    • Tectospinal: visual information
    • Reticularspinal: controls muscles
• Motor Problems
• Parkinson’s Disease
  • Symptoms
    • First symptom is loss of smell
    • Slow movements
    • Resting tremor
    • Rigidity
    • Difficulty initiating movement
    • Cognitive deficits
    • Depression (no outbursts)
    • Can still do
      • Follow visual cues
      • Follow parade
      • Climb stairs
      • “Step on the cracks” (sidewalk)
  • Incidence
    • 1–2% of those over 65
    • 50% more men than women
  • Progression
    • Gradual progressive death of neurons
    • Especially in substantia nigra
  • Substantia nigra
    • Less $ of motor cortex
    • Slower onset of movements
    • When over 45
    • Neuron loss of 1% per year
    • Most have enough to spare
  • Early onset
    • Probably genetic
  • Late onset
    • More common
    • Not genetic
  • Chances decrease if
    • Drink coffee
    • Smoke
    • Decaffeinated coffee and nicotine free cigarettes work just as well
    • Reduce damage to mitochondria
  • Progressive death of neurons
    • Gradual
    • Decrease in dopamine
    • Decreased neural activity
    • Atrophy
    • Cell death
  • L-Dopa Treatment
    • Precursor to dopamine
    • Crosses BBB
    • Hope it converts to dopamine
    • Not prevent continued loss
      • may contribute to neuron death
    • Harmful side effects
    • Effective in early stages?
    • Could do harm?
    • Doesn’t stop the disease
  • Other Therapies
    • Antioxidant drugs
    • Dopamine agonists
    • Glutamate antagonists
• Huntington’s Disease
  • Genetic disease
    • 1:10k
  • Symptoms
    • Can’t learn new movements
    • Restless, fidgeting
    • Tremors spread
    • Jerky arm movements
    • Facial twitch
    • Hallucinations & delusions
    • Alcoholism & drug abuse
    • Depression & anxiety
    • Memory deficits
  • Onset at any age
    • Mostly 30-50
    • Early onset, worse symptoms
    • Can occur in kids and teens
  • Excessive movement (chorea)
  • Gradual brain damage
  • Inevitably fatal
  • Misdiagnosed as schizophrenia
• Myasthenia Gravis
  • Immune system anti-bodies
  • Attack acetylcholine receptors
  • Symptoms
    • Weakness
    • Rapid fatigue
    • Motor neurons can’t produce enough acetylcholine