Role of the Cerebral Role of the Cerebral CortexCortex

Primary Motor CortexPrimary Motor CortexPrecentral gyrus of the frontal cortex Precentral gyrus of the frontal cortex stimulation elicits movementsstimulation elicits movements

Axons from Primary Motor Cortex go to Axons from Primary Motor Cortex go to basal ganglia while other motor axons basal ganglia while other motor axons go to the brainstem & spinal cordgo to the brainstem & spinal cord

Cerebral Cortex & Cerebral Cortex & Complex ActionsComplex ActionsStimulation of motor cortex elicits Stimulation of motor cortex elicits complex movement patternscomplex movement patterns

The motor cortex is stimulated when The motor cortex is stimulated when movement is imaginedmovement is imagined

Connections from the Brain Connections from the Brain & Spinal Cord& Spinal Cord

Dorsolateral Dorsolateral TractTractAxons from the primary motor Axons from the primary motor cortex & red nucleus synapse in the cortex & red nucleus synapse in the spinal cordspinal cord

Pyramids in medulla contain Pyramids in medulla contain dorsolateral tract crossing that dorsolateral tract crossing that contralaterally controls movements contralaterally controls movements of the fingers, toes, hands, etc.of the fingers, toes, hands, etc.

Connections from the Brain Connections from the Brain & Spinal Cord& Spinal Cord

Ventromedial Ventromedial TractTractContains axons from the primary Contains axons from the primary motor cortex, supplementary motor motor cortex, supplementary motor cortex, midbrain tectum, reticular cortex, midbrain tectum, reticular formation & the vestibular nucleusformation & the vestibular nucleus

Axons from the ventromedial tract Axons from the ventromedial tract go to both sides of the spinal cord & go to both sides of the spinal cord & are largely responsible for neck, are largely responsible for neck, shoulder, & trunk movementsshoulder, & trunk movements

The Role of the The Role of the CerebellumCerebellum

Involved in Motor Involved in Motor Control & Learned Control & Learned Motor BehaviorMotor Behavior

Linked to Habit Linked to Habit Formation, Formation, Aspects of Aspects of Attention, Timing, Attention, Timing, & Other & Other Psychological Psychological Motor FunctionsMotor Functions

The The CerebellumCerebellum

Cellular OrganizationReceives input from the spinal cord, from Receives input from the spinal cord, from each sensory system via the cranial nerve each sensory system via the cranial nerve nuclei, & cerebral cortex where it eventually nuclei, & cerebral cortex where it eventually reaches the cerebellar cortexreaches the cerebellar cortex

Neurons in the cerebellar cortex are:Neurons in the cerebellar cortex are:

1. Arranged in precise geometrical patterns 1. Arranged in precise geometrical patterns with multiple repetitions of the same unitwith multiple repetitions of the same unit

2. Action potentials of parallel fibers excite 2. Action potentials of parallel fibers excite one Purkinje cell after anotherone Purkinje cell after another

3. Purkinje cells inhibit cells of the nuclei of 3. Purkinje cells inhibit cells of the nuclei of the cerebellum & the vestibular nuclei in the the cerebellum & the vestibular nuclei in the brain stembrain stem

4. Output of Purkinje cells control the timing 4. Output of Purkinje cells control the timing of movements including turning on & offof movements including turning on & off

Basal GangliaBasal GangliaIncludes: Caudate Includes: Caudate Nucleus, Putamen, Nucleus, Putamen, & Globus Pallidus& Globus PallidusCaudate nucleus & Putamen are input, globus pallidus is output

Important for Habit Important for Habit Learning & the Learning & the Selection of Selection of MovementMovementObsessive-compulsive disorder is linked to increased activity in the caudate nucleus & prefrontal cortex

Parkinson’s Parkinson’s DiseaseDisease

SymptomsSymptomsRigidity, resting tremor, slow movements & Rigidity, resting tremor, slow movements & difficulty initiating physical & mental difficulty initiating physical & mental activity, cognitive defects in memory & activity, cognitive defects in memory & reasoningreasoning

1 in 100 with onset after age 501 in 100 with onset after age 50

Immediate cause: gradual progressive Immediate cause: gradual progressive death of neurons in Substantia Nigradeath of neurons in Substantia Nigra

Possible causes: Genetics; MPTP, a Possible causes: Genetics; MPTP, a chemical that the body converts into MPP (a chemical that the body converts into MPP (a toxin destroys dopamine neurons; probably toxin destroys dopamine neurons; probably a mixture of causesa mixture of causes

Parkinson’s Parkinson’s DiseaseDisease

Standard Standard TreatmentTreatmentL-DopaL-Dopa

Precursor to dopaminePrecursor to dopamine

Effectiveness variesEffectiveness varies

Doesn’t prevent the loss of dopamine Doesn’t prevent the loss of dopamine containing neurons & may contribute to the containing neurons & may contribute to the death of neuronsdeath of neurons

Produces harmful side-effectsProduces harmful side-effects

Alternative Alternative TreatmentsTreatmentsAntioxidant drugsAntioxidant drugs

Direct dopamine agonistsDirect dopamine agonists

Glutamate antagonistsGlutamate antagonists

NeurotrophinsNeurotrophins

Apoptosis blockersApoptosis blockers

High frequency electrical stimulation of the High frequency electrical stimulation of the Globus PallidusGlobus Pallidus

Surgical damage to the Globus Pallidus or Surgical damage to the Globus Pallidus or parts of the Thalamusparts of the Thalamus

Huntington’s Huntington’s DiseaseDisease

Severe Degenerative Severe Degenerative Neurological DisorderNeurological DisorderSymptoms: twitches, tremors, Symptoms: twitches, tremors, & writing movements; & writing movements; depression, memory deficits, depression, memory deficits, anxiety, hallucinations, anxiety, hallucinations, delusions, poor judgment, delusions, poor judgment, alcoholism, drug abuse, & alcoholism, drug abuse, & sexual disorderssexual disorders

Affects 1 in 1000Affects 1 in 1000

Gradual, extensive brain Gradual, extensive brain damage especially in the damage especially in the Caudate Nucleus, Putamen, & Caudate Nucleus, Putamen, & Globus PallidusGlobus Pallidus

Huntington’s Huntington’s DiseaseDisease

OnsetOnsetMost often appears between Most often appears between 30 & 50 years30 & 50 years

The earlier the onset, the The earlier the onset, the faster the deteriorationfaster the deterioration

HeredityHeredityCaused by an autosomal Caused by an autosomal dominant dominant gene on gene on chromosome 4chromosome 4

Abnormal form of Abnormal form of huntingtinhuntingtin, , a protein found in neurons a protein found in neurons that interferes with several that interferes with several metabolic pathwaysmetabolic pathways