Chapter 9 Flashcards by Cambell Meier

Motor cortex plans and

initiates movement

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Basal ganglia and cerebellum

coordinate movement

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Spinal cord conducts

information to the muscles

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Initiating and producing movement requires

the interaction of information from the senses and the entire brain

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Sequential Production of Movement (1-8)

1.visual info required to locate target 2.frontal motor areas plan the reach and command the movement 3.spinal cord carries information to hand 4.motor neurons carry message to muscles of the hand and forearm 5. sensory receptors on the fingers send messages to sensory cortex saying that the cup has been grapst 6. spinal cord carries sensory information to the brain 7.basal ganglia judge grasp forces and cerebellum corrects movement errors 8. sensory cortex receives message that cup has been graspt

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Parietal cortex (Brodmann areas 5 and 7)

integrates information from the senses and initiates movements based on sensory information

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prefrontal cortex

plans movements based on experiences, goals, and sensory input

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Premotor cortex

coordinates whole-body movements and organizes action sequences

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Primary motor cortex

produces simple movements, such as hand movements to use or manipulate tools

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order of movement within the brain

parietal cortex sends goals - prefrontalcortex plans - premotor cortex sequences - motor cortex executes

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As movement complexity increases

additional brain areas are recruited to coordinate the movement

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Electrical stimulation of the precentral gyrus triggered

triggered movements of different parts of the body

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Stimulation of the cortex immediately anterior to the primary motor cortex also elicited

movement

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The motor homunculus is similar to the somatosensory homunculus, with the body represented

upside down, the feet in the central fissure, and the head near the inferior lateral surface

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The motor homunculus has larger representations for the

hands and tongue, areas associated with fine motor control

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Original mapping of the motor cortex was relatively crude, using

large electrodes

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Brief electrical stimulation produces movement of

a specific body part

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longer stimulations result in

ethological behaviors, or behaviors the animal might use in everyday activities

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ethological behaviors

Defensive postures
Reaching movements
Climbing and leaping postures

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Ethological movements

include the part of the body to be moved, the destination to which the movement is directed, and the function of the movement

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Organization of the homunculus is somewhat maintained by the

ethological movements

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hand movments and the homunculus

Hand movements are ventral

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hand movements from hand to mouth and the homunculus

Movements of hand to mouth are most ventral

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More complex, whole-body movements are in

premotor area

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Ethological movements can be elicited from

parietal cortex stimulation

Movements evoked from the parietal lobe map - dorsal stimulation

Stepping movements

Movements evoked from the parietal lobe map - ventral stimulation

Hand movements

Movements evoked from the parietal lobe map - most ventral stimulation

Mouth movements

The pincer grip is a developmental milestone in the

first few months of life that gets refined over time

Damage to cortical motor areas impairs

the entire movement, not just the one part of the body or muscle that corresponds to the damage

Movements to replace the impaired movement are controlled by an

intact part of the cortex, such as the pincer grip being replaced by the whole hand grip

Evidence from stroke studies suggests that movements are encoded

in multiple places in the cortex

Damage to the primary motor cortex produces

muscle weakness and impairs individual movements

Damage to premotor cortex impairs

complex movements involving multiple body parts

Movements coordinated by the motor planning areas

integrate and refine more basic movements, such as walking or climbing movements

The role of the neocortex and motor planning areas seems to involve

blending these prelearned movements

Corticomotor-Neuron Activity in monkeys lifting weights

Electrodes implanted into the wrist area of the primary motor cortex,Neuronal activity increased while the monkey was planning the movement, before actually moving, Activity increased further during the actual movement, Neuronal activity was even higher when there was more weight on the bar, Neurons encode direction, firing during flexion movements but not during extension, Movement is encoded by a population of neurons, not a single cell

Many movements are learned and are modified based on our

interaction with others

Mirror neurons are found in the

ventral premotor areas

Mirror neurons are found in the ventral premotor area and are active both when the animal is

performing a movement and when it observes someone else making that same movement

Some mirror neurons are specific to the

size of the target object

Some mirror neurons discharge only when the object is

in reach

Core mirror neurons are less

specific and respond to broad classes of movement

Additional mirror neurons have been identified in the

temporal and parietal lobes

Basal ganglia, cerebellum, and brainstem are important for the

control of movement

Basal ganglia includes the

caudate, putamen, and globus pallidus

Basal ganglia receive input from the

cortex and the substantia nigra in the midbrain

Basal ganglia receive input from the cortex and the substantia nigra in the midbrain and send projections

back to these areas

Hyperkinetic symptoms Result from damage to the

caudate and putamen

Hyperkinetic disorders

Huntington disease, Tourette syndrome

Hypokinetic symptoms Result from loss of

dopamine input from the substantia nigra

Hypokinetic symptoms Associated with difficulty

making voluntary movements

Hypokinetic disorders

Parkinsons disease

the role of the basal ganglia is to

modulate movements

basial ganglia and movement force and movement disorders

One hypothesis is that the basal ganglia control movement force, and the movement disorders are issues with too much or too little force

Output from the interior portion of the globus pallidus (GPi) projects

to the thalamus and motor cortex

If the predominant input to GPi is inhibitory, then the region

fails to inhibit the thalamus and movement occurs

If the predominant input is excitatory, then the GPi

inhibits the thalamus and movement is prevented

Decreasing activity in the GPi

descreases the symptoms of Parkinson disease

Cerebellum is important for

acquiring and maintaining motor skills

Cerebellum includes two

hemispheres and a small horizontal lobe, the flocculus

Different parts of the cerebellum are involved in

different aspects of motor control

Flocculus receives information from the

vestibular system and is involved in balance

Midline areas of the cerebellum control the

midline of the body

Lateral areas of the cerebellum are involved in

movements of the limbs and hands

Cerebellum is important in

timing movements

Damage to the cerebellum impairs the ability to

move at a regular rhythm

Damage to the cerebellum also impairs the ability to accurately

perceive time

Cerebellum is important for monitoring

movement accuracy

cerebellar experiments and throwing darts

2 groups were given glasses that distorted their vision and were asked to throw darts initially patients with an intact cerebellum adjusted their throws so that they hit the target Patients with cerebellar damage were unable to adjust their movements to hit the target,When the goggles were removed, patients with an intact cerebellum threw incorrectly again and had to compensate, but patients with cerebellar damage were on target and did not have to correct

Cerebellum and Motor Feedback 1

If the movement does not reach the intended target, some adjustment is needed

Cerebellum and Motor Feedback 2

Cortex sends the motor command to the spinal cord, but sends a copy to the cerebellum

Cerebellum and Motor Feedback 3

Sensory information from the muscles and the visual system is sent to the cerebellum

Cerebellum and Motor Feedback 4

Cerebellum compares the intention (motor output) with the results (sensory input) and generates a correction to achieve the desired result

Cognitive processes, such as language, use a similar error correction strategy based in the

cerebellum

Main motor control pathway originates in the

motor cortex

multiple pathways originate in the

brainstem

Spinal cord pathways provide input about

balance and posture to refine the movement commanded by the cortex

Movements specified by the brainstem tend to be

coarse movements of the entire body

Electrical stimulation of brainstem areas produces behaviors such as

an arched back and erect hair in a cat or walking or running behaviors

The timing of the behavior depended on the timing of the

stimulation

the intensity of the behavior was determined by the

magnitude of the stimulation

The spinal cord is the final

pathway to convert motor plans into movements

Corticospinal and corticobulbar tracts project from

the cortex to the spinal cord

Corticobulbar tracts control

facial movements

Corticospinal tracts influence

movement of the limbs, digits, and body

Corticospinal tracts originate in

somatosensory areas, motor cortex, and premotor cortex

Input from somatosensory areas modulates

afferent sensory information

Input from motor areas projects to

motor neurons of the brainstem and spinal cord to influence movement

Corticobulbar and corticospinal tracts originate in layer

Approximately 95% of the descending motor pathways decussate on the

ventral surface of the brainstem, resulting in a bump called the pyramids

The lateral corticospinal tract decussates and influences the movements of

limbs and digits contralateral to the hemisphere where the motor command originated

The anterior corticospinal tract does not decussate and controls

movements of the trunk

Motor neurons of the spinal cord provide the output connection between the

nervous system and the muscles

Neurons from the corticospinal tracts synapse on both

interneurons and motor neurons

Spinal motor neurons and interneurons are arranged in a

homunculus

Lateral motor neurons influence the

fingers and hand

Intermediate motor neurons control the

limbs

Medial motor neurons control the

trunk

Muscles that control the limbs are arranged in

pairs

Extensor muscles move the limb

away from the trunk

Flexor muscles move the limb

toward the trunk

Circuits in the spinal cord cause one muscle of the pair to

relax while the other muscle is excited