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Flashcards in Chapter 11 Deck (118):
1

neuroprosthetics

computer assisted devices replace lost biological function

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computer brain interface (CBI)

employs electrical signals from a computer to instruct the brain

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brain computer brain interface (BCBI)

combine the BCI and CBI approaches

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brain computer inferface

employs electrical signals from the brain to direct computer controlled devices

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Major components of the motor system?

cerebrum (forebrain); brainstem; spinal cord

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cerebrum

contributes to our conscious control of movement

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Brainstem & Spinal cord

perform our more automatic movements

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what happens if the brainstem or spinal cord is impaired?

the forebrain can imagine move- ments but can no longer produce them

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Visual systems role in picking up object

relays this information through somatosensory regions of the neocortex to the motor regions of the neocortex that plan and initiate the movement.

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basal ganglia's role in picking up object

produces appropriate amount of force when picking up an object

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brain stem & cerebellum's role in picking up object

helps to regulate the timing and accuracy of the movement.

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8 steps to pick up object

1 Visual information required to locate the target.
2 Frontal-lobe motor areas plan the reach and command the movement.
3 Spinal cord carries information to the hand
4 Motor neurons carry message to muscles of the hand and forearm
5 Sensory receptors on the fingers send message to sensory cortex saying that the cup has been grasped
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 the cup has been grasped.

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Afferent

somatosensory information travels from the body inward via the somatic nervous system

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efferent

movement information travels out of the central nervous system

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cross section of spinal cord: Outer part

consists of white matter; dorsal tracts are sensory and ventral tracts are motor

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cross section of spinal cord: inner part

gray matter; shaped like a butterfly;

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tracts

bundles of nerve fibers in the CNS

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nerves

bundles of nerve fibers in the PNS

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dermatomes

cervical, thoracic, lumbar, sacral, coccygeal

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Nervous system organization

hypothesized to be organized in a number of levels, Successively higher levels control more complex aspects of behavior by acting through the lower levels. The three major levels: forebrain, brainstem, and spinal cord. Proposed that further levels of organization exist within these divisions,

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Do higher levels replace lower levels?

no, they act by controlling them

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Motor sequence

Movement modules preprogrammed by the brain and produced as a unit.

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Mirror Neuron

cell in the primate premotor cortex that fires when an individual observes a specific action taken by another individual

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frontal lobe

responsible for planning and initiating motor sequences

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Prefrontal Cortex

plans complex behavior; specifies the goal not the specific movements

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Where does the prefrontal cortex send instructions?

premotor cortex

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premotor cortex

which produces the appropriate complex movement se- quences.

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Primary Motor Cortex

produces specific movements

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Movement Hierarchy

After the prefrontal cortex has for- mulated a plan of action, it instructs the premotor cortex to organize the appropriate sequence of behaviors, and the primary motor cortex executes the movements

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What does the brainstem control?

species typical behaviors (actions displayed by every member of a species); also produce complex patterns of adaptive behavior. These patterns include movements used in eat- ing and drinking and in sexual behavior)

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effect of context

how the neural site stimulated interacts both with the object presented and with the stimulation’s duration.

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How do we know that the brainstem is involved in species typical behavior?

Stimulation of some brainstem sites produces behavior that depends on context, suggesting that an important function of the brainstem is to produce appropriate species-typical behavior.

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locked-in syndrome

patient is aware and awake but cannot move or communicate verbally due to complete paralysis of nearly all voluntary muscles except the muscles of the eyes.

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cerebral palsy

a disorder primarily of motor function: voluntary movements become difficult to make whereas conscious behavior controlled by the cortex may remain intact.

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anoxia

lack of oxygen

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cerebral palsy

group of brain disorders that result from brain damage acquired perinatally (at or near birth).

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quadriplegia

paralysis of the legs and arms due to spinal-cord injury.

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paraplegia

paralysis of the legs due to spinal- cord injury.

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scratch reflex

automatic response in which an animal’s hind limb reaches to remove a stimulus from the surface of the body.

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severed spinal cord

spinal reflexes still function, even though the spinal cord is cut off from communication with the brain. As a result, the paralyzed limbs may display spontaneous movements or spasms.

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Homunculus

representation of the human body in the sensory or motor cortex; also any topographical representation of the body by a neural area.

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Is there 1 or 2 motor cortex?

2; one on each side of body

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motor cortex control movement on contralateral or ipsilateral part of body?

contalateral

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Topographic Organization

Neural spatial representation of the body or areas of the sensory world perceived by a sensory organ; functional layout of the primary motor cortex

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What does the motor cortex represent

the motor cortex represents not muscles but rather a repertoire of fundamental movement categories.

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what does the motor cortex encode?

motor cortex maps appear to represent basic “types” of movement that learning and practice can modify. In other words, the motor cortex encodes not muscle twitches but a “lexicon,” or dictionary, of movements that is not large

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Motor cortex neurons

take part in planning the movement as well as initiating

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Overall, what doe the motor cortex do?

The motor cortex takes part in planning movement, executing movement, and adjusting the force and duration of a movement.

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restraint-induced therapy

procedure in which restraint of a healthy limb forces a patient to use an impaired limb to enhance recovery of function.

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corticospinal tract

bundle of nerve fibers directly connecting the cerebral cortex to the spinal cord, branching at the brainstem into an opposite-side lateral tract that informs movement of limbs and digits and a same- side ventral tract that informs movement of the trunk; also called pyramidal tract; main efferent pathways from the motor cortex to the brainstem to the spinal cord

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Do axons stay on the same side of the body on corticospinal tracts?

some of the axons descending from the left hemisphere cross over to the right side of the brainstem. Like- wise, some of the axons descending from the right hemisphere cross over to the left side of the brainstem

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What forms the spinal cord tracts?

The dual tracts on each side of the brainstem (corticospinal tracts) then descend into the spinal cord, forming the two spinal-cord tracts.

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laterial corticospinal tract

formed by the fibers that cross to the opposite side of the brainstem descend the spinal cord in a lateral (side) position

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ventral corticosinal tract

formed by the fibers that remain on their original side continue from the brainstem down the spinal cord in a ventral (front) position

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what forms the spinal column's ventral horns?

The spinal-cord motor neurons that connect to muscles are located in the ventrolateral part of the spinal cord and jut out to form the horns

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what do interneurons in the spinal cord project to?

Interneurons lie just medial to the motor neurons and project onto them.

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what do the motor neurons in the left hemisphere control?

trunk on both sides of the body and the limbs on the body's right side

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what do the motor neurons in the right hemisphere control?

control the trunk on both sides of the body and the limbs on the body’s left side.

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How are limb muscles arranged?

in pairs

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extensor

one member of the pair of muscles; moves (extends) the limb away from the trunk

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flexor

one member of the pair of muscles; moves (flexes) the limb in toward the trunk

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Tricepts

(extensor muscle) extends the lower arm away from the body.

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Biceps

(flexor muscle) moves the lower arm toward the body.

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caudate putamen

prominent structure in the basal ganglia; a large cluster of nuclei that extends as a “tail” into the temporal lobe, ending in the amygdala

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Where does the basal ganglia receive input from?

1. All areas of the neocortex and limbic cortex, including the motor cortex, project to the basal ganglia.
2. The nigrostriatial dopaminergic activating system projects to the basal ganglia from the substantia nigra, a cluster of darkly pigmented cells in the midbrain.

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Dyskinesia

caused by cells of the caudate putamen being damaged; unwanted writhing and twitching movements

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What disease is known for dyskinesia?

Huntington's disease

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hyperkinetic symptom

symptom of brain damage (basal ganglia) that results in excessive involuntary movements, as seen in tourette’s syndrome.

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hypokinetic symptom

symptom of brain damage (basal ganglia) that results in a paucity of movement, as seen in parkinson’s disease

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What causes Parkinson's disease?

caused by the loss of dopamine cells in the substantia nigra that project into forebrain basal ganglia nuclei, and the disease is characterized by hypokinetic symptoms.

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What is the role of the basal ganglia?

may play a role not just in producing force but also in computing the effortful costs of making movements.

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What are the two pathways from the basal ganglia that affect the motor cortex?

an inhibitory pathway and an excitatory pathway

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how many ways can the cortex influence the basal ganglia?

two; direct and indirect pathways

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direct pathway to the basal ganglia

If the direct pathway is activated, the globus pallidus internal (GPi) is inhibited, and the pathway is freed to produce movement

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indirect pathway to the basal ganglia

If the indirect pathway is activated, the globus pallidus internal (GPi) is activated and inhibits the thalamus, thus blocking movement.

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Globus pallidus Internal

acts like volume control. If it is turned up, movement is blocked; if it is turned down, movement is allowed.

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What do diseases of the basal ganglia affect?

affect this volume control function, resulting in impairments of excessive or slowed movement.

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What is the cerebellum important for?

critical for acquiring and maintaining motor skills.

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flocculus

part of cerebellum; small lobe; projects from its ventral, or inferior, surface.

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where does the flocculus receive projections from?

the middle-ear vestibular system,

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what does the middle-ear vestibular system do?

takes part in controlling balance

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How many homunculus does the cerebellum have?

at least 2

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Medial homunculus of cerebellum

controls the face and the midline of the body.

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lateral homunculus of cerebellum

connect to areas of the motor cortex and are associated with movements of the limbs, hands, feet, and digits.

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Summary of cerebellum's topographic organization

the midline of the homunculus is represented in its central part; the limbs and digits are represented in the lateral parts. Tumors or damage to midline areas of the cerebellum disrupt balance, eye movement, upright posture, and walking but do not substantially disrupt other movements such as reaching, grasping, and using the fingers.

86

how many layers of cells does the cerebellar cortex have?

3

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what cells make up the 2nd layer of the cerebellar cortex?

purkinje cells

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what do the purkinje cells do for the cerebellum

they are the output cells of the cerebellum

89

what is the cerebellum responsible for?

not only for online adjustments of movement but also for learning relatively permanent movement skill

90

Dart Experiment

The cortex sends instructions to the spinal cord to throw a dart at the target. A copy of the same instructions is sent to the cerebellum through the inferior olive, a nucleus in the brainstem that projects to the cerebellum. When you next throw the dart, the sensory receptors in your arm and shoulder code the actual movement that you make and send a message about it back to the cerebellum through the spinocerebellar tract. The cerebellum now has information about both versions of the movement—what you intended to do and what you actually did—and can calculate the error and tell the cortex how to correct the movement

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Primary somatosensory

cortex receives sensory information from the body.

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Secondary somatosensory cortex

receives sensory information from the primary somatosensory cortex.

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where does the primary somatosensory cortex receive projections from?

thalamus

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what does the primary somatosensory cortex consist of?

Brodmann's areas 3-1-2

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what does the primary somatosensory cortex do?

begins the process of constructing perceptions from somatosensory information. It mainly consists of the postcentral gyrus just behind the central fissure in the parietal lobe

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where does the primary somatosensory cortex lie?

lies adjacent to the primary motor cortex, on the other side of the central fissure in the frontal lobe.

97

Are more sensitive areas of the body accorded larger cortical areas?

Yes

98

how many representational areas does the somatosensory cortex have of the body?

4

99

Somatosensory Area 3a cells

responsive to muscle receptors

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Somatosensory Area 3b cells

responsive to slow-responding skin receptors.

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Somatosensory Area 1 cells

responsive to rapidly adapting skin receptors

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Somatosensory Area 2 cells

responsive to deep tissue pressure and joint receptors

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Somatosensory Area 4 cells

cells respond to muscle and joint receptors.

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How are perceptions formed?

Perceptions constructed from elementary sensations depend on combining the elementary sensations.

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where does combining of perceptions take place?

takes place as areas 3a and 3b project onto area 1, which in turn projects onto area 2.

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what do cells in area 2 respond to?

stimulation in a number of different locations on a number of different fingers as well as to stimulation from different kinds of somato- sensory receptors

107

What types of cells are in Area 2?

multimodal neurons

108

multimodal neurons

that are responsive to movement force, orientation, and direction

109

how is the somatosensory cortex organized?

arranged in functional columns running from layer I to layer VI, similar to the functional columns found in the visual cortex.

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Cells in a single column respond to what?

a single class of receptors

111

where do all neurons in a functional column receive information?

from the same local area of skin

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What is the elementary functional unit of the somatosensory cortex?

neurons lying within a column

113

gargalesis

the pleasurable effect of hard rhythmic probing

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kinismesis

the sensation from a light caress

115

damage to the primary somatosensory cortex

impairs the ability to make even simple sensory discriminations and movements; also impairs simple movements

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apraxia

inability to make voluntary movements in the absence of paralysis or other motor or sensory impairment, especially an inability to make proper use of an object.

117

How does the somatosensory cortex contribute to movement?

participating in both the dorsal and the ventral visual streams. The dorsal (how) stream, working without conscious awareness, provides vision for action, as when we automatically shape a hand as we reach to grasp a cup. The ventral (what) stream, in contrast, works with conscious awareness to identify the object as a cup

118

referred pain

Pain felt on the surface of the body that is actually due to pain in one of the internal organs of the body.