Chapter 11 Flashcards
neuroprosthetics
computer assisted devices replace lost biological function
computer brain interface (CBI)
employs electrical signals from a computer to instruct the brain
brain computer brain interface (BCBI)
combine the BCI and CBI approaches
brain computer inferface
employs electrical signals from the brain to direct computer controlled devices
Major components of the motor system?
cerebrum (forebrain); brainstem; spinal cord
cerebrum
contributes to our conscious control of movement
Brainstem & Spinal cord
perform our more automatic movements
what happens if the brainstem or spinal cord is impaired?
the forebrain can imagine move- ments but can no longer produce them
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.
basal ganglia’s role in picking up object
produces appropriate amount of force when picking up an object
brain stem & cerebellum’s role in picking up object
helps to regulate the timing and accuracy of the movement.
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.
Afferent
somatosensory information travels from the body inward via the somatic nervous system
efferent
movement information travels out of the central nervous system
cross section of spinal cord: Outer part
consists of white matter; dorsal tracts are sensory and ventral tracts are motor
cross section of spinal cord: inner part
gray matter; shaped like a butterfly;
tracts
bundles of nerve fibers in the CNS
nerves
bundles of nerve fibers in the PNS
dermatomes
cervical, thoracic, lumbar, sacral, coccygeal
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,
Do higher levels replace lower levels?
no, they act by controlling them
Motor sequence
Movement modules preprogrammed by the brain and produced as a unit.
Mirror Neuron
cell in the primate premotor cortex that fires when an individual observes a specific action taken by another individual
frontal lobe
responsible for planning and initiating motor sequences
Prefrontal Cortex
plans complex behavior; specifies the goal not the specific movements
Where does the prefrontal cortex send instructions?
premotor cortex
premotor cortex
which produces the appropriate complex movement se- quences.
Primary Motor Cortex
produces specific movements
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
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)
effect of context
how the neural site stimulated interacts both with the object presented and with the stimulation’s duration.
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.
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.
cerebral palsy
a disorder primarily of motor function: voluntary movements become difficult to make whereas conscious behavior controlled by the cortex may remain intact.
anoxia
lack of oxygen
cerebral palsy
group of brain disorders that result from brain damage acquired perinatally (at or near birth).
quadriplegia
paralysis of the legs and arms due to spinal-cord injury.
paraplegia
paralysis of the legs due to spinal- cord injury.
scratch reflex
automatic response in which an animal’s hind limb reaches to remove a stimulus from the surface of the body.
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.
Homunculus
representation of the human body in the sensory or motor cortex; also any topographical representation of the body by a neural area.
Is there 1 or 2 motor cortex?
2; one on each side of body
motor cortex control movement on contralateral or ipsilateral part of body?
contalateral
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
What does the motor cortex represent
the motor cortex represents not muscles but rather a repertoire of fundamental movement categories.
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
Motor cortex neurons
take part in planning the movement as well as initiating
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.
restraint-induced therapy
procedure in which restraint of a healthy limb forces a patient to use an impaired limb to enhance recovery of function.
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
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
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.
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
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
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
what do interneurons in the spinal cord project to?
Interneurons lie just medial to the motor neurons and project onto them.
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
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.
How are limb muscles arranged?
in pairs
extensor
one member of the pair of muscles; moves (extends) the limb away from the trunk
flexor
one member of the pair of muscles; moves (flexes) the limb in toward the trunk
Tricepts
(extensor muscle) extends the lower arm away from the body.
Biceps
(flexor muscle) moves the lower arm toward the body.
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
Where does the basal ganglia receive input from?
- All areas of the neocortex and limbic cortex, including the motor cortex, project to the basal ganglia.
- The nigrostriatial dopaminergic activating system projects to the basal ganglia from the substantia nigra, a cluster of darkly pigmented cells in the midbrain.
Dyskinesia
caused by cells of the caudate putamen being damaged; unwanted writhing and twitching movements
What disease is known for dyskinesia?
Huntington’s disease
hyperkinetic symptom
symptom of brain damage (basal ganglia) that results in excessive involuntary movements, as seen in tourette’s syndrome.
hypokinetic symptom
symptom of brain damage (basal ganglia) that results in a paucity of movement, as seen in parkinson’s disease
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.
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.
What are the two pathways from the basal ganglia that affect the motor cortex?
an inhibitory pathway and an excitatory pathway
how many ways can the cortex influence the basal ganglia?
two; direct and indirect pathways
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
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.
Globus pallidus Internal
acts like volume control. If it is turned up, movement is blocked; if it is turned down, movement is allowed.
What do diseases of the basal ganglia affect?
affect this volume control function, resulting in impairments of excessive or slowed movement.
What is the cerebellum important for?
critical for acquiring and maintaining motor skills.
flocculus
part of cerebellum; small lobe; projects from its ventral, or inferior, surface.
where does the flocculus receive projections from?
the middle-ear vestibular system,
what does the middle-ear vestibular system do?
takes part in controlling balance
How many homunculus does the cerebellum have?
at least 2
Medial homunculus of cerebellum
controls the face and the midline of the body.
lateral homunculus of cerebellum
connect to areas of the motor cortex and are associated with movements of the limbs, hands, feet, and digits.
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.
how many layers of cells does the cerebellar cortex have?
3
what cells make up the 2nd layer of the cerebellar cortex?
purkinje cells
what do the purkinje cells do for the cerebellum
they are the output cells of the cerebellum
what is the cerebellum responsible for?
not only for online adjustments of movement but also for learning relatively permanent movement skill
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
Primary somatosensory
cortex receives sensory information from the body.
Secondary somatosensory cortex
receives sensory information from the primary somatosensory cortex.
where does the primary somatosensory cortex receive projections from?
thalamus
what does the primary somatosensory cortex consist of?
Brodmann’s areas 3-1-2
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
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.
Are more sensitive areas of the body accorded larger cortical areas?
Yes
how many representational areas does the somatosensory cortex have of the body?
4
Somatosensory Area 3a cells
responsive to muscle receptors
Somatosensory Area 3b cells
responsive to slow-responding skin receptors.
Somatosensory Area 1 cells
responsive to rapidly adapting skin receptors
Somatosensory Area 2 cells
responsive to deep tissue pressure and joint receptors
Somatosensory Area 4 cells
cells respond to muscle and joint receptors.
How are perceptions formed?
Perceptions constructed from elementary sensations depend on combining the elementary sensations.
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.
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
What types of cells are in Area 2?
multimodal neurons
multimodal neurons
that are responsive to movement force, orientation, and direction
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.
Cells in a single column respond to what?
a single class of receptors
where do all neurons in a functional column receive information?
from the same local area of skin
What is the elementary functional unit of the somatosensory cortex?
neurons lying within a column
gargalesis
the pleasurable effect of hard rhythmic probing
kinismesis
the sensation from a light caress
damage to the primary somatosensory cortex
impairs the ability to make even simple sensory discriminations and movements; also impairs simple movements
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.
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
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.
