Neural Control of Human Movement EP4703 Exam 3

What are the primary functions of the cerebral cortex?

most visually guided movements, perception, conscious decisions, planning, execution, and accuracy of movement

What are the two primary types of cells in the cerebral cortex?

pyramidal and stellate cells

what happens is Layer II of the CC?

-known as the external granular layer

-contains many small pyramidal cells and stellate cells

what happens in Layer III of the CC?

-external pyramidal layer

-pyramidal cells dominate

intracortical communication

-the pyramidal cells in layers 2 and 3 project to other neurons within the same cortical ares as well as neurons in other cortical areas (intracortical communication)

what happens in layer IV of the CC?

-internal granular

-stellate and pyramidal cells

-receives sensory info from the thalamus

-thalamic inputs make synaptic connections

what happens in layer V of the CC?

-ganglionic

-large pyramidal cells

-major output from cortex

where does intracortical communication take place?

layers II & III

primary function of the primary motor area

execution and control of voluntary movements

primary function of premotor cortex

prepare and plan movements, mainly guided by sensory information

(visual sensory signals generate motor signals for arm movements and hand grasping)

two sub-divisions of the premotor cortex

-dorsal premotor cortex (PMD)

-ventral premotor cortex (PMV)

dorsal premotor cortex PMD

-receives information from the parietal reach region which encodes the direction of reaching movements and integrates visual information with proprioceptive info

-integrations of sensory information into motor commands and specifying amplitude, direction and speed

(reaching and grasping for an object)

ventral premotor cortex (PMV)

-contains mirror neurons

-fire when a person tries to repeat an action performed by others and during imitation learnining

-encodes planning of higher level planning of goals (what objects to reach for)

-processes object properties relative to grasping and helps shape the hand and wrist to grasp an object

mirror neurons

special class of neurons that modulate their activity when a person executes a motor action and observes a motor action (mimic what someone is doing)

supplementary motor area (SMA)

-located in the dorsomedial frontal cortex

-involved in the sequencing and initiation of movements

pre-SMA

-more involved in higher level motor planning

(actions that take more of a cognitive effort)

primary somatosensory area

-area responds to tactile information and joint movements (proprioceptive info)

-patients with lesions in this area are unable to reach towards objects efficiently

parietal association cortex

sensory guidance of motor behavior and spacial awareness (without using vision)

temporal association cortex

recognition of behavior and working memory

frontal association cortex

organization of behavior and working memory (pull info from long/short term memory to help with task)

limbic association cortex

complex functions related to emotion and episodic memory (something that has happened, emotional)

information (ascending information) comes into the cerebral cortex from what two primary places?

cerebellum and basal ganglia

outgoing (descending information) from the cerebral cortex goes to what five places?

basal ganglia, cerebellum, red nucleus, reticular formation, spinal cord

what is the difference between convergence and divergence?

-divergence: can stimulate one or more similar cortical cells to activate different motor groups and move different body parts

-convergence: stimulating different cortical cells may activate the same group of motor units and result in similar motions

disease or disorder of the basal ganglia leads to what types of problems?

-can lead to parkinson's and or huntington's disease.

-can develop an increase of involuntary movements, coordination deficits, shuffling gate, and postural problems.

what are the five paired nuclei of the basal ganglia?

caudate nucleus, putamen, globus pallidus, substantia nigra, subthalamic nuclei

input into the basal ganglia comes from what two areas? which two nuclei of the basal ganglia receive this information?

-cerebral cortex and nuclei of the thalamus.

-caudate nucleus and the putamen (striatum)

what is the difference between the direct and indirect pathways, in terms of being excitatory or inhibitory, and the function of each pathway?

direct pathway: projects medium spiny neurons of the striatum to the internal segment of the GPi; facilitates inhibition of voluntary movements by releasing cortical neurons from the tonic inhibition of the thalamic cells. (gets excitatory response)

indirect pathway: projects medium spiny neurons on the striatum of the external segment of the GPe; opposes the activity of the direct pathway (movement cannot happen until a certain action is done).

what are the primary signs and symptoms of huntingtons and parkinsons disease? which part of the basal ganglia is affected in each one?

parkinsons: less direct, hypo-kinetic disorder; symptoms include tremor during rest that lessens with movement and sleep, slow movements, muscle stiffness, speech difficulties, and lack of facial expressions

-affected by loss of dopaminergic neurons in the substantia nigra

huntingtons: less indirect, hyperkinesia disorder; symptoms include increase in voluntary movements, abnormal gait, coordination deficits, and rapid//jerky movements

-caused by gradual atrophy of the striatum

-leads to a lack of inhibitory output of the basal ganglia that leads to cortical neurons responding to small inputs, resulting in undesirable movements

what are the primary functions of the basal ganglia

1. Involved in action selection, movement preparation, movement sequencing, and reinforcement learning.

2. Involved in force control; controlling the antagonist muscle group.

3. Helps prevent unwanted movements

4. Also plays a role in linking emotion, executive function, reward, and mood regulation

5. May also have specific relevance for adaptive shaping of behavior and action selection

6. Also plays a role in short-term memory, attention and cognition

what is the ratio of inputs to outputs in the cerebellum?

extremely high input to output ratio

what are the four common symptoms of cerebellar disorders, and what issues do they cause with movement?

1. Hypotonia: diminished resistance to passive limb displacements (muscle weakness; low muscle tone)

2. Astasia-abasia: inability to walk

-astasia: loss of the ability to maintain a steady limb or body posture across multiple joints

-abasia: loss of the ability to maintain upright stance against gravity

3. Ataxia: lack of coordination (biggest issue with cerebellum)

4. Tremor: at end of movement when attempting to stop (action or intention tremor) different than parkinson's tremor

granule cells

excitatory; they excite golgi cells

-found in cerebellum

golgi cells

excited by parallel fibers

inhibit granule cells (recurring inhibition)

-helps control the flow of information into the cerebellum

stellate cells and basket cells

interneurons within the cerebellum; inhibit purkinje cells

-control the flow of information out of the cerebellum

purkinje cells

only output of the cerebellum; inhibitory neurons

mossy fibers

carry any kind of sensory info related to movement to cerebellum (input)

-synapse on granule cells

-primarilly excitatory

climbing fibers

synapse on purkinje cells; specialized for event detection

-excitatory

-input and output in cerebellum

what type of information is brought into the cerebellum by the input neurons?

sensory and motor information

where does information go when it leaves the cerebellum?

thalamus and red nucleus

IX glossopharyngeal nerve

sensory functions: taste, general sensation, baroreception, salavation

motor functions: elevates the pharynx during swallowing and speech, gag reflex, swallowing

X vagus nerve

processes sensory input from the GI tract, regulates brain function, controls inflammation, influences gut function

XI spinal accessory nerve

helps with neck movements and shoulder movements

XII hypoglossal nerve

controls the muscles of the tounge

what is the difference between dualism, reductionism, and neodualism as it relates to memory?

dualism: responsible for thinking; body obeys soul and laws of nature

-considered mind a uniquely human feature independent of the body

reductionism: all features of human behavior are reflected in measurable physical properties of neurons and synapses

-everything can be measured, including specific sites of memory at specific synapses

neodualism: function of a complex system is an emergent property of all the system elements and connot be assigned to certain changes in neurons and synapses

-the mind is an emergent part of the body, not a separate feature

what is the difference between declarative and non-declarative memory?

declarative memory is explicit, semantic, and episodic (facts and events)

-hippocampus, medial temporal lobe, and diencephalon

non-declarative memory is implicit and procedural (skills and habits

-amygdala, cerebellum, Bg, cortex

habitutation

learning not to respond to a stimulus following multiple presentations (usually, when it is not very meaningful)

-fire alarm is continuously going off

dishabituation

the restoration or recovery of a habituated response (usually requires a new, strong stimulus)

-actually is a fire, bad weather

-opposite of habituation

sensitization

learning to respond to smaller magnitudes of a stimulus (usually, if it is very meaningful)

-recongnize changes, but respond in smaller magnitudes

motor skills and motor learning is an example of what type of memory?

non-declarative memory

what are the four stages of memory? what happens at each stage?

1. Encoding: putting an event into an internal code

2. Storage: maintaining the code over time (if code is not used, it will go away)

3. Consolidation: the process that makes the temporarily stored and still liable information more stable (takes practice; more you consolidate it, easier it is ti unlock)

4. Retrieval: using a key to recover the code/event (intrinsic or extrinsic)

what is the difference between operant conditioning and classical conditioning?

classical conditioning: associating a response with a stimulus based on repetitive presentations (ringing a bell is associated with getting food); the animal has no initiative.

-considered conditioned reflex, rather than inborn reflex

operant conditioning: searching for an action that leads to a desired consequence; active exploration, requires thousands of repetitions

-getting a treat, rewarded

what is the typical storage capacity of short-term memory?

7 items, plus or minus 2

how do memories become consolidated?

processing a sensory stimulus may lead to creating a short-term memory trace in parallel with producing an effector (motor) output

-short-term memory can be consolidated into long-term memory

do synapses serve as the site of memories? what is the current thing on this idea?

no, synapses do not serve as the site of memories

-little evidence supports this, very uneconomical, would require numerous synapses to memorize a single fact or event, and an infinite number of synapses to memorize/learn everything

-memories are stored all over the brain

-involves whole-brain mechanisms

what are the types of amnesia?

amnesia is a loss of memory

anterograde: affects the ability to recollect events that occurred AFTER the injury (trauma)

retrograde: affects the ability to recollect events that occurred BEFORE to an injury

what is korsakoff's syndrome?

chronic alcohol abuse or thiamine deficiency (not eating properly)

-defective retrieval of memories

how is the hippocampus involved with memory?

crucial for transferring short term memories to long term memories, specifically explicit memories (MTL)

-important in storing declarative memory

how is the cerebellum involved with memory?

long hypothesized to store long term effects of training, specically motor memories

brainstem anatomy

-consists of the midbrain, pons, and medulla oblongata.

-acts as a conduit between the brain and the spinal cord.

-serves as a passageway from the ascending tract from the spinal cord, the motor tracts of the head and neck, and the descending motor tracks from the cerebral cortex.

-also contains local neural networks that regulate eye movement.

reticular formation

-collection of nuclei scattered all over the brainstem

-neurons facilitate limb motor, oculomotor, autonomic, sensory, circadian, and mood-regulated functions

-plays a role in posture and balance

superior colliculus

-transforms sensory input from multiple sensory modalities into motor output

-helps direct the eyes toward visual stimuli of interest, a behavior known as orienting

red nucleus

-large group of cells located in the rostral midbrain that is redish-pink in color

-maybe involved in motor control of the upper extremities

-communicates withe the cerebellum through the inferior olive

vestibular nuclei

-located in the medulla and pons

-consists of four major nuclei that integrate information from the vestibular afferents, the somatosensory receptors, and the cerebellum

-play a major role in maintaining equilibrium, postural control, and eye movements during head rotation

what is the difference between first, second, and third order neurons?

first order: carry somatosensory information (proprioceptive and tactile) into the spinal cord; cell bodies are located in the dorsal root ganglia, synapse directly onto motoneurons or interneurons

second order: relays between first-order neurons and the thalamus

third order: relay information from the thalamus to the somatosensory cortex

dorsal column pathway

-first order neurons bring somatosensory information into the dorsal column of the spinal cord

-information from the lower limbs travel in the gracile tract and terminate in the gracile nucleus of the medulla

-information from the upper limbs travel in the cuneate tract and terminate in the cuneate nucleus of the medulla

-from the medulla, info travels through the medial lemniscus pathway (second order neurons) to the talamus

-third order neurons carry the information from the thalamus to the primary somatosensory cortex

spinothalamic tract

(will end up in the thalamus)

-the spinothalamic tract consists of the axons neurons whose bodies lie in the dorsal and intermediate parts of the gray matter.

-the axons cross the midline and travel along the contralateral side of the spinal cord in the ventrolateral funiculus

-this tract conveys the sensations of touch, pressure, temperature, and pain

spinocerebellar tract

(goes to cerebellum)

-the cerebellum receives information from peripheral sensory receptors by means of the dorsal, ventral, and rostral spinocerebellar tracts; the cuneocerebellar tract; and the spino-olivary-cerebellar tract

---> DSCT-RSCT-upper

dorsal spinocerebellar tract

ascends in clarke's column; carries information from proprioceptors (M.S >O) in the lower extremities

-also has projections to nucleus Z (medulla) and the VPL thalamus

cuneocerebellar tract

carries proprioceptive information from the upper extremities

ventral spinocerebellar tract

ascends laterally in the central horn; carries FRA (flexor reflex afferent's) information from the lower extremities and other afferent signals (only sends info during active movements)

rostral spinocerebellar tract

carries FRA information from upper extremities and other afferent signals (only sends info during active movements)

spinoreticular tract

(going to reticular information)

ascends in the ventrolateral fasciculus directly to the reticular formation

-plays a role in controling the sense of pain

pyramidal tract

consists of two major groups of axons

--axons of the first group go down to the spinal cord (corticospinal tract)

-some fibers leave the pyramidal tract and innervate the nuclei of the cranial nerves (corticobulbar tract)

originates from the primary motor cortex, premotor cortex, supplementary motor areas, and somatosensory cortex

-involved in the control of the musculature of the limbs and trunk

corticospinal tract

a bundle of nerve fibers that connects the cerebral cortex to the spinal cord

-plays a crucial role in controlling voluntary movements

-originates at the primary motor cortex

-fibers descend through the brain stem and spinal cord

corticobulbar tract

innervates the motor nuclei of the cranial nerves

-orginates in the primary motor cortex

rubrospinal tract

-originates in the red nucleus

-receives input from the motor cortex, the cerebellum and the olives

-located in the lateral white matter of the spinal cord

-possibly involved in the upper extremity motor control

-- (arms, hands, fingers)

-damage disturbs voluntary movement

vestibulospinal tract

-arise from the vestibular nuclei in the midbrain

-receive information from the cerebellum, the labyrinth in the inner ear, the eighth cranial nerve, and proprioceptive information from the spinal cord

-involved in the initiation of coordinated postural extensor activity in the limbs and trunk

-lesions to these tracts cause ataxia and postural instability (coordination issues)

reticulospinal tract

originates in the reticular formation and is an important descending tract for motor control and a hub for sensorimotor integration that allows the nervous system to make limb movements while stabilizing overall posture

-lesions on this tract can also cause ataxia and postural instability

tectospinal tract

*it comes from neurons in the superior colliculus

*projects to neurons (motor control of the eyes) in the cervical spinal cord that coordinate eye, head, and neck movements

I olfactory nerve

sensory, smell

II optic nerve

sensory, vision

III oculomotor nerve

motor, eye movements (1)

IV trochlear nerve

motor, eye movements (2)

V trigeminal nerve

sensory and motor: somatic sensation from face, mastication muscles

VI abducens nerve

motor, eye movements (3)

VII facial nerve

sensory and motor: facial expression muscles, taste from tongue

IX glossopharyngeal nerve

sensory a motor: sensations from the tongue, chemoreceptors

X vagus nerve

sensory and motor: vocal cord muscles, swallowing

XI spinal accessory nerve

motor: shoulder and neck muscles

XII hypoglossal nerve

motor: tongue movements

why would an engineer think that skeletal muscles are slow?

*muscles are relatively slow

-(takes time for signal to reach muscle)

*muscles and their interaction with the nervous system are non-linear

what is the difference between inverse kinematics and inverse dynamics?

inverse kinematics: what is the order of joint actions in order to produce a movement

inverse dynamics: which muscles flex/extend joints

what is the general premise of force-control approach?

*the CNS produces active changes in muscle force by sending signals to the muscle.

*force depends on neural signals sent to the muscles AND external loading conditions, which change with the motion.

*CNS must try and predict changes that will occur to muscle length and force during the movement

what is the general premise of the generalized motor program (think about movement formulas)?

*brain has "movement fomulas" that knows what joint/muscle to use to perform a certain motor task.

--developed by Schmidt in the 1970s

with internal models, what is the difference between the direct models/process and inverse models/process?

direct: has less delay in producing a movement, and is like a feedforward control

inverse: more of a delay in producing a movement, more of a feedback control.

-in order to make a certain movement, it takes calculations on what muscle groups need to be activated in order for a task to happen.

what are some experiments that support the idea of internal models?

1. Demonstrations of changes in the brain (cerebellar) activity with motor learning (Kawato)

-possible link between this and internal models

2. Experiments with adaptation to changing force fields and after-effects when the force is turned off (Wolpert Shadmehr, Ostry)

-learning how to predict

what are some problems with internal models?

a common explanation: an internal model is quickly updated (recomputed) based on feedback signals

-this implies an amazingly quick and accurate computational process

-compare typical, simple, and choice reaction times (how long it takes you to respond to one stimulus)

how does the equilibrium point hypothesis resolve the movement-posture paradox?

the principle of reafference

what is the principle of reafference?

*neural commands for any active movement re-address afferent signals from proprioceptors to a new posture.

-these signals will allow movement to occur and be used to stabilize at a new posture.

-the ability to resolve the posture-movement paradox is unique to the EP hypothesis