NEU 202 Midterm Flashcards

What is action?

The system that’s involved in executing motor movements. Whether this be controlling muscles or regulating neural activity so that you ca move your limbs and interact with the world around you, this is all considered action.

What is the role of the parietal cortex in action?

Planning motor movements.

What is the role of the somatosensory cortex in action?

Measuring where our limbs position are.

Why are the somatosensory cortex and motor cortex neighbors?

Information related to planning movement such as limb position feeds from the somatosensory cortex into the motor cortex to execute the action.

True or False: The primary motor cortex is anterior to the central sulcus.

True

True or False: The premotor cortex is posterior to the primary motor cortex.

False

What percentage of all neurons is in the cerebellum?

>50%

You’re walking down the road and notice a tire in the middle. Now, you need to figure out what to do with it. Go through the steps of the motor behavior after this comes into vision.

1. When you first notice the tire, the superior colliculus sends information to the prefrontal cortex to signal “Hey, watch out. There’s something in front of you.” Prefrontal cortex communicates with the parietal cortex of the dorsal stream to identify where the object is.

2. You decide that you want to get left and around it. Prefrontal cortex sends this choice to the premotor cortex to plan the movements needed to execute this action.

3. Planned movement signals then travel to the primary cortex where it can be sent to multiple places. Some projects to the pontine nuclei in the brainstem and into the cerebellum. Some others project to the basal gangli. Some others project straight into the spinal cord.

What white matter tract connects the prefrontal cortex and the parietal cortex?

Superior Longitudinal Fasiculus

Where is the pontine nuclei located?

Brainstem

What is the corticospinal tract (CST)?

White matter tract that connects the cortex to the spine.

How does the cerebellum work with error correction?

Cerebellum sends output signals to the thalamus. Specifically, the ventrolateral nucleus. Then, signals from the ventrolateral nucleus will be sent to the premotor and primary motor cortex to update outgoing signals.

True or False: Actions are not a one-and-done event.

True

Why are actions not considered a one-and-done event?

Outgoing signals are continuously adjusted according to visual and sensory information, largely mediated by the cerebellum, basal ganglia, and ventrolateral thalamus.

True or False: A large portion of motor output goes straight to the spine.

False; The majority of motor output actually percolates through the basal ganglia circuitry.

What are corticomotor neurons?

Neurons that project directly from cortex to the motor units of the spine.

What layer are Betz Cells located?

Layer V

Why are Betz cells located in layer V?

Layer V neurons are the output of cortex. Betz cells carry outgoing signals that make their way from the motor cortex to the spinal cord.

What are Betz cells?

Corticomotor neurons that have very large somas.

True or False: You can see Betz cells with the naked eye.

True

True or False: Betz cells are all over the motor cortex.

False; Betz cells tend to only be in motor representations of the upper limbs (such as hands and arms) that deal with fine motor control.

What is the current theory to why Betz cells are so large?

The current theory is that they’re so large because Betz cells need to generate gigantic action potentials that will survive the journey all the way down from the motor cortex to the spine to execute movements.

What percent of motor neurons in the cortex are Betz cells?

10%

Compare the cytoarchitecture of the precentral gyrus to the postcentral gyrus. Mention input/output arguements.

Precentral gyrus has a cell density gradient, whereas postcentral gyrus has two bands with prominent and visible layer IV. Layer IV is the input region of the cortex, so this makes sense considering the somatosensory cortex receives a lot of information about sensation in the body. In comparison, the motor cortex mostly products outgoing signals, so it doesn’t have as pronounced layer IV.

What is an anterograde tracer?

A virus you can inject into the cortex to infect cells, which then will spread as action potentials propagate down the axon to jump across on synapse to infect downstream cells.

What are alpha motor neurons?

Termination points from M1 neurons that project directly to the spine that synapse directly to the muscles.

Where do alpha motor neurons project?

Muscles

Where are alpha motor neurons located?

Spinal Chord

What is released when alpha motor neurons synapse to the muscles?

Acetylcholine

What is acetylcholine?

A neurotransmitter that causes the muscles to contract.

True or False; Direct projects from M1 to the spine is evolutionarily novel

True; the number of alpha motor neurons increases as you move up the evolutionary tree to higher order primates.

True or False: Mice have direct projects from M1 to the spinal chord.

False; direct projects from M1 to the spinal chord is evolutionarily novel.

Which parts of the body are corticomotor neurons largely involved in?

Hands and Arms

Use an experiment to justify the role corticomotor neurons play in fine-motor skills.

A monkey was given three tasks to get a juice reward. In the first task, the monkey had to pinch something with light resistence. In the second task, the monkey had to pinch something with heavy resistance. In the third task, the monkey has to hold a power grip. In the first and second tasks, corticomotor neuron activity was high before the movement was initiated. In the third task, corticomotor neuron activity was virtually silent before and after the movement was initiated. Therefore, corticomotor neurons are largely involved in fine-motor skills like pinching a grip compared to hold a power grip.

Besides Betz cells, where do other 90% of motor neurons project to?

Basal Ganglia and Cerebellum

What does ganglia mean?

A cluster or cells in the peripheral nervous system.

What does nucleus mean?

A cluster of cells in the central nervous system.

True or False: The Basal Ganglia is located in the peripheral nervous system.

False; Despite the name, the Basal Ganglia is located in the central nervous system.

What role does Basal Ganglia play in movement?

The basal ganglia plays an important role in gating motor output from M1 and cortex. It can be thought of as a gatekeeper of motor signals, making sure that not all random activity gets through, only strong, intentional actions.

What region suffers the most in conditions like Parkinson’s Disease?

Basal Ganglia

What type of damage causes Ataxia?

Damage to the cerebellum.

What is ataxia?

Difficulty maintaining balance and producing well-coordinated movement.

Why does damage to the cerebellum cause ataxia?

The cerebellum is involved in error-correcting signals that allow for micro-adjustments in movement. When you get damage to the cerebellum, you can get lateralized ataxia for different limbs depending on where that damage is.

True or False: The striatum is two seperate structures.

False; The striatum is one structure, but looks like two separate structures because of the way it’s oriented.

What are the two parts of the striatum?

Putamen and caudate

What role does the striatum play in action?

The striatum plays an important role in learning and selecting motor movements from cortex. It essentially changes the synaptic structure from the cortex to the striatum in order to make movements more precise and easier to execute over time.

What are the major parts of the basal ganglia?

Striatum (Putamen & Caudate), Globus Pallidum (Exterior/Interior)

Describe the pathway of signals from the motor cortex to the basal ganglia.

A neuron of the motor cortex synapses onto one or multiple of the structures of the basal ganglia. Once information is percolated in the basal ganglia circuitry, signals will either project to the spinal chord or the ventrolateral thalamus.

Why is it important for signals from the cerebellum and basal ganglia to be inputted to the ventrolateral thalamus?

Cerebellum also sends error correction signals. Therefore, the ventrolateral thalamus is integrating information about the type of movement about to be made from the basal ganglia and how the movement should be done from the cerebellum to project back into the cortex so that motor behavior can be updated.

Compare the projects of the corticomotor neurons and a typical motor neuron.

Corticomotor neurons project directly to the spinal chord. Typical motor neurons project to the basal ganglia.

What types of neurons are part of the hyper direct pathway?

Corticomotor Neurons

What are the three pathways of motor behavior?

1. Hyperdirect Pathway

2. Indirect Pathway

3. Direct Pathway

What are the striatal pathways of movement?

1. Indirect Pathway

2. Direct Pathway

What is the difference between the indirect pathway and direct pathway of movement?

The indirect pathway goes through the globus pallidus exterior before going to globus pallidus interior and substantia nigra pars reticulata. The direct pathway goes through the globus pallidus interior and the substantia nigra reticulata.

What is the goal of the indirect pathway?

The ultimate goal of the indirect pathway is to inhibit motor activity.

How does the indirect pathway inhibit motor activity?

The globus pallidus exterior inhibits the subthalamic nucleus which excites the global pallidus exterior. The global pallidus exterior inhibits the thalamus which reduces excitation of the cortex.

What is the ultimate goal of the direct pathway?

The ultimate goal of the direct pathway is to promote motor activity.

How does the direct pathway promote motor activity?

The striatum inhibits the globus pallidus interior, so the thalamus is no longer inhibited and can excite the cortex.

How does the indirect and direct pathways of movement exhibit the gating power of the basal ganglia?

Unintended movements would likely be processed through the indirect pathway and be inhibited, while voluntary, intended movements would likely be processed through the direct pathway and be promoted.

Where is the substantia nigra pars compacta connected?

The substantia nigra pars compacta is connected to the striatum.

What neurotransmitter does the substantia nigra pars compacta release?

Dopamine

What does the striatum need dopamine for?

The striatum relies on dopamine to function.

What region of the basal ganglia undergoes a massive neurodegeneration in Parkinson’s disease?

substantia nigra pars compacta

Why does neurodegeneration of the substantia nigra pars compacta cause Parkinsons disease?

Loss of cells in the substantia nigra pars compacta results in a less active striatum, which in turn makes it more difficult to initiate voluntary movement.

Why is L-DOPA used as a treatment for Parkinson’s Disease?

L-DOPA mimics the structure of dopamine to help increase function in the striatum when there is a lack of dopamine due to neurodegeneration of the substantia nigra pars compacta.

What part of the basal ganglia undergoes massive neurodegeneration in Huntington’s disease?

globus pallidus exterior

How does neurodegeneration of the globus pallidus exterior cause Huntington’s disease?

Gradual loss of function in the inhibitory neurons of the indirect pathway results in a loss of inhibition and patients exhibit involuntary movements and emotional and attention issues.

True or False: The basal ganglia is heavily connected to cortex outside of the primary motor cortex.

True

True or False: The basal ganglia is involved in filtering thoughts in addition to motor actions.

True

True or False: The human body is represented topographically in the primary motor cortex.

True

True or False: Topographic maps cannot be found beyond the cortex.

False; The cerebellum, thalamus, and basal ganglia all have topographic maps.

Which part of the cortex is involved in the planning of movements?

pre- and supplementary motor cortex.

What is the role of the pre-motor cortex (PMC) in movement?

The PMC is involved with planning movements in regards to their spatial position (where to reach, how far).

How does the pre-motor cortex plan movements?

To accomplish planning movements, the PMC has strong connectivity with the parietal cortex which has representations of space.

Describe the Graziano work with monkeys and the pre-motor cortex.

The Graziano group realized that the pre-motor cortex is organized based on upper/lower space. For example, when stimulating the part of the pre-motor cortex involved in upper space, the monkey moves its hands to its mouth. When stimulating the part of the pre-motor cortex involved in lower space, the monkey moves its hands to a location in lower space.

What is the role of the supplementary motor area (SMA) in movement?

The supplementary motor area (SMA) is connected to the medial frontal lobe where information about value, reward, and goals are represented. The SMA plays the role in choosing which object to reach for and how to execute the reach based on the task.

Which parts of the brain are involved in reflexive action?

Superior colliculus and frontal eye fields

True or False: Reflexive actions are not synonymous with reflexive attention.

False; reflexive attention involves reorienting your eyes and head towards a sudden sound or light source.

True or False: The frontal eye fields are retinotopic maps.

True

Where are the frontal eye fields located?

The precentral sulcus (secondary motor cortex)

Describe how reflexive attention is synonymous with reflexive action.

When a visual anomaly is detected in the upper visual receptive field of the superior colliculus, neurons in that superior colliculus would fire to the corresponding upper visual spaces in the pre-central sulcus maps in the premotor cortex to initiate eye movement there.

What did the monkey moving the joystick experiment prove?

Population activity determines precise limb movement.

Describe population coding.

A neural representation method where information is conveyed by the joint, simultaneous activity of a large group of neurons, rather than by a single neuron.

Describe brain-machine interfaces.

Interfaces trained to convert neural activity to machine movement.

True or False: As long as you can read neural activity, you can hook anyone up to a prosthetic arm and have them move it with just their mind immediately.

False; It’s not the case that we can just stick an electrode into someone’s brain and immediately they can control a robotic arm. Everyone’s neural population is different, so you have to train the computer to assign specific weights in the preferred direction to certain neurons in an individual’s neural population.

True or False; The motor cortex at the fine scale of individual neurons is not consistent enough across people.

True

True or False; The premotor cortex (PMC) is the holding center of complex motor plans.

True

True or False: The premotor cortex remains active when the movement occurs

False; The premotor cortex is only activity during the waiting stage when an individual knows what movements it can make and the planning stage when an individual plans how to make the movement. By the the time the movement occurs, the premotor cortex is effectively silent.

Describe multivoxel pattern analysis (MVPA).

MVPA is a measure of voxel bold activity across voxels in multiple brain regions.

Describe the findings of the Haar reaching experiment.

When participants wore goggles that switched things left-right, they found that the MVPA in the premotor cortex and primary cortex does not change, suggesting that the PMC and M1 only rely on the tuned direction of the movement itself. On the other hand, the posterior parietal cortex adapts its MVPA to what the goggles show, suggesting that our remapping of the visual environment on an action that we make is a role played by the posterior parietal cortex which is part of the dorsal stream.

True or False: The success of a motor activity requires integration with visuospatial representations in the dorsal stream, and it is the adaptability of the parietal cortex that helps us remap a motor action onto the visual world.

True

What does cerebellum mean?

Little Brain

What is the role of the cerebellum in movement?

The cerebellum is the processing center for error correction.

True or False: The cerebellum is connected to the brain.

False; The cerebellum is connected to the brainstem via white matter tracts.

True or False; Purkinje cells are found all over the nervous system.

False; Purkinje care a type of neuron only found in the cerebellum.

Describe the corticocerebellar circuit.

Planned movement information from the premotor cortex sends information to the pontine nuclei which sends information to the cerebellum. Then, the cerebellum sends information out to the thalamus, which can project out to the primary and premotor cortex.

How many layers does the cerebellum have?

3

What are the three cortical layers of the cerebellum? Write them in order where one is the most interior and three is the most exterior.

1. Granule Cell Layer

2. Purkinje Cell Layer

3. Molecular Layer

What are the two major inputs to the cerebellum?

1. Mossy Fibers

2. Climbing Fibers

What type of signals do the mossy fibers carry? Where do they project to?

Multisensory inputs; Project to granule cells.