Neuroscience of Movement Control

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Questions and Answers

Which of the following is NOT a symptom of Parkinson's disease?

Muscle rigidity

Resting tremor

Involuntary muscle jerks (correct)

Bradykinesia

What is the primary cause of Huntington's disease?

A deficiency in dopamine

A single dominant gene (correct)

Damage to the cerebellum

Environmental factors

How does the basal ganglia contribute to movement?

It helps fine-tune and coordinate movements (correct)

It initiates voluntary movements

It controls posture and balance

It sends signals to muscles for contraction

What is the effect of the degeneration of output neurons from the striatum in Huntington's disease?

Decreased inhibition of motor function Signup and view all the answers

Which of these is NOT a key point highlighted in the text regarding movement control?

Advanced movements rely on a single, specific pathway for execution Signup and view all the answers

Which area of the brain is most associated with linking actions to visual objects and selecting appropriate movements?

Premotor Cortex (PMA) Signup and view all the answers

Which of these brain areas is primarily involved in the execution of voluntary movements?

Primary motor cortex (PMC) Signup and view all the answers

What is the primary function of the supplementary motor cortex (SMA)?

Performing well-learned actions that don't require constant environmental monitoring. Signup and view all the answers

According to the warm up quiz, what is the meaning of the Latin word ‘cerebellum’?

Little brain Signup and view all the answers

What is the term used to describe an area of the brain that is involved in planning?

Posterior parietal cortex Signup and view all the answers

How long does it take, according to the Atlanta Ballet Association, to become a professional ballet dancer?

8-10 years Signup and view all the answers

Which of the following is NOT a factor to consider in motor coordination, based on the text?

Monitoring the environment Signup and view all the answers

According to Rodolfo Llinàs, what happens to a sea squirt's brain upon finding a stationary object?

It absorbs much of its own brain and returns to a primitive condition. Signup and view all the answers

What is a key function of the supplementary motor cortex (SMA)?

Producing uncued movements. Signup and view all the answers

What would likely result from deactivation of the supplementary motor cortex?

Severe disruption of learned sequences. Signup and view all the answers

How does the cerebellum contribute to motor control?

By acting as the primary source of motor error correction. Signup and view all the answers

What is characteristic of 'ballistic' movements?

They occur very rapidly and can not be corrected with sensory feedback during execution. Signup and view all the answers

Which of the following is a consequence of cerebellar dysfunction?

Dysdiadochokinesia, impaired ability to perform rapid movements. Signup and view all the answers

What does the term 'hypometria' refer to in the context of cerebellar dysfunction?

Errors in the range and direction of movement. Signup and view all the answers

How does the cerebellum contribute to motor learning?

By refining the motor program through repetition and making movements more accurate over time. Signup and view all the answers

What is the cerebellum's role when a motor act has been repeated many times?

It establishes a specific motor program for that learned movement. Signup and view all the answers

Which of these is a function of the basal ganglia?

Action selection and initiation Signup and view all the answers

What effect does the direct pathway have on movement?

It stimulates movement Signup and view all the answers

What neurotransmitter is primarily involved in the excitatory actions of the direct pathway?

Glutamate Signup and view all the answers

What is the primary function of the sensorimotor transformation involved in reaching?

To convert visual location information into reaching movement direction. Signup and view all the answers

What is a common result of insufficient direct pathway output and excess indirect pathway output?

Hypokinesia Signup and view all the answers

Which brain areas are directly involved in the sensorimotor transformation for grasping, as described in the text?

Dorsal extrastriate (ES) cortex, Anterior Intraparietal sulcus (AIP), and ventral premotor area (PMv). Signup and view all the answers

Which of the following brain regions is most sensitive to the effects of ethanol?

The Cerebellum Signup and view all the answers

What is the critical function of the Supplementary Motor Area (SMA) according to the text?

Generating linked self-generated movements. Signup and view all the answers

What effect does dopamine have on the indirect pathway via D2 receptors?

It inhibits the pathway, leading to reduced movement Signup and view all the answers

Optic ataxia is primarily characterized by which of the following?

A difficulty in reaching accurately under visual guidance. Signup and view all the answers

In the basal ganglia loop, what is the effect of the striatum’s inhibition?

It inhibits the SNr-Gpi Signup and view all the answers

What is the function of the indirect pathway within the basal ganglia?

To inhibit movement through a complex series of projections Signup and view all the answers

In terms of successful docking solutions what is the role of sensorimotor transformations?

To facilitate the conversion of visual information into motor commands. Signup and view all the answers

What is the significance of Milner's Posting Task in the context of visuomotor transformations?

It provides evidence for the role of the parietal cortex in visually guided reaching. Signup and view all the answers

Which of the following BEST describes a 'visuomotor transformation'?

The process of converting visual information into motor commands. Signup and view all the answers

What is involved when the brain generates reaching movements to a visual target?

The brain transforms between multiple coordinate systems. Signup and view all the answers

Study Notes

Brain Mechanisms of Action and Decision

Session 2: Advanced Movement
Check-In Code: TBC

How Is Monty Doing?

A humorous icebreaker question about appropriate animal attire.
A visual comparison of dog attire versus human attire (a celebrity).

Quick Recap

Premotor cortex (PMA):
- Links actions to visual objects.
- Selects appropriate movements.
- Regulates the primary motor cortex.
- Acts as an 'intention' area.
Supplementary motor cortex (SMA):
- Also known as the supplementary motor area.
- Controls well-learned actions without extensive environmental monitoring.
Posterior parietal cortex:
- Functions as a 'planning' area.
- Involves spatial reasoning and attention.
Primary motor cortex (PMC):
- Executes all voluntary movements.
- Acts as the 'doing' area.

Advanced Movement

Sea squirts, upon finding a rock or stationary object, transition to a sessile body state, absorbing a large part of their brain.
This process is paralleled by human academics.

High Stakes Skills

Motor coordination factors include:
- Body perspective position.
- Arm and hand relative position to the object.
- Feedback mechanism.
- Speed and altitude are factors.

Graded and Competitive Goal Selection

This section details the process of selecting actions/goals based on graded activation.
Movement threshold is influenced by coherence (high, medium, low).

Sensorimotor Transformation: Reaching

The visual system transforms information about objects into reaching movements.
A pathway connects parieto-occipital area, mediodorsal parietal area, medial intraparietal area and dorsal premotor area.

Sensorimotor Transformation: Grasping

This system translates visual information about object properties (size, shape) into effective grasping commands.
A pathway connects dorsal extrastriate cortex, anterior intraparietal sulcus, and ventral premotor area.

Successful Docking!

Motor coordination solutions include:
- Environmental attention.
- Goal selection.
- Sensorimotor transformation.

Optic Ataxia

Optic ataxia is an inability to accurately reach under visual guidance.
It involves issues in visuomotor sensory transformation.
Subjects have difficulties with scaling and orienting, which is visual guidance.

Dorsal and Ventral Parietal Streams

Damaged parietal cells lose the ability to locate visual stimuli.
The brain converts between multiple coordinate systems to control reaching.
Double dissociation demonstrates how parietal cortex coordinates visual information for premotor areas.

Linking Sequences

Supplementary motor area (SMA) is crucial for linked movements.
Without the SMA, well-learned motions are no longer possible, demanding external cues instead.
The functional dissociation between pre-motor cortex and SMA produces cued/uncued movements.

The Cerebellum

It is dense, 'silent', and difficult to measure.
Its location is analogous to road signs.

Error Correction

Signals from the motor cortex travel through the cerebellum and gather information on what body parts are doing (spinal cord).
The cerebellum compares these signals, making adjustments to produce smooth movements.
This process is referred as the stabilizing process/mechanism.

Motor Learning

Cerebellar neuronal circuits enhance movement accuracy over time.
Repetitive motor acts (like motor training) lead to greater precision in movement.
The cerebellum crafts a specific motor program for each repeated action.

'Ballistic' Movements

These rapid movements (writing, typing, running) are heavily dependent on the sensory feedback loop.
Sensory feedback has minimal impact on the trajectory once the action begins.

Cerebellum: Input and Output

Cerebellum's input and output pathways are organized.
Inputs come from frontal areas, pons, and midline nuclei.
Outputs are to premotor and primary motor cortices.

Motor Error Correction

The motor cortex triggers sensory feedback through cerebellum reentrant circuits.
The cerebellum predicts sensory consequences of motor output and compares them for error signals.

Cognitive Error Correction

This is similar to motor error, but also involves cognitive feedback in frontal areas.

The Cerebellum Saves!

An example of successful motor control, using Nastia Liukin's performance.

Cerebellar Dysfunction

Cerebellar ataxia:
- Errors in direction and range of movement
- Uncontrolled eye movements
- Unsteady gait/slurred speech.
Hypometria and Response Delays:
- Movements fall short of the desired goal.
- Delayed response to initiated movements.
Dysdiadochokinesia: Difficulties in performing rapid alternating movements.

Alcohol & Field Sobriety Tests

Field sobriety tests (FSTs) measure cerebellar function, impacted by alcohol.
FSTs evaluate balance, coordination, and eye-hand coordination, tasks that depend heavily on a healthy cerebellum.

The Basal Ganglia

The basal ganglia are responsible for initiating and selecting actions.
They also contribute to behavior inhibition.

The Basal Ganglia Loop

A description of the interconnected components and pathways involved in the basal ganglia.

The Direct and Indirect Pathways

Direct pathway:
- Excitatory glutamate signals stimulate movements.
- Modulatory dopamine signals influence movement.
- Insufficient direct output leads to hypokinesia (reduced movement)
Indirect pathway:
- Inhibitory GABA signals prevent unwanted movements.
- Modulatory dopamine signals modulate movement.
- Excessive indirect output can lead to hyperkinesia (increased movement).

The Direct Pathway

Cortex stimulates striatum, reduces inhibition on thalamus.
Thalamus activates cortex, leading to motor movement.

The Indirect Pathway

Cortex stimulates striatum, increasing inhibition on thalamus.
Thalamus is less activated leading to decreased movement or flaccid muscles.

Parkinson's Disease

Symptoms:
- Resting tremors (4-5 Hz, absent during movement/sleep).
- Muscle rigidity (resistance to movement; jerky, cogwheel).
- Akinesia (reduced involuntary movement).
- Bradykinesia (slowness of movement).
Neurology:
- Degeneration of substantia nigra pars compacta (dopamine-producing neurons) causes reduced dopamine.
- Overactive pathways lead to reduced movement and hyperkinesia.

Huntington's Disease

Symptoms:
- Progressive involuntary muscle jerks.
- Intellectual deterioration, depression, and psychosis.
- Genetic etiology (single dominant gene).
Neurology:
- Degeneration of striatal output neurons reduces inhibitory modulation of motor functions.
- Reduced inhibitory control leads to hyperkinesia.

Bringing it all Together in a Figure

Overview of connections between cerebral cortex, basal ganglia, cerebellum, and brain stem in controling voluntary movements.

Bringing it All Together in a Figure Skater

Example of how these systems work together in complex human motions.

Monty and I Would Like You to Remember

Summary of key concepts discussed regarding movement and their associated brain structures.
Goal selections, complex movements, fine tuning of movement by cerebellum/basal ganglia, and feedback-dependent movements are highlighted.

Studying That Suits You

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Description

This quiz explores key concepts related to the neuroscience of movement control, including the roles of different brain areas in motor function and specific diseases affecting movement, such as Parkinson's and Huntington's diseases. Test your knowledge on symptoms, causes, and the brain's mechanisms in coordinating actions effectively.