Thalamus & Basal Ganglia Overview

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Questions and Answers

What is the consequence of disrupting the indirect pathway in primates?

It reduces excessive grooming.

It enhances the termination of motor programs.

It induces stereotypical behaviours. (correct)

It strengthens the direct pathway.

Which statement best describes the role of the indirect pathway in motor control?

It directly executes motor commands.

It increases the amount of dopamine in the system.

It inhibits motor commands to prevent repetition. (correct)

It selects motor commands for performance.

What is a likely effect of excess dopamine on motor behavior?

Improved inhibition in the striatum.

Increased motor program termination.

Imbalance favoring direct pathways. (correct)

Decreased occurrence of stereotypical behaviours.

In the context of motor behaviours, what does GABA antagonism in the GPe indicate?

It disrupts the functioning of the indirect pathway. Signup and view all the answers

Which behaviour is associated with stereotypy in non-human animals due to imbalance in the motor pathways?

Excessive grooming. Signup and view all the answers

What effect does GABA antagonist injection in the anterior GPe have on monkey behavior?

It causes persistent repetition of a grooming behavior. Signup and view all the answers

What does the indirect 'No-Go' pathway primarily result in?

Inhibiting motor commands effectively. Signup and view all the answers

How did GABA antagonist injection in the dorsal GPe affect the monkeys?

It increased hyperactivity and exploration. Signup and view all the answers

Which brain regions are primarily involved in the direct 'Go' pathway?

Cortex, STN, GPi, and SNr. Signup and view all the answers

During what behavior do monkeys primarily spend their time before injection?

Resting or observing their own hands. Signup and view all the answers

What role does the globus pallidus external segment (GPe) play in the normal functioning of the indirect pathway?

It functions as an inhibitory connection in the pathway. Signup and view all the answers

Which neurotransmitter is primarily associated with excitatory connections in the indirect pathway?

Glutamate Signup and view all the answers

What is the effect of injecting a GABA antagonist in the GPe on motor commands?

It decreases inhibition of the motor command. Signup and view all the answers

Which structure is responsible for strong inhibition of the thalamus in the indirect pathway?

Globus pallidus internal segment (GPi) Signup and view all the answers

What behavior was observed in monkeys when the indirect pathway was disrupted?

Stereotypical behaviors such as finger biting Signup and view all the answers

What happens to the thalamus when the indirect pathway functions normally?

It experiences stronger inhibition than usual. Signup and view all the answers

Which component is not part of the indirect pathway as described?

Cerebellum Signup and view all the answers

Which type of connection does GABA represent in the context of the indirect pathway?

Inhibitory connection Signup and view all the answers

What effect does interference with the anterior GPe have on behavior?

Prevents exiting repetitive behavior loops Signup and view all the answers

How does the posterior GPe affect behavior in monkeys?

Allows irrelevant behaviors to occur Signup and view all the answers

What behavioral trait was observed more in certain mice compared to others?

Increased stereotypical jumping Signup and view all the answers

What is suggested to cause higher stereotypical behavior in some mice?

Increased activity in the direct pathway Signup and view all the answers

What substance's concentration reflects activity in the direct pathway of the striatum?

Dynorphin Signup and view all the answers

What role do the basal ganglia play according to the content provided?

In selecting actions and inhibiting irrelevant patterns Signup and view all the answers

What type of behaviors were studied in animals to understand individual differences?

Stereotypical behaviors and anxiety signs Signup and view all the answers

What has been linked to stereotypical behaviors in animal studies?

Variability in basal ganglia functioning Signup and view all the answers

What is correlated with the increase in tic severity in Tourette syndrome?

Increased striatal dopaminergic activity Signup and view all the answers

How do antipsychotics affect OCD symptoms?

They block dopamine receptors Signup and view all the answers

What learning tendency is associated with individuals having Tourette syndrome?

Increased learning from reward Signup and view all the answers

What can contribute to the maintenance of compulsive behavior in OCD?

Enhanced reward learning Signup and view all the answers

What effect does excessive dopamine release have on action selection?

It facilitates the selection of learnt habits Signup and view all the answers

How does anxiety influence behavior regarding learned habits?

It increases the likelihood of behaving habitually Signup and view all the answers

What is a direct consequence of the imbalance created by excessive dopamine release?

Difficulty in selecting alternative actions Signup and view all the answers

What aspect of punishment learning is noted in individuals with OCD?

They learn less from punishment Signup and view all the answers

Study Notes

Thalamus & The Basal Ganglia

The thalamus plays a crucial role in relaying sensory information to the cortex
The basal ganglia, specifically the direct and indirect pathways, are involved in selecting and inhibiting motor commands.

Direct vs. Indirect Pathways

The direct pathway promotes movement by exciting the thalamus, leading to the selection of a motor command.
The indirect pathway inhibits movement by suppressing the thalamus. This is often referred to as the "No-Go" pathway.
An imbalance, with the direct pathway being more active than the indirect pathway, can lead to a "Go" bias, potentially causing repetitive behaviors.

Stereotypical Behavior

Animals with a direct > indirect imbalance can exhibit stereotypical behaviors, such as excessive grooming or repetitive movements like lever pressing.
Disrupting the indirect pathway, by injecting a GABA antagonist into the GPe, can induce stereotypical behaviors in monkeys, highlighting the role of the indirect pathway in inhibiting unwanted motor programs.

Individual Differences

Naturally occurring variations in animals, including differences in stereotypic behavior, suggest a role for the basal ganglia in individual differences.
Mice with a high incidence of stereotypic jumping show lower activity in the indirect pathway.
This imbalance is further evidenced by lower enkephalin (indirect pathway) and higher dynorphin (direct pathway) concentrations in their striatum.

Humans & Dopaminergic Hyperactivity

Individuals with OCD and Tourette syndrome display heightened dopaminergic activity in the striatum, suggesting a direct > indirect imbalance.
This imbalance may explain the increased tic severity in Tourette syndrome after amphetamine administration, a dopamine stimulant.
Antipsychotic medications, which block dopamine receptors, can alleviate OCD symptoms.

Decision-Making vs Learning

An excessive dopamine release leading to a direct > indirect imbalance can influence both action selection and learning.
In action selection, it becomes easier to select and harder to inhibit familiar habits, contributing to the persistence of repetitive behaviors.
In learning, this imbalance can lead to a stronger learning from rewards (potentially reinforcing the habit) and weaker learning from punishment, which can contribute to the maintenance of unwanted behaviors.

Anxiety

Elevated anxiety can exacerbate habit-like behaviors by reducing goal-directed behavior and making it easier to select habitual actions.
While anxiety may not directly influence learning, it can impact how habits are expressed and executed.

Summary

Imbalances in the basal ganglia, specifically the direct and indirect pathways, are implicated in repetitive behaviors and possibly disorders like OCD and Tourette syndrome.
This imbalance can influence both action selection and learning, and factors like anxiety can further amplify these effects.

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Description

This quiz explores the functions of the thalamus and basal ganglia, focusing on their direct and indirect pathways. Understand how these pathways influence movement selection and inhibition, as well as the implications of pathway imbalances on behavior. Test your knowledge of motor command regulation and stereotypical behaviors in animals.