Week 2 In Depth

Brain fundamentals, cerebral cortex, limbic system

What is the function of the hypothalamus?

What is the function of the thalamus

What gland is formed by the epithalamus? What does it do?

What is the general process of the basal nuclei circuit?

1. cortex sends EPSP signals to basal nuclei

2. basal nuclei send signals to the globus pallidus

3. globus pallidus sends signal to the thalamus

4. thalamus sends signal back to cerebral cortex

5. subthalamic nucelus and substantia nigra also influence this process

At rest, what is happening in the motor loop?

• Putamen is off

• GP is only receiving EPSP from subthalamic nucleus

• globus pallidus is on —> IPSP signals to the thalamus

• this keeps thalamus off/prevents thalamus from sending EPSP to cortex

• so no movement occurs

What happens in the motor loop when the body wants to move?

1. cortex sends EPSP signal to putamen

2. Putamen sends IPSP to globus pallidus

3. Now GP turns “off” and stops sending IPSP signal to thalamus, so thalamus no longer inhibited from sending EPSP to cortex

4. thalamus sends EPSP to cortex and movement occurs

What is the role of the substantia nigra in the motor loop?

• at rest

  • SN sends IPSP to putamen which keeps it “off”

  • if putamen is “off” then GP is “on”

  • if GP is “on” then it is sending IPSP signals to the thalamus

  • if thalamus is receiving IPSP signals, it is not going to send EPSP to the cortex

  • no movement occurs

• during movement

  • cerebral cortex sends EPSP signals to SN which change its function

  • this causes SN to then send EPSP signals to putamen to turn it “on”

  • If putamen is “on” it is sending IPSP to GP which means now thalamus is no longer receiving IPSP

  • thalamus sends EPSP back to cortex and movement occurs

How does Parkinson’s affect the motor loop?

What is the role of the motor loop?

• scales muscle contractions appropriate for task: picking up water bottle vs. heavy box

• helps coordinate movements

• stores learned motor programs —> different from cognitive loop that writes new programs that then get stored in putamen

  • damage to putamen affects learned motor programs

What is the role of the cognitive loop?

• receives signals from association areas in cortex for processing

• assisting with motor learning

  • writes programs into putamen and cerebeullum

• script writer whereas putamen is the manager of the actors

  • caudate nucleus writes the script for the actors (muscles) to perform. The actors (muscles) are told what to do by the manager (putament)

• helps with planning, decision-making, goal-setting