EXAM PRACTICE QUESTIONS

Question 1

A) What is the tripartite hypothesis of the subthalamic nucleus (STN) (Alkemade et al., 2015)?

B) Briefly describe 3 techniques that can be applied and what relevant information they would provide.

Answer 1

A)
The tripartite hypothesis of the subthalamic nucleus (STN) posits that the STN performs three distinct functional roles. This hypothesis reflects the STN’s integrative role in modulating motor, cognitive, and emotional behaviors via its widespread neural connections.

• Motor Control: It plays a key role in regulating movement through its connections with the motor circuit of the basal ganglia.
• Cognitive Control: It contributes to higher-order functions, such as decision-making and impulse control, by influencing the prefrontal cortex and related circuits.
• Limbic Control: It is involved in emotional and motivational processes through its connectivity with the limbic system.

B)
1. Deep Brain Stimulation (DBS):
- Information Provided: DBS of the STN is often used to treat movement disorders like Parkinson’s disease. It provides insights into the STN’s role in motor function regulation by altering its activity and observing the effects on symptoms.

2. Functional MRI (fMRI):
   - Information Provided: By measuring blood oxygen level-dependent (BOLD) signals, fMRI can track STN activity in real-time during cognitive or motor tasks, elucidating its involvement in these processes.
3. Single-Unit Electrophysiology:
   - Information Provided: This technique records the firing patterns of individual STN neurons. It provides detailed information about the neuronal coding and dynamics underlying the STN’s involvement in motor and cognitive functions.

Question 2

The linear, ballistic accumulator (LBA) models and the diffusion decision model (DDM) belong to the same class of decision-making models.

A) Explain the core assumption these two models share

B) Explain the most important difference between these two models

Answer 2

A)
Both models assume evidence accumulation as the basis for decision-making. They posit that decisions are made by continuously accumulating noisy evidence over time until a decision threshold is reached. The first accumulator (or pathway) to cross the threshold determines the choice.

B)
- The LBA model assumes a linear accumulation process with constant rates for each accumulator. It does not incorporate diffusion (random noise) during the accumulation phase.
- The DDM, on the other hand, models evidence accumulation as a stochastic process, incorporating moment-to-moment variability (diffusion) in evidence accumulation. This results in a more detailed characterization of decision-making dynamics under uncertainty.

Question 3

A) Name two microstructural features that MRI is sensitive to.

B) For each, describe which type of imaging sequence you would use to measure them.

Answer 3

A)
1. Myelination: The density and integrity of myelin in white matter tracts.
2. Cellular density/organization: Variations in the density and size of cellular structures in gray matter or white matter.

B)
1. Myelination:
- Imaging Sequence: Diffusion-weighted imaging (DWI) or quantitative T1 mapping.
- - These techniques reveal white matter tract integrity and myelin content by measuring water diffusion and relaxation properties.

2. Cellular Density/Organization:
   - Imaging Sequence: Diffusion tensor imaging (DTI) or magnetic resonance spectroscopy (MRS).
   - - DTI provides information about the organization of fiber tracts, while MRS can quantify metabolites linked to cell density.