Marr’s 3 levels of analysis

Brain: hierarchy of complexities

  • Computational level - 1
    • What is the objective of the system?
    • How close is it to optimal?
  • Algorithmic level - 2
    • What are the data structures?
    • What are the approximations?
    • What is the runtime?
  • Implementation level - 3
    • What is the hardware?
      • Neurons? Synapses? Molecules?

Diversity of modeling goals

  1. Useful: good at solving real-world problems?
  2. Normative: provide the optimal solutions to problems that exist in the real world?
  3. Clinically relevant: produce insights relevant for developing or evaluating clinical interventions?
  4. Inspire experiments: change the way we think about a problem, raising interesting new hypotheses & experiments?
  5. Microscopic realism: describe the microscopic properties of the brain?
  6. Macroscopic realism: describe properties of brain areas and networks?
  7. Behavioral realism: can faithfully describe and explain behavioral phenomena?
  8. Representational: use representations of info that are similar to representations in the brain?
  9. Compact: can be succinctly expressed in math or code, making them easy for humans to understand?
  10. Analytically tractable: understandable through equations instead of numerical simulations, therefore generalizable?
  11. Interpretable?
  12. Beauty: symmetrical, balanced, or resonate well with the way we think?

1. Asking your own question

  • What exact aspect of data needs modeling?
    • Answer this question clearly and precisely! Otherwise you will get lost (almost guaranteed)
    • Write everything down!
    • Also identify aspects of data that you do not want to address (yet)
  • Define an evaluation method!
    • How will you know your modeling is good?
    • E.g. comparison to specific data (quantitative method of comparison?)
  • For computational models: think of an experiment that could test your model
    • You essentially want your model to interface with this experiment, i.e. you want to simulate this experiment