List of Important Problems in Neuroscience

In 1900 the mathematician David Hilbert presented a lecture entitled "Mathematical Problems", in which he stated 23 problems towards whose solution mathematicians of coming generations should strive (see www.sonoma.edu/math/faculty/falbo/hilbert.html). Each problem had to have some kernel that made it important (and difficult) enough to be interesting, and it had to have the potential to lead to some wider results.

In a similar vein follows a list of neuroscientific problems which outline the goals towards which neuroscientists may strive. These problems are regarded as difficult but not completely inaccessible. It is hoped that neuroscientists look them over and select the ones which seem to show promise of being solvable or important. Progress may be made already by presenting clearer formulations of a problem so that it becomes more accessible to theoretical or experimental analyses.

Why should anyone try to formulate such questions or find solutions to them? Few researchers choose their fields of study freely and according to scientific criteria. In addition, there are many different motivations for doing neuroscientific research, among these to cure diseases, to get inspirations for building better technical devices, or to enjoy research for its own sake. This list, however, aims to focus on the core of the neuroscientific enterprise. This marks the difference that it makes whether one investigates the brain or, for example, the kidney: both are highly complex organs whose functions are incompletely understood. A fundamental difference is that with regard to the kidney one thinks that, in principle, it is clear how it works and that only the details still have to be worked out. With the brain remains the impression that in order to understand it at all we are still missing some fundamental insights and that this principal problem blocks significant progress despite a huge amount of detailed research being carried out. Thus, in order to make a significant contribution to brain research it seems important to focus on the most interesting problems which concern the mechanisms that explain structure/function relationships in the brain.

Here is a start moving from motor and sensory systems to integrative functions including both general and specific problems:

  1. How are intentions to move decomposed into parameters for muscle innervation? What are the mechanims for launching and controlling movements?
  2. What parameters of voluntary movements are specified by the motor cortices? What is the contribution of the spinal cord?
  3. If the supplementary motor area (SMA) shows the first measurable activation before self-initiated voluntary movements occur - what generates the activity in SMA?
  4. What is the mechanism for transforming new movements into learned movements?
  5. What mechanism link related (sensory) processing streams in different parts of the brain?
  6. What mechanism generates the complete (visual) perceptive scenery (including "objects") if the brain decomposes sensory input into individual features and processes them in separate areas?
  7. What neuronal mechanisms are required for the generation of language (that apes appear not to have)?
  8. How do ontogenetic and the subsequent structural restrictions of the brain limit what it can do? - or another way around: what are the structural correlates of extraordinary mental capacities such as seen in mathematical geniuses?
  9. What mechanism constructs the continuous "stream of consciousness"?
  10. What is the biological advantage of having awareness/consciousness/self-consciousness, how has it evolved?
  11. What generates the inner voice? Are there different modes of thinking: with and without inner voice - and how are they produced?
  12. Does logical thinking depend on neuronal elements that perfom logic functions? - or more generally: what is the relationship between neuronal processes and the results of neuronal processing?
  13. Is the global activity of the cerebral cortex regulated locally (e.g. by inhibitory interneurons) or globally (e.g. by subcortical feedback loops) - and how is it done?
  14. What is the neurophysiological role of sleeping?
  15. What is the neurophysiological role of dreaming?
  16. How do learning processes and recall processes in the brain interact? (there seems to be no separation between teaching and performance phases as commonly made in artificial neural networks)
  17. Is there a control hierarchy among brain structures or how can one describe the interactions between different processing modules of the brain?
  18. What happens in the brain when we suddenly find a solution or understand a joke? Perhaps more easily investigated: what happens in the brain if we shift attention to a different feature of the same stimulus
  19. What are the neuronal correlates of "one off" learning? - How can a single brief event permanently change neuronal processing?
  20. What are the mechanisms of reinforcement learning in the brain?
  21. What is the code of neuronal firing patterns - is there a universal code, at all? (inputs may be encoded by spatial patterns of activation of neurons in the input layer or in the time structure of the inputs, i.e. rate-place or labelled-line neural codes versus temporal pattern codes; one scalar signal conveyed per element versus multiplexing of multiple signals onto the same lines; rate integrations versus coincidence detection; rate integration coding versus rate coding versus rate of change coding)
  22. Are we laughing because we are happy or are we happy because we are laughing? What is the relationship between emotional expressions and emotional perceptions?

The next steps are:

If you want to make valuable contributions towards an improvement of this list, please, contact me at RK@hirn.uni-duesseldorf.de

Last update: 7.7.97. [Rolf Kötter Home Page]