After a bit of a hiatus, I'm back with the last three installments of "Grand Challenges in Neuroscience".
Topic 4: Time
Cognitive Science programs typically require students to take courses in Linguistics (as well as in the philiosphy of language). Besides the obvious application of studying how the mind creates and uses language, an important reason for taking these courses is to realize the effects of using words to describe the mental, cognitive states of the mind.
In fact — after having taken courses on language and thought, it seems that it would be an interesting coincidence if the words in any particular language did map directly onto mental states or brain areas. (As an example, consider that the amygdala is popularly referred to as the "fear center".)
It seems more likely that mental states are translated on the fly into language, which only approximates their true nature. In this respect, I think it's important to realize that time may be composed of several distinct subcomponents, or time may play very different roles in distinct cognitive processes.
Time. As much as it is important to have an objective measure of time, it is equally important to have an understanding of our subjective experience of time. A number of experimental results have confirmed what has been known to humanity for some time: Time flies while you're having fun, but a watched pot never boils.
Time perception strongly relates cognition, attention and reward. The NSF committee proposed that understanding time is going to be integrative, involving brain regions whose function is still not understood at a "systems" level, such as the cerebellum, basal ganglia, and association cortex.
The NSF committee calls for the develpoment of new paradigms for the study of time. I agree that this is critical. To me, one of the most important issues is the dissociation of reward from time (e.g., "time flies when your having fun"): most tasks involving time perception in both human and non-human primates involved rewarding the participants.
In order to get a clearer read on the neurobiology of time perception and action, we need to observe neural representations that are not colored by the anticipation of reward.
Brain image from http://www.cs.princeton.edu/gfx/proj/sugcon/models/
Clock image from http://elginwatches.org/technical/watch_diagram.html