Complementary Learning Systems, Dreams

The motivation for this post stems from my recent reading on McClelland's complementary learning systems on “Hippocampus (HC) and Neocortex”. This paper is also kind of survey papers from certain perspective. In particular, the authors smartly put relevant theories together to reach the goal of demonstrating his own idea, which is: "the HC provides training trials, allowing the cortical system to select representations for itself through interleaved learning." The paper, of course, starts with two key question s of interest:

1. Why is the HC system needed? If we have neocortex system that owns more neurons, why do we want HC to do?
2. Why do the changes in neocortical connections take so long? In other words, can the new materials fully absorbed rapidly?

It looks like HC system is responsible for storing recent memory, and neocortex is used to reserve remote memory. To avoid interference with the knowledge stored in neocortex, HC is here to help accommodate the initial storage from a new learning event; in the meanwhile, to not bother existing system of knowledge structure, the changes should be made slowly within neocortex. There are certainly “communications” between HC and neocortex, otherwise, no information will be transferred, and no changes will be made.

Marr (1971) propose that the HC systems stores experience in the day time, and replayed the memories in the HC back to neocortex in the night. Does it imply that brain activities in the night are caused by consolidation (or the opposite)? For example, dream.

A researcher in this domain indicates that dreams can be emotional as we replay old memories and update them with novel information from recent events. Associating with personal experience, I agree with it, but I become more interested in the verb “update” in terms of its functionality. Specifically, why the brain needs to update in what sub-systems of our brains?

So a ROUGH idea here is that: if the dream happens partially owing to the connection changes (learning) in neocortex system from HC’s input, let us contemplate on some questions below:

1. Is it due to too many computations requested from day-time tasks, so we better carry this out in the night time?
2. Why should it appear in the form of visual imagery? Does it facilitate the learning process?
3. Why cannot we dream every single night? If it stops dreaming, does it mean dreams are not caused by learning in HC and neocortex systems? Perhaps dream causes learning, not the opposite.
4. The memory trace in HC will decay, if we have an exceptional set of material, will it take more priority to be incorporated into existing knowledge structure using this precious period of dreaming?
5. What is the implication for HCI? Designing novel interfaces “encouraging” people to dream, thus users can learn it faster? This question may be addressed after knowing why exactly people dream.

Reference:

Web article: http://www.livestrong.com/article/78256-parts-brain-produce-dreams/

Marr, D. (1971). Simple memory: A theory for archicortex. The Philosophical Transactions of the Royal Society of London, 262(Series B), 23–81.

McClelland, J. L., McNaughton, B. L., & O'Reilly, R. C. (January 01, 1995). Why there are complementary learning systems in the hippocampus and neocortex: insights from the successes and failures of connectionist models of learning and memory. Psychological Review, 102, 3, 419-57.

(© 2012 Miaoqi Zhu)