Essays

I just finished writing my 12th essay in preparation for the neuroscience final (Wed.).  Now I need to actually learn them so I can reproduce them on the exam.  I was able to do this for the midterm, so I'm going to believe that it is possible this time, too, even though it seems like an unfathomably large amount of information to commit to memory.  Luckily I have two nights of short-wave sleep before the exam during which time my brain can consolidate the information, as described in this excerpt from essay 9:

Consolidation refers to the processes that continue after learning and stabilize, transform, or enhance the newly-encoded memory trace.  Consolidation makes memories more resistant against interference and decay.  During system consolidation, neural memory representations undergo a reorganization so that they become represented by different neural networks.  We consolidate memory more effectively when we are asleep because we use the same processes for taking in (encoding) information and consolidating memories.  Therefore, there is interference in the consolidation process when we are awake (and we are also taking in information) but not when we are asleep.  During sleep, the covert reactivation of the networks that were involved in encoding the information leads to improved memory consolidation.

REM sleep appears to be important for procedural memory (skill at a task).  Depriving people of REM sleep makes it harder for them to learn tasks, and people who have practiced a difficult procedural task tend to engage in greater levels of REM sleep afterward.  The first stage of procedural memory consolidation, stabilization, appears not to be dependent on sleep, but can be improved with sleep.  The second stage, enhancement, might require sleep.

Slow wave sleep (SWS) is involved in the consolidation of hippocampus-dependent declarative memory (explicit memories of facts and events).  Studies have shown that retrieval performance is better when tested shortly after a period of night-time sleep than daytime wakefulness, even after controlling for differences in fatigue and eliminating circadian rhythm confounds.  However, some studies examining memory over a longer time span, such as one week, do not show a benefit to post-learning sleep.  Because consolidation of declarative memory may occur over several nights, sleep in the subsequent nights might compensate for the lack of sleep the first night.  During SWS, newly encoded representations are repeatedly activated in the hippocampus in conjunction with thalamacortical spindle activity (which propogates to the entire neocortex).  These coordinated activations could achieve a transfer of information and a strengthening of weak memory traces.  During sleep, lower levels of ACh (enabling a feedback of information from the hippocampus to the neocortex) and cortisol (reducing interference with memory retrieval) create an environment favorable to memory reactivation and consolidation.