Your brain does a ton of stuff every second of every day. It suppresses or inhibits information it doesn't need, it processes information, it holds onto enough data to fill a library.
When you read, which is my focus, it takes in a sentence and processes it somehow. There are several theories about what happens. As aforementioned, your brain, it seems, goes through its semantics and its syntax. It makes sure that it's all okay, and then moves on to the next one.
The pathway sentences mentioned before hone in on the meaning you're going for. There are several studies (and I'm just getting to these, myself) that track eyemovements with ambiguous sentences and ambiguous subjects. The most notable of these are homographs (words that are spelled and pronounced the same, but have several meanings, such as "bat" "bow" "hearing" "boxer" "race." There are three main theories about how we process these ambiguities, specifically homographs.
Since I'm pressed for time at this very moment, but am really excited to have begun reading these, the dominant theory is that we hold on to all of these meanings until we are given data to suppress "or inhibit" the other meaning. Some homographs have dominant and subordinate meanings. Bow: bow and arrow, bow on a present, or bow on a ship? Bat: baseball or animal? Hearing: they can be hard with lawyers, or they can be hard in general. And so on.
What potentially triggers the N400 is that the brain is then going back and checking which of these homographs should work. It has been shown that people with better working memory are able to come to the conclusions faster. Why? Because they remember more, need to go back less, and therefore have smaller N4's because their brain needs to do less work.
Therefore, it is my hypothesis that people with better working memory will have larger N4's in my study because they will have been holding onto all possible meanings of a sentence, even ambiguous ones, and when they get to the end and it is or isn't what they thought could happen, it will effect them more.
BAM! That's where my Div3's direction is going now. Bet you never saw all that coming.
Now that I've described to you, my captive audience, what my Div3 is and its background, I can probably get more specific for you; tell you about other specific studies, or how mine is going. We'll see as time progresses and my commitments take care of themselves.
Kumar, N., Debuille., B. (2004) Semantics and N400: insights for schizophrenia Journal of Psychiatry and Neuroscience 29(2) 89-98
Fiebach, CJ. Vos, SH. Friderici, AD (2004) Neural Correlates of Syntactic Ambiguity in Sentence Comprehension for Low and High Span Readers Journal of Cognitive Neuroscience 16(9) 1562-1575
Gunter, TC., Jackson, JL., Mulder., G (1995) Language, memory and aging: an electrophysiological exploration of the N400 during reading of memory-demanding sentences Psychophysiology 32, 215-229