Wednesday, January 31, 2007

All this is related

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

Monday, January 22, 2007

Does a canary breathe?

I like to start out with questions. The question above might have taken you a second to figure out. In the 70's-mid 80's, it was very popular to study language associations. There are so many journals I cite that ended in 86-89. Most of which contain foundational articles and amazing linguistic theory. Comsky, Daneman and Carpenter, Meyer and Schanvedlt (sp?) are all buried in dusty microfilm, books on the second floor of the library where only a select few of us go, and in works-cited page after works cited page.

The 80's brought on the advent of working memory studies. most of what I read that was foundational for working memory was done then. I guess popular topics come and go.

The latest thing in cognitive neuroscience is aggression, attention, and gendered behavior (or the lack thereof). Look at the launch dates of journals, and their end dates, and you can see when society wanted to better itself and how.

70's= what we say. 80's=where those words come from. 90's=why can't our kids sit still? Are we destined to have the NAS as featured in Johnny Mnemonic?

But I digress. Does a canary breathe? A question like that is answered in longer time, usually, than "Does a canary sing?" Collins and Quillian (1969, 1972, 1975) developed a theory of what is known as "semantic memory." There are maps in your head. D. Mook (2004)describes semantic memory as "in contrast with short-term or working-memory, the amount of information that is stored in semantic memory is enormous. It includes the facts that Rome is the capital of Italy, that Madrid is the capital of Spain, that Columbus crossed the ocean in 1492, and that Zebras do not wear overcoats."

Mook describes the theory much better than Collins and Quillian ever do (brilliant researchers, crappy writers). He describes semantic memory as a massive library, with each word cross-referenced in several-to-millions of different ways. Wickens (1970) clarifies that nouns most likely to be cross referenced this well and even then, some verbs are adjectives, some verbs are nouns, some nouns are adjectives, (you can be chicken, you can eat a chicken; you go for a run, have a run in your stockings, or run from the police; you can jam your toast, your traffic, or music, or a "jam" can just be a song...etc.).

But, on the whole, it still stands true that most words exist in a phenomenal store. Back to the library motif, "In a library, entries will be classified in a hierarchical system or network, such that books about (say) animals will be in a place reserved for them. Then books about birds will likely be found within that section, and so on. There may be a number of different routes, in other words, by which we can get to the informtion that we need, but the point is that from a given starting place, we only have to search among a limited number of entries that are connecte3d to that starting pkace, rather than plodding through the entire library" (Mook, 2004, p210).

In 1969, Collins and Quillian tested the semantic hierarchy. They even included a nice little graphic which is roughly similar to this: .

Note Canary can sing and is yellw, but to find out if it breathes, your cognitive network has to go up to birds, to animals. If I asked "can a canary fly?" you would have to go up only one level.

The experiment was as follows: the researchers sat college students in front of a computer (sound familiar?) with different questions being presented. Some involving only one step in the above hierarchy (Is a canary a bird?) and more. The more steps it had to take, the longer the response took.

The results? It actually took longer to answer "does a canary breathe" than "does a canary sing?" by about half a second.

*hold onto the seat of your pants, you're about to fall over*

In my experiment, I have college students in front of a computer screen deciding if a sentence makes conceptual sense. 1/3 of these sentences are found not to make sense, 1/3 are found to make sense, and 1/3 could go either way. I'm looking at the N400, a rection to semantics and semantic memory. In theory, reaction time (RT) should be longer for type2 (could go either way) than the other two.

Each sentence leads you down a garden-path (Stanovich, 1979), or high-cloze probability. Such as, "The frog caught a fly with its ____" tongue would be one answer. But if I said "A frog caught a fly with its vacuum," the N4 would be triggered. We already discsussed this in prior entries.

Since the brain takes longer, and the brain reacts stronger, to a sentence that makes no sense, it could be because your brain is following these pathways and not getting what it expected (Stanovich, 1979, Neville, Coffey, Holcomb, 1992). Therefore, it could be argued, that there is neurological evidence for this sort of pathway to exist.

A good follow-up experiment would be to simply replicate these questions and see if the N4 is triggered. In doing this research, I've thought of a thousand more questions to be answered. But until then, I ask you, is a stagecoach a vehicle?

Mook, D (2004) Classic Experiments in Psychology. Greenwood Press, Westport, CT.

Collins, AM., Loftus, EF., (1975) A Spreading Activation Theory of Semantic Processing Psychological Review 82(6) 407-428.

Collins, AM., Quillian., MR., (1972) Experiments on semantic memory and language comprehension, In LW Gregg (Ed) Cognition in learning and memory New York: Wiley 1972

Collins, AM., Quillian, MR., (1969) Retrieval Time from Semantic Memory J. Verbal Learning and Verbal Behavior (8) 240-247

Stanovich, KE, Nathan, RG., West, RF., Vala-Rossi, M., (1985) Children's Word Recognition in context: Spreading Activation, Expectancy, and Modularity. Child Development (56) 1418-1428

Meyer, DE., Schvanveldt., (1971) Facillitation in recognizing pairs of words: evidence of a dependence between retrieval operations. Journal of Experimental Psychology (90) 227-234

Saturday, January 20, 2007

Working Memory Continued

There was a pretty direct correlation in Daneman and Carpenter (1980) between the then-new Reading Span Task and reading comprehension. This was compared to reading samples and scores on the verbal portion of the SAT. What's important about this particular study is that they were the first people to really concretise the notion that 1) people's working memory varied individually. Exactly how (same volume with different command centers, or different volumes same command center, or a combination?) is still being discussed. 2) It birthed the concept of "complex span" (Hitch, 2006). Simple span are basic tasks like: "remember this list of words: parsely, thyme, rosemary, sage" for a verbal span, "remember these numbers: 34, 4, 54" for a math span, and "remember these locations" for a visuo-spatial span. Daneman and Carpenter birthed the idea of processing into these tasks.

There are a variety of people who are studying how these tasks demand and tax memory. There is a significant bleed over from attentional, behavioral, and memory studies to accomplish this task. They look at everything from eye movements to ERP's to fMRI. I'm of the belief that you have a certain capacity for working memory that is divvied up depending on the task. That is why I can do complex long division, but not when I'm also watching TV or driving.

Oh don't get me started on memory and driving...that's a whole field unto itself.

But people our age (though I'm afraid I'm at the tail end of it) are at the peak of their working memory spans. What does that mean per se? Probably that we're more efficient at remembering what we need to remember, so we don't really need a higher-capacity working memory. Hence adults tend to be far worse at playing video games, but far better at using the internet.

So what does this all have to with N400, my first entry? Well that, my dear readers, will have to wait for another entry.

Daneman, M., Carpenter PA., (1980) Individual Differences in Working Memory Journal of Verbal Learning and Verbal Behavior

Hitch, G., (2006), Working Memory in Children, A Cognitive Approach in Bialystock, E., and Craik FIM., (Eds.) Lifespan Cognition. Oxford University Press, New York.

Thursday, January 18, 2007

so wait, what does that have to do with anything?

Working Memory (WM) is hard to track down and manipulate. We fill it up and empty it out so rapidly we don't even know it. We go from map to walking so fast, we calculate out a tip, we figure out what time our laundry will be out of the dryer, we read a paragraph and absorb the message of a book so quickly. So why bother studying it?

Like many things in life, a small thing like WM has prfound implications. It has generally been isolated in the DorsoLateral Pre-Frontal Cortex (DLPFC) with a few other locations in the Temporal Lobe. In people with DLPFC damage, they are unable to remember how they got where they got where they were, or what you just said; their long-term memory, however, remains intact.

In a nutshell, without WM, we can't really function as a human is expected. We can't talk complexly, we can't do basic math. Hypothetically, and generally speaking, of course.

How does it tie into language? Remember (ha ha!) in my last entry, I discussed how there were three components of working memory? They were the phonological loop, the visuo-spatial sketchpad and the central executive. The phonological loop is a cache that takes in all the language data and sends it to the central executive. The central executive then decides what to do next: look up a definition from your 11th grade english class, keep listening for further context, respond with physiological responses in the fight or flight. The phonological loop takes care of the reading, as well as the verbal.

To remember an item, there is a slight corrolary that has been dubbed the "articulatory loop" in which you are remembering an item by rehearsing it, such as that pesky phone number, or address, or username on MySpace. When you rehearse in your head "soccergrrl28, soccergrrl28" until you can type it in, that's the articulatory loop in effect.

These are important for my Div3 in a variety of ways. One half of my Div3 is dedicated towards a Reading Span task which relies on both articulatory loop and the phonological loop. The Reading Span Task (see Daneman and Carpenter, 1980) requires people to read sentences one at a time, and remember the last word of the sentences they were presented. These are presented in 2 to 6 sentence chunks. What it does is make the articulatory loop work, while the phonological loop is trying to work and shove new information in it. Some people are very good at this and they are known as "high span" people. Most college students, I've found, have a high span. I would have preffered a community sample, but what can you do?

This little find, that people have an individual difference in their working memory capacity and ability to manipulate that information, has had a ripple effect in the psycholinguistic field. It has been shown that the verbal WM (as the span task shows) is separate from mathematical working memory and serial recall (Shah and Miyake, 1996). Language, it seems, is a bit more hardwired in the brain than we give ourselves credit. It also used to be thought that everyone had the same capacity (6 digits, I think). But now it is inidividualized.

Why is this part of my Div3? The ability to manipulate language in whatever center of the brain that it's doing it in has several implications. People with higher WM capacities can untangle verbal knots faster, acquire vocabulary faster (but not better), and figure out sentence context better. The aforementioned generally are all related.

So, since what I'm presenting on screen is presented one word at a time, these words need to be held in working memory until they are dumped out. It was hypothesized that children don't have the ability to create sentence context the way adults do, and that is why their N400 is smaller than in adult subjects. But I think that's all for a later post.

At the present, I'm still parsing out what I mean. It makes total sense in my head how this is all related, but I can't even get a bubble-chart out at the moment. When I do, you'll be the third to know.

Citations pending.

Daneman, M., Carpenter PA., (1980) Individual Differences in Working Memory Journal of Verbal Learning and Verbal Behavior

Gathercole, SE., Baddeley, AD (1993) Working Memory and Language. Erlbaum and Associates: Hillsdale.

Shah, P., Miyake A., (1996) The Separability of Working Memory Resources for Spatial Thinking and Language Processing Journal of Experimental Psychology:General 125(1) 4-27

MacDonald, MC., Just, MA., Carpenter, PA (1992) Working Memory Constraints on the Processing of Syntactic Ambiguity Cognitive Psychology Jan(24)1 56-98

Tuesday, January 16, 2007

wait, what did you just say?

Remember this sequence: 1 cherry 45 chair

If you remembered everything that ever happened, and perceived everything on this earth there was to perceive, you would be either or both: completely crazy, or a super human.

Your brain is very good at filtering out things. White noise (fans in the room, industrial lighting, your nagging in-laws), light, sensations (that pebble in your shoe you got 3 miles ago but weren't able to get out, the tag that itches), and even individual words.

Without looking, what was the very first word I wrote? What was the last sentence of that clause. Can't remember? Can you remember the context of that sentence?

This is known as working memory. It's kind of like the RAM in a computer (or, RAM is kind of like this, since we've been around much, much longer). It's a cache of random bits that you actively hold in your head. How does this apply to my Div3? You generally do not remember the words of a sentence, rather the sentence as a whole.

But what if that sentence doesn't make sense? Ah, here's where it gets complicated.

There is ample data that suggests those who can remember more items in their working memory (words, numbers, shapes, locations are all things you hold in your memory) are better comprehenders of language. They can untie linguistic knots such as: "The horse raced past the barn fell." Or "He was kind of spooked out so he went to the closet where his baseball equipment was. He saw a bat, it was brown and flying about the ceiling." I, of course, am copying this all from my own memory, so it probably doesn't matter.

What was the first sentence of that last paragraph?

Working memory has rapid, rapid decay. What was that sequence I asked you to remember at the top of this entry?

Oddly, there is weird evidence that suggests that the more you use it, the better you get. In my own experiments, the average college student figures out tricks to remember things more and more as we go along. But that's a whole other story.

There are three parts of the working memory system, as it stands. There have been variations and violations, but this is a theory that is generally well supported, and there has been neurological evidence that supports it, as well. One is the articulatory loop, the other the visuo-spatial sketchpad. These go into the central executive. The central executive does things like hold onto it, process it by retrieving things from other parts of memory (definitions of obscure words, whatever the last phrase might have said). The visuo-spatial sketch pad holds objects themselves in working memory: where you just put the keys down, the order of the piles of index cards in front of you).

1 cherry 45 chair

Working memory improves from childhood to adulthood. Look at babies' difficulty with object permanence (playing peak a boo is hilarious to a baby, for instance) compared with an adults complex knowledge of where everything in their life is located. This, of course, degrades after around age 21. But it peaks at 18, and plateaus until a graduale drop-off.

So in conclusion, working memory is essentially incredibly short-span memory. Short term memory is longer than WM. WM only holds about 6-7 items, and degrades as the brain's resources are drawn.

For further information, read:
Baddeley, AD (1986) Working Memory. Oxford Press, England.

More detail to follow, especially on development of working memory.

Monday, January 15, 2007

So, take it from the top...

Someone famous once said, "the best place to start is from the beginning."

The past entry kind of skipped that. So, if you're just tuning in, here it goes.

"Reading, The Brain, and Reading the Brain" is the title of my Div3 (aka thesis) project at Hampshire College in Amherst, Massachusetts. It combines three fields I'm intensely interested in: neuroscience/neuropsychology, language, and human development. I can't just tell you what it is, though. If I were to say to you, "It's an investigation into the link between working memory and the N400 in children and adults," I'd bet 10 dollars you wouldn't understand more than half of that statement.

Let's start with the basics: what is an N400? It's a component (aka, part of) an ERP. An ERP stands for Event Related Potential. An Event Related Potential is a specific electronic peak that your brain gives in response to various stimuli. That is, your brain reacts differently when it's analyzing a face versus when it reads a normal sentence versus is neutral. We've been able to track down various stimuli-response events, and they're temporally related, most times.

What is an ERP, though? Every moment of every day that you live (and sometimes, after death) your brain is sending electricity around itself and to your body. That electricity extends through your bones, guts, and skin. If we limit motion, we can isolate the brain's response to various stimuli. ERP's are measured in microvolts; using just your potential brain electricity, we'd need about 9,000 people to have the same charge as a AA battery. That's why millions of people charge what is known as the Matrix.

P=positive N=negative. P=N in terms of the effect. Just like negative current is the same
as positive. P100=P1=Positive charge 100 miliseconds post-stimulus. P3=positive wave 300 miliseconds post-stimulus. N4=negative wave 400ms p-s.

With me so far? So, to recap: brain gives off electricity, we can isolate electronic components (the waves are referred to as components because these timings aren't exact). The N400 is semantically related. That is, almost no other stimulus besides words makes the N400. Grammar doesn't even trigger the N400, that's been isolated to the P600, which is an up-and-coming field of research; that there could very well be hard-wired brain function related to grammar.

To learn more, read these:
Luck, SJ (2005) An Introduction to the Event-Related Potentials and Their Neural Origins
in An Introduction to the Event-Related Potential Technique. MIT Press, Boston. 1-50.

Kutas, M., Hillyard, SA., 1980 Reading Senseless Sentences: Brain Potentials Reflect Semantic Incongruity. Science 207(4427) 203-205

Osterhout, L, Nicol, J. (1999) On the Distinctiveness, Independence, and Course of the Brain Responses to Syntactic and Semantic Anomalies. Language and Cognitive Processes 14 (3) 283-317

I think that's enough for this lesson. When I'm back to procrastinating, I'll be back with you.

Sunday, January 14, 2007

Mildly Academic Post

So, another come and go and so much for all that work I was going to do.

The thing is, I've found this amazing book that's a little more than half-relevant. The quote I posted before comes from it. Most research I can skim, this I just want to read every page of.

At the present, I'm confused about my study in that there are a bajillion ways I can go about it. I recently came back to the original material I used over the summer to form my hypothesis: that working memory in schizophrenics is strongly linked both neuro-and-psychologically irregular N4 patterns. Which opens up another door I don't have time or resources to walk through.

But it's compelling and I'm starting to see why my hypothesis holds water. If this study shows nothing, I want to do a developmental P6 study, since that hasn't been done yet at all so far as I can tell.

I also want to fund studies, but there is so little available to people who aren't PhD candidates. Basically, I want to achieve everything I possibly can ever.

This is my first academic entry

This made me really happy to read:
Regarding fMRI's: "It is assumed that the BOLD (blood oxygenation level dependent) response indirectly reflects neural activity. Although these methods represent major advances for the field of cognitive neuroscience, they are not without complications as tools for studying real-time language comprehension. First, the hemodynamic response to an event is delayed several seconds and eveloves over 10-15 s. Thus speakers produce (on average) three words, four syllables, and 12 phonemes per sec. Furthermore, the processing of asingle linguistic unit, for example, a word, most liekly involves a constellation of processes, each having temporal durations of considerably less than 1s [the time it takes for an fMRI to read neural activity in a human brain]" Osterhout, L., McLaughlin, J., Kim, A, et al. 2004 Sentences in the Brain: Event-Related Potentials as Real-Time Reflections of Sentence Comprehension and Language Learning in: Carreiras, M., and Clifton, C [eds.] The On-Line Study of Sentence Comprehension