Wednesday, May 25, 2011

Spatial Navigation for MightBeLying

Over at TNC's blog, there was a big discussion about evolutionary psych, which bled into me defending cognitive psych as a real science not dependent on neuroscience. I volunteered to try to explain the links between cognition and neuroscience for any given topic. Here is my response to the first brave soul to shout: spatial navigation:

Ok, first, with a little bit of an intro.
Insight into how the mind and brain work, and how our conscious experience and behavior map onto the biology can be found in several main ways:
1) Extirpation: Damaging the brain of an animal and seeing what happens. This has been happening for a very long time. Rats do spatial navigation. Rats have brains. Understanding an animal model can help. Of course, you have to map the rat brain to the human brain, which is tricky. But not impossible.
2) Clinical method: Someone gets brain damage, then we figure out how it affects their behavior, and relate it to the brain damage. In general, relating behavior, or experience, to some sort of activity (or lack of activity) in the brain. Some fMRI falls into this category.
3) Electrical stimulation: Again, mostly with animals, but not entirely. Direct stimulation of the brain, then seeing what happens to behavior.
Let's start back with the demise of Skinnerian behaviorism. Skinner and his adherents did rely on rats to do many experiments, but they believed that rats learn responses to stimuli, nothing else. In other words, there is no need to talk about spatial navigation in the rat (or in the human), there is only a set of responses to a set of environmental situations.
Edward Tolman, who investigated rats in mazes, started coming up with evidence that rats have mental maps. This was kind of a big deal (in 1948). It means that we have to investigate what the shapes of those maps are, and we have to open the black box of the brain. … and a lot of stuff happens, and we now have models where a certain kind of damage to the rat hippocampus, in a certain place, lead to a certain pattern of them being lost, or forgetting, or being unable to learn new mazes.
So, given that rats have maps in the brain, of course we do too. So what kinds of maps do we have in our brain? How does the software relate to the hardware?
Well, one snarky way of summarizing 50 years of cognitive psychology research is that rats are smart and people are dumb. So, we suck at spatial navigation, especially compared to a lot of our animal cousins. We navigate with vision, not with smell, like salmon, or super-vision, like desert ants (not to be confused with dessert ants). And the way that we navigate with vision (and memory) utilizes shortcuts and biases.  We regularize, impose a pattern when there isn’t one, make things line up north south, or east west. Many people think that Reno is east of San Diego (it isn’t) because we don’t really have an accurate map in our heads, we have a map biased by some easy to remember rules (California is west of Nevada).
Ok, the neuroscience side: hippocampus seems important. You mess with rat hippocampus, you mess with their navigation. With brain scanning, we can look at people’s hippocampi. One famous study imaged the brains of London cab drivers at different stages of their careers. The amount of experience was related to the amount of knowledge, was related to the size of a particular part of their hippocampus.
Of course, spatial navigation can't be understood in a vacuum, because it involves perception and memory (at least), both in behavior, as well as networks of brain areas. It is not quite right to say that memory (or spatial navigation) happens in the hippocampus, and that perception happens in the back of your brain (occipital cortex), but it isn’t as wrong as the phrenology of the past. We are not, for example, going to realize that we’ve been totally wrong, and that vision happens in the front of the brain, not the back, and that language areas are actually buried under everything in the midbrain. But we may discover that the way we have been thinking about the hippocampus is slightly wrong, in that it is a critical part of the memory circuit, not the place where memory happens.
Or you could read people who know much more than me, put it in a much better, clearer, and more organized fashion:">Barbara Tversky at Stanford. This is a">
more comprehensible paper for the layperson, at least the first few pages.
Or do some of the reading for this course :
Just taking a look at this course should tell you that, within one course, you can see the work being done from the level of neurochemistry within neurons, to single neurons, to brain structures, to behavior. All complementing each other, filling in gaps, mutually dependent. 

Ok, that was not very well organized, but it gives a taste of what the research on spatial navigation looks like. It involves cells, brain areas, brains, bees, salmon, rats, London cabbies and regular people. Not all of it converges on a great explanation for how exactly spatial navigation works in all brains, or even in our brain. But we know more than we did twenty years ago.

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