[From Bill Powers (951008.1250 MDT)]
Bruce Abbott (951008.1230 EST) --
Our mapping study shows that the MSH receptors concentrate heavily
in just those areas where our "wiring" studies show some of the
important neural components of the system to lie.
Of course -- how else would the MSH have an effect? What other receptors
are in that same area? What other systems are in that same area? What
other substances could have the same effect?
We still don't have much, but I contend that we've made progress.
We're starting to nail down the "circuit diagram," the anatomical
map of the control system whose actions typically produce DVs (and
other outputs) in young chicks when separated from their mothers
and the brood.
Ok, so what are these control systems? They would include the systems
for recognizing other chicks and the mother, for perceiving the distance
(or visual size) of the others, for determining the direction to them
relative to the perceiver's orientation, for converting errors in
distance to reference directions for motion, for converting errors in
direction into adjustments of reference signals for walking, and so on
and so on. There might be some higher-level systems involved as well.
All these control systems would be active no matter what they are being
used for -- expressing anxiety and trying to get back to mama, seeking
cover when some danger appears, foraging for bits of food, and whatever
else chicks do that requires moving toward or away from objects and
otherwise behaving relative to them.
So this is not the "control system whose actions typically produce DVs
(and other outputs)." You are looking at multiple control systems at
several levels that are involved in many forms of behavior. The only
reason they seem to be involved specifically in the distress reactions
is that you are studying distress reactions; the only reason they seem
to be affected by MSH is that you are studying the effects of MSH. You
could probably find hundreds of other substances that would interfere
with some aspect of this behavior; you could probably find many other
behaviors in which the same regions of the brain showed activity. In
fact, I'll bet that you can measure activity in this region of the brain
ALL THE TIME, and you're just picking up variations from the background
activity, subtracting out the uncorrelated activities.
The problem lies not in your techniques for measuring brain activity,
but in your classification of the behavior. In my not-so-humble opinion,
the first step in any investigation of the brain has to be to determine
the variables that the organism can control. The words we use to
describe behavior are, despite the scientific trappings of the
situations in which we use them, informal and intuitive, and oriented
around the observer's background and interests instead of the test
subject's structure of perceptions and goals. Instead of just
classifying the peeping and the movements as "distress vocalizations,"
you could look at what the chick is actually doing, and find out what is
being controlled by those actions. Obviously the peeping is only part of
what is going on, the part you chose as a measure of the whole. The
vocalizations are what a human being hears; there may be lots of fine
structure in it that the human observer doesn't notice, particularly at
frequencies beyond human hearing. The "mute" chick might not have been
mute at all. And along with the vocalizations are, I have no doubt, lots
of other motor activities.
I just don't think there's any shortcut. We have to do the basic studies
of what animals are controlling before we can even characterize behavior
in a relevant way, a way that's not conditioned by the observer's
private interpretations, categories, and labels.
My grandson is standing at my elbow demanding that I send this and turn
the computer over to him. I have no defenses -- he wins. Bye for now.
Best to all,