May 2, 2010 10 Comments
I seem to have hit some kind of word limit or bug in the comments thread to my last post, because I don’t seem to be able to reply to anyone there any more. I’ll just have to do it as a separate post instead. Thanks to all of you for such interesting comments! It’s both helpful and encouraging!
Jonet: Thanks for the link on blindsight. I’d read about this a number of times before, but never heard of anyone capable of obstacle avoidance after severe occipital damage before. It goes to show that the superior colliculus is a lot more powerful than was originally assumed. That makes sense, because it evolved from the optic tectum in amphibians, which is the top of their visual system and probably responsible for all their visually guided behavior. The inferior colliculus right next to it has auditory maps of space, so it was interesting to see mention of head-direction and place cells in that general area of the thalamus. I was talking with torea about those the other day.
John: Thanks, that’s a very interesting breakdown! Viewing attention as goal-directed like this makes it central to all action, perhaps. Since attending to a high-level goal, such as “avoid bodily harm”, requires the organism to carry out a sequence of actions to achieve the goal, some of which may themselves require attentional shifts, then it makes sense to hypothesize that the same mechanism is at work in selecting the actual actions. This would make attention the mechanism of volition, right down to the triggering of individual movements. Don’t you think?
For example, a bottom-up attentional shift in response to a sudden visual movement might orient the organism’s eyes to that stimulus. Something subcortical might then detect a snake-like pattern to the stimulus and raise the alarm, triggering the organism to select a high-level goal – to run or to fight. Fighting the snake would be a complex action schema. This might involve gathering more information from the senses – hence an attentional shift in the visual and auditory systems driven by the action schema itself. It would also involve hitting the snake with something, which in turn involves smaller goals, such as raising the arm, orienting the body and smiting the snake. Each sub-goal would be triggered in exactly the same way, but not top-down from the PFC, nor bottom-up from the senses, but from the middle-down, as part of the schema.
Does that make sense? A hierarchy of ideomotor actions, each of which specifies a goal state in some subsystem. This is very reminiscent of setting the target state in a servomotor, whose output then sets the targets in other servos lower down. It would make attention and intention exactly the same thing (as I surmised in my Lucy book, in fact!).
What is going on??? Now I can’t reply to an earlier post either! I’m being ostracized by my own blog!!! Maybe these comments will show up eventually, or maybe it’ll sort itself out in time for my next post. Oh well, any other replies to your comments will appear here until I know better…
Daniel: Thanks, I’d forgotten about PCA (mostly because I’m a klutz at math!). Fascinating that male-female might form an axis in face space. That would be biologically very valuable, as you say! I’ll see if I can get my head around PCA for inspiration.