Philosopher's list might help paint big picture of the brain

SAN FRANCISCO - Even scientists enjoy Top 10 lists, Letterman's or otherwise. The difference is, scientists' favorite lists usually consist of questions that don't have funny answers - or any

Tuesday, April 18th 2000, 12:00 am

By: News On 6

SAN FRANCISCO - Even scientists enjoy Top 10 lists, Letterman's or otherwise. The difference is, scientists' favorite lists usually consist of questions that don't have funny answers - or any answers at all.

In some fields, it seems that the more researchers discover, the more their questions outnumber answers.

One such field is neuroscience, where even the experts struggle to keep up with the flood of new research data. They may stay in tune with their specialized subfields, but have trouble keeping the whole big picture in view.

The same problem afflicts people who specialize in big pictures - namely, philosophers. Such as Patricia Churchland, a philosopher who specializes in the brain.

"In all fields, including molecular biology and cell biology, there is a vast proliferation of data," Dr. Churchland, of the University of California, San Diego, said at a neuroscience meeting last week. "But I think the feeling of being overwhelmed is a little more present . . . in neuroscience."

She reached that conclusion after consulting several leading neuroscience authorities for their assessment of what was going on.

"What I discovered," she said, "was most people were just as overwhelmed as I was."

So she resolved to take 10 small steps toward putting the big neuroscience picture into clearer focus - by listing 10 unsolved problems, posed in the form of questions. The questions have to observe the Goldilocks rule - not too big or wide, not too small or narrow. For example, "How does the brain work?" is a great question, but too broad to be useful in this exercise. Similarly, you would not want to include something like what brain cells govern the top air speed of an unladen swallow.

In other words, the questions have to be in the middle, "just-right" size.

So now, from the Cognitive Neuroscience Society's annual meeting in San Francisco, here are Dr. Churchland's Top 10 Questions About the Brain:

1. How do nerve cells code information? Scientists used to think that nerve cells, or neurons, carry information just by virtue of how fast they fire electrical pulses known as spikes. But now it seems that neurons don't represent information only by how fast they fire, but by precisely when they fire.
2.
"It looks from a variety of sources of data that the actual timing of an individual spike makes a difference, and that the time of the spike is something that carries information," Dr. Churchland said.

3. How does the brain manage time? Or to keep the question narrow enough, what is the role of synchrony? Synchronous activity - different neurons firing simultaneously, for example - shows up in many aspects of brain activity, such as perception and learning.

4. How specific is genetic control for wiring up neurons? Or, perhaps more broadly, how will the story unfold that begins with genes, begets the brain and ultimately accounts for behavior?

5. What are the roles of "back projections"? Nerve signaling carries information throughout various relay stations in the brain - visual signals, for example, start in the eye, travel to the back of the brain and then on to other brain areas for more advanced processing. Yet in many cases signals are also sent in the reverse direction. Such reverse signaling may play a role in learning or even conscious awareness, but nobody knows for sure what back projections do.

6. What's the role of spontaneous activity? A lot of stuff happens in the brain all on its own, without the need for some stimulus evoking a response. It would be nice to know why, and what for.

7. What would make a good integrated theory of emotions and cognition? Brains are the seat of rational thought, but mixed in are the drives and moods of the emotions. How do they fit together in the brain's information processing systems? In other words, in a brain, just what is information?

8. What are the mechanisms of learning? Some are known, but there are others to be discovered.

9. How is memory consolidated? Specifically, how do people remember only some of the things that happen, and how and why do people recall both important and trivial information?

10. How are decisions about movements made?

11. What experiments could yield insights into brain mechanisms for awareness?

No. 10 impinges on the grand question of what is consciousness, surely too big for Goldilocks. In fact, Dr. Churchland declares, it might not even be a good question for anybody, for the idea of consciousness may turn out to be too primitive to be useful when the brain is fully understood.

Answering all of the above questions may bring science a lot closer to possessing such understanding. But no doubt other questions will be important, too. For this kind of list, 10 may not be enough.

"Of course," Dr. Churchland pointed out, "if you asked all of the important questions, you would have so many questions that once again you would feel overwhelmed."