Nobel laureate: Brain still a mystery

BY JENNIFER EVANS
Rice News staff

Understanding brain operation “is a fascinating problem” to French scientist Pierre-Gilles de Gennes, one that he predicts will be the challenge of the century. Despite the incredible advances in scientists’ understanding of brain function, “there are many more mysteries than solutions,” he said. The Nobel Prize-winning physicist made no suggestion that he has the answers in his Oct. 9 lecture, “The Nature of Memory Objects,” the first in of the 2006-2007 President’s Lecture Series. In fact, he began with a caveat: “What I will describe to you is very naïve; take it with a huge grain of salt.”

Describing himself as “an old student,” de Gennes noted he is just learning about the brain. “I have been learning for something like three years, so I am still an undergraduate in brain work,” he said.

Nonetheless, de Gennes has distinct ideas about memory objects. He explained that some believe that in vertebrates, memories, such as the smell of a rose, are a sort of cloud floating among a community of cells, whereas others think a memory is stored in a single cell.

De Gennes argued that memory is actually a process relying on a group of cells working together in a communication system that is simultaneously complex and crude and yet “still achieves something as beautiful as a mouse sniffing and recognizing cheese.”

But the question at the root of the memory object, he said, is how does the memory get there to begin with? How does a certain signal get “printed” in our nervous system? If a person memorizes something, the smell of a rose, for instance, how is that memory stored?

The process involves a dance of biology and chemistry. For each of the thousands of “chemical types” — alcohols or keytones, for example — humans have one type of protein detector in their nose to recognize it.

Upon sensing the chemical type, the appropriate detector sends a signal toward a storage area where there are many neurons — probably a million —where the brain can store information.

While one neuron in the storage area receives this input from the nose, it also receives input from neighboring neurons and in turn sends out signals to other parts of the brain.

“Each neuron is coupled to many neighbors,” he said. “This is not like electronics. There is no blueprint for this.”

To further explain these workings, de Gennes used a concept he calls “flares.”
Suppose a signal is sent to Neuron 1, he said. Neuron 1 will send signals to its neighbors. That signal will reach Neuron 2, which will excite its neighbors.
When signals from two channels converge on a single cell, for instance, when Neuron 2 gets a signal from Neuron 1 as well as from a source emitter, such as the nose, the convergence would cause printing to occur on Neuron 2.

“This is very similar to chemical kinetics when you do reactions where many molecules have to be together to build a new molecule,” he said.

So a person shown a rose would be storing information about smell, appearance and texture, and many different parts of the brain might be involved in these different associations building the full concept of a rose.

That’s why years after experiencing a rose, a person can be shown a photo of one and think of the fragrance or can smell a rose-scented perfume and imagine the rose’s color.

De Gennes said looking forward in this area of research, he imagines brain implants will be an important development.

“We can act on brain function in a very useful way by implants,” he said. For example, implants can be used to act on some human diseases, such as Parkinson’s. Surgeons already can stimulate certain areas of a Parkinson’s patient’s brain while the patient is conscious and find areas that when stimulated, cause the patient’s tremors to stop.

He imagines possible dramatic medical applications for implants in parapalegics and stroke patients, although he admits there are problems still to be overcome.

And in what he called the “more science fiction realm,” he considered the idea of implants to detect and control movement and even the intention of a movement. For example, a pilot with an implant sees a mountain approaching and knows he must alter the path of the plane. Rather than executing a movement, de Gennes said, the pilot’s intentions will be translated to a robotic system that will direct the plane.

De Gennes said the simple model of memory system he described is not an important achievement, but understanding the incredible advancements in this area of science is promising. “It will lead us to beautiful discoveries but also ethically challenging ones.”