UC faculty study animal brain waves

BERKELEY, Calif. (U-WIRE) - A University of California at Berkeley scientist and fellow researchers announced this month they have found a new way to reconstruct visual information that passes through the brains of animals.

Yang Dan, an assistant neurobiology professor at UC-Berkeley, collaborated with Garrett Stanley, a Harvard professor in the Division of Engineering and Applied Science and Fei Li, a Princeton graduate. The Journal of Neuroscience published the experiment last week.

The experiment, conducted from 1997 to 1998, was designed to reveal new information about the inner workings of the brain, Dan said.

"Our goal was to understand how information is coded in electrical signals," she said. "The electrical signals can be compared to Morse code. We wanted to decode the end of the message."

The research is a small step toward a larger goal, Dan added.

"If we are able to analyze how the brain sees and hears, we will be able to understand how the brain works," Dan said. "Once we understand this, we will be able to aid those who are mentally ill by building devices that interact with the brain."

Such devices would provide access to data stored in the brain. The data would then allow researchers to analyze the mentally ill.

In the experiment, the scientists recorded the activity of neurons, the type of cell that communicates information in the brain.

The researchers studied the way a cat's brain processes visual information by analyzing neurons, which communicate with each other through electrical signals. Then they analyzed images of the brain activity using a decoding technique known as a mathematical model.

"We need to analyze the language of the brain and how we see and hear using electrical signals," Dan said.

Visual images are processed by the brain in the thalamus region. The thalamus region of the brain is connected directly to the eye by the optic nerve. The optic nerve is the link between the eye and the thalamus, Dan said.

A component of the visual system, the thalamus is the last place visual information travels before it enters the cerebral cortex. Once images reach cells in the thalamus region, the neurons transmit information to the cortex.

The transferring of information occurs when the neurons "fire" the information. The "firing" is a result of electrical signals in the form of impulses reacting to the contrasts between light and dark objects, Dan said.

"For example, the neurons fire if they see a light circular object surrounded by a dark background," she said. "Or they fire if they see a light object that stands out."

After the cells "fire," the cat's brain is able to reconstruct the image it has recorded.

"By recording the activity of the neurons in the cat's brains, we were able to decode the electrical signals and put together an image which we viewed on the computer," Dan said.

From the thalamus region, the image is transmitted to the cortex of the brain. Although the researchers did not analyze the activities of the cortex, the neurons in the cortex region only "fire" if they see an edge.

An edge is the contrast between black and white, Dan said.

"The cortex has nothing to do with our experiment," Dan said. "In the future, the cortex will pose the biggest challenge for scientists because that is where the most complex images are analyzed."

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