Wired Brain: Conventional Notion of How We Sense Information Overturned

Scientists are moving forward by leaps and bounds when it comes to studying the brain. Now, a series of studies has toppled the conventional notion of how the brain is wired. The new research has revealed that sensory information travels to two places at once: not only to the brain's mid-layer, but also directly to its deeper layers.

When we see, hear or touch something, sensory information travels to our brain. There, it's processed in the six-layered cerebral cortex in a serial fashion--or at least that's what scientists once thought. The information is first processed in the middle layer, then the upper layers and finally the deeper layers. Yet it seems as if this particular process doesn't work the way scientists have thought it did for decades.

In order to better study how we process information, the scientists used the well-understood sensory system of rat whiskers. Operating like human fingers, these whiskers provide tactile information about shape and texture to the brain.

The researchers monitored how signals moved across synapses from one neuron to the next in a live animal. To do this, they used a glass micropipette with a tip filled with fluid that conducts nerve signals. They then recorded nerve impulses resulting from whisker stimulation in 176 neurons in the cortex and 76 neurons in the thalamus. It turned out that signals are relayed from the thalamus to deeper layers of the brain at the same time. In order to confirm this, the scientists then blocked all signals from layer 4, but activity in the deeper layer remained unchanged.

"This was very surprising," said Christine Constantinople, one of the researchers, in a news release. "We expected activity in the lower layers to be turned off or very much diminished when we blocked layer 4. This raises a whole new set of questions about what the layers actually do."

So what are they doing? It's possible that the upper and lower layers of the cerebral cortex form separate circuits and play separate roles in processing sensory information. Basic sensory processing could be done in the lower layers--for example, visually tracking a tennis ball to coordinating movement needed to make contact. Processing that requires learning could be done in the upper layers--for example, watching where an opponent is hitting a ball and planning where to place the return shot.

The findings have enormous implications for understanding how the brain works. It's a game-changer when it comes to learning how we process sensory information, and could help with future research in the area.

The findings are published in the journal Science.