"For the last five years or so, a growing number of people have been exploring the theoretical possibility that the timing of the arrival of electrical spikes is useful for performing neural computations," says David Noelle, assistant professor of computer science and psychology at Vanderbilt, who did not participate in the study. "The Bonds paper can be seen as the first step towards providing a test of these theoretical models."
Scientists studying vision have known for some time that different groups of neurons in the visual cortex respond selectively to the way in which objects are oriented. For example, when a subject views a horizontal bar, one group of neurons begins firing, while a different group begins firing when the bar becomes vertical.
"People have the ability to discriminate between orientations that differ by only a third of a degree. That is pretty remarkable when you consider that individual neurons normally don't respond to changes in orientation of ten degrees or more! It is even more amazing when you stop to think that a neuron is basically a little sack of salt water!" Bonds exclaims.
Until recently, attempts to study interactions between groups of neurons have been hindered by the fact that researchers were limited to using single microelectrodes to measure electrical activity. Although this technique does a superb job of recording the electrical activity of one or two neurons, attempts to use it to record the activity of a larger number of neurons at the same time has had limited success. (The other method major method for mapping brain activity functional MRI measures chemical changes in the brain, not electrical ones, so cannot be used for this purpose.)