( area of about five feet if stretched ...)Brains response to visual stimuli helps us to focus on what we should see, rather than all there is to see

Research in the 1960s showed that these columns contain brain cells with similar functions, suggesting that "like-minded" neurons needed to be networked together to perform a function. To account for the tasks carried out in the larger areas, scientists assumed that the function of these columns varied smoothly across the cortex surface. Later research demonstrated that each of the six layers in the cortex is also wired into distinct circuits.

But Callaway and Yoshimura tested the prevailing notion of columnar function by devising an experimental method that used glass microelectrodes to "listen" to two neurons at a time. They used rats, whose brain organization mirrors that of a human, and dissected tiny vertical slices to preserve the circuitry. With fine glass pipettes, they recorded tiny impulses in individual live neurons and listened to their responses when other neurons were optically stimulated. If impulses occurred at precisely the same times in both neurons, this indicated that they both shared the same inputs.

The Salk scientists found that the thousands of neighboring neurons that make up these columns are not the same, and they often don't communicate directly with each other. In February, they reported in Nature how excitatory neurons were organized into sub-networks that were found within the same column but which had nothing to do with other cells nearby.

That meant that the brain's circuitry is organized on a much finer scale than was previously suspected. And this makes sense, explained Callaway, because neuroscientists were puzzled as to why so many neurons were needed in the same part of the brain to carry out the same function.

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Source:Salk Institute