Brain`s code for 3-D structure
New York, Oct 28: Scientists have discovered patterns of brain activity which they claim might underlie our remarkable ability to see and understand the three-dimensional structure of objects.
A team at Johns Hopkins University has found that higher-level visual regions of the brain represent objects as spatial configurations of surface fragments, something like a structural drawing. Individual neurons are tuned to respond to surface fragment substructures.
For instance, one neuron from the study responded to the combination of a forward-facing ridge near the front and an upward-facing concavity near the top. Multiple neurons with different tuning sensitivities could combine like a three -dimensional mosaic to encode the entire object surface.
“Human beings are keenly aware of object structure, and that may be due to this clear structural representation in the brain,” lead researcher Charles E. Connor said.
In the study, the team trained two rhesus monkeys to look at a computer monitor while 3-D pictures of objects were flashed on the screen. At the same time, the researchers recorded electrical responses of individual neurons in higher-level visual regions of the brain.
A computer algorithm was used to guide the experiment gradually toward object shapes that evoked stronger responses.
This evolutionary stimulus strategy let the experimenters pinpoint the exact 3-D shape information that drove a given cell to respond, the researchers found.
Bureau Report
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