Researchers have developed a real-time optical imaging method that exploits a specific voltage-sensitive dye to demonstrate brain multiplexing in the visual cortex, says Dr. Dirk Jancke, neuroscientist at the Ruhr-University in Bochum, Germany.

Neurons synchronize with different partners at different frequencies. Optical imaging allows fine grained resolution of cortical pattern activity maps in which local groups of active nerve cells represent grating orientation. A particular grating orientation activates different groups of nerve cells resulting in unique patchy patterns.

The researchers used simple oriented gratings with alternating black-and-white stripes drifting at constant speed across a monitor screen. They detected brain activity that signals both the grating’s orientation and its motion simultaneously.

They used a voltage-sensitive dye that changed fluorescence whenever nerve cells receive or send electrical signals. High resolution camera systems simultaneously captured the activities of millions of nerve cells across several square millimeters of a brain.

The study showed that motion direction and speed can be estimated independently from orientation maps. This resolves ambiguities occurring in visual scenes of everyday life, and starts to show how the brain handles complex data to create a stable perception at a given moment of time, says Jancke.

Ref.: “Independent encoding of grating motion across stationary feature maps in primary visual cortex visualized with voltage-sensitive dye imaging,” Neuroimage, January 4, 2011.