Functional imaging with cellular resolution reveals precise micro-architecture in visual cortex.

Area of Science:

• Neuroscience
• Systems Neuroscience
• Cortical Circuits

Background:

• The cerebral cortex exhibits functional architecture organized into columns, with neurons sharing properties like stimulus orientation selectivity.
• Previous imaging techniques lacked the resolution to determine the precision of these functional maps and their borders.

Purpose of the Study:

• To investigate the fine-scale organization of functional maps in the visual cortex at single-cell resolution.
• To resolve the precision of neuronal tuning and the structure of functional domains.

Main Methods:

• In vivo labeling of thousands of visual cortex neurons with a calcium-sensitive indicator.
• High-resolution two-photon microscopy to image neuronal activity up to 400 micrometers deep.

Main Results:

• In rat primary visual cortex, orientation selectivity was observed, but no clear local structure of neuronal responses.
• In cat visual cortex (area 18), neurons with opposing stimulus preferences were precisely segregated in 3D, with borders only one to two cells wide.

Conclusions:

• Cortical functional maps can be organized with single-cell precision, challenging previous assumptions based on lower-resolution techniques.
• The precise segregation of neuronal function suggests a highly organized microcircuitry in certain cortical areas.