The world as the brain sees it. Optical ‘polar’ maps of the visual cortex are generated by measuring micro-changes in blood oxygenation as the left eye (left panel) or right eye is stimulated by bars of light of different orientations (0-180 degrees). The cortical response to each stimulus is pseudo-colored to represent the orientation that best activates visual cortical neurons. If vision is blocked in an eye (the right eye in this example) during a critical period of development, neurons no longer respond to input from the deprived eye pathway (indicated by a loss of color in the right panel) and begin to respond preferentially to the non-deprived eye pathway. These changes are accompanied by alterations in synaptic connections in single neurons. This process, known as ocular dominance plasticity, is enhanced by sleep via activation of NMDA receptors and intracellular kinase activity. Through these mechanisms, sleep strengthens synaptic connections in the non-deprived eye pathway.
Credit: Marcos Frank, PhD University of Pennsylvania
Download high-resolution version.