By Dajun Xing, Beijing Normal University 

One of the functions of the cerebral cortex is to increase the selectivity for stimulus features. Both theoretical work and experimental studies in multiple cortical areas have suggested that suppressive mechanisms are involved in feature selectivity. However, the magnitude of the contribution of suppression to tuning selectivity is not yet determined. We studied orientation selectivity in macaque primary visual cortex, V1, as an archetypal example of feature selectivity in the brain and develop a method to estimate the magnitude of the contribution of suppression to orientation selectivity. Our studies showed that untuned suppression, one form of cortical suppression, decreases the orthogonal-to-preferred response ratio (O/P ratio) of V1 cells and untuned suppression has an especially large effect on orientation selectivity for highly selective cells. We conclude that untuned suppression is crucial for the generation of highly orientation-selective cells in V1 cortex.