Commentary: Express saccades and superior colliculus responses are sensitive to short-wavelength cone contrast

摘要

Recently, Hall and Colby (2016) showed in non-human primates that the superior colliculus (SC) can use short-wavelength-sensitive cone (S-cone) stimuli. The authors used express saccades, a subclass of eye movements which critically depends on the SC (Schiller et al., 1987). Behaviorally they evidenced that S-cone stimuli increase the proportion of express saccades. Physiologically they show that S-cone stimuli yield two neural hallmarks of express saccades in intermediate layer neurons of the SC: larger initial burst of visuomotor activity and stronger preparatory activity, as compared to regular saccades. Taken together with previous reports from other teams leading to the same conclusion (e.g., Chang et al., 2016), these findings have put an end to the dogma according to which the SC does not carry color information. For 14 years, this idea based on the fact that anatomy and physiology had failed to find S-cone input to the SC has echoed two streams of cognitive sciences: naive cognitivism assuming that the brain may work as its inventions, e.g., some thermometer or computer, and Jacksonian neurology suggesting the deeper the brain structure lies the less evolved its function is. In this context the SC has been seen as processing black and white stimuli like the screen of a first generation computer. This view was also incompatible with phylogenetics given that the SC is the most important center for vision in species like inferior vertebrates.