TY - JOUR T1 - Cortico-Cortical Feedback Controls Spatial Summation in Primate Visual Cortex JF - bioRxiv DO - 10.1101/094680 SP - 094680 AU - Lauri Nurminen AU - Sam Merlin AU - Maryam Bijanzadeh AU - Frederick Federer AU - Alessandra Angelucci Y1 - 2016/01/01 UR - http://biorxiv.org/content/early/2016/12/16/094680.abstract N2 - Our visual perception of the external world relies on neural activity across a hierarchy of visual cortical areas, communicating via complex feedforward-feedback pathways. While feedforward pathways have been a focus of study, the role of the feedback pathway has remained poorly understood. Here we have developed a novel viral vector combination allowing for selective optogenetic inactivation of feedback pathways in the non-human primate brain. We show that even the most fundamental response properties of visual neurons, such as the receptive field size, are regulated by feedback signals from other regions of the visual cortex. Depending on its activity regime, cortico-cortical feedback can regulate receptive field size and contextual modulation of visual responses or the overall response gain of neurons. ER -