TY - JOUR T1 - Visual areas exert feedforward and feedback influences through distinct frequency channels JF - bioRxiv DO - 10.1101/004804 SP - 004804 AU - Andre M. Bastos AU - Julien Vezoli AU - Conrado A. Bosman AU - Jan-Mathijs Schoffelen AU - Robert Oostenveld AU - Jarrod R. Dowdall AU - Peter De Weerd AU - Henry Kennedy AU - Pascal Fries Y1 - 2014/01/01 UR - http://biorxiv.org/content/early/2014/05/06/004804.abstract N2 - Visual cortical areas are thought to form a hierarchy and to subserve cognitive functions by interacting in both feedforward and feedback directions1. While feedforward influences convey sensory signals, feedback influences modulate brain responses to a given sensory stimulus according to the current behavioural context. Many studies have demonstrated effects of feedback influences on feedforward driven responses2 and on behaviour3. Also, anatomical projections in both directions have been identified1, 4. However, although these studies have revealed the anatomical paths and the neurophysiological consequences of influences in both directions, the neurophysiological mechanisms through which these influences are exerted remain largely elusive. Here we show that in the primate visual system, feedforward influences are carried by theta-band (∼4 Hz) and gamma-band (∼60-80 Hz) synchronization, and feedback influences by beta-band (∼14-18 Hz) synchronization. These frequency-specific asymmetries in directed influences were revealed by simultaneous local field potential recordings from eight visual areas and an analysis of Granger-causal influences across all 28 pairs of areas. The asymmetries in directed influences correlated directly with asymmetries in anatomy and enabled us to build a visual cortical hierarchy from the influence asymmetries alone. Across different task periods, most areas stayed at their hierarchical position, whereas particularly frontal areas moved dynamically. Our results demonstrate that feedforward and feedback signalling use different frequency channels, which might subserve their differential communication requirements and lead to differential local consequences. The possibility to infer hierarchical relationships through functional data alone might make it possible to derive a cortical hierarchy in the living human brain. ER -