Keynote Speaker: Pascal Fries
Chair: Kate Watkins

Thursday, August 28, 6:15 – 7:15 pm, Effectenbeurszaal

Professor Pascal Fries is the Director of the Ernst Strüngmann Institute (ESI) for Neuroscience in Cooperation with Max Planck Society. Pascal Fries started his career at the Max Planck Institute for Brain Research in Frankfurt, in the department of Wolf Singer. After receiving his PhD, he was a postdoctoral fellow at NIMH, in the lab of Robert Desimone. From 2001-2009 he led his own research group as PI at the Donders Centre for Cognitive Neuroimaging of the Radboud University Nijmegen. In 2009 he started as the founding director of the Ernst Strüngmann Institute for Neuroscience in Frankfurt. Pascal Fries has published high impact papers in Science, Nature, PNAS, and all major neuroscience journals.  He is famous for his theory about communication-through-coherence. This theory claims that neuronal communication mechanistically depends on neuronal coherence, i.e. the phase-locking among neuronal oscillations that are pervasive in nervous systems. According to Fries, functional networks of neurons are thought to be determined through the coherence topography rather than solely by their anatomical connections. This theory explains how cognitive systems level analysis can be linked to underlying principles of neuronal network organization.

Brain rhythms for bottom-up and top-down signaling

Our brain generates rhythms continuously, and I will show in this lecture how some of these rhythms serve the communication between brain areas. One of the most intriguing rhythms is the gamma-band rhythm, which is strongly enhanced when a brain region is activated. When the gamma in one brain region entrains a gamma rhythm in another brain region, then signals can be sent over. If this entrainment or synchronization does not happen, then also no signal will flow, as I will demonstrate for the case of selective attention studied with high-resolution electrocorticography in monkeys. Thus, the selective gamma-band synchronization serves as a selective communication protocol. In these experiments, we found that gamma, together with theta, generally serves the bottom-up signaling of sensory information. By contrast, top-down signaling was served by beta-band synchronization. The pattern of inter-areal influences in the theta, beta and gamma bands was closely related to the hierarchical relationship between areas, as determined by laminar anatomical connection patterns. In fact, a hierarchy of visual areas derived purely from directed inter-areal influences was almost identical to the anatomical hierarchy. I will demonstrate that this holds for visual areas in human subjects studied with magnetoencephalography. It might hold also for other human brain areas, including language areas. Finally, I will show that bottom-up signaling in the gamma band is structured by a theta rhythm. The theta cycle implements one cycle of visual attentional sampling, as can be seen from human psychophysics and magnetoencephalography.