Reminder: _______________________________________________________ The CEU Department of Cognitive Science cordially invites you to its talk as part of the Departmental Colloquium series by Pascal Fries (Max-Planck Institute) Date: Wednesday, December 14, 2016 - 17:00-18:30 Host: Barbara Pomiechowska Title: Rhythms for Cognition: Communication through Coherence Abstract: I will show that free viewing induces gamma-band oscillations in early visual cortex. If the gamma rhythm in a lower visual area entrains a gamma rhythm in a higher visual area, this might establish an effective communication protocol: The lower area sends a representation of the visual stimulus rhythmically, and the higher area is most excitable precisely when this representation arrives. At other times, the higher area is inhibited, which excludes competing stimuli. I refer to this scenario as the Communication-through-Coherence (CTC) hypothesis. I will show that the gamma rhythm in awake macaque V4 modulates the gain of synaptic inputs. I will further show that constant optogenetic stimulation in anesthetized cat area 21a (homologue to V4) induces a local gamma rhythm, and that this isolated gamma is sufficient to produce similar gain modulation. These gain modulation effects would be ideal to lend enhanced effective connectivity to attended stimuli. I will show that this is indeed the case between macaque V1 and V4. When two visual stimuli induce two local gamma rhythms in V1, only the one induced by the attended stimulus entrains V4. I will then investigate how these changes in gamma synchronization between visual areas are controlled by influences from parietal cortex. I will show that posterior parietal cortex influences visual areas primarily via beta-band synchronization. I will show that generally, beta-band influences are stronger in the top-down direction, while gamma-band influences are stronger in the bottom-up direction. This holds across macaques and human subjects, and in both species it allows building a hierarchy of visual areas based on the directed influences. Finally, I will show that attentional selection occurs at a theta rhythm. When two objects are monitored simultaneously, attentional benefits alternate at 4 Hz, consistent with an 8 Hz sampling rhythm, sampling them in alternation. Location: Department of Cognitive Science, CEU, Oktober 6 street 7, room 101. See more at: https://cognitivescience.ceu.edu/events/2016-12-14/departmental-colloquium-… We are looking forward to see you there! Cognitive Science Events at CEU: http://cognitivescience.ceu.edu/events Györgyné Finta (Réka) Department Coordinator ~~~~~~~~~~~~~~~~~~~~~~~~ Central European University Department of Cognitive Science H-1051 Budapest Oktober 6 utca 7. tel: (36-1) 887-5138 fax: (36-1) 887-5010 http://www.ceu.edu http://cognitivescience.ceu.edu ______________________________________________ Subscribe by sending an empty mail to talks-subscribe(a)cogsci.ceu.edu Unsubscribe by sending an empty mail to talks-unsubscribe(a)cogsci.ceu.edu