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
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