Donders Institute for Brain, Cognition and Behaviour
Zoek in de site...

Thesis defense Benjamin Kausch-Blecken von Schmeling (Donders Series 607)

18 September 2023

Promotor: Pascal Fries
Co-Promotor: David Poeppel

On the genesis and function of gamma oscillations in human early visual cortex

Visual gamma oscillations are a network phenomenon generated by excitation-inhibition interactions in early visual cortex. They depend on stimulus drive and homogeneity, can be influenced by cognitive and stimulus-history factors, and have been proposed to underlie both the binding of visual information into objects, and selective neuronal communication. While tremendous progress has been achieved over the last thirty years, many questions on the mechanisms, prerequisites, and functions of gamma oscillations remain.
Using MEG and psychophysical experiments in human participants, I have demonstrated that a) colored stimuli of equal L-M retinal cone contrast induce equally strong gamma oscillations, that b) gamma oscillations show gamma repetition suppression over few stimulus repetitions and gamma repetition enhancement over many repetitions, that gamma repetition enhancements are stimulus-specific, persist over many minutes and strengthen feedforward functional connectivity along the visual hierarchy, and that c) as predicted by the CTC hypothesis of gamma function, phase-leading stimuli are processed and perceived more intensely than phase-lagging stimuli.
Thereby, this work advances the understanding of gamma oscillations in humans and integrates recent research into a comprehensive account of their stimulus dependencies and effects.