Thesis defense Jim Herring (Donders series 296)

8 December 2017

Promotors: prof. dr. O. Jensen, copromotor: dr. T. Bergmann

Driving visual cortex to study neuronal oscillations

On a daily basis, the brain is overloaded with sensory information. To cope with this, the brain must apply a mechanism to prioritize bottom-up sensory input. Irrelevant information has to be blocked, while at the same time important, salient stimuli should be allowed access. For example, to focus on working on your manuscript on a sunny day in the park, you may have to block out irrelevant auditory input while at the same time still be able to process relevant, salient, stimuli such as your phone ringing. Additionally, relevant sensory input has to be grouped, or bound, low in the visual hierarchy, while segregated on a higher level. With my thesis, I hoped to gain important insights into the role of posterior alpha band oscillations in this process (Figure 1). More specifically, I aimed to answer the following questions:

1. Are cortical alpha oscillations an intrinsic property of the visual system?
2. Do cortical alpha oscillations serve as a mechanism of functional inhibition by phasically modulating visual processing?
3. Can rapid frequency tagging be used as a tool to study the role of neuronal oscillations in visual information processing?

The studies reported in my thesis confirm neuronal alpha band oscillations to be a fundamental property of the visual system. In general, this thesis highlights the role of alpha band oscillations in inhibiting irrelevant stimuli. More specifically, I have provided evidence that this inhibition is phasic in nature and has consequences for behavior. Importantly, both non-invasive brain stimulation as well as rapid frequency tagging have been shown to be a valuable tool in studying the (causal) role of neuronal oscillations in sensory processing.