Thesis defense Freek van Ede (Donders Series 145)

18 March 2014

Promotor: Prof.dr. M. Ullsperger, copromotor: Dr. E.G.G. Maris

Preparing for perception. On the attentional modulation, perceptual relevance and physiology of oscillatory neural activity

Our senses are continuously confronted with a far greater amount of sensory information than can be perceived. As a consequence, a major challenge that must be resolved by our nervous system is to selectively process those aspects of our environment that are relevant to current goals, while ignoring others. Often, this selective processing relies on the ability to prepare for anticipated sensory information. For example, while grasping for a cup of coffee, you must prepare for incoming touch sensations on your finger tips such that, upon initial contact with the cup, you can perceive this with immediate high fidelity. A fundamental question is how the nervous system accomplishes this. In other words, what are the neurophysiological mechanisms by which preparatory selective attention improves perception?

The thesis presents a series of eight studies that target different aspects of this central question. These studies focus on the role of oscillatory neural activity, mainly in the human somatosensory modality(i.e. the modality concerned with touch perception).

Conceptually, the thesis can be divided into three parts. Part 1 puts forward the primary phenomenon detailed in the thesis; that orienting attention to an expected touch sensation involves a preparatory suppression of alpha and beta oscillations in the contralateral primary somatosensory cortex (the first stage at which tactile information is processed in the cortex). Part 2 builds on this central observation by addressing how this relates to the attentional improvement in perception, and via which neural mechanisms during stimulus processing this improvement might be mediated. Finally, part 3 places this central observation into a broader perspective by (1) comparing it to the attentional modulation of neural oscillations during stimulus processing, (2) investigating attentional modulations throughout the widely distributed somatomotor network, and (3) investigating the mechanisms underlying observed modulations of oscillatory amplitude.