Thesis defense Casper van Heck (Donders series 375)

3 June 2019

Promotors: prof. dr. R. Kessels
Co-promotors~: dr. T. van Rijn, dr. M. Jongsma, dr. J. Oosterman.

Probing attentional biases", with a subtitle of "The presence and presentation of individual attentional biases in relation to salient stimuli

‘To probe’ is to investigate how something works, where the ‘probe’ (noun) itself is used to ‘probe’ (verb) the object, phenomenon, or process of interest. In this thesis, one of the major ‘probes’ is the ‘dot-probe paradigm’. This paradigm utilizes a dot, which is known as the ‘probe’; hence the name ‘dot-probe’.
The (re)directing of attention towards relevant information is one of the more basic and important phenomena involved in cognition. What is defined as ‘relevant’ differs per situation, but also between individuals; people are different, after all.
However, some of the differences in the attribution of attentional relevance can be very pronounced, up to the point of interfering in normal functioning. These are commonly termed ‘attentional biases’, where an individual shows a disproportionally strong attentional shift in relation to a specific type of information.
These attentional biases have been linked with various disorders and syndromes, such as chronic fatigue syndrome and chronic pain syndromes. Attentional biases are also thought to have relations with depression and quality of life, and have been cited as affecting recovery after an injury.

Literature surrounding attentional biases is, however, inconsistent. Some studies find significant (both statistical and not) effects of and relations with attentional biases, while other do not find these, or find effects and relations with opposing directions. As a result, some have expressed criticism towards the existence of attentional biases, or towards the validity of the dot-probe task.

The goal of this thesis is to study and describe attentional processes, where differences between individuals play a central role, while also placing emphasis on neural phenomena. To do this, the dot-probe task is employed together with the electro-encephalogram. The dot-probe task allows us to map attentional processes, while the electro-encephalogram allows us to objectively measure the activity of the brain. Both of these techniques require careful and stringent analysis using correct methods, which is another important aspect of this thesis.

In addition, this thesis will attempt to partially explain attentional biases using the fear-avoidance model. This model is commonly employed to explain aspects of chronic pain by using a positive feedback-loop, where fear and avoidance (of pain) are fed back in the experience.

In this thesis the following four postulates are proposed:

1. Attentional biases, as present in the Chronic Fatigue syndrome, are partially compatible with the Fear-Avoidance model.
2. These biases exist in the general population, and present themselves in otherwise considered ’healthy’ individuals; there are differences between individuals, even without disorder or disease being present.
3. Differences between individuals affect objectively measured brain activity and neural functioning, in relation to the processing of pain-related stimuli.
4. These attentional biases elude detection and investigation due to them having non-linear relationships with clinical measures.

This thesis sheds light on attentional biases, with specific focus on appropriate methods, correct analysis, and interindividual differences. This thesis emphasises the complexity of attentional biases and their relations with psychological constructs. Moreover, differences between individuals are taken into account, where it is shown that attentional biases are not solely a clinical phenomenon, but also exists in healthy individuals. Future studies are required to elucidate the exact relations between attentional biases and psychological constructs, in both patient populations as in healthy individuals. However, future studies are advised to take the non-linear nature of attentional biases into account, and to employ larger groups of participants.