Neuroplasticity of attention How brain stimulation and mental fatigue affect attentional performance

Attention allows us to focus on what is relevant and to ignore what is not. While we call upon attention at every waking moment, it is not static: we cannot sustain attention indefinitely, and often fall prey to distractions. This PhD thesis is a study of the short-term neuroplasticity of attentional processes: how susceptible is attention to change, and what processes in the brain (neuro-) give rise to changes in attention (-plasticity)? In Chapters 2–5, I examined whether attention can be improved with electrical stimulation of the brain, in the form of transcranial Direct Current Stimulation (tDCS). Previous studies that attempted to use tDCS to enhance attention have yielded promising, but inconsistent results (reviewed in Chapter 2). My attempt to enhance spatial attention with tDCS (Chapter 3) was unsuccessful, as stimulation of the frontal eye fields did not lead to changes in eye movements. Applying tDCS over the dorsolateral prefrontal cortex also did not enhance temporal attention (Chapters 4 and 5), as participants’ performance on an attentional blink task remained unchanged. In Chapter 6, I investigated the opposite effect: decreases in attention, when attention has to be sustained for a long time. Using EEG, I tracked whether similar decreases occurred in different attention-related signals in the brain. tDCS may one day be used to counteract these declines, or to relieve other deficits in attention. However, barring a deeper understanding of the technique and more large-scale studies of its efficacy, such practical applications of tDCS are not yet feasible.