The role of the frontoparietal cortices in feature-selective attention

In everyday life our brains receive a huge amount of information from our senses. Since we cannot process it all, we must select the information that is most relevant for our current activity and prioritise it over other, irrelevant, information. This ‘selective attention’ process is critical for making sense of the world around us and for functioning successfully within it. Certain regions of frontal and parietal cortex have long been implicated as sources of selective attention in the brain. In particular, the ‘adaptive coding hypothesis’ proposes that certain neural populations adjust to selectively code the information that is required for current behaviour (Duncan 2001). This may serve as a source of bias, supporting related information processing across the rest of the brain (Desimone and Duncan 1995, Miller and Cohen 2001). The primary aims of this thesis were to investigate if adaptive coding provides a mechanism for feature-selective attention in the frontoparietal cortices and whether this in turn modulates responses across the rest of the brain. In Chapter 1, I present an overview of the relevant literature. In Chapter 2 I used multi-voxel pattern analysis (MVPA) of functional magnetic resonance imaging (fMRI) data to demonstrate that regions of the frontoparietal cortices prioritise coding of task relevant features over equivalent irrelevant feature information. In Chapter 3 I replicated this finding and examined the adaptive response of these regions in greater detail, investigating the extent to which single voxels in these regions can be re-used to code information across multiple tasks. In Chapter 4 I developed a paradigm that tracks the extent to which irrelevant information interferes with behavioural performance, and tested the causal contribution of the right dorsolateral prefrontal cortex (dlPFC) to this task using transcranial magnetic stimulation (TMS). In Chapter 5 I used this paradigm to examine the behavioural and neural consequences of disrupting activity in the frontal lobe, using concurrent TMS-fMRI. Using MVPA, I found that disrupting the right dlPFC with TMS affected the multi-voxel coding of both relevant and irrelevant feature information in frontal, parietal and visual cortices. Finally, in Chapter 6, I discuss the implications of these results in a broader context and suggest some areas for future research. Together, the experiments presented in this thesis advance the understanding of flexible mechanisms employed in the frontoparietal cortices in the context of feature-selective attention.