The role of the cholinergic system via muscarinic receptors in selective attention

In everyday life, we are surrounded by more information than we can take in. Selective spatial attention ability allows us to direct our attention to task relevant stimuli at specific spatial locations whilst ignoring distractors at other spatial locations. As a result of selective attention, there is an increase in neural activity for attended stimuli as compared to unattended stimuli. Research has shown that the cholinergic system plays an important role in our ability to selectively attend to task relevant stimuli. However, what is unclear from the existing literature is how the cholinergic system modulates the neural processes underlying selective attention ability. This thesis investigated the influence of the cholinergic system on visual spatial selective attention ability using a frequency tagging Steady State Visually Evoked Potentials (SSVEPs) paradigm. A double-blind, placebo-controlled, cross-over design was used with the order of scopolamine (an anti-cholinergic agent) and placebo counter-balanced across participants. Nineteen male participants attended to cued flickering symbol streams whilst ignoring the un-cued streams, and responded when the targets appeared in the cued symbol streams. Selectively attending to cued symbol streams resulted in increased SSVEP amplitude for three out of the four symbol streams. In addition, scopolamine impaired the ability to selectively attend to only one of the cued symbol streams. The results obtained in this study suggest that there may be additional factors modulating the influence of the cholinergic system in selective attention as assessed by SSVEPs. Future research should investigate the role of these factors so as to allow a better understanding of the underlying cholinergic neural mechanisms involved in selective attention