"This proposal aims to study the modulation of neural activity by attention in rodents, and its mechanisms. There has been substantial work done in this field using monkeys, which has revealed a number of interesting facts. However, these studies are limited in a number of ways. Firstly, there is a limit to the extent of invasive procedures that can be conducted in monkeys. Secondly, one cannot use molecular and genetic tools that have exploded in recent years in other model systems, in particular, optogenetics.The fundamental questions I will address in this proposal are: (i) What are the changes occurring in the brain when an animal switches its attention, and (ii) What are the mechanisms the brain uses to implement these changes? While work done primarily in primates has shed some light on the first question, very little is known about the second question. By addressing these questions in mice, I aim to take advantage of the powerful genetic tools available in this species to investigate the neural circuits underlying attention.I will train mice on a novel attention switching task, and optically record stimulus evoked calcium transients from multiple regions of the visual cortex at cellular resolution. I will compare the response to the same stimulus in attending and not attending conditions and I expect to find a difference due to attentional effects. I will further express Channel Rhodopsin in cholinergic neurons and excite the nerve terminals selectively in the visual cortex. In this manner I will test the hypothesis that elevated acetylcholine levels in the visual cortex can cause attention to shift and be maintained towards visual stimuli.This study will be relevant in the context of the European Commission's Europe 2020 strategy, since it will lead to innovation of novel techniques and synthesise multiple cutting edge research areas to result in an innovative research project, which will help in establishing the eminence of the ERA in the global scenario"