To build a coherent representation of the world, the brain combines inputs from different sensory modalities in a process named multisensory integration. Multisensory processing involves computations distributed across brain areas and cell types and it is profoundly shaped by neuromodulation. Correct perception of our multisensory environment is highly beneficial for survival as it enables accurate responses to external stimuli. Sensory neocortical areas continuously encode, integrate and elaborate multisensory information even at the primary sensory level. In these areas, multisensory neurons respond to multimodal stimuli aligned in time and space. Astrocytes integrate signals coming from neuronal populations. In turn, astrocytes can modulate neuronal activity. These cells are thus ideally placed to integrate and mediate multisensory information. Yet, if astrocytes regulate sensory perception is unclear. Additionally, due to technical limitations, most studies of multisensory processing focused on single areas separately. With this project, I will reveal the role of astrocytes in encoding multisensory stimuli across sensory areas. This will be achieved by performing, for the first time, two-photon mesoscopic imaging on both neurons and astrocytes. With advanced computational methods, I aim to decipher if information about multisensory perceptual behaviour encoded by astrocytes is complementary to that in neurons. Additionally, stimulus detection relies on external input, but is also influenced by internal states, such as attention. Acetylcholine (ACh) is correlated with attention and affects neuronal circuit responses. Hence, I will test if astrocytes are behavioural state regulators by investigating if ACh release correlates with astrocytic responses during task engagement. In conclusion, I will combine state-of-the-art molecular and optical approaches with analytical methods to understand the role of astrocytes multisensory perception influences at the mesoscale.