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      Perceptual awareness is one of the most basic prerequisites for living a normal life. For every act we perform and every decision we make, we rely on information about the environment that has been processed by our sensory systems. In order to be able to drink a cup of coffee, we first to need to know that there is a cup of coffee in the first place. Luckily, the detection of objects in our surroundings happens ‘automatically’ and we rarely make mistakes. However, psychophysical studies have made it clear that the detection of stimuli can be quite inaccurate in laboratory settings. For example, when stimulus duration is very short or the contrast very low, chances are that we might miss these stimuli altogether and never know that they were there.

     While the failure to detect stimuli might be considered undesirable, these hiccups in the brain can actually tell us a lot about the inner workings of the mind. Psychophysics can report stimulus detection thresholds under certain task conditions, but it is still unclear what happens at the level of neurons. What are the differences in spatial and temporal structure of neural activation patterns under different conditions of visual processing? How does successful visual discrimination differ from unsuccessful attempts? And what are the effects of varying attention and motivation on visual processing?

Techniques We intend to study these activation patterns on a network-level by using in vivo two-photon Ca²⁺ imaging of neuronal networks in layer 2/3 of the visual cortex during processing of visual information.

The advantage of using two-photon calcium imaging is the wide field of view that allows us to precisely localize neuronal somata, as well as measure many neurons simultaneously (see figure) Using this technique, we will be able to characterise the spatial and temporal structure of neuronal assembly dynamics.