Primary visual cortex (VI) in the mammalian brain computes on the fly perceptual primitives (form, motion, visual flow) from the feedforward bombardment of retinal events channeled through the thalamus. At the same time, it integrates the distributed feedback of higher cortical areas involved in more elaborate cognitive functions. The reverberating activity evoked by the interplay between these two streams has been hypothesized to form the trace of the low-level computational operations written on the "high resolution buffer" of primary cortical areas [1]. In vivo intracellular electrophysiology in VI offers the unique possibility of listening to the synaptic echoes of the effective perceptual network at work. On the basis of the comparison between functional synaptic imaging and voltage sensitive dye imaging, I will show that the emergence of macroscopic features of perception (Gestalt and motion flow related percepts) in early sensory cortical areas can be predicted from the read-out of analog graded events (synaptic potentials) operating at a more microscopic integration level.
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