We use multi-electrode recordings from cat primary visual cortex and investigate whether a simple linear classifier ca n extract information about the presented stimuli. We find that information is extractable and that it even las ts for several hundred milliseconds after the stimulus has b een removed. In a fast sequence of stimulus presentation, information about both new and old stimuli is present simultaneously and nonlinear relations between these stimuli can be extracted. These results suggest nonlinear properties of cortical representat ions. The implications of these properties for the nonlinear brain theory are discussed.