Neuronal correlates of perceptual stability during eye movements.

We are usually unaware of retinal image motion resulting from our own movement. For instance, during slow-tracking eye movements the world around us remains perceptually stable despite the retinal image slip induced by the eye movement. It is commonly held that this example of perceptual invariance is achieved by subtracting an internal reference signal, reflecting the eye movement, from the retinal motion signal. If the two cancel each other, visual objects, which do not move, will also be perceived as non-moving. If, however, the reference signal is too small or too large, a false eye movement-induced motion of the external world, the Filehne illusion, will be perceived. We have exploited our ability to manipulate the size of the reference signal in an attempt to identify neurons in the visual cortex of monkeys, influenced by the percept of self-induced visual motion or the reference signal rather than the retinal motion signal. We report here that such 'percept-related' neurons can already be found in the primary visual cortex area, although few in numbers. They become more frequent in areas middle temporal and medial superior temporal in the superior temporal sulcus, and comprise almost 50% of all neurons in area visual posterior sylvian (VPS) in the posterior part of the lateral sulcus. In summary, our findings suggest that our ability to perceive a visual world, which is stable despite self-motion, is based on a neuronal network, which culminates in the VPS located in the lateral sulcus below the classical dorsal stream of visual processing.