FEEDFORWARD, HORIZONTAL, AND FEEDBACK PROCESSING IN THE VISUAL-CORTEX

The cortical visual system consists of many richly interconnected area s. Each area is characterized by more or less specific receptive field tuning properties. However, these tuning properties reflect only a su bset of the interactions that occur within and between areas. Neuronal responses may be modulated by perceptual context or attention. These modulations reflect lateral interactions within areas and feedback fro m higher to lower areas. Recent work is beginning to unravel how horiz ontal and feedback connections each contribute to modulatory effects a nd what the role of these modulations is in vision. Whereas receptive field tuning properties reflect feedforward processing, modulations ev oked by horizontal and feedback connections may reflect the integratio n of information that underlies perception.