The responses to illusory contours of neurons in cortex areas 17 and 18 ofthe cats

Responses to illusory contours (ICs) were sampled from neurons in cortical areas 17 and 18 of the anesthetized cats. For ICs sensitive cells, the diff erences of receptive field properties were compared when ICs and real conto ur stimuli were applied. Two hundred orientation or direction selective cel ls were studied, We find that about 42 percent of these cells were the ICs sensitive cells. Although their orientation or direction tuning curves to I Cs bar and real bars were similar, the response modes (especially latency a nd time course) were different, The cells' responses to ICs were independen t of the spatial phases of sinusoidal gratings, which composed the ICs, The cells' optimal spatial frequency to composing gratings the ICs was much hi gher than the one to moving gratings. Therefore, these cells really respond ed to the ICs rather than the line ends of composing gratings. For some kin ds of velocity-tuning cells, the optimal velocity to moving ICs bar was muc h lower than the optimal velocity to moving bars. The present results demon strate that some cells in areas 17 and 18 of cats have the ability to respo nd to ICs and have different response properties of the receptive fields to ICs and luminance boundaries via different neural mechanisms.