physiological responses of new world monkey v1 neurons to stimuli defined by coherent motion we studied the responses of neurons in area v1 of marmosets to visual stimuli that moved against dynamic textured backgrounds the stimuli were defined either by a firstorder cue solid bars which were either darker or lighter than the background or by a secondorder cue camouflaged bars defined only by coherent motion fortytwo per cent of the neurons demonstrated a similar selectivity for the direction of motion of the solid and camouflaged bars thereby characterizing a population of cueinvariant ci cells the other cells either showed different selectivity to the movement of solid and camouflaged bars noncueinvariant or nci cells or responded equally well to movement in all directions ci neurons which were rare in layer 4 tended to have larger receptive fields and to be more strongly direction selective than nci cells although v1 neurons tended to show maximal responses to camouflaged bars that were longer than the optimal solid bars many ci neurons preferred first and secondorder stimuli of similar lengths finally the activity evoked by the camouflaged bars was delayed in relation to that evoked by solid bars these results demonstrate that motion ci responses are relatively common in primate v1 especially among a population of strongly directionselective neurons they also indicate that this response property may depend on feedback from extrastriate areas or on complex intrinsic interactions within v1