Temporal specificity in patterning of the rabbit nictitating membrane response

Rabbits were trained in either positive patterning (AX+, A-, X-) or negativ e patterning (A+, X+, AX-) using one of four intervals between the onset of A and the onset of X on AX trials. These intervals were 0, 800, 2,400, and 5,600 msec. In each task, all groups acquired an appropriate pattern of di scriminative responding. Following acquisition, all rabbits were tested wit h the four different A-X intervals. All positive patterning groups showed a n excitatory gradient, in which the highest level of responding occurred at the interval used in training. Conversely, all but one of the negative pat terning groups showed an inhibitory gradient, in which the lowest level of responding occurred at the interval used in training. The one exception was the negative patterning group trained with simultaneous AX stimuli (0 msec ), which showed a low, broad gradient, indicating transfer of inhibition ac ross all the intervals. The results are discussed with respect to temporal encoding mechanisms and accounts of conditional discriminations.