This effect was present irrespective of whether the failure to obtain a reward occurred on the second (one-of-a-kind trial), third (two-of-a-kind trial), or fourth (three-of-a-kind trial) tumbler.
The example shows a two-of-a-kind trial in which the nonidentical stimulus appears on the third tumbler.
If I-Lost neurons reflected the rewarding properties of advancing to the next trial it seems logical that the activity following the presentation of the first nonidentical stimulus on the second (one-of-a-kind trial) or third (two-of-a-kind trial) tumbler would persist for the duration of the trial.
Finally, four-of-a-kind trials were those on which the same stimulus appeared on all four tumblers.
Consistent with the human literature [32], we found that the latency following four-of-a-kind (winning) trials was longer than that following one-of-a-kind, two-of-a-kind, and three-of-a-kind trials, and that the latency following one-of-a-kind, two-of-a-kind, and three-of-a-kind trials was no different.
Post-hoc Scheffe tests (evaluated at p<.05) were then used to determine if the latency following four-of-a-kind (winning) trials was longer than that following one-of-a-kind, two-of-a-kind, and three-of-a-kind trials, and that the latency following one-of-a-kind, two-of-a-kind, and three-of-a-kind trials was no different.
One-of-a-kind, two-of-a-kind, and three-of-a-kind trials resulted in no reward and direct entry into the ITI.
For the reward related neurons, neural responses to the first two tumblers on two-of-a-kind trials, the first three tumblers on three-of-a-kind trials, and the four tumblers on four-of-a-kind (winning) trials were analyzed together.
Specifically, we looked to see whether a neuron increased or decreased its activity across the first two tumblers on two-of-a-kind trials, across the first three tumblers on three-of-a-kind trials, and across all four tumblers on four-of-a-kind (winning) trials.
One-of-a-kind trials were those on which the stimulus appearing on the first tumbler was not repeated on any of the other tumblers.
Only four-of-a-kind trials resulted in the delivery of 3-sec access to reward, which was followed by entry into the ITI.
