The hypothesis that there is a 1:1 correspondence between LTP and lear
ning is simplistic, and the correlation approach to testing it is ther
efore too limited. The alternative hypothesis that LTP plays a role in
arousal is consistent with activity-dependent neuromodulation, but ig
nores the Hebbian properties of LTP. LTP may involve both types of mec
hanisms, suggesting a possible synthesis of the two hypotheses.