Controversy surrounds several experiments that have addressed whether selective synaptic strengthening occurs during learning. To date, the evidence suggests that widespread alterations in synaptic strength, through either kindling or electroconvulsive shock, can disrupt this hypothetical process. The lack of evidence for selective modification of learning through LTP stimulation, however, provides difficulties for both the prevailing hypothesis and the hypothesis advanced by Shors & Matzel. Subsequent experiments may indicate a role for LTP in both learning and arousal.