Is anterograde amnesia a special case of retrograde amnesia?

In anterograde amnesia, memory loss is obtained for events that occur subsequent to the traumatic insult. But because the effects of an anterograde agent or treatment usually last for minutes, or even hours, after the nominal training event, processing of information may be altered during the postacquisition period as well as during acquisition. Since posttraining manipulations are themselves capable of modulating memory, or inducing retrograde amnesia, the memory loss due to a putative anterograde treatment may instead represent retrograde processes. The present experiment examined this potential source of confounding by using an amnestic treatment that can be quickly reversed after training in order to remove postacquisition effects. Thus, the presence of amnesia would isolate anterograde contributions as the source of loss. For induction of anterograde amnesia, rats were trained while at reduced body temperature (29 degrees C). A rapid rewarming procedure was introduced for some animals immediately after training to ensure that the hypothermic state did not extend into the postacquisition period. Other subjects were rapidly rewarmed 1 hr after training to control for any effects of the rewarming manipulation. Both groups showed severe anterograde amnesia that was indistinguishable from that obtained in the gradually rewarmed controls. These data provide an empirical example of an anterograde-induced memory deficit that is independent of retrograde influences.