A reappraisal of acute doses of benzodiazepines as a model of anterograde amnesia.

OBJECTIVE: Acute administration of benzodiazepines is considered a pharmacological model of general organic anterograde amnesias (OAA). We sought to determine which type of amnesia these drugs best model by comparing the effects of diazepam with those reported in amnesiacs regarding working memory capacity (WMC), susceptibility to retroactive interference (RI), and accelerated forgetting. METHODS: In this double-blind, parallel-group design study, 30 undergraduates were randomly allocated to acute oral treatments with 15 mg diazepam or placebo. WMC and story recall were assessed pre- and post-treatment. Story presentation was succeeded by 10 min of RI (spotting differences in pictures) or minimal RI (doing nothing in a darkened room). Delayed story recall was assessed under diazepam and 7 days later in a drug-free session to assess accelerated forgetting. RESULTS: Recall of stories encoded under diazepam, whether reactivated or not, was severely impaired (anterograde amnesia). However, diazepam did not impair WMC, increase susceptibility to RI, or accelerate forgetting. CONCLUSIONS: Diazepam's amnestic effects mirror those in patients with probable severe medial temporal damage, mostly restricted to initial consolidation and differ from other OAA (Korsakoff syndrome, frontal, transient epileptic, posttraumatic amnesia, and most progressive amnesias) in terms of WMC, susceptibility to RI and accelerated forgetting.

Wakeful rest benefits before and after encoding in anterograde amnesia.

Objective: Studies have shown that patients with anterograde amnesia forget less episodic information after a delay if encoding is immediately followed by an unfilled period of wakeful rest. This benefit has been attributed to the reduced interference with the consolidation process. However, this account cannot directly explain improved retention in healthy adults resulting from pre-encoding rest. While benefits resulting from pre- and post-encoding rest can be alternatively explained via improved distinctiveness at retrieval, it has yet to be established whether both benefits are observable in amnesics. The aim of the current study was to assess whether amnesic patients showed improved retention of prose material after 10 min following both pre- and post-encoding unfilled intervals of wakeful rest. Method: Twelve patients with anterograde amnesia were recruited. Participants completed four conditions. A short prose passage was aurally presented in each condition. Prose presentation was preceded and followed by a 9-min delay interval. Delay intervals were either filled (spot-the-difference task) or unfilled (wakeful rest). Prose retention was assessed immediately after presentation and after 10 min. Results: Prose retention was consistently better when wakeful rest followed prose encoding in comparison to a condition where an effortful task was encountered both before and after encoding. Conclusions: Post-encoding wakeful rest alone substantially improves retention in amnesic patients. While pre-encoding wakeful rest elicits inconsistent benefits in amnesics, reduced retention following both pre- and post-encoding task engagement suggests that pre-encoding activity may still be relevant. Overall, our findings support consolidation interference explanations of forgetting in anterograde amnesia. (PsycInfo Database Record (c) 2020 APA, all rights reserved).