Propofol and Midazolam Inhibit Conscious Memory Processes Very Soon after Encoding: An Event-related Potential Study of Familiarity and Recollection in Volunteers

Abstract

Background-Intravenous drugs active via gamma-aminobutyric acid receptors produce memory impairment during conscious sedation. Memory function was assessed using event related potentials (ERPs) while drug was present.

Sedation and regional anesthesia

“…It is known that the difference in dose that produces conscious amnesia from one that produces memory impairment from sedation is quite small. A recent study [14 ] compared the effects of propofol and midazolam on memory. In this investigation, propofol and midazolam were administered at sufficient doses to produce a significant effect on recognition memory during the continuous recognition task (CRT) while maintaining adequate task performance (sufficient encoding into long-term memory to track subsequent memory decay or forgetting).…”

Feasibility of measuring memory response to increasing dexmedetomidine sedation in children

“…Amnestic doses of midazolam or propofol, for example, allow a memory to be formed, which is rapidly lost over time (forgetting). [28][29][30] As the memory effect of amnestic drugs is changing rapidly during a 10-30 min period after encoding, subsequent recognition memory testing is best done beyond this time frame, and in current study was done after imaging and recovery from sedation. 29 31 Thus, amnesia in the sense of lack of memory for events occurring at drug concentrations causing little sedation, is most evident when drug concentrations are increasing slowly, or are held constant over increasing steps such as in studies using volunteers.…”

The Problem with Amnesia

“…Recollection is a memory where contextual details are clearly remembered, and these are the memories lost over time when propofol or midazolam are present. 4 Memory processes associated with familiarity recognition ("I remember the face, but not the name") are more difficult to clearly identify, as there is less confidence associated with such judgments. Hayama et al Robert A. Veselis…”

“…These represent the nonspecific sedation common to most centrally depressant drugs, and a specific benzodiazepine-type effect that produces lack of memory for events even when sedation is largely absent. 4 Recently Pryor et al modeled memory impairment induced by various intravenous drugs using a negative power function to separate drug actions on initial memory formation (encoding) from memory loss over time. 3 The question is how to refer to this latter effect, and that is the problem with "amnesia.…”