Authors: Vogt KM et al.
Anesthesiology 143(2):313-329, August 2025. | DOI: 10.1097/ALN.0000000000005489
This randomized, placebo-controlled, single-blind crossover study investigated how low (sedative) doses of propofol, dexmedetomidine, and fentanyl affect memory encoding and pain perception in healthy adults using 7 Tesla functional MRI. Ninety-two participants (ages 18–40) underwent four sessions where they listened to 80 words, with 30 paired with a painful electrical stimulus. The primary outcome was next-day memory performance (d′ score).
Propofol significantly impaired recollection (d′ = 0.51) compared to the no-drug condition (d′ = 1.16; P = 0.006), while dexmedetomidine (d′ = 1.04; P = 0.99) and fentanyl (d′ = 0.98; P = 0.99) had no significant effect on memory performance. fMRI revealed that propofol reduced activation in the hippocampus, amygdala, insula, and anterior cingulate cortex during memory and pain processing. Dexmedetomidine reduced hippocampal activation for memory tasks but did not affect pain-processing areas. Fentanyl reduced activation in the somatosensory cortex and insula during pain but increased activation in the anterior cingulate, hippocampus, and amygdala.
The study concludes that propofol significantly impairs memory encoding and pain-related neural activity, while dexmedetomidine and fentanyl exhibit more selective neuroanatomic effects on cognition and pain without broadly suppressing recollection.
Editor’s Perspective
What We Already Know about This Topic
- Different classes of anesthetic drugs—such as fentanyl, propofol, and dexmedetomidine—produce quite different brain states, as estimated using functional magnetic resonance imaging.
- From previous clinical and brain imaging results, it is believed that propofol is the most potent and fentanyl the least potent drug in impairing memory encoding.
- The functional brain imaging of how these classes of anesthetic drugs alter the interaction between memory and pain is unknown.
What This Article Tells Us That Is New
- Subjects receiving painful stimulation under mild sedation with propofol showed less pain intensity and less activation in brain regions associated with attention and memory encoding.
- At similar levels of sedation, dexmedetomidine resulted in no amnesia and no changes in pain perception or increased activity in pain-related brain regions.
- Those subjects who received fentanyl demonstrated no amnesia but decreased activation of memory encoding systems. On painful stimulation, there was less activation in sensory attention brain regions but increased activity in memory systems.
References:
Authors: Vogt KM et al. 2025.
Anesthesiology 143(2):313-329. doi:10.1097/ALN.0000000000005489
Thank you to the International Anesthesia Research Society for allowing us to share this article and highlight their journal.