Information processing during general anesthesia: Evidence for unconscious memory

Abstract

Memory for words presented during general anesthesia was studied in two experiments. In Experiment 1,surgical patients (n = 80) undergoing elective procedures under general anesthesia were presented shortly before and during surgery with words via headphones. At the earliest convenient time after surgery (within 5 h) and 24 h later, memory was tested by asking patients to complete auditorily presented word stems with the first word that came to mind and to leave out words they remembered having heard earlier (exclusion task). Moreover, patients were requested to perform a "yes/no" forcedchoice recognition task to assess recognition memory for both the pre-and intraoperative words. Memory for the material presented during anesthesia was demonstrated immediately after surgery and 24 h later by means of both tasks. In a second similar experiment (n = 80), the results were replicated. These findings show that anesthetized patients can process information that was presented intraoperatively.Over the past few years, perception and memory during general anesthesia have become major scientific topics. Both anesthesiologists and psychologists attempt to find out whether patients can perceive information presented during general anesthesia, and, ifso, what the preconditions for such nonconscious cognition are. Some

Memory for Unconsciously Perceived Events: Evidence from Anesthetized Patients

“…Bovill, & Zwaveling (1988) .12 53 Bonke, Schmitz, Verhage, & Zwaveling (1986) .06 55 Caseley-Rondi, Merikle, & Bowers (1994) Ϫ.11 96 De Houwer, Demeyere, Verhamme, & Eelen (1995) a .18 40 Evans & Richardson (1988) .50 39 Furlong & Read (1993) Ϫ.13 108 Jelicic, .10 82 Korunka, Guttmann, Schleiitz, Hilpert, Haas, & Fitzal (1992) .03 108 Liu, Standen, & Aitkenhead (1992) Ϫ.13 48 Liu, Standen, & Aitkenhead (1993) .14 82 Pearson (1961) .28 81 Steinberg, Hord, Reed, & Sebel (1993) .19 60 Van der Laan, van Leeuwen, Sebel, Winograd, & Bonke (1996) .13 40 Woo, Seltzer, & Marr (1987) . 20 Caseley-Rondi, Merikle, & Bowers (1994) .23 74 McClintock, Aitken, Downie, & Kenny (1990) .29 60 Steinberg, Hord, Reed, & Sebel (1993) .20 60 Van der Laan, Van Leeuwen, Sebel, Winograd, Bauman, & Bonke (1996) Ϫ.04 40 Charlton, Wang, & Russell (1993) .15 44 Cork, Kihlstrom, & Schacter (1992) Ϫ.14 25 De Roode, Jelicic, Bonke, & Bovill (1995) Ϫ.08 83 Donker, Phaf, Porcelijn, & Bonke (in press) .09 58 Jelicic, Bonke, Wolters, & Phaf (1992) .29 50 Jelicic, De Roode, Bovill, & Bonke (1992) .48 43 Khilstrom, Schacter, Cork, Hurt, & Behr (1990) .31 25 Roorda-Hrdlickova, Wolters, Bonke, & Phaf (1990) .59 81 Villemure, Plourde, Lussier, & Normandin (1993) .54 10 Westmoreland, Sebel, Winograd, & Goldman (1993) .08 48 Direct measures Bonebakker, Bonke, Klein, Wolters, Stijnen, Passchier, & Merikle (1996) .24 160 Block, Ghoneim, Sum Ping, & Ali (1991b) .06 72 Dwyer, Bennett, Eger, & Peterson (1992) .00 45 Humphreys, Asbury, & Millar (1990) Ϫ.13 20 Jelicic, Asbury, .04 …”

Patients' memories of events during general anaesthesia

“…The authors suggest that pre-existing knowledge may be activated during general anaesthesia and unconscious learning may take place [34]. Block et al used a word completion test [35] and Bonnebakker et al used a forced choice recognition test [36] to also demonstrate the possibility of unconscious learning during general anaesthesia.…”

Is the unconscious “smart,” or “dumb?” and if it’s smart, how smart is it?: one more time—with feeling

“…Similarly, a review by Johnston and Dark (1986) on selective attention also has shown that a semantic analysis of words presented in a secondary channel only occurs if the words have significant relevance to the subject. There is also research on memory under general anaesthesia (e.g., Andrade, 1995;Bennett, 1993;Bonebakker, et al, 1996;Kihlstrom, and Couture, 1992;Kihlstrom, Schacter, Cork, Hurt and Behr, 1990;Merikle and Daneman, 1996) with some suggesting that only personally meaningful events heard in the operating room while a patient is under general anaesthesia are able under certain conditions to be later recalled (Andrade, 1995).…”