title: Glucose and memory: the influence of drink, expectancy, and beliefs.
abstract: BACKGROUND
  An increasing number of studies suggest that glucose can enhance aspects of memory and the central methodology is the use of the glucose-placebo design. One critical issue therefore is separating the pharmacological effects of glucose from the expectancies created by consuming a drink that might contain glucose.
  
  
  OBJECTIVE
  A modified balanced placebo design examined the role that expectancy and belief about the drink consumed has on the pharmacological changes observed following glucose consumption.
  
  
  METHODS
  Ninety-three participants, allocated according to a drink (glucose, placebo) × message (told glucose, told nothing, told placebo) unrelated design, were administered tasks assessing immediate and delayed verbal free recall, spatial recognition and semantic verification. Each task has some evidence for hippocampus involvement, and variations in task difficulty were used to assess the idea that glucose effects are sensitive to task difficulty.
  
  
  RESULTS
  While the messages biased drink judgements in the expected direction, judgements of drink content were at chance and glucose only enhanced delayed free recall. The subtle effects of the messages did not modify the glucose enhancement. However, believing glucose had been consumed showed an independent improvement in delayed free recall. There was no evidence that task complexity enhanced the glucose effect.
  
  
  CONCLUSIONS
  The findings indicate that expectancy effects are unlikely to be confused with glucose enhancements, but beliefs about consuming glucose can augment performance on delayed free recall. The discussion considers the hippocampus and complexity hypotheses of glucose's mode of action and proposes the routine collection of drink beliefs in future studies.
authors.affiliation: School of Experimental Psychology, University of Bristol, 12a Priory Road, Bristol, BS8 1TU, UK. Brian.Stollery@Bristol.ac.uk
authors.forename: Brian
authors.initials: B
authors.lastname: Stollery
authors.forename: Leonie
authors.initials: L
authors.lastname: Christian
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D005947:Glucose / Q000008:administration & dosage / Q000494:pharmacology*; D006624:Hippocampus / Q000378:metabolism*; D006801:Humans; D008297:Male; D008568:Memory / Q000187:drug effects*; D011939:Mental Recall / Q000187:drug effects*; D015990:Placebo Effect; D021641:Recognition, Psychology / Q000187:drug effects; D012107:Research Design; D012660:Semantics; D055815:Young Adult
chemical_list: D005947:Glucose
references.citation: Neurotoxicol Teratol. 1996 Jul-Aug;18(4):493-7
references.pmid: 8866543
references.citation: Behav Brain Res. 2002 Aug 21;134(1-2):505-16
references.pmid: 12191837
references.citation: Nutr Res. 2011 May;31(5):370-7
references.pmid: 21636015
references.citation: J Stud Alcohol. 2002 Nov;63(6):745-54
references.pmid: 12529075
references.citation: Trends Cogn Sci. 2011 Nov;15(11):527-36
references.pmid: 22001867
references.citation: Psychopharmacology (Berl). 1999 Aug;145(4):378-85
references.pmid: 10460314
references.citation: Eur J Clin Nutr. 2009 Apr;63(4):566-71
references.pmid: 18270528
references.citation: Behav Neurosci. 1999 Jun;113(3):431-8
references.pmid: 10443771
references.citation: Learn Mem. 2011 Apr 18;18(5):301-5
references.pmid: 21502337
references.citation: Eur J Pharmacol. 2004 Apr 19;490(1-3):33-57
references.pmid: 15094072
references.citation: Neurosci Biobehav Rev. 2011 Jan;35(3):770-83
references.pmid: 20883717
references.citation: Trends Neurosci. 2006 Jul;29(7):374-381
references.pmid: 16750273
references.citation: Front Hum Neurosci. 2012 May 25;6:146
references.pmid: 22661938
references.citation: Neuron. 2003 Apr 10;38(1):127-33
references.pmid: 12691670
references.citation: Learn Mem. 2011 Dec 16;19(1):15-25
references.pmid: 22180053
references.citation: Br J Nutr. 2008 Nov;100(5):1128-34
references.pmid: 18377687
references.citation: Biol Psychol. 2008 Oct;79(2):209-15
references.pmid: 18555581
references.citation: Nutr Neurosci. 2005 Aug;8(4):227-32
references.pmid: 16491647
references.citation: Psychopharmacology (Berl). 2003 Sep;169(2):198-204
references.pmid: 12759808
references.citation: Psychopharmacology (Berl). 1998 Apr;136(4):349-56
references.pmid: 9600580
references.citation: Br J Nutr. 2001 Aug;86(2):173-9
references.pmid: 11502230
references.citation: Cereb Cortex. 2009 Dec;19(12):2767-96
references.pmid: 19329570
references.citation: Appetite. 2009 Dec;53(3):426-9
references.pmid: 19660507
references.citation: Clin Pharmacol Ther. 1998 Jul;64(1):1-7
references.pmid: 9695713
references.citation: Br J Soc Clin Psychol. 1978 Sep;17(3):283-4
references.pmid: 687885
references.citation: J Anat. 2005 Jul;207(1):35-66
references.pmid: 16011544
references.citation: J Psychopharmacol. 2011 Aug;25(8):1076-87
references.pmid: 20488830
references.citation: Hum Psychopharmacol. 2005 Apr;20(3):193-202
references.pmid: 15742338
references.citation: Hum Psychopharmacol. 2004 Dec;19(8):523-35
references.pmid: 15486961
references.citation: Psychopharmacology (Berl). 2002 Apr;160(4):387-97
references.pmid: 11919666
references.citation: Br J Nutr. 2001 Aug;86(2):117-8
references.pmid: 11502223
references.citation: Physiol Behav. 2000 Feb;68(4):549-53
references.pmid: 10713296
references.citation: Neuron. 2002 Aug 15;35(4):625-41
references.pmid: 12194864
references.citation: Psychopharmacology (Berl). 1993;113(1):83-8
references.pmid: 7862833
references.citation: Psychopharmacology (Berl). 2001 Oct;157(4):373-80
references.pmid: 11605096
references.citation: Br J Nutr. 2006 Feb;95(2):414-20
references.pmid: 16469161
references.citation: Psychopharmacology (Berl). 1998 Jun;137(3):259-70
references.pmid: 9683004
references.citation: Psychopharmacology (Berl). 2001 Aug;157(1):46-54
references.pmid: 11512042
references.citation: J Exp Psychol Gen. 1988 Mar;117(1):34-50
references.pmid: 2966230
references.citation: Psychopharmacology (Berl). 1994 Jul;115(3):383-8
references.pmid: 7871080
references.citation: Curr Opin Neurobiol. 2006 Apr;16(2):179-90
references.pmid: 16564688