title: Near-infrared imaging of the effects of glucose ingestion and regulation on prefrontal activation during dual-task execution in healthy fasting older adults.
abstract: BACKGROUND
  Glucose enhancing effects in older adults have mostly been observed for episodic memory, but have recently been found for attentional control performance. Yet, brain activation patterns underlying these effects are still unknown.
  
  
  OBJECTIVE
  The present study examined the acute effects of glucose ingestion on prefrontal brain activation during the execution of a divided attention task in fasting non-diabetic older adults.
  
  
  METHODS
  Twenty older adults (60 years and older) took part in the study that included two experimental sessions. After an overnight fast, participants received either a glucose drink (50 g) or a placebo (saccharin) drink, following which they completed a dual-task. During task execution, prefrontal activation was recorded with functional near-infrared spectroscopy (fNIRS). A repeated-measures design was used such that each participant served as his or her own control. The two experimental sessions were counterbalanced among participants and were performed two weeks apart.
  
  
  RESULTS
  When participants were in the glucose condition, they showed similar dual-task costs for both tasks, whereas in the placebo condition they prioritized one task over the other, with a significantly larger dual-task cost for the non-prioritized task (p<0.01). Differential brain activation was also observed in right ventral-lateral prefrontal regions for oxygenated hemoglobin and deoxygenated hemoglobin, with more activation apparent in the glucose condition (p<0.05). Furthermore, behavioral and activation data were influenced by individual differences in glucose regulation.
  
  
  CONCLUSIONS
  Glucose ingestion appears to momentarily enhance fasting seniors' capacity to coordinate more equally two concurrent tasks and this is reflected in brain activation patterns.
authors.affiliation: Université du Québec à Montréal, Case postale 8888, succursale, Centre-Ville, Montréal, QC, H3C 3P8, Canada. christine.gagnon@gmail.com
authors.forename: Christine
authors.initials: C
authors.lastname: Gagnon
authors.forename: Laurence
authors.initials: L
authors.lastname: Desjardins-Crépeau
authors.forename: Isabelle
authors.initials: I
authors.lastname: Tournier
authors.forename: Michèle
authors.initials: M
authors.lastname: Desjardins
authors.forename: Frédéric
authors.initials: F
authors.lastname: Lesage
authors.forename: Carol E
authors.initials: CE
authors.lastname: Greenwood
authors.forename: Louis
authors.initials: L
authors.lastname: Bherer
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019540:Area Under Curve; D001786:Blood Glucose / Q000378:metabolism; D015992:Body Mass Index; D005071:Evoked Potentials / Q000187:drug effects; D005215:Fasting / Q000502:physiology*; D005260:Female; D005403:Fixation, Ocular / Q000502:physiology; D005947:Glucose / Q000494:pharmacology*; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D007206:Individuality; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D010108:Oxyhemoglobins / Q000378:metabolism; D017397:Prefrontal Cortex / Q000187:drug effects*; D011597:Psychomotor Performance / Q000187:drug effects*; D011930:Reaction Time / Q000187:drug effects; D019265:Spectroscopy, Near-Infrared
chemical_list: D001786:Blood Glucose; D006454:Hemoglobins; D010108:Oxyhemoglobins; C100003:deoxyhemoglobin; D005947:Glucose