title: Cerebral hemodynamic lateralization during memory tasks as assessed by functional transcranial Doppler (fTCD) sonography: effects of gender and healthy aging.
abstract: BACKGROUND
  Previous neuropsychological, lesional and functional imaging studies deal with the lateralization of memory processes, suggesting that they could be determined by the stage of processing (encoding vs retrieval) or by content (verbal vs non-verbal stimuli). The aims of the present study were: 1) to investigate if tasks that can be carried out using different strategies depending on the verbalizability of the material induce a lateralization of the mean cerebral blood flow velocity (mCBFV) in the middle cerebral arteries (MCAs), as monitored by a functional transcranial Doppler (fTCD); 2) to evaluate if these patterns of cerebral activation differ in relation to age, gender and task performance.
  
  
  METHODS
  Using TCD bilateral monitoring, we recorded mCBFV variations in 35 male and 35 female healthy, right-handed volunteers, classified as "young" (age range 21-40 years, n=35) or "old"(age range 41-60 years, n=35), performing four different cognitive tasks: encoding and recognition of Geometric Figures (GF), encoding and recall of Object Localization (OL) on a picture, encoding of a verbal Room Description (RD) and Arithmetic Skill (AS).
  
  
  RESULTS
  We found a significant right lateralization for the OL recall phase, and a significant left lateralization for RD and AS. When we took into consideration gender, age and performance, there was a strong effect of age on both OL encoding and recall phase, with significant right lateralization in young volunteers not seen in the older ones. No difference in gender was detected. We found a gender×performance interaction for RD, with poor performance females showing significant left lateralization.
  
  
  CONCLUSIONS
  According to our findings, hemispheric lateralization during memory encoding is material specific in both men and women, depending on the verbalizability of the material. mCBFV right lateralization during scene encoding and recall appears lost in older people, suggesting that healthy elderly could take advantage of mixed verbal and non-verbal strategies.
authors.affiliation: Department of Neurological and Psychiatric Sciences, University of Florence, Italy. bracco@unifi.it
authors.forename: Laura
authors.initials: L
authors.lastname: Bracco
authors.forename: Valentina
authors.initials: V
authors.lastname: Bessi
authors.forename: Fabiana
authors.initials: F
authors.lastname: Alari
authors.forename: Angela
authors.initials: A
authors.lastname: Sforza
authors.forename: Alessandro
authors.initials: A
authors.lastname: Barilaro
authors.forename: Marinella
authors.initials: M
authors.lastname: Marinoni
mesh_terms: D000328:Adult; D000367:Age Factors; D000375:Aging / Q000502:physiology*; D001783:Blood Flow Velocity / Q000502:physiology; D001921:Brain / Q000098:blood supply / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000502:physiology; D003071:Cognition / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008568:Memory / Q000502:physiology*; D008875:Middle Aged; D009483:Neuropsychological Tests; D012737:Sex Factors; D017585:Ultrasonography, Doppler, Transcranial