title: Altered frontal and temporal brain function during olfactory stimulation in adult attention-deficit/hyperactivity disorder.
abstract: OBJECTIVE
  Olfactory processing depends on dopamine metabolism and orbitofrontal cortex functioning, both known to be disturbed in attention-deficit/hyperactivity disorder (ADHD). Some investigations suggested alterations in olfactory processing (identification and sensitivity) in childhood and adult ADHD.
  
  
  METHODS
  In the present study we investigated olfactory function (Sniffin' Sticks) of 29 adult patients with ADHD (17 combined, 11 inattentive, and 1 hyperactive/impulsive subtype) and 29 controls matched for sex, handedness, age, intelligence, and education. Additionally, we measured frontal, temporal, and somatosensory cortical activity during olfactory perception. This was performed with functional near-infrared spectroscopy (fNIRS) during presentation of 2-phenylethanol (olfactory stimulant) and linalool (mixed olfactory/trigeminal stimulant) in two concentrations each.
  
  
  RESULTS
  Adult patients with ADHD and controls did not differ in sensitivity for and discrimination and identification of olfactory stimuli. Functional brain imaging measures with fNIRS generally revealed diminished activation in olfaction-associated brain regions in patients with ADHD. Only for a high concentration of linalool, oxygenated haemoglobin (O₂Hb) concentrations in patients were similar to controls (significant increase in the temporal, somatosensory, and inferior-frontal cortex). O₂Hb concentrations in active brain regions positively correlated with ADHD symptoms during childhood and trait impulsivity. These effects were carried for the subgroup with combined subtype.
  
  
  CONCLUSIONS
  Although we could not replicate altered clinical performance in ADHD, our fNIRS findings suggest an association of cortical olfactory processing with hyperactivity and impulsivity in adult ADHD.
authors.affiliation: Department of Psychiatry, Psychosomatics and Psychotherapy, University Hospital Würzburg, University of Würzburg, Würzburg, Germany. schecklman_m@klinik.uni-wuerzburg.de
authors.forename: Martin
authors.initials: M
authors.lastname: Schecklmann
authors.forename: Eva
authors.initials: E
authors.lastname: Schenk
authors.forename: Andreas
authors.initials: A
authors.lastname: Maisch
authors.forename: Susanne
authors.initials: S
authors.lastname: Kreiker
authors.forename: Christian
authors.initials: C
authors.lastname: Jacob
authors.forename: Andreas
authors.initials: A
authors.lastname: Warnke
authors.forename: Manfred
authors.initials: M
authors.lastname: Gerlach
authors.forename: Andreas J
authors.initials: AJ
authors.lastname: Fallgatter
authors.forename: Marcel
authors.initials: M
authors.lastname: Romanos
mesh_terms: D000328:Adult; D001289:Attention Deficit Disorder with Hyperactivity / Q000175:diagnosis / Q000503:physiopathology*; D001931:Brain Mapping; D005625:Frontal Lobe / Q000503:physiopathology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D055696:Olfactory Perception / Q000502:physiology*; D010626:Phenylethyl Alcohol; D011569:Psychiatric Status Rating Scales; D012903:Smell / Q000502:physiology*; D019265:Spectroscopy, Near-Infrared; D011795:Surveys and Questionnaires; D013702:Temporal Lobe / Q000503:physiopathology*
chemical_list: D010626:Phenylethyl Alcohol