title: Frontal lobe γ-aminobutyric acid levels during adolescence: associations with impulsivity and response inhibition.
abstract: BACKGROUND
  The brain undergoes major remodeling during adolescence, resulting in improved cognitive control and decision-making and reduced impulsivity, components of behavior mediated in part by the maturing frontal lobe. γ-Aminobutyric acid (GABA), the main inhibitory neurotransmitter system, also matures during adolescence, with frontal lobe GABA receptors reaching adult levels late in adolescence. Thus, the objective of this study was to characterize in vivo developmental differences in brain GABA levels.
  
  
  METHODS
  Proton magnetic resonance spectroscopy was used at 4 T to acquire metabolite data from the anterior cingulate cortex (ACC) and the parieto-occipital cortex (POC) in adolescents (n=30) and emerging adults (n = 20).
  
  
  RESULTS
  ACC GABA/creatine (Cr) levels were significantly lower in adolescents relative to emerging adults, whereas no age differences were observed in the POC. Lower ACC GABA/Cr levels were significantly associated with greater impulsivity and worse response inhibition, with relationships being most pronounced for ACC GABA/Cr and No-Go response inhibition in adolescent males.
  
  
  CONCLUSIONS
  These data provide the first human developmental in vivo evidence confirming frontal lobe GABA maturation, which was linked to impulsiveness and cognitive control. These findings suggest that reduced GABA may be an important neurobiological mechanism in the immature adolescent brain, contributing to the reduced yet rapidly developing ability to inhibit risky behaviors and to make suboptimal decisions, which could compromise adolescent health and safety.
authors.affiliation: Neurodevelopmental Laboratory on Addictions and Mental Health, McLean Hospital, Belmont, MA 02478, USA. msilveri@mclean.harvard.edu
authors.forename: Marisa M
authors.initials: MM
authors.lastname: Silveri
authors.forename: Jennifer T
authors.initials: JT
authors.lastname: Sneider
authors.forename: David J
authors.initials: DJ
authors.lastname: Crowley
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Covell
authors.forename: Deepa
authors.initials: D
authors.lastname: Acharya
authors.forename: Isabelle M
authors.initials: IM
authors.lastname: Rosso
authors.forename: J Eric
authors.initials: JE
authors.lastname: Jensen
mesh_terms: D000293:Adolescent; D002648:Child; D005260:Female; D005625:Frontal Lobe / Q000378:metabolism*; D006801:Humans; D007175:Impulsive Behavior / Q000378:metabolism*; D008297:Male; D055815:Young Adult; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D005680:gamma-Aminobutyric Acid
keywords: ACC; GABA; MRS; adolescent; emerging adult; menstrual cycle