[18F]FPEB	3-[18F]fluoro-5-(2-pyridinylethynyl)benzonitrile
ADI-R	Autism Diagnostic Interview-Revised [50]
ADOS	Autism Diagnostic Observation Schedule [51]
ANOVA	analysis of variance
ASD	autism spectrum disorder
BMI	basal metabolic index
BPND	non-displaceable binding potential
CEA	Commissariat à l’Énergie Atomique et aux Énergies Alternatives
CDC	Centers for Disease Control and Prevention
CN	caudate nucleus
CNAMI	CNS Neuropsychopharmacology and Multimodal Imaging
CNMT	Certified Nuclear Medicine Technologist
CNRS	Centre National de la Recherche Scientifique
CNS	central nervous system
DSM-5	Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition [1]
DTI	diffusion tensor imaging
EEG	electroencephalography
ERK	extracellular signal-regulated kinase
ERP	event-related brain potential
FORWARD	Fragile X Online Registry With Accessible Research Database of the National Fragile X Foundation (NFXF)
FMR1	fragile X mental retardation 1 gene
fmr1	fmr1 gene in knockout mouse model of fragile X syndrome
FMRP	Fragile X Mental Retardation Protein
FXS	fragile X syndrome
FXS-M	fragile X syndrome allele size mosaicism
GABA	gamma amino butyric acid
HRRT	high resolution research tomograph [53]
HSD	Honest Standard Differences [31]
IASD	idiopathic autism spectrum disorder
ID	intellectual disability
IND	Institute for Neurodegenerative Disorders
IJMS	International Journal of Molecular Sciences
JHU	Johns Hopkins University
KO	knockout
LTD	long-term depression
MDPI	Multidisciplinary Digital Publishing Institute
MPAK	mitogen-activated protein kinase (MAPK)
MBq	megabecquerel
mCi	millicurie
mGluR1/5	metabotropic glutamate receptors subtypes 1 and 5
mGluR5	metabotropic glutamate receptor subtype 5
mGluR-LTD	metabotropic glutamate receptor dependent longterm depression
MIRCen	Molecular Imaging Research Center
MR	magnetic resonance
MRS	magnetic resonance spectroscopy
mTOR	mammalian target of rapamycin
mTp	medial temporal cortex
NAM	negative allosteric modulator
NFXF	National Fragile X Foundation
NMTCB	Nuclear Medicine Technology Certification Board
Oc	occipital cortex
Pa	parietal cortex
pCg	posterior cingulate cortex
PCR	polymerase chain reaction
PET	positron emission tomography
PET/MRI	positron emission tomography/magnetic resonance imaging
Pu	putamen
ROI	region of interest
rs-fMRI	resting state functional magnetic resonance imaging
RTGA	reference tissue graphical analysis
SPM	Statistical Parametric Mapping
TD	typical development
Th	thalamus
Tp	temporal cortex
(period)	missing data