From the perspective of the preoccupation/anticipation stage, a genetic knock-in mouse that bio logically recapitulates a common human mutation in the gene for fatty acid amide hydrolase (C385A [Pro129Thr], rs324420) presented a reduction of fatty acid amide hydrolase expression associated with the variant allele that selectively enhanced fronto-amygdala connectivity and fear extinction learning and decreased anxiety-like behaviours; this result suggests another possible molecular genetic target for neuroplasticity in the preoccupation/anticipation and withdrawal/negative affect stages.165
