The influence of the dopaminergic system on cognitive functioning: A molecular genetic approach.

Many pharmacological and clinical studies have demonstrated the importance of the dopaminergic (DA) system for cognitive functioning but little is known about the genetic basis of general cognitive ability that has been demonstrated to be highly heritable. Attempts to detect associations between certain gene loci and endophenotypes of general cognitive ability have turned out to be more promising. Therefore, the aim of the present study was to investigate two dopaminergic candidate genes (COMT VAL158MET and DRD2 TAQ IA) for endophenotypes of cognitive functioning i.e. attention, vigilance, interference, time estimation and sensoric and motoric reaction times. Out of a gene data bank of more than 600 healthy Caucasian participants, 96 subjects (n = 48 males and n = 48 females) were recruited according to their genotype/allele pattern, resulting in six independent groups (COMT: VAL/VAL, VAL/MET, MET/MET)x(DRD2: A1-, A1+) of n = 16 subjects each. Results showed associations of the COMT gene with attention and with time estimation but most noteworthy was an interaction effect DRD2xVAL on interference performance as measured by the STROOP-test explaining 13% of the variance. Findings suggest that a balance between DA related catabolic enzyme activity and receptor density are good predictors for the endophenotype of cognitive interference and that the COMT gene is in accordance with previous studies related to cognitive functioning.