| Abstract |
The aim of the present study is on the effects of the Schizophrenia risk candidate
polymorphism Val158Met of the Catechol-O-methyl trasnferase (COMT) and its
implications in cognitive functionality and personality traits. The sample population was
a large cohort of healthy males who underwent neuropsychological and personality
assessment and genotyping of the COMT Val158Met polymorphism.
In the introduction, a brief report on Schizophrenia, its symptomatology, subtype
division, heredity and general population frequency is presented followed by disordered
cognitive functions and the implication of the prefrontal cortex (PFC). The functional
specialization and the implications of PFC dysfunction are presented. Three personality
models, Eysenck’s Personality model, Cloninger’s Biosocial Theory and Gray’s
Reinforcement Sensitivity Theory which are among the most empirically supported
personality models, are then presented. The next chapter is on COMT, summarizing its
biochemical properties and review its implications in cognition and personality traits,
focusing on the rs4680 (or Val158Met) polymorphism.
In the Materials and Methods, we present information about the cohort that
participated in the study, the personality scales ([EPQ, TCI, BIS/BAS, Spielberger’s
State-Trait Anxiety Inventory-Trait Scale (STAI-T) and Schizotypal Traits Questionnaire
(STQ)] and the neuropsychological tasks [Wisconsin Card Sorting Test (WCST), Iowa
Gambling Task (IGT), Word List Task (WL), Stroop Interference Task, N-Back task and a
subset of Cambridge Neuropsychological Test Automated Battery (CANTAB) including
Spatial Working Memory task (SWM), Rapid Visual Information Processing (RVP) and
Stocking of Cambridge (SoC)]. The cohort was divided into two groups, val/val (N=217)
and met carriers (N=548), and separate Principal Component Analysies (PCA) both for
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neupsychological and personality variables were conducted followed by and correlational
analyses.
The categorical analyses did not reveal any significant differences between groups
in any PCA personality or neuropsychological factor. However, when correlational
analyses were conducted, a significant negative correlation between Novelty Seeking and
declarative memory and a significant positive correlation between Novelty Seeking in the
val/val homozygotes and between Novelty Seeking and Perseveration in the met-carriers’
group was revealed.
Consistent with the present results, Novelty Seeking has been found to correlate
with the Val allele and lower dopamine levels in the prefrontal cortex and reduced
dopamine levels in the prefrontal cortex is associated with poorer memory retrieval..
Also, consistent with the present findings, an effect of the val158met genotype on
Wisconsin Card Sorting Test perseveration and an association between the Met allele and
increased cognitive stability over cognitive flexibility has been reported.
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Cognitive functionality and personality traits.impact of Va1158Met polymorphism of Catechol-O-methytransferase (COMT)
