| The current method for diagnosing psychotic disorders is based on clinical symptoms despite the overlapping behavioral, biological, and genetic features among these disorders (Insel et al., 2010). To better incorporate neurocognitive and neurophysiological features of psychotic disorders, Clementz et al. (2015) identified three diagnosis-independent subgroups, or 'biotypes' of psychosis. The primary aim of this study was to examine the degree to which spatial working memory, a key cognitive deficit of schizophrenia and psychosis (Park and Lee, 2005), varies across the three biotypes. Additionally, because Catechol-O-Methyltransferase (COMT) modulates dopamine and impacts working memory (Egan et al., 2001), this investigation was designed to assess whether COMT genotypes (Val/Val vs. Val/Met vs. Met/Met) were evenly distributed across biotypes compared to healthy controls, and the degree to which COMT impacts the relationship between spatial working memory and biotype. Findings indicated that Biotype 1 showed the greatest impairment on forward and backward span followed by Biotype 2, and then Biotype 3. Additionally, findings revealed that Biotype 3 had a disproportionate number of Met/Met genotypes. However, there was no main effect of COMT genotype on spatial working memory and no interaction between COMT genotype and biotype on spatial working memory. The results validate the distinctiveness of the biotypes using an external measure for spatial working memory. The lack of a main effect of COMT may indicate a domain specific effect of COMT on verbal, but not spatial, working memory. An alternative explanation is that many genes contribute modestly to complex phenotypes such as spatial working memory. |
