Brain morphology does not clearly map to cognition in individuals on the bipolar-schizophrenia-spectrum: a cross-diagnostic study of cognitive subgroups

• Published in: Journal of affective disorders 2021-02, Vol.281, p.776-785
• Main Authors: Karantonis, James A., Rossell, Susan L., Carruthers, Sean P., Sumner, Philip, Hughes, Matthew, Green, Melissa J., Pantelis, Christos, Burdick, Katherine E., Cropley, Vanessa, Van Rheenen, Tamsyn E.
• Format: Article
• Language: English
• Subjects: Bipolar Disorder - diagnostic imaging; bipolar disorder, schizophrenia spectrum, neuroimaging, cognition, cluster analysis; Brain - diagnostic imaging; Cognition; cognitive heterogeneity; Humans; Magnetic Resonance Imaging; Schizophrenia - diagnostic imaging
• ISSN: 0165-0327; 1573-2517
• DOI: 10.1016/j.jad.2020.11.064

•The patterns of brain morphology in cognitive subgroups were not consistent across global, regional, and vertex-wise analyses.•Contrary to expectations, the subgroup with the greatest cognitive impairments demonstrated relative increases in volume and cortical thickness.•Our findings suggest that variation in cognitive performance may not map cleanly onto variation in brain morphology in SSD and BD. Characterisation of brain morphological features common to cognitively similar individuals with bipolar disorder (BD) and schizophrenia spectrum disorders (SSD) may be key to understanding their shared neurobiological deficits. In the current study we examined whether three previously characterised cross-diagnostic cognitive subgroups differed among themselves and in comparison to healthy controls across measures of brain morphology. T1-weighted structural magnetic resonance imaging scans were obtained for 143 individuals; 65 healthy controls and 78 patients (SSD, n = 40; BD I, n = 38) classified into three cross-diagnostic cognitive subgroups: Globally Impaired (n = 24), Selectively Impaired (n = 32), and Superior/Near-Normal (n = 22). Cognitive subgroups were compared to each other and healthy controls on three separate analyses investigating (1) global, (2) regional, and (3) vertex-wise comparisons of brain volume, thickness, and surface area. No significant subgroup differences were evident in global measures of brain morphology. In region of interest analyses, the Selectively Impaired subgroup had greater right accumbens volume than those Superior/Near-Normal subgroup and healthy controls, and the Superior/Near-Normal subgroup had reduced volume of the left entorhinal region compared to all other groups. In vertex-wise comparisons, the Globally Impaired subgroup had greater right precentral volume than the Selectively Impaired subgroup, and thicker cortex in the postcentral region relative to the Superior/Near-Normal subgroup. Exploration of medication effects was limited in our data. Although some differences were evident in this sample, generally cross-diagnostic cognitive subgroups of individuals with SSD and BD did not appear to be clearly distinguished by patterns in brain morphology.